From 75375feb0e85dfe737fff8beae4f56bb0852e518 Mon Sep 17 00:00:00 2001
From: Timon ter Braak <timon@terbraak.org>
Date: Sat, 4 Jan 2020 22:39:04 +0100
Subject: [PATCH 1/9] Draw grid behind bounding rectangle for cleaner look.

---
 python/lognplot/qt/render/chart.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/python/lognplot/qt/render/chart.py b/python/lognplot/qt/render/chart.py
index 1024ca7..e63428b 100644
--- a/python/lognplot/qt/render/chart.py
+++ b/python/lognplot/qt/render/chart.py
@@ -21,14 +21,14 @@ def __init__(
     def render(self):
         """ Main entry point to start rendering a graph. """
 
-        self.draw_bouding_rect()
-
         x_ticks = self.calc_x_ticks(self.chart.x_axis)
         y_ticks = self.calc_y_ticks(self.chart.y_axis)
 
         if self.options.show_grid:
             self.draw_grid(x_ticks, y_ticks)
 
+        self.draw_bouding_rect()
+
         if self.options.show_axis:
             self.draw_x_axis(x_ticks)
             self.draw_y_axis(y_ticks)

From 9639985278faaa324ad979124c3082ca8bc7c55b Mon Sep 17 00:00:00 2001
From: Timon ter Braak <timon@terbraak.org>
Date: Sat, 4 Jan 2020 23:39:37 +0100
Subject: [PATCH 2/9] Added handles left of the chart area corresponding to the
 plotted signals.

---
 python/lognplot/chart/curve.py       |  1 +
 python/lognplot/qt/render/chart.py   | 38 +++++++++++++++++++++++++---
 python/lognplot/qt/render/layout.py  | 12 ++++++++-
 python/lognplot/qt/render/options.py |  4 +++
 4 files changed, 51 insertions(+), 4 deletions(-)

diff --git a/python/lognplot/chart/curve.py b/python/lognplot/chart/curve.py
index 4c2f9c1..3664495 100644
--- a/python/lognplot/chart/curve.py
+++ b/python/lognplot/chart/curve.py
@@ -14,6 +14,7 @@ def __init__(self, db, name, color):
         self._db = db
         self.name = name
         self.color = color
+        self.average = 0 # Average of the visual part of the curve
 
     def __repr__(self):
         return "Database proxy-curve"
diff --git a/python/lognplot/qt/render/chart.py b/python/lognplot/qt/render/chart.py
index e63428b..20b8945 100644
--- a/python/lognplot/qt/render/chart.py
+++ b/python/lognplot/qt/render/chart.py
@@ -33,8 +33,13 @@ def render(self):
             self.draw_x_axis(x_ticks)
             self.draw_y_axis(y_ticks)
 
+        if self.options.show_handles:
+            self._draw_handles()
+
         self._draw_curves()
-        self._draw_legend()
+
+        if self.options.show_legend:
+            self._draw_legend()
 
     def shade_region(self, region):
         """ Draw a shaded box in some region.
@@ -76,9 +81,9 @@ def _draw_curve(self, curve):
 
         if data:
             if isinstance(data[0], Aggregation):
-                self._draw_aggregations_as_shape(data, curve_color)
+                curve.average = self._draw_aggregations_as_shape(data, curve_color)
             else:
-                self._draw_samples_as_lines(data, curve_color)
+                curve.average = self._draw_samples_as_lines(data, curve_color)
 
     def _draw_samples_as_lines(self, samples, curve_color: QtGui.QColor):
         """ Draw raw samples as lines! """
@@ -96,6 +101,8 @@ def _draw_samples_as_lines(self, samples, curve_color: QtGui.QColor):
             rect = QtCore.QRect(point.x() - 3, point.y() - 3, 6, 6)
             self.painter.drawEllipse(rect)
 
+        return sum(p.y() for p in points) / len(points)
+
     def _draw_aggregations_as_shape(
         self, aggregations: Aggregation, curve_color: QtGui.QColor
     ):
@@ -187,6 +194,8 @@ def _draw_aggregations_as_shape(
             min_line = QtGui.QPolygon(min_points)
             self.painter.drawPolyline(min_line)
 
+        return sum(p.y() for p in mean_points) / len(mean_points)
+
     def _draw_legend(self):
         """ Draw names / color of the curve next to eachother.
         """
@@ -212,6 +221,29 @@ def _draw_legend(self):
                 color,
             )
 
+    def _draw_handles(self):
+        x = self.layout.handles.left()
+        y = self.layout.handles.top() + self.layout.handles.height() / 3
+
+        for _, curve in enumerate(self.chart.curves):
+            handle_y = curve.average
+            x_full = self.options.handle_width #self.layout.handles.right()
+            x_half = x_full / 2
+            y_full = self.options.handle_height
+            y_half = y_full / 2
+
+            polygon = QtGui.QPainterPath(QtCore.QPoint(x, handle_y))
+            polygon.lineTo(QtCore.QPoint(x, handle_y))
+            polygon.lineTo(QtCore.QPoint(x + x_half, handle_y))
+            polygon.lineTo(QtCore.QPoint(x + x_full, handle_y + y_half))
+            polygon.lineTo(QtCore.QPoint(x + x_half, handle_y + y_full))
+            polygon.lineTo(QtCore.QPoint(x, handle_y + y_full))
+
+            color = QtGui.QColor(curve.color)
+            self.painter.fillPath(polygon, QtGui.QBrush(color))
+
+            handle_y = handle_y + self.options.handle_height
+
     def to_x_pixel(self, value):
         return transform.to_x_pixel(value, self.chart.x_axis, self.layout)
 
diff --git a/python/lognplot/qt/render/layout.py b/python/lognplot/qt/render/layout.py
index b9b5e20..8d8590b 100644
--- a/python/lognplot/qt/render/layout.py
+++ b/python/lognplot/qt/render/layout.py
@@ -12,6 +12,11 @@ def __init__(self, rect: QtCore.QRect, options):
         # print(rect, type(rect))
         self.rect = rect
 
+        self.handles = QtCore.QRect(self.rect.left() + self.options.padding,
+                                    self.rect.top(),
+                                    self.options.handle_width,
+                                    self.rect.height())
+
         # Endless sea of variables :)
         self.do_layout()
 
@@ -19,7 +24,12 @@ def do_layout(self):
         # self.right = self.rect.right()
         # self.bottom = self.rect.bottom()
         self.chart_top = self.rect.top() + self.options.padding
-        self.chart_left = self.rect.left() + self.options.padding
+
+        if self.options.show_handles:
+            self.chart_left = self.handles.right() + 1
+        else:
+            self.chart_left = self.rect.left() + self.options.padding
+
         if self.options.show_axis:
             axis_height = self.axis_height
             axis_width = self.axis_width
diff --git a/python/lognplot/qt/render/options.py b/python/lognplot/qt/render/options.py
index e355f84..dc20b2c 100644
--- a/python/lognplot/qt/render/options.py
+++ b/python/lognplot/qt/render/options.py
@@ -2,4 +2,8 @@ class ChartOptions:
     def __init__(self):
         self.show_axis = True
         self.show_grid = True
+        self.show_legend = False
+        self.show_handles = True
         self.padding = 10
+        self.handle_width = 20
+        self.handle_height = 15
\ No newline at end of file

From ce4ce7ccee1bc854d5cf2ed29b272f68486eb811 Mon Sep 17 00:00:00 2001
From: Timon ter Braak <timon@terbraak.org>
Date: Sat, 4 Jan 2020 23:59:52 +0100
Subject: [PATCH 3/9] Force repaint on panning / zooming.

---
 python/lognplot/qt/render/chart.py        | 20 ++++++++------------
 python/lognplot/qt/widgets/chartwidget.py |  7 +++++++
 2 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/python/lognplot/qt/render/chart.py b/python/lognplot/qt/render/chart.py
index 20b8945..7bc38a6 100644
--- a/python/lognplot/qt/render/chart.py
+++ b/python/lognplot/qt/render/chart.py
@@ -223,27 +223,23 @@ def _draw_legend(self):
 
     def _draw_handles(self):
         x = self.layout.handles.left()
-        y = self.layout.handles.top() + self.layout.handles.height() / 3
 
         for _, curve in enumerate(self.chart.curves):
             handle_y = curve.average
-            x_full = self.options.handle_width #self.layout.handles.right()
+            x_full = self.options.handle_width
             x_half = x_full / 2
-            y_full = self.options.handle_height
-            y_half = y_full / 2
+            y_half = self.options.handle_height / 2
 
-            polygon = QtGui.QPainterPath(QtCore.QPoint(x, handle_y))
-            polygon.lineTo(QtCore.QPoint(x, handle_y))
-            polygon.lineTo(QtCore.QPoint(x + x_half, handle_y))
-            polygon.lineTo(QtCore.QPoint(x + x_full, handle_y + y_half))
-            polygon.lineTo(QtCore.QPoint(x + x_half, handle_y + y_full))
-            polygon.lineTo(QtCore.QPoint(x, handle_y + y_full))
+            polygon = QtGui.QPainterPath(QtCore.QPointF(x, handle_y - y_half))
+            polygon.lineTo(QtCore.QPointF(x, handle_y - y_half))
+            polygon.lineTo(QtCore.QPointF(x + x_half, handle_y - y_half))
+            polygon.lineTo(QtCore.QPointF(x + x_full, handle_y))
+            polygon.lineTo(QtCore.QPointF(x + x_half, handle_y + y_half))
+            polygon.lineTo(QtCore.QPointF(x, handle_y + y_half))
 
             color = QtGui.QColor(curve.color)
             self.painter.fillPath(polygon, QtGui.QBrush(color))
 
-            handle_y = handle_y + self.options.handle_height
-
     def to_x_pixel(self, value):
         return transform.to_x_pixel(value, self.chart.x_axis, self.layout)
 
diff --git a/python/lognplot/qt/widgets/chartwidget.py b/python/lognplot/qt/widgets/chartwidget.py
index 29809a2..7ca9a52 100644
--- a/python/lognplot/qt/widgets/chartwidget.py
+++ b/python/lognplot/qt/widgets/chartwidget.py
@@ -53,6 +53,7 @@ def pan(self, dx, dy):
         print("pan", dx, dy)
         options1 = ChartOptions()
         layout = ChartLayout(self.rect(), options1)
+        self.repaint()
 
     def add_curve(self, name, color=None):
         if not self.chart.has_curve(name):
@@ -76,31 +77,37 @@ def horizontal_zoom(self, amount):
         self.chart.horizontal_zoom(amount)
         # Autoscale Y for a nice effect?
         self.chart.autoscale_y()
+        self.repaint()
         self.update()
 
     def vertical_zoom(self, amount):
         self.chart.vertical_zoom(amount)
+        self.repaint()
         self.update()
 
     def horizontal_pan(self, amount):
         self.chart.horizontal_pan(amount)
         # Autoscale Y for a nice effect?
         self.chart.autoscale_y()
+        self.repaint()
         self.update()
 
     def vertical_pan(self, amount):
         self.chart.vertical_pan(amount)
+        self.repaint()
         self.update()
 
     def zoom_fit(self):
         """ Autoscale all in fit! """
         self.chart.zoom_fit()
+        self.repaint()
         self.update()
 
     def zoom_to_last(self, span):
         """ Zoom to fit the last x time in view.
         """
         self.chart.zoom_to_last(span)
+        self.repaint()
         self.update()
 
     def enable_tailing(self, timespan):

From 9a4ffd78147055649b60275ef6d25e71134288e4 Mon Sep 17 00:00:00 2001
From: Timon ter Braak <timon@terbraak.org>
Date: Sun, 5 Jan 2020 01:55:22 +0100
Subject: [PATCH 4/9] Working vertical pan using mouse on handles (including
 bug)

---
 python/lognplot/chart/curve.py            |  7 +++-
 python/lognplot/qt/render/chart.py        | 42 ++++++++++++++---------
 python/lognplot/qt/widgets/basewidget.py  | 12 +++++++
 python/lognplot/qt/widgets/chartwidget.py | 40 ++++++++++++++++++---
 4 files changed, 79 insertions(+), 22 deletions(-)

diff --git a/python/lognplot/chart/curve.py b/python/lognplot/chart/curve.py
index 3664495..3ce2cdd 100644
--- a/python/lognplot/chart/curve.py
+++ b/python/lognplot/chart/curve.py
@@ -14,7 +14,12 @@ def __init__(self, db, name, color):
         self._db = db
         self.name = name
         self.color = color
-        self.average = 0 # Average of the visual part of the curve
+        # Average of the visual part of the curve
+        self.average = 0
+        # Corresponding handle (polygon area)
+        self.handle = []
+        # Vertical adjustment by user
+        self.vertical_offset = 0
 
     def __repr__(self):
         return "Database proxy-curve"
diff --git a/python/lognplot/qt/render/chart.py b/python/lognplot/qt/render/chart.py
index 7bc38a6..7b4cfe3 100644
--- a/python/lognplot/qt/render/chart.py
+++ b/python/lognplot/qt/render/chart.py
@@ -78,20 +78,22 @@ def _draw_curve(self, curve):
         data = curve.query(timespan, min_count)
         # print("query result", type(data), len(data))
         curve_color = QtGui.QColor(curve.color)
+        # vertical offset
+        v_offset = curve.vertical_offset
 
         if data:
             if isinstance(data[0], Aggregation):
-                curve.average = self._draw_aggregations_as_shape(data, curve_color)
+                curve.average = self._draw_aggregations_as_shape(data, curve_color, v_offset)
             else:
-                curve.average = self._draw_samples_as_lines(data, curve_color)
+                curve.average = self._draw_samples_as_lines(data, curve_color, v_offset)
 
-    def _draw_samples_as_lines(self, samples, curve_color: QtGui.QColor):
+    def _draw_samples_as_lines(self, samples, curve_color: QtGui.QColor, v_offset):
         """ Draw raw samples as lines! """
         pen = QtGui.QPen(curve_color)
         pen.setWidth(2)
         self.painter.setPen(pen)
         points = [
-            QtCore.QPoint(self.to_x_pixel(x), self.to_y_pixel(y)) for (x, y) in samples
+            QtCore.QPoint(self.to_x_pixel(x), self.to_y_pixel(y) + v_offset) for (x, y) in samples
         ]
         line = QtGui.QPolygon(points)
         self.painter.drawPolyline(line)
@@ -104,7 +106,7 @@ def _draw_samples_as_lines(self, samples, curve_color: QtGui.QColor):
         return sum(p.y() for p in points) / len(points)
 
     def _draw_aggregations_as_shape(
-        self, aggregations: Aggregation, curve_color: QtGui.QColor
+        self, aggregations: Aggregation, curve_color: QtGui.QColor, v_offset
     ):
         """ Draw aggregates as polygon shapes.
 
@@ -125,12 +127,12 @@ def _draw_aggregations_as_shape(
             # x2 = self.to_x_pixel(metric.x2)
 
             # max line:
-            y_max = self.to_y_pixel(aggregation.metrics.maximum)
+            y_max = self.to_y_pixel(aggregation.metrics.maximum) + v_offset
             max_points.append(QtCore.QPoint(x1, y_max))
             # max_points.append(QtCore.QPoint(x2, y_max))
 
             # min line:
-            y_min = self.to_y_pixel(aggregation.metrics.minimum)
+            y_min = self.to_y_pixel(aggregation.metrics.minimum) + v_offset
             min_points.append(QtCore.QPoint(x1, y_min))
             # min_points.append(QtCore.QPoint(x2, y_min))
 
@@ -138,17 +140,17 @@ def _draw_aggregations_as_shape(
             stddev = aggregation.metrics.stddev
 
             # Mean line:
-            y_mean = self.to_y_pixel(mean)
+            y_mean = self.to_y_pixel(mean) + v_offset
             mean_points.append(QtCore.QPoint(x1, y_mean))
             # mean_points.append(QtCore.QPoint(x2, y_mean))
 
             # stddev up line:
-            y_stddev_up = self.to_y_pixel(mean + stddev)
+            y_stddev_up = self.to_y_pixel(mean + stddev) + v_offset
             stddev_up_points.append(QtCore.QPoint(x1, y_stddev_up))
             # stddev_up_points.append(QtCore.QPoint(x2, y_stddev_up))
 
             # stddev down line:
-            y_stddev_down = self.to_y_pixel(mean - stddev)
+            y_stddev_down = self.to_y_pixel(mean - stddev) + v_offset
             stddev_down_points.append(QtCore.QPoint(x1, y_stddev_down))
             # stddev_down_points.append(QtCore.QPoint(x2, y_stddev_down))
 
@@ -194,7 +196,7 @@ def _draw_aggregations_as_shape(
             min_line = QtGui.QPolygon(min_points)
             self.painter.drawPolyline(min_line)
 
-        return sum(p.y() for p in mean_points) / len(mean_points)
+        return (sum(p.y() for p in mean_points) / len(mean_points))
 
     def _draw_legend(self):
         """ Draw names / color of the curve next to eachother.
@@ -230,12 +232,18 @@ def _draw_handles(self):
             x_half = x_full / 2
             y_half = self.options.handle_height / 2
 
-            polygon = QtGui.QPainterPath(QtCore.QPointF(x, handle_y - y_half))
-            polygon.lineTo(QtCore.QPointF(x, handle_y - y_half))
-            polygon.lineTo(QtCore.QPointF(x + x_half, handle_y - y_half))
-            polygon.lineTo(QtCore.QPointF(x + x_full, handle_y))
-            polygon.lineTo(QtCore.QPointF(x + x_half, handle_y + y_half))
-            polygon.lineTo(QtCore.QPointF(x, handle_y + y_half))
+            curve.handle = [
+                QtCore.QPointF(x, handle_y - y_half),
+                QtCore.QPointF(x, handle_y - y_half),
+                QtCore.QPointF(x + x_half, handle_y - y_half),
+                QtCore.QPointF(x + x_full, handle_y),
+                QtCore.QPointF(x + x_half, handle_y + y_half),
+                QtCore.QPointF(x, handle_y + y_half)
+            ] 
+
+            polygon = QtGui.QPainterPath(curve.handle[0])
+            for p in curve.handle[1:]:
+                polygon.lineTo(p)
 
             color = QtGui.QColor(curve.color)
             self.painter.fillPath(polygon, QtGui.QBrush(color))
diff --git a/python/lognplot/qt/widgets/basewidget.py b/python/lognplot/qt/widgets/basewidget.py
index 80a438f..d50d867 100644
--- a/python/lognplot/qt/widgets/basewidget.py
+++ b/python/lognplot/qt/widgets/basewidget.py
@@ -24,6 +24,7 @@ def mousePressEvent(self, event):
         super().mousePressEvent(event)
         self.disable_tailing()
         self._mouse_drag_source = event.x(), event.y()
+        self.mousePress(event.x(), event.y())
         self.update()
 
     def mouseMoveEvent(self, event):
@@ -34,6 +35,7 @@ def mouseReleaseEvent(self, event):
         super().mouseReleaseEvent(event)
         self._update_mouse_pan(event.x(), event.y())
         self._mouse_drag_source = None
+        self.mouseRelease(event.x(), event.y())
 
     def _update_mouse_pan(self, x, y):
         if self._mouse_drag_source:
@@ -41,10 +43,20 @@ def _update_mouse_pan(self, x, y):
             if x != x0 or y != y0:
                 dy = y - y0
                 dx = x - x0
+                self.mouseDrag(x, y, dx, dy)
                 self.pan(dx, dy)
                 self._mouse_drag_source = (x, y)
                 self.update()
 
+    def mousePress(self, x, y):
+        pass
+
+    def mouseRelease(self, x, y):
+        pass
+
+    def mouseDrag(self, x, y, dx, dy):
+        pass
+
     def pan(self, dx, dy):
         """ Intended for subclasses to override.
         """
diff --git a/python/lognplot/qt/widgets/chartwidget.py b/python/lognplot/qt/widgets/chartwidget.py
index 7ca9a52..e5a7a15 100644
--- a/python/lognplot/qt/widgets/chartwidget.py
+++ b/python/lognplot/qt/widgets/chartwidget.py
@@ -7,7 +7,7 @@
 
 from ..qtapi import QtCore, QtWidgets, QtGui, Qt, pyqtSignal
 from ...utils import bench_it
-from ...chart import Chart
+from ...chart import Chart, Curve
 from ..render import render_chart_on_qpainter, ChartLayout, ChartOptions
 from . import mime
 from .basewidget import BaseWidget
@@ -29,6 +29,8 @@ def __init__(self, db):
         # Accept drop of signal names
         self.setAcceptDrops(True)
 
+        self._drag_handle = None
+
         # Tailing mode, select last t seconds
         self._last_span = None
         self._tailing_timer = QtCore.QTimer()
@@ -48,12 +50,42 @@ def dropEvent(self, event):
             self.logger.debug(f"Add curve {name}")
             self.add_curve(name)
 
+    def curveHandleAtPoint(self, x, y) -> Curve:
+        for curve in self.chart.curves:
+            topleft = curve.handle[0]
+            middleright = curve.handle[3]
+            bottomleft = curve.handle[-1]
+            if (x >= topleft.x() and
+                x <= middleright.x() and
+                y >= topleft.y() and
+                y <= bottomleft.y()
+            ):
+                return curve
+        return None
+
     # Mouse interactions:
+    def mousePress(self, x, y):
+        if self._drag_handle is None:
+            curve = self.curveHandleAtPoint(x,y)
+            if curve is not None:
+                self._drag_handle = curve
+
+    def mouseRelease(self, x, y):
+        self._drag_handle = None
+
+    def mouseDrag(self, x, y, dx, dy):
+        if self._drag_handle is not None:
+            #self.vertical_pan(float(dy) * 0.01) #self.PAN_FACTOR)
+            self._drag_handle.vertical_offset = self._drag_handle.vertical_offset + dy
+            self.repaint()
+
+    # Intended to work together with the WIP minimap?
     def pan(self, dx, dy):
         print("pan", dx, dy)
-        options1 = ChartOptions()
-        layout = ChartLayout(self.rect(), options1)
-        self.repaint()
+        # TODO: fix
+        #options1 = ChartOptions()
+        #layout = ChartLayout(self.rect(), options1)
+        #self.repaint()
 
     def add_curve(self, name, color=None):
         if not self.chart.has_curve(name):

From 50e41e8a3f25491a6d01ea18d64b9ee3e168d5f1 Mon Sep 17 00:00:00 2001
From: Timon ter Braak <timon@terbraak.org>
Date: Sun, 5 Jan 2020 23:54:54 +0100
Subject: [PATCH 5/9] Supplied each curve with its own vertical axis; thus,
 multi-axis support.

---
 python/lognplot/chart/chart.py            |  7 +++++
 python/lognplot/chart/curve.py            |  6 ++---
 python/lognplot/qt/render/__init__.py     |  2 +-
 python/lognplot/qt/render/base.py         |  8 +++---
 python/lognplot/qt/render/chart.py        | 32 +++++++++++------------
 python/lognplot/qt/widgets/chartwidget.py |  4 +--
 6 files changed, 32 insertions(+), 27 deletions(-)

diff --git a/python/lognplot/chart/chart.py b/python/lognplot/chart/chart.py
index 449ed21..641c957 100644
--- a/python/lognplot/chart/chart.py
+++ b/python/lognplot/chart/chart.py
@@ -18,6 +18,7 @@ def __init__(self, db):
         self.x_axis = Axis()
         self.y_axis = Axis()
         self.curves = []
+        self.activeCurve = None
         self.db = db
 
     def has_curve(self, name):
@@ -30,9 +31,15 @@ def add_curve(self, name, color):
         if not self.has_curve(name):
             curve = Curve(self.db, name, color)
             self.curves.append(curve)
+            self.change_active_curve(curve)
 
     def clear_curves(self):
         self.curves.clear()
+        self.y_axis = Axis()
+
+    def change_active_curve(self, curve):
+        self.activeCurve = curve
+        self.y_axis = self.activeCurve.axis
 
     def info(self):
         print(f"Chart with {len(self.curves)} series")
diff --git a/python/lognplot/chart/curve.py b/python/lognplot/chart/curve.py
index 3ce2cdd..73e3c39 100644
--- a/python/lognplot/chart/curve.py
+++ b/python/lognplot/chart/curve.py
@@ -1,5 +1,5 @@
 from ..tsdb.aggregation import Aggregation
-
+from .axis import Axis
 
 class Curve:
     """ A curve is a view onto a signal in the database.
@@ -18,8 +18,8 @@ def __init__(self, db, name, color):
         self.average = 0
         # Corresponding handle (polygon area)
         self.handle = []
-        # Vertical adjustment by user
-        self.vertical_offset = 0
+        # Each curve has its own vertical axis
+        self.axis = Axis()
 
     def __repr__(self):
         return "Database proxy-curve"
diff --git a/python/lognplot/qt/render/__init__.py b/python/lognplot/qt/render/__init__.py
index bfe5eca..4f695b3 100644
--- a/python/lognplot/qt/render/__init__.py
+++ b/python/lognplot/qt/render/__init__.py
@@ -5,7 +5,7 @@
 from .render import Renderer
 from .layout import ChartLayout
 from .options import ChartOptions
-
+from .transform import *
 
 def render_chart_on_qpainter(chart: Chart, painter: QtGui.QPainter, rect: QtCore.QRect):
     """ Call this function to paint a chart onto the given painter within the rectangle specified.
diff --git a/python/lognplot/qt/render/base.py b/python/lognplot/qt/render/base.py
index 0eb8e03..af1132a 100644
--- a/python/lognplot/qt/render/base.py
+++ b/python/lognplot/qt/render/base.py
@@ -35,7 +35,7 @@ def calc_y_ticks(self, axis):
         y_ticks = axis.get_ticks(amount_y_ticks)
         return y_ticks
 
-    def draw_grid(self, x_ticks, y_ticks):
+    def draw_grid(self, y_axis, x_ticks, y_ticks):
         """ Render a grid on the given x and y tick markers. """
         pen = QtGui.QPen(Qt.gray)
         pen.setWidth(1)
@@ -46,7 +46,7 @@ def draw_grid(self, x_ticks, y_ticks):
             self.painter.drawLine(x, self.layout.chart_top, x, self.layout.chart_bottom)
 
         for value, _ in y_ticks:
-            y = self.to_y_pixel(value)
+            y = self.to_y_pixel(y_axis, value)
             self.painter.drawLine(self.layout.chart_left, y, self.layout.chart_right, y)
 
     def draw_x_axis(self, x_ticks):
@@ -69,7 +69,7 @@ def draw_x_axis(self, x_ticks):
             text_y = y + 10 - text_rect.y()
             self.painter.drawText(text_x, text_y, label)
 
-    def draw_y_axis(self, y_ticks):
+    def draw_y_axis(self, y_axis, y_ticks):
         """ Draw the Y-axis. """
         pen = QtGui.QPen(Qt.black)
         pen.setWidth(2)
@@ -77,7 +77,7 @@ def draw_y_axis(self, y_ticks):
         x = self.layout.chart_right + 5
         self.painter.drawLine(x, self.layout.chart_top, x, self.layout.chart_bottom)
         for value, label in y_ticks:
-            y = self.to_y_pixel(value)
+            y = self.to_y_pixel(y_axis, value)
 
             # Tick handle:
             self.painter.drawLine(x, y, x + 5, y)
diff --git a/python/lognplot/qt/render/chart.py b/python/lognplot/qt/render/chart.py
index 7b4cfe3..6487d9c 100644
--- a/python/lognplot/qt/render/chart.py
+++ b/python/lognplot/qt/render/chart.py
@@ -1,5 +1,5 @@
 from ..qtapi import QtGui, QtCore, Qt
-from ...chart import Chart
+from ...chart import Axis, Chart
 from ...utils import bench_it
 from ...tsdb import Aggregation
 from .layout import ChartLayout
@@ -25,13 +25,13 @@ def render(self):
         y_ticks = self.calc_y_ticks(self.chart.y_axis)
 
         if self.options.show_grid:
-            self.draw_grid(x_ticks, y_ticks)
+            self.draw_grid(self.chart.y_axis, x_ticks, y_ticks)
 
         self.draw_bouding_rect()
 
         if self.options.show_axis:
             self.draw_x_axis(x_ticks)
-            self.draw_y_axis(y_ticks)
+            self.draw_y_axis(self.chart.y_axis, y_ticks)
 
         if self.options.show_handles:
             self._draw_handles()
@@ -78,22 +78,20 @@ def _draw_curve(self, curve):
         data = curve.query(timespan, min_count)
         # print("query result", type(data), len(data))
         curve_color = QtGui.QColor(curve.color)
-        # vertical offset
-        v_offset = curve.vertical_offset
 
         if data:
             if isinstance(data[0], Aggregation):
-                curve.average = self._draw_aggregations_as_shape(data, curve_color, v_offset)
+                curve.average = self._draw_aggregations_as_shape(curve.axis, data, curve_color)
             else:
-                curve.average = self._draw_samples_as_lines(data, curve_color, v_offset)
+                curve.average = self._draw_samples_as_lines(curve.axis, data, curve_color)
 
-    def _draw_samples_as_lines(self, samples, curve_color: QtGui.QColor, v_offset):
+    def _draw_samples_as_lines(self, y_axis: Axis, samples, curve_color: QtGui.QColor):
         """ Draw raw samples as lines! """
         pen = QtGui.QPen(curve_color)
         pen.setWidth(2)
         self.painter.setPen(pen)
         points = [
-            QtCore.QPoint(self.to_x_pixel(x), self.to_y_pixel(y) + v_offset) for (x, y) in samples
+            QtCore.QPoint(self.to_x_pixel(x), self.to_y_pixel(y_axis, y)) for (x, y) in samples
         ]
         line = QtGui.QPolygon(points)
         self.painter.drawPolyline(line)
@@ -106,7 +104,7 @@ def _draw_samples_as_lines(self, samples, curve_color: QtGui.QColor, v_offset):
         return sum(p.y() for p in points) / len(points)
 
     def _draw_aggregations_as_shape(
-        self, aggregations: Aggregation, curve_color: QtGui.QColor, v_offset
+        self, y_axis: Axis, aggregations: Aggregation, curve_color: QtGui.QColor
     ):
         """ Draw aggregates as polygon shapes.
 
@@ -127,12 +125,12 @@ def _draw_aggregations_as_shape(
             # x2 = self.to_x_pixel(metric.x2)
 
             # max line:
-            y_max = self.to_y_pixel(aggregation.metrics.maximum) + v_offset
+            y_max = self.to_y_pixel(y_axis, aggregation.metrics.maximum)
             max_points.append(QtCore.QPoint(x1, y_max))
             # max_points.append(QtCore.QPoint(x2, y_max))
 
             # min line:
-            y_min = self.to_y_pixel(aggregation.metrics.minimum) + v_offset
+            y_min = self.to_y_pixel(y_axis, aggregation.metrics.minimum)
             min_points.append(QtCore.QPoint(x1, y_min))
             # min_points.append(QtCore.QPoint(x2, y_min))
 
@@ -140,17 +138,17 @@ def _draw_aggregations_as_shape(
             stddev = aggregation.metrics.stddev
 
             # Mean line:
-            y_mean = self.to_y_pixel(mean) + v_offset
+            y_mean = self.to_y_pixel(y_axis, mean)
             mean_points.append(QtCore.QPoint(x1, y_mean))
             # mean_points.append(QtCore.QPoint(x2, y_mean))
 
             # stddev up line:
-            y_stddev_up = self.to_y_pixel(mean + stddev) + v_offset
+            y_stddev_up = self.to_y_pixel(y_axis, mean + stddev)
             stddev_up_points.append(QtCore.QPoint(x1, y_stddev_up))
             # stddev_up_points.append(QtCore.QPoint(x2, y_stddev_up))
 
             # stddev down line:
-            y_stddev_down = self.to_y_pixel(mean - stddev) + v_offset
+            y_stddev_down = self.to_y_pixel(y_axis, mean - stddev)
             stddev_down_points.append(QtCore.QPoint(x1, y_stddev_down))
             # stddev_down_points.append(QtCore.QPoint(x2, y_stddev_down))
 
@@ -251,8 +249,8 @@ def _draw_handles(self):
     def to_x_pixel(self, value):
         return transform.to_x_pixel(value, self.chart.x_axis, self.layout)
 
-    def to_y_pixel(self, value):
-        return transform.to_y_pixel(value, self.chart.y_axis, self.layout)
+    def to_y_pixel(self, y_axis, value):
+        return transform.to_y_pixel(value, y_axis, self.layout)
 
     def x_pixel_to_domain(self, pixel):
         axis = self.chart.x_axis
diff --git a/python/lognplot/qt/widgets/chartwidget.py b/python/lognplot/qt/widgets/chartwidget.py
index e5a7a15..20d660c 100644
--- a/python/lognplot/qt/widgets/chartwidget.py
+++ b/python/lognplot/qt/widgets/chartwidget.py
@@ -69,14 +69,14 @@ def mousePress(self, x, y):
             curve = self.curveHandleAtPoint(x,y)
             if curve is not None:
                 self._drag_handle = curve
+                self.chart.change_active_curve(curve)
 
     def mouseRelease(self, x, y):
         self._drag_handle = None
 
     def mouseDrag(self, x, y, dx, dy):
         if self._drag_handle is not None:
-            #self.vertical_pan(float(dy) * 0.01) #self.PAN_FACTOR)
-            self._drag_handle.vertical_offset = self._drag_handle.vertical_offset + dy
+            self._drag_handle.axis.pan(dy / self.rect().height())
             self.repaint()
 
     # Intended to work together with the WIP minimap?

From 38e3cf7ec497db420cd68311b7490314f9990f88 Mon Sep 17 00:00:00 2001
From: Timon ter Braak <timon@terbraak.org>
Date: Mon, 6 Jan 2020 00:06:54 +0100
Subject: [PATCH 6/9] Increase clearance between signal handles and plot area.

---
 python/lognplot/qt/render/layout.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/python/lognplot/qt/render/layout.py b/python/lognplot/qt/render/layout.py
index 8d8590b..1f0a84f 100644
--- a/python/lognplot/qt/render/layout.py
+++ b/python/lognplot/qt/render/layout.py
@@ -26,7 +26,7 @@ def do_layout(self):
         self.chart_top = self.rect.top() + self.options.padding
 
         if self.options.show_handles:
-            self.chart_left = self.handles.right() + 1
+            self.chart_left = self.handles.right() + 3
         else:
             self.chart_left = self.rect.left() + self.options.padding
 

From 28336ad4e68c66237095caae6b244c719fb5332a Mon Sep 17 00:00:00 2001
From: Timon ter Braak <timon@terbraak.org>
Date: Mon, 6 Jan 2020 00:30:24 +0100
Subject: [PATCH 7/9] Merge with upstream cursor feature.

---
 lognplot/src/chart/axis.rs                | 23 ++++++++--
 lognplot/src/chart/chart.rs               |  8 ++--
 lognplot/src/render/mod.rs                | 15 ++++++
 lognplotgtk/src/chart_widget.rs           | 11 +++--
 lognplotgtk/src/state.rs                  | 30 ++++++++----
 python/docs/index.rst                     |  2 +-
 python/docs/reference.rst                 | 37 ---------------
 python/docs/reference/chart.rst           | 11 +++++
 python/docs/reference/index.rst           | 13 ++++++
 python/docs/reference/misc.rst            | 16 +++++++
 python/docs/reference/tsdb.rst            | 15 ++++++
 python/lognplot/__main__.py               |  5 ++
 python/lognplot/chart/axis.py             | 35 ++++++++++++--
 python/lognplot/chart/chart.py            | 25 +++++++---
 python/lognplot/chart/curve.py            |  3 ++
 python/lognplot/qt/render/__init__.py     |  6 +--
 python/lognplot/qt/render/chart.py        | 55 ++++++++++++++++++++++
 python/lognplot/qt/render/render.py       | 14 ++++--
 python/lognplot/qt/render/transform.py    | 17 +++++++
 python/lognplot/qt/widgets/basewidget.py  | 14 +++---
 python/lognplot/qt/widgets/chartwidget.py | 56 +++++++++++++++++------
 python/lognplot/qt/widgets/eventwidget.py |  6 +--
 python/lognplot/qt/widgets/logwidget.py   |  6 +--
 python/lognplot/time/timespan.py          |  1 +
 python/lognplot/tsdb/btree.py             | 37 +++++++++++++++
 python/lognplot/tsdb/db.py                |  4 ++
 python/lognplot/tsdb/metrics.py           | 11 ++++-
 python/lognplot/tsdb/series.py            |  3 ++
 python/setup.py                           |  2 +-
 29 files changed, 375 insertions(+), 106 deletions(-)
 delete mode 100644 python/docs/reference.rst
 create mode 100644 python/docs/reference/chart.rst
 create mode 100644 python/docs/reference/index.rst
 create mode 100644 python/docs/reference/misc.rst
 create mode 100644 python/docs/reference/tsdb.rst

diff --git a/lognplot/src/chart/axis.rs b/lognplot/src/chart/axis.rs
index 226fe25..0d86c7c 100644
--- a/lognplot/src/chart/axis.rs
+++ b/lognplot/src/chart/axis.rs
@@ -45,7 +45,8 @@ impl ValueAxis {
         self.end() - self.begin()
     }
 
-    pub fn zoom(&mut self, amount: f64) {
+    /// Zoom the axis by a certain percentage, optionally centered around some value.
+    pub fn zoom(&mut self, amount: f64, around: Option<f64>) {
         let domain = self.domain();
         if (domain < 1.0e-18) && (amount < 0.0) {
             return;
@@ -55,9 +56,23 @@ impl ValueAxis {
             return;
         }
 
-        let step = domain * amount;
-        let begin = self.begin() - step;
-        let end = self.end() + step;
+        let (left_percent, right_percent) = if let Some(around) = around {
+            if self.begin() < around && around < self.end() {
+                let left_percent = (around - self.begin()) / domain;
+                assert!(left_percent < 1.0);
+                let right_percent = 1.0 - left_percent;
+                (left_percent, right_percent)
+            } else {
+                (0.5, 0.5)
+            }
+        } else {
+            (0.5, 0.5)
+        };
+
+        let step = domain * amount * 2.0;
+        let begin = self.begin() - step * left_percent;
+        let end = self.end() + step * right_percent;
+
         self.set_limits(begin, end);
     }
 
diff --git a/lognplot/src/chart/chart.rs b/lognplot/src/chart/chart.rs
index f6274be..9115a59 100644
--- a/lognplot/src/chart/chart.rs
+++ b/lognplot/src/chart/chart.rs
@@ -2,7 +2,7 @@
 
 use super::axis::ValueAxis;
 use super::curve::Curve;
-use crate::time::TimeSpan;
+use crate::time::{TimeSpan, TimeStamp};
 use crate::tsdb::{Aggregation, Sample, SampleMetrics};
 
 /// A single 2D-chart
@@ -58,13 +58,13 @@ impl Chart {
     }
 
     /// Zoom horizontally.
-    pub fn zoom_horizontal(&mut self, amount: f64) {
-        self.x_axis.zoom(amount);
+    pub fn zoom_horizontal(&mut self, amount: f64, around: Option<f64>) {
+        self.x_axis.zoom(amount, around);
     }
 
     /// Perform vertical zooming
     pub fn zoom_vertical(&mut self, amount: f64) {
-        self.y_axis.zoom(amount);
+        self.y_axis.zoom(amount, None);
     }
 
     /// Perform a bit of relative horizontal panning
diff --git a/lognplot/src/render/mod.rs b/lognplot/src/render/mod.rs
index 3ebd517..63aaec7 100644
--- a/lognplot/src/render/mod.rs
+++ b/lognplot/src/render/mod.rs
@@ -23,6 +23,7 @@ pub use cairo_canvas::CairoCanvas;
 
 use crate::chart::ValueAxis;
 use crate::geometry::Size;
+use crate::time::TimeStamp;
 
 /// Calculate how many domain values a covered by the given amount of pixels.
 pub fn x_pixels_to_domain(size: Size, axis: &ValueAxis, pixels: f64) -> f64 {
@@ -37,3 +38,17 @@ pub fn x_pixels_to_domain(size: Size, axis: &ValueAxis, pixels: f64) -> f64 {
         pixels * a
     }
 }
+
+pub fn x_pixel_to_domain(pixel: f64, axis: &ValueAxis, size: Size) -> f64 {
+    let options = ChartOptions::default();
+    let mut layout = ChartLayout::new(size);
+    layout.layout(&options);
+
+    let domain = axis.domain();
+    if layout.plot_width < 1.0 {
+        0.0
+    } else {
+        let a = domain / layout.plot_width;
+        a * (pixel - layout.plot_left) + axis.begin()
+    }
+}
diff --git a/lognplotgtk/src/chart_widget.rs b/lognplotgtk/src/chart_widget.rs
index a328f1b..3258545 100644
--- a/lognplotgtk/src/chart_widget.rs
+++ b/lognplotgtk/src/chart_widget.rs
@@ -62,12 +62,15 @@ pub fn setup_drawing_area(draw_area: gtk::DrawingArea, app_state: GuiStateHandle
 
     draw_area.connect_scroll_event(clone!(@strong app_state => move |w, e| {
         // println!("Scroll wheel event! {:?}, {:?}, {:?}", e, e.get_delta(), e.get_direction());
+        let size = get_size(w);
+        let pixel_x_pos = e.get_position().0;
+        let around = Some((pixel_x_pos, size));
         match e.get_direction() {
             gdk::ScrollDirection::Up => {
-                app_state.borrow_mut().zoom_in_horizontal();
+                app_state.borrow_mut().zoom_in_horizontal(around);
             },
             gdk::ScrollDirection::Down => {
-                app_state.borrow_mut().zoom_out_horizontal();
+                app_state.borrow_mut().zoom_out_horizontal(around);
             },
             _ => {}
         }
@@ -155,10 +158,10 @@ fn on_key(draw_area: &gtk::DrawingArea, key: &gdk::EventKey, app_state: GuiState
             app_state.borrow_mut().zoom_out_vertical();
         }
         gdk::enums::key::KP_Add | gdk::enums::key::l => {
-            app_state.borrow_mut().zoom_in_horizontal();
+            app_state.borrow_mut().zoom_in_horizontal(None);
         }
         gdk::enums::key::KP_Subtract | gdk::enums::key::j => {
-            app_state.borrow_mut().zoom_out_horizontal();
+            app_state.borrow_mut().zoom_out_horizontal(None);
         }
         gdk::enums::key::Home | gdk::enums::key::Return => {
             app_state.borrow_mut().zoom_fit();
diff --git a/lognplotgtk/src/state.rs b/lognplotgtk/src/state.rs
index 61d9df4..bb97785 100644
--- a/lognplotgtk/src/state.rs
+++ b/lognplotgtk/src/state.rs
@@ -4,7 +4,7 @@ use std::time::Instant;
 
 use lognplot::chart::{Chart, Curve, CurveData};
 use lognplot::geometry::Size;
-use lognplot::render::x_pixels_to_domain;
+use lognplot::render::{x_pixel_to_domain, x_pixels_to_domain};
 use lognplot::time::TimeStamp;
 use lognplot::tsdb::{Aggregation, Observation, Sample, SampleMetrics, TsDbHandle};
 
@@ -184,27 +184,37 @@ impl GuiState {
 
     pub fn zoom_in_vertical(&mut self) {
         info!("Zoom in vertical");
-        self.disable_tailing();
-        self.chart.zoom_vertical(0.1);
+        self.zoom_vertical(0.1);
     }
 
     pub fn zoom_out_vertical(&mut self) {
         info!("Zoom out vertical");
+        self.zoom_vertical(-0.1);
+    }
+
+    fn zoom_vertical(&mut self, amount: f64) {
         self.disable_tailing();
-        self.chart.zoom_vertical(-0.1);
+        self.chart.zoom_vertical(amount);
     }
 
-    pub fn zoom_in_horizontal(&mut self) {
+    pub fn zoom_in_horizontal(&mut self, around: Option<(f64, Size)>) {
         info!("Zoom in horizontal");
-        self.disable_tailing();
-        self.chart.zoom_horizontal(-0.1);
-        self.chart.fit_y_axis();
+        self.zoom_horizontal(-0.1, around);
     }
 
-    pub fn zoom_out_horizontal(&mut self) {
+    pub fn zoom_out_horizontal(&mut self, around: Option<(f64, Size)>) {
         info!("Zoom out horizontal");
+        self.zoom_horizontal(0.1, around);
+    }
+
+    fn zoom_horizontal(&mut self, amount: f64, around: Option<(f64, Size)>) {
+        let around = around.map(|p| {
+            let (pixel, size) = p;
+            let timestamp = x_pixel_to_domain(pixel, &self.chart.x_axis, size);
+            timestamp
+        });
         self.disable_tailing();
-        self.chart.zoom_horizontal(0.1);
+        self.chart.zoom_horizontal(amount, around);
         self.chart.fit_y_axis();
     }
 
diff --git a/python/docs/index.rst b/python/docs/index.rst
index 5b2c903..f23bbae 100644
--- a/python/docs/index.rst
+++ b/python/docs/index.rst
@@ -52,7 +52,7 @@ Table of Contents
     motivation
     architecture
     protocol
-    reference
+    reference/index.rst
 
 
 Indices and tables
diff --git a/python/docs/reference.rst b/python/docs/reference.rst
deleted file mode 100644
index 40662db..0000000
--- a/python/docs/reference.rst
+++ /dev/null
@@ -1,37 +0,0 @@
-
-
-Reference
-=========
-
-.. automodule:: lognplot
-    :members:
-
-.. automodule:: lognplot.client
-    :members:
-
-.. automodule:: lognplot.chart.curve
-    :members:
-
-.. automodule:: lognplot.chart.chart
-    :members:
-
-.. automodule:: lognplot.chart.axis
-    :members:
-
-.. automodule:: lognplot.tsdb.db
-    :members:
-
-.. automodule:: lognplot.tsdb.aggregation
-    :members:
-
-.. automodule:: lognplot.tsdb.btree
-    :members:
-
-.. automodule:: lognplot.tsdb.metrics
-    :members:
-
-.. automodule:: lognplot.time.timespan
-    :members:
-
-.. automodule:: lognplot.time.duration
-    :members:
diff --git a/python/docs/reference/chart.rst b/python/docs/reference/chart.rst
new file mode 100644
index 0000000..6c9c05a
--- /dev/null
+++ b/python/docs/reference/chart.rst
@@ -0,0 +1,11 @@
+Chart module reference
+======================
+
+.. automodule:: lognplot.chart.curve
+    :members:
+
+.. automodule:: lognplot.chart.chart
+    :members:
+
+.. automodule:: lognplot.chart.axis
+    :members:
diff --git a/python/docs/reference/index.rst b/python/docs/reference/index.rst
new file mode 100644
index 0000000..e34d3e0
--- /dev/null
+++ b/python/docs/reference/index.rst
@@ -0,0 +1,13 @@
+
+
+Reference
+=========
+
+
+.. toctree::
+    :maxdepth: 2
+    :caption: Contents:
+
+    chart
+    tsdb
+    misc
diff --git a/python/docs/reference/misc.rst b/python/docs/reference/misc.rst
new file mode 100644
index 0000000..2da9040
--- /dev/null
+++ b/python/docs/reference/misc.rst
@@ -0,0 +1,16 @@
+
+Misc modules
+============
+
+.. automodule:: lognplot
+    :members:
+
+.. automodule:: lognplot.client
+    :members:
+
+
+.. automodule:: lognplot.time.timespan
+    :members:
+
+.. automodule:: lognplot.time.duration
+    :members:
diff --git a/python/docs/reference/tsdb.rst b/python/docs/reference/tsdb.rst
new file mode 100644
index 0000000..ecde337
--- /dev/null
+++ b/python/docs/reference/tsdb.rst
@@ -0,0 +1,15 @@
+
+Time series database reference
+==============================
+
+.. automodule:: lognplot.tsdb.db
+    :members:
+
+.. automodule:: lognplot.tsdb.aggregation
+    :members:
+
+.. automodule:: lognplot.tsdb.btree
+    :members:
+
+.. automodule:: lognplot.tsdb.metrics
+    :members:
diff --git a/python/lognplot/__main__.py b/python/lognplot/__main__.py
index bc14995..52ba78c 100644
--- a/python/lognplot/__main__.py
+++ b/python/lognplot/__main__.py
@@ -6,6 +6,7 @@
 
 import argparse
 import logging
+import sys
 
 
 def main():
@@ -30,6 +31,10 @@ def main():
         loglevel = logging.INFO
 
     logging.basicConfig(level=loglevel)
+    logging.info("Python version: {}".format(sys.version))
+    from .qt.qtapi import QtCore
+
+    logging.info("Qt version: {}".format(QtCore.qVersion()))
 
     from .qt.apps import run_server_gui
 
diff --git a/python/lognplot/chart/axis.py b/python/lognplot/chart/axis.py
index 6d88003..b17812a 100644
--- a/python/lognplot/chart/axis.py
+++ b/python/lognplot/chart/axis.py
@@ -3,11 +3,18 @@
 
 
 class Axis:
+    """ Implement an axis with a minimum and maximum value.
+
+    This class can also be used to generate appropriate tick values
+    for the axis.
+    """
+
     def __init__(self):
         self.minimum = -30
         self.maximum = 130
 
-    def zoom(self, amount):
+    def zoom(self, amount, around=None):
+        """ Zoom this axis by a certain amount, optionally around the given value. """
         domain = self.domain
         if domain < 1e-18 and amount < 0:
             return
@@ -16,12 +23,26 @@ def zoom(self, amount):
             return
 
         step = domain * amount
-        self.minimum -= step
-        self.maximum += step
+        if around is not None and self.minimum < around < self.maximum:
+            left_part = (around - self.minimum) / domain
+            assert left_part < 1.0
+            right_part = 1.0 - left_part
+            step_left = step * left_part
+            step_right = step * right_part
+        else:
+            step_left = step_right = step
+
+        self.minimum -= step_left
+        self.maximum += step_right
 
-    def pan(self, amount):
+    def pan_relative(self, amount):
+        """ Pan a percentage of the axis range. """
         domain = self.domain
         step = domain * amount
+        self.pan_absolute(step)
+
+    def pan_absolute(self, step):
+        """ Move the axis view by an absolute amount. """
         self.minimum += step
         self.maximum += step
 
@@ -38,6 +59,12 @@ def get_timespan(self):
         return TimeSpan(begin, end)
 
     def get_ticks(self, n_ticks):
+        """ Get tick values for this axis.
+
+        This function should take care of the following:
+        - tick values are rounded to logical multiples, such as 1, 2 or 0.2
+        - tick values are returned as tuples of values and the string label.
+        """
         domain = self.domain
 
         # Check for too small domain:
diff --git a/python/lognplot/chart/chart.py b/python/lognplot/chart/chart.py
index 641c957..e7cb4e7 100644
--- a/python/lognplot/chart/chart.py
+++ b/python/lognplot/chart/chart.py
@@ -19,6 +19,7 @@ def __init__(self, db):
         self.y_axis = Axis()
         self.curves = []
         self.activeCurve = None
+        self.cursor = None
         self.db = db
 
     def has_curve(self, name):
@@ -46,18 +47,30 @@ def info(self):
         for index, curve in enumerate(self.curves):
             print(f"serie {index} with {len(curve)} samples")
 
-    def horizontal_zoom(self, amount):
+    def set_cursor(self, value):
+        """ Set cursor position onto this chart.
+
+        Use None to hide the cursor.
+        """
+        self.cursor = value
+
+    def horizontal_zoom(self, amount, around):
         """ Zoom in horizontal manner. """
-        self.x_axis.zoom(amount)
+        self.x_axis.zoom(amount, around=around)
 
     def vertical_zoom(self, amount):
         self.y_axis.zoom(amount)
 
-    def horizontal_pan(self, amount):
-        self.x_axis.pan(amount)
+    def horizontal_pan_relative(self, amount):
+        """ Pan a percentage of the current axis range. """
+        self.x_axis.pan_relative(amount)
+
+    def horizontal_pan_absolute(self, amount):
+        """ Pan horizontally by a certain amount. """
+        self.x_axis.pan_absolute(amount)
 
-    def vertical_pan(self, amount):
-        self.y_axis.pan(amount)
+    def vertical_pan_relative(self, amount):
+        self.y_axis.pan_relative(amount)
 
     def autoscale_y(self):
         """ Automatically adjust the Y-axis to fit data in range. """
diff --git a/python/lognplot/chart/curve.py b/python/lognplot/chart/curve.py
index 73e3c39..cb8c96e 100644
--- a/python/lognplot/chart/curve.py
+++ b/python/lognplot/chart/curve.py
@@ -33,3 +33,6 @@ def query_summary(self, timespan=None) -> Aggregation:
     def query(self, selection_timespan, min_count):
         # TODO: cache calls here?
         return self._db.query(self.name, selection_timespan, min_count)
+
+    def query_value(self, timestamp):
+        return self._db.query_value(self.name, timestamp)
diff --git a/python/lognplot/qt/render/__init__.py b/python/lognplot/qt/render/__init__.py
index 4f695b3..4ec4bcb 100644
--- a/python/lognplot/qt/render/__init__.py
+++ b/python/lognplot/qt/render/__init__.py
@@ -7,9 +7,9 @@
 from .options import ChartOptions
 from .transform import *
 
-def render_chart_on_qpainter(chart: Chart, painter: QtGui.QPainter, rect: QtCore.QRect):
+def render_chart_on_qpainter(chart: Chart, painter: QtGui.QPainter, layout, options):
     """ Call this function to paint a chart onto the given painter within the rectangle specified.
     """
-    renderer = Renderer(painter, chart)
+    renderer = Renderer(painter, chart, layout, options)
     # with bench_it("render"):
-    renderer.render(rect)
+    renderer.render()
diff --git a/python/lognplot/qt/render/chart.py b/python/lognplot/qt/render/chart.py
index 6487d9c..a5a2394 100644
--- a/python/lognplot/qt/render/chart.py
+++ b/python/lognplot/qt/render/chart.py
@@ -40,6 +40,7 @@ def render(self):
 
         if self.options.show_legend:
             self._draw_legend()
+        self._draw_cursor()
 
     def shade_region(self, region):
         """ Draw a shaded box in some region.
@@ -221,6 +222,60 @@ def _draw_legend(self):
                 color,
             )
 
+    def _draw_cursor(self):
+        if self.chart.cursor:
+            # Draw cursor line:
+            x = self.to_x_pixel(self.chart.cursor)
+            pen = QtGui.QPen(Qt.black)
+            pen.setWidth(1)
+            self.painter.setPen(pen)
+            self.painter.drawLine(x, self.layout.chart_top, x, self.layout.chart_bottom)
+
+            # Draw values of signals at position:
+            font_metrics = self.painter.fontMetrics()
+            legend_x = x + 10
+            y = self.layout.chart_top + 10
+            text_height = font_metrics.height()
+            color_block_size = text_height * 0.8
+            for index, curve in enumerate(self.chart.curves):
+                color = QtGui.QColor(curve.color)
+                curve_point = curve.query_value(self.chart.cursor)
+                if not curve_point:
+                    continue
+                curve_point_timestamp, curve_point_value = curve_point
+
+                # Draw circle indicator around selected point:
+                pen = QtGui.QPen(color)
+                pen.setWidth(2)
+                self.painter.setPen(pen)
+                marker_x = self.to_x_pixel(curve_point_timestamp)
+                marker_y = self.to_y_pixel(self.chart.y_axis, curve_point_value)
+                marker_size = 10
+                indicator_rect = QtCore.QRect(
+                    marker_x - marker_size // 2,
+                    marker_y - marker_size // 2,
+                    marker_size,
+                    marker_size,
+                )
+                self.painter.drawEllipse(indicator_rect)
+
+                # Legend:
+                text = "{} = {}".format(curve.name, curve_point_value)
+                text_rect = font_metrics.boundingRect(text)
+                # legend_y = y + index * text_height
+                legend_x = marker_x + 10
+                legend_y = marker_y
+                text_x = legend_x + color_block_size + 3 - text_rect.x()
+                text_y = legend_y - text_rect.y() - text_rect.height() / 2
+                self.painter.drawText(text_x, text_y, text)
+                self.painter.fillRect(
+                    legend_x,
+                    legend_y - color_block_size / 2,
+                    color_block_size,
+                    color_block_size,
+                    color,
+                )
+
     def _draw_handles(self):
         x = self.layout.handles.left()
 
diff --git a/python/lognplot/qt/render/render.py b/python/lognplot/qt/render/render.py
index 944fabe..949dc30 100644
--- a/python/lognplot/qt/render/render.py
+++ b/python/lognplot/qt/render/render.py
@@ -15,14 +15,18 @@ class Renderer:
     Optionally include a minimap?
     """
 
-    def __init__(self, painter: QtGui.QPainter, chart: Chart):
+    def __init__(
+        self, painter: QtGui.QPainter, chart: Chart, layout: ChartLayout, options
+    ):
         self.painter = painter
         self.chart = chart
+        self.layout = layout
+        self.options = options
 
-    def render(self, rect: QtCore.QRect):
-        options1 = ChartOptions()
-        layout = ChartLayout(rect, options1)
-        chart_renderer = ChartRenderer(self.painter, self.chart, layout, options1)
+    def render(self):
+        chart_renderer = ChartRenderer(
+            self.painter, self.chart, self.layout, self.options
+        )
         chart_renderer.render()
 
         # self.render_minimap(rect)
diff --git a/python/lognplot/qt/render/transform.py b/python/lognplot/qt/render/transform.py
index c2fbebc..b0c86eb 100644
--- a/python/lognplot/qt/render/transform.py
+++ b/python/lognplot/qt/render/transform.py
@@ -17,3 +17,20 @@ def to_y_pixel(value, axis, layout):
     a = layout.chart_height / domain
     y = layout.chart_bottom - a * (value - axis.minimum)
     return clip(y, layout.chart_top, layout.chart_bottom)
+
+
+def to_x_value(pixel, axis, layout):
+    """ Given a pixel, determine its domain value. """
+    domain = axis.domain
+    a = domain / layout.chart_width
+    value = axis.minimum + a * (pixel - layout.chart_left)
+    return value
+    # return clip(x, layout.chart_left, layout.chart_right)
+
+
+def x_pixels_to_domain(pixels, axis, layout):
+    """ Convert a pixel distance to a domain distance """
+    domain = axis.domain
+    a = domain / layout.chart_width
+    shift = a * pixels
+    return shift
diff --git a/python/lognplot/qt/widgets/basewidget.py b/python/lognplot/qt/widgets/basewidget.py
index d50d867..9baca82 100644
--- a/python/lognplot/qt/widgets/basewidget.py
+++ b/python/lognplot/qt/widgets/basewidget.py
@@ -29,7 +29,9 @@ def mousePressEvent(self, event):
 
     def mouseMoveEvent(self, event):
         super().mouseMoveEvent(event)
-        self._update_mouse_pan(event.x(), event.y())
+        x, y = event.x(), event.y()
+        self._update_mouse_pan(x, y)
+        self.mouse_move(x, y)
 
     def mouseReleaseEvent(self, event):
         super().mouseReleaseEvent(event)
@@ -88,11 +90,11 @@ def pan_down(self):
     # Zooming helpers:
     ZOOM_FACTOR = 0.1
 
-    def zoom_in_horizontal(self):
-        self.horizontal_zoom(-self.ZOOM_FACTOR)
+    def zoom_in_horizontal(self, around=None):
+        self.horizontal_zoom(-self.ZOOM_FACTOR, around)
 
-    def zoom_out_horizontal(self):
-        self.horizontal_zoom(self.ZOOM_FACTOR)
+    def zoom_out_horizontal(self, around=None):
+        self.horizontal_zoom(self.ZOOM_FACTOR, around)
 
     def zoom_in_vertical(self):
         self.vertical_zoom(self.ZOOM_FACTOR)
@@ -101,7 +103,7 @@ def zoom_out_vertical(self):
         self.vertical_zoom(-self.ZOOM_FACTOR)
 
     # Overridable methods:
-    def horizontal_zoom(self, amount):
+    def horizontal_zoom(self, amount, around):
         pass
 
     def vertical_zoom(self, amount):
diff --git a/python/lognplot/qt/widgets/chartwidget.py b/python/lognplot/qt/widgets/chartwidget.py
index 20d660c..ff287ff 100644
--- a/python/lognplot/qt/widgets/chartwidget.py
+++ b/python/lognplot/qt/widgets/chartwidget.py
@@ -9,6 +9,7 @@
 from ...utils import bench_it
 from ...chart import Chart, Curve
 from ..render import render_chart_on_qpainter, ChartLayout, ChartOptions
+from ..render import transform
 from . import mime
 from .basewidget import BaseWidget
 
@@ -24,8 +25,13 @@ class ChartWidget(BaseWidget):
     def __init__(self, db):
         super().__init__()
         self.chart = Chart(db)
+        self.chart_options = ChartOptions()
+        self.chart_layout = None  # Set when resized
+
         self._colors = cycle(color_wheel)
 
+        self.setMouseTracking(True)
+
         # Accept drop of signal names
         self.setAcceptDrops(True)
 
@@ -37,6 +43,9 @@ def __init__(self, db):
         self._tailing_timer.timeout.connect(self._on_tailing_timeout)
         self._tailing_timer.start(50)
 
+    def resizeEvent(self, event):
+        self.chart_layout = ChartLayout(self.rect(), self.chart_options)
+
     # Drag drop events:
     def dragEnterEvent(self, event):
         if event.mimeData().hasFormat(mime.signal_names_mime_type):
@@ -50,6 +59,27 @@ def dropEvent(self, event):
             self.logger.debug(f"Add curve {name}")
             self.add_curve(name)
 
+    # Mouse interactions:
+    def wheelEvent(self, event):
+        # print(event)
+        event.accept()
+        pos = event.pos()
+        x, y = pos.x(), pos.y()
+        value = transform.to_x_value(x, self.chart.x_axis, self.chart_layout)
+        delta = event.angleDelta().y()
+        if delta > 0:
+            self.zoom_in_horizontal(around=value)
+        elif delta < 0:
+            self.zoom_out_horizontal(around=value)
+        else:
+            pass
+
+    def mouse_move(self, x, y):
+        # Update cursor!
+        value = transform.to_x_value(x, self.chart.x_axis, self.chart_layout)
+        self.chart.set_cursor(value)
+        self.update()
+
     def curveHandleAtPoint(self, x, y) -> Curve:
         for curve in self.chart.curves:
             topleft = curve.handle[0]
@@ -76,16 +106,15 @@ def mouseRelease(self, x, y):
 
     def mouseDrag(self, x, y, dx, dy):
         if self._drag_handle is not None:
-            self._drag_handle.axis.pan(dy / self.rect().height())
+            self._drag_handle.axis.pan_relative(dy / self.rect().height())
             self.repaint()
 
-    # Intended to work together with the WIP minimap?
     def pan(self, dx, dy):
-        print("pan", dx, dy)
-        # TODO: fix
-        #options1 = ChartOptions()
-        #layout = ChartLayout(self.rect(), options1)
-        #self.repaint()
+        # print("pan", dx, dy)
+        shift = transform.x_pixels_to_domain(dx, self.chart.x_axis, self.chart_layout)
+        self.chart.horizontal_pan_absolute(-shift)
+        self.chart.autoscale_y()
+        self.update()
 
     def add_curve(self, name, color=None):
         if not self.chart.has_curve(name):
@@ -101,12 +130,14 @@ def paintEvent(self, e):
         # Contrapt graph via QPainter!
         painter = QtGui.QPainter(self)
         # with bench_it("render"):
-        render_chart_on_qpainter(self.chart, painter, self.rect())
+        render_chart_on_qpainter(
+            self.chart, painter, self.chart_layout, self.chart_options
+        )
 
         self.draw_focus_indicator(painter, self.rect())
 
-    def horizontal_zoom(self, amount):
-        self.chart.horizontal_zoom(amount)
+    def horizontal_zoom(self, amount, around):
+        self.chart.horizontal_zoom(amount, around)
         # Autoscale Y for a nice effect?
         self.chart.autoscale_y()
         self.repaint()
@@ -118,15 +149,14 @@ def vertical_zoom(self, amount):
         self.update()
 
     def horizontal_pan(self, amount):
-        self.chart.horizontal_pan(amount)
+        self.chart.horizontal_pan_relative(amount)
         # Autoscale Y for a nice effect?
         self.chart.autoscale_y()
         self.repaint()
         self.update()
 
     def vertical_pan(self, amount):
-        self.chart.vertical_pan(amount)
-        self.repaint()
+        self.chart.vertical_pan_relative(amount)
         self.update()
 
     def zoom_fit(self):
diff --git a/python/lognplot/qt/widgets/eventwidget.py b/python/lognplot/qt/widgets/eventwidget.py
index fd8d333..714b033 100644
--- a/python/lognplot/qt/widgets/eventwidget.py
+++ b/python/lognplot/qt/widgets/eventwidget.py
@@ -47,11 +47,11 @@ def clear_curves(self):
         self.update()
 
     def horizontal_pan(self, amount):
-        self.event_tracks.x_axis.pan(amount)
+        self.event_tracks.x_axis.pan_relative(amount)
         self.update()
 
-    def horizontal_zoom(self, amount):
-        self.event_tracks.x_axis.zoom(amount)
+    def horizontal_zoom(self, amount, around):
+        self.event_tracks.x_axis.zoom(amount, around=around)
         self.update()
 
     def zoom_fit(self):
diff --git a/python/lognplot/qt/widgets/logwidget.py b/python/lognplot/qt/widgets/logwidget.py
index ada2964..c18b306 100644
--- a/python/lognplot/qt/widgets/logwidget.py
+++ b/python/lognplot/qt/widgets/logwidget.py
@@ -45,9 +45,9 @@ def clear_curves(self):
         self.update()
 
     def horizontal_pan(self, amount):
-        self.log_bar.x_axis.pan(amount)
+        self.log_bar.x_axis.pan_relative(amount)
         self.update()
 
-    def horizontal_zoom(self, amount):
-        self.log_bar.x_axis.zoom(amount)
+    def horizontal_zoom(self, amount, around):
+        self.log_bar.x_axis.zoom(amount, around=around)
         self.update()
diff --git a/python/lognplot/time/timespan.py b/python/lognplot/time/timespan.py
index 4b1cbbc..2a8039f 100644
--- a/python/lognplot/time/timespan.py
+++ b/python/lognplot/time/timespan.py
@@ -30,6 +30,7 @@ def overlaps(self, other):
         return (self.begin <= other.end) and (other.begin <= self.end)
 
     def contains_timestamp(self, timestamp):
+        """ Test if this timespan contains the given timestamp. """
         return self.begin <= timestamp <= self.end
 
     def central_timestamp(self):
diff --git a/python/lognplot/tsdb/btree.py b/python/lognplot/tsdb/btree.py
index 0ffe54f..360d6fe 100644
--- a/python/lognplot/tsdb/btree.py
+++ b/python/lognplot/tsdb/btree.py
@@ -4,6 +4,7 @@
 """
 
 import abc
+import bisect
 from .metrics import Metrics
 from .aggregation import Aggregation
 from ..time import TimeSpan
@@ -101,6 +102,13 @@ def query_metrics(self, selection_timespan: TimeSpan) -> Aggregation:
         if selected_aggregations:
             return Aggregation.from_aggregations(selected_aggregations)
 
+    def query_value(self, timestamp):
+        """ Query value closest to the given timestamp.
+
+        Return a timestamp value pair as an observation point.
+        """
+        return self.root_node.query_value(timestamp)
+
     def last_value(self):
         """ Get last item in the collection """
         return self.root_node.last_value()
@@ -149,6 +157,10 @@ def select_range(self, selection_span: TimeSpan):
     def select_all(self):
         raise NotImplementedError()
 
+    @abc.abstractmethod
+    def query_value(self, timestamp):
+        raise NotImplementedError()
+
     @abc.abstractmethod
     def last_value(self):
         raise NotImplementedError()
@@ -233,6 +245,18 @@ def select_range(self, selection_span: TimeSpan):
     def select_all(self):
         return self._children
 
+    def query_value(self, timestamp):
+        full_span = self.aggregation.timespan
+        if timestamp < full_span.begin:
+            child_node = self._children[0]
+        elif timestamp > full_span.end:
+            child_node = self._children[-1]
+        else:
+            for child_node in self._children:
+                if child_node.aggregation.timespan.contains_timestamp(timestamp):
+                    break
+        return child_node.query_value(timestamp)
+
     def last_value(self):
         return self._children[-1].last_value()
 
@@ -308,5 +332,18 @@ def select_all(self):
         """
         return self.samples
 
+    def query_value(self, timestamp):
+        if not self.samples:
+            return
+
+        # Create a theoretical sample for insertion:
+        sample = (timestamp, 0)
+
+        index = bisect.bisect_left(self.samples, sample)
+        if index >= len(self.samples):
+            index = len(self.samples) - 1
+        # raise NotImplementedError()
+        return self.samples[index]
+
     def last_value(self):
         return self.samples[-1]
diff --git a/python/lognplot/tsdb/db.py b/python/lognplot/tsdb/db.py
index 112014b..84caf77 100644
--- a/python/lognplot/tsdb/db.py
+++ b/python/lognplot/tsdb/db.py
@@ -60,6 +60,10 @@ def query(self, name: str, timespan: TimeSpan, count: int):
         serie = self.get_or_create_serie(name)
         return serie.query(timespan, count)
 
+    def query_value(self, name, timestamp):
+        serie = self.get_or_create_serie(name)
+        return serie.query_value(timestamp)
+
     def last_value(self, name):
         """ Retrieve last value of a trace """
         serie = self.get_or_create_serie(name)
diff --git a/python/lognplot/tsdb/metrics.py b/python/lognplot/tsdb/metrics.py
index 7ca9667..ef63c79 100644
--- a/python/lognplot/tsdb/metrics.py
+++ b/python/lognplot/tsdb/metrics.py
@@ -43,12 +43,17 @@ class ValueMetrics(Metrics):
     For example, we have the count of samples about which
     these metrics are a summary. Also, we have minimum and
     maximum values.
+
+    Note that addition is not commutative, the chunks are ordered
+    in sequence.
     """
 
-    def __init__(self, count, minimum, maximum, mean, m2):
+    def __init__(self, count, minimum, maximum, first, last, mean, m2):
         self.count = count
         self.minimum = minimum
         self.maximum = maximum
+        self.first = first  # First observed value
+        self.last = last  # Last observed value
         self._mean = mean
         # The M2 value is a handy value for calculating the
         # variance online. See welford method on wikipedia.
@@ -58,7 +63,7 @@ def __init__(self, count, minimum, maximum, mean, m2):
     @classmethod
     def from_value(cls, value):
         """ Convert a single sample into metrics. """
-        return cls(1, value, value, value, 0.0)
+        return cls(1, value, value, value, value, value, 0.0)
 
     def __add__(self, other):
         if isinstance(other, ValueMetrics):
@@ -75,6 +80,8 @@ def __add__(self, other):
                 count=count,
                 minimum=min(self.minimum, other.minimum),
                 maximum=max(self.maximum, other.maximum),
+                first=self.first,
+                last=other.last,
                 mean=mean,
                 m2=m2,
             )
diff --git a/python/lognplot/tsdb/series.py b/python/lognplot/tsdb/series.py
index 1448bb5..3f4366d 100644
--- a/python/lognplot/tsdb/series.py
+++ b/python/lognplot/tsdb/series.py
@@ -72,5 +72,8 @@ def query_summary(self, selection_timespan=None) -> Aggregation:
         else:
             return self._tree.aggregation
 
+    def query_value(self, timestamp):
+        return self._tree.query_value(timestamp)
+
     def last_value(self):
         return self._tree.last_value()
diff --git a/python/setup.py b/python/setup.py
index 891135c..5b78562 100644
--- a/python/setup.py
+++ b/python/setup.py
@@ -6,7 +6,7 @@
     author="Windel Bouwman",
     description="Log and plot data. This project basically implements a software scope.",
     url="https://github.com/windelbouwman/lognplot",
-    install_requires=['cbor'],
+    install_requires=["cbor"],
     packages=find_packages(),
     license="GPLv3",
     classifiers=[

From a364b185f852c41b18eaf965ccd0888c7bb3381d Mon Sep 17 00:00:00 2001
From: Timon ter Braak <timon@terbraak.org>
Date: Mon, 6 Jan 2020 00:34:28 +0100
Subject: [PATCH 8/9] Fix cursor position on each signal's axis.

---
 python/lognplot/qt/render/chart.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/python/lognplot/qt/render/chart.py b/python/lognplot/qt/render/chart.py
index a5a2394..ea15a5d 100644
--- a/python/lognplot/qt/render/chart.py
+++ b/python/lognplot/qt/render/chart.py
@@ -249,7 +249,7 @@ def _draw_cursor(self):
                 pen.setWidth(2)
                 self.painter.setPen(pen)
                 marker_x = self.to_x_pixel(curve_point_timestamp)
-                marker_y = self.to_y_pixel(self.chart.y_axis, curve_point_value)
+                marker_y = self.to_y_pixel(curve.axis, curve_point_value)
                 marker_size = 10
                 indicator_rect = QtCore.QRect(
                     marker_x - marker_size // 2,

From d2b5dece87219a6533625331cf1a1fe98cc7007f Mon Sep 17 00:00:00 2001
From: Timon ter Braak <timon@terbraak.org>
Date: Mon, 6 Jan 2020 00:43:42 +0100
Subject: [PATCH 9/9] Fix panning feature due to upstream changes.

---
 python/lognplot/qt/render/options.py      |  1 +
 python/lognplot/qt/widgets/chartwidget.py | 22 ++++++++--------------
 2 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/python/lognplot/qt/render/options.py b/python/lognplot/qt/render/options.py
index dc20b2c..6bf6e33 100644
--- a/python/lognplot/qt/render/options.py
+++ b/python/lognplot/qt/render/options.py
@@ -4,6 +4,7 @@ def __init__(self):
         self.show_grid = True
         self.show_legend = False
         self.show_handles = True
+        self.autoscale_y_axis = False
         self.padding = 10
         self.handle_width = 20
         self.handle_height = 15
\ No newline at end of file
diff --git a/python/lognplot/qt/widgets/chartwidget.py b/python/lognplot/qt/widgets/chartwidget.py
index ff287ff..dbfde22 100644
--- a/python/lognplot/qt/widgets/chartwidget.py
+++ b/python/lognplot/qt/widgets/chartwidget.py
@@ -95,25 +95,19 @@ def curveHandleAtPoint(self, x, y) -> Curve:
 
     # Mouse interactions:
     def mousePress(self, x, y):
-        if self._drag_handle is None:
-            curve = self.curveHandleAtPoint(x,y)
-            if curve is not None:
-                self._drag_handle = curve
-                self.chart.change_active_curve(curve)
-
-    def mouseRelease(self, x, y):
-        self._drag_handle = None
-
-    def mouseDrag(self, x, y, dx, dy):
-        if self._drag_handle is not None:
-            self._drag_handle.axis.pan_relative(dy / self.rect().height())
-            self.repaint()
+        curve = self.curveHandleAtPoint(x,y)
+        if curve is not None:
+            self._drag_handle = curve
+            self.chart.change_active_curve(curve)
 
     def pan(self, dx, dy):
         # print("pan", dx, dy)
         shift = transform.x_pixels_to_domain(dx, self.chart.x_axis, self.chart_layout)
         self.chart.horizontal_pan_absolute(-shift)
-        self.chart.autoscale_y()
+        if self.chart_options.autoscale_y_axis:
+            self.chart.autoscale_y()
+        else:
+            self._drag_handle.axis.pan_relative(dy / self.rect().height())
         self.update()
 
     def add_curve(self, name, color=None):