fix keyboard text selection bug where selection always start at 0

Author: mike-ward

titlebar.c.v

@@ -1,5 +1,10 @@
 module gui
 
+// Utilities for controlling the native window titlebar appearance on Windows.
+// Provides `titlebar_dark(dark bool)` which toggles the dark/light titlebar
+// using the Desktop Window Manager (DWM) API on Windows 10+.
+// The code is compiled and active only on Windows via `$if windows`.
+//
 import sokol.sapp
 
 $if windows {

view_input.v

@@ -2,7 +2,7 @@ module gui
 
 // view_input.v provides input field functionality for GUI applications.
 // It handles text input, cursor management, copy/paste operations, and undo/redo functionality.
-// The file implements both single-line and multiline input modes with customizable styling
+// This file implements both single-line and multiline input modes with customizable styling
 // and behavior through the InputCfg struct. Key features include:
 // - Text selection and cursor positioning
 // - Clipboard operations (copy, cut, paste)
@@ -11,33 +11,45 @@ module gui
 // - Placeholder text
 // - Custom callbacks for text changes and enter key
 // - Themeable appearance
+// - Copy/paste operations
+// - Icon support
 //
 import log
 import datatypes
 import arrays
 
 // The management of focus and input states poses a problem in stateless views
 // because...they're stateless. Instead, the window maintains this state in a
-// map where the key is the w.view_state.id_focus. This state map is cleared when a new
-// view is introduced.
+// map where the key is the w.view_state.id_focus. This state map is cleared
+// when a new view is introduced.
 @[minify]
 struct InputState {
 pub:
-	// positions are number of runes relative to start of input text
+	// number of runes relative to start of input text
 	cursor_pos int
 	select_beg u32
 	select_end u32
 	undo       datatypes.Stack[InputMemento]
 	redo       datatypes.Stack[InputMemento]
+	// cursor_offset is used to maintain the horizontal offset of the cursor
+	// when traversing vertically through text. It is reset when a non-vertical
+	// navigation operation occurs.
+	cursor_offset f32
 }
 
+// InputMemento is admittedly a naive implementation of undo/redo operations.
+// Storing all the text instead of the text operation and text fragment is less
+// memory efficient, but it is much easier to implement and debug. Most of the time,
+// input text fields are small so the actual savings vs. the additional complexity
+// is worth the tradeoff. It can always be refactored later if it becomes an issue.
 @[minify]
 struct InputMemento {
 pub:
-	text       string
-	cursor_pos int
-	select_beg u32
-	select_end u32
+	text          string
+	cursor_pos    int
+	select_beg    u32
+	select_end    u32
+	cursor_offset f32
 }
 
 pub enum InputMode as u8 {

view_text.v

@@ -354,6 +354,7 @@ fn (tv &TextView) on_key_down(layout &Layout, mut e Event, mut w Window) {
 			// If there's no selection, start one from the old cursor position.
 			if new_select_beg == new_select_end {
 				new_select_beg = u32(old_cursor_pos)
+				new_select_end = u32(old_cursor_pos)
 			}
 
 			// Move the selection boundary that was at the old cursor position.
@@ -370,7 +371,6 @@ fn (tv &TextView) on_key_down(layout &Layout, mut e Event, mut w Window) {
 					new_select_end = u32(new_cursor_pos)
 				}
 			}
-
 			// Ensure beg is always less than or equal to end
 			if new_select_beg > new_select_end {
 				new_select_beg, new_select_end = new_select_end, new_select_beg

xtra_text.v

@@ -30,9 +30,9 @@ pub fn get_text_width(text string, text_style TextStyle, mut window Window) f32
 	}
 }
 
+// text_width measures the visual width of the shape's lines, mirroring render rules:
+// - when in password mode (and not placeholder), measure '*' repeated for visible rune count
 fn text_width(shape &Shape, mut window Window) f32 {
-	// Measure the visual width of the shape's lines, mirroring render rules:
-	// - when in password mode (and not placeholder), measure '*' repeated for visible rune count
 	mut max_width := f32(0)
 	mut text_cfg_set := false
 	htx := fnv1a.sum32_struct(shape.text_style).str()
@@ -72,6 +72,7 @@ fn line_height(shape &Shape) f32 {
 	return shape.text_style.size + shape.text_style.line_spacing
 }
 
+// text_wrap applies text wrapping logic to a given shape based on its text mode.
 fn text_wrap(mut shape Shape, mut window Window) {
 	if shape.text_mode in [.wrap, .wrap_keep_spaces] && shape.shape_type == .text {
 		style := shape.text_style
@@ -197,7 +198,7 @@ fn wrap_text_keep_spaces(text string, text_style TextStyle, max_width f32, tab_s
 				field_index++
 			}
 
-			// We must flush the decided output line even if it's empty (e.g., max_width == 0)
+			// Flush the decided output line even if it's empty (e.g., max_width == 0)
 			lines << output_line
 			current_line = ''
 			continue
@@ -233,7 +234,7 @@ fn wrap_text_keep_spaces(text string, text_style TextStyle, max_width f32, tab_s
 			}
 		}
 
-		// 2) If we still can't add a space and line is non-empty & not ending with space,
+		// 2) If space can't be added and line is non-empty & not ending with space,
 		//    try to wrap earlier at a space.
 		if !can_add_space && is_line_non_empty && !line_ends_with_space {
 			mut should_wrap_early := false
@@ -256,7 +257,7 @@ fn wrap_text_keep_spaces(text string, text_style TextStyle, max_width f32, tab_s
 				current_line = field
 			}
 		} else if is_line_non_empty {
-			// We either added spaces or the line already ended with a space
+			// Either added spaces or the line already ended with a space
 			current_line = field
 		} else {
 			// Line is empty but field is too wide – place it anyway to avoid infinite loop