From a1751d8e193687ccfe558cf585ac6a4386963dea Mon Sep 17 00:00:00 2001
From: kasinadhsarma1 <218753575+kasinadhsarma1@users.noreply.github.com>
Date: Tue, 14 Apr 2026 13:25:55 +0530
Subject: [PATCH] fix: enforce OpenGL 3.3 Core profile, initialize global VAO,
 and correct camera mouse tracking

---
 gui/application.py | 17 ++++++++++++++---
 opengl/camera.py   |  1 +
 opengl/main.py     | 20 +++++++++++++++++++-
 3 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/gui/application.py b/gui/application.py
index 32f6e81..aa06067 100644
--- a/gui/application.py
+++ b/gui/application.py
@@ -32,14 +32,25 @@ class to maintain QT parameters
     """
     def __init__(self, glob, argv):
         self.env = glob.env
-        super().__init__(argv)
 
-        # Alphacover (if available), is used to use more than one alpha-layer
+        # QSurfaceFormat must be set BEFORE QApplication is created so that
+        # the OpenGL widget picks up the correct format on all platforms.
+        # On Linux/Mesa the system default is OpenGL 2.0 with no depth buffer,
+        # which causes shaders (#version 330) to fail and the desktop to bleed
+        # through the viewport.  Explicitly request OpenGL 3.3 Core + depth buffer.
         #
         self.sformat = QSurfaceFormat()
+        self.sformat.setVersion(3, 3)
+        self.sformat.setProfile(QSurfaceFormat.OpenGLContextProfile.CoreProfile)
+        self.sformat.setDepthBufferSize(24)
+        self.sformat.setStencilBufferSize(8)
+        self.sformat.setSwapBehavior(QSurfaceFormat.SwapBehavior.DoubleBuffer)
+        # Alphacover (if available), is used to use more than one alpha-layer
         if self.env.noalphacover is False:
             self.sformat.setSamples(4)
-        self.sformat.setDefaultFormat(self.sformat)
+        QSurfaceFormat.setDefaultFormat(self.sformat)
+
+        super().__init__(argv)
 
     def getFormat(self):
         return self.sformat
diff --git a/opengl/camera.py b/opengl/camera.py
index 1082fe0..42e9653 100644
--- a/opengl/camera.py
+++ b/opengl/camera.py
@@ -303,6 +303,7 @@ def arcBallRotation(self, x, y):
         """
         xAngle = (self.last_mousex - x) * self.deltaAngleX
         yAngle = (self.last_mousey - y) * self.deltaAngleY
+        self.setLastMousePosition(x, y)
         self.rotation(xAngle, yAngle)
 
     def mousePanning(self, x, y):
diff --git a/opengl/main.py b/opengl/main.py
index c90d5f0..9c7274a 100644
--- a/opengl/main.py
+++ b/opengl/main.py
@@ -9,7 +9,8 @@
 from PySide6.QtOpenGLWidgets import QOpenGLWidget
 from PySide6.QtWidgets import QSizePolicy
 from PySide6.QtCore import QSize, Qt, QTimer
-from PySide6.QtGui import QMatrix4x4, QVector3D
+from PySide6.QtGui import QMatrix4x4, QVector3D, QSurfaceFormat
+from PySide6.QtOpenGL import QOpenGLVertexArrayObject
 
 # try to keep only constants here
 #
@@ -28,6 +29,10 @@ def __init__(self, glob):
         self.glob = glob
         self.env = glob.env
         super().__init__()
+        # Explicitly apply the default surface format to this widget so that
+        # Linux/Mesa always gets OpenGL 3.3 Core + depth buffer regardless of
+        # the order in which Qt processes the global default format.
+        self.setFormat(QSurfaceFormat.defaultFormat())
         self.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.MinimumExpanding)
         self.setMinimumSize(QSize(300, 560))
         self.setMaximumSize(QSize(2000, 2000))
@@ -52,6 +57,7 @@ def __init__(self, glob):
         self.glfunc = None
         self.marker = None
         self.scene = None
+        self.vao = None
 
     def setFPS(self, value, callback=None):
         self.fps = value
@@ -221,6 +227,15 @@ def initializeGL(self):
         self.glob.openGLBlock = False
         self.glfunc = self.context().functions()
 
+        # OpenGL 3.3 Core Profile requires at least one VAO to be bound before
+        # any vertex attribute pointer calls (glVertexAttribPointer /
+        # glEnableVertexAttribArray).  Create a single VAO and keep it bound
+        # for the lifetime of this widget so all existing BindBuffersToShader
+        # calls work without needing per-object VAOs.
+        self.vao = QOpenGLVertexArrayObject()
+        self.vao.create()
+        self.vao.bind()
+
         deb = GLDebug(self.env.osindex)
         if deb.checkVersion() is False:
             self.env.logLine(1, "Shader version is not sufficient, minimum version is " + str(deb.minVersion() + ". Available languages are:") )
@@ -423,3 +438,6 @@ def cleanUp(self):
         if self.skybox is not None:
             self.skybox.delete()
             self.skybox = None
+        if self.vao is not None:
+            self.vao.destroy()
+            self.vao = None