avoid unwanted updates by ignoring the expose event on openglwindows …

…with explicit paint and swap

src/widget/openglwindow.cpp

@@ -10,8 +10,7 @@
 #include "widget/wglwidget.h"
 
 OpenGLWindow::OpenGLWindow(WGLWidget* pWidget)
-        : m_pWidget(pWidget),
-          m_dirty(false) {
+        : m_pWidget(pWidget) {
     setFormat(WaveformWidgetFactory::getSurfaceFormat());
 }
 
@@ -25,13 +24,8 @@ void OpenGLWindow::initializeGL() {
 }
 
 void OpenGLWindow::paintGL() {
+    // will only be called when m_pWidget useExplicitPaintAndSwap is false
     if (m_pWidget && isExposed()) {
-        if (m_dirty) {
-            // Extra render and swap to avoid flickering when resizing
-            m_pWidget->paintGL();
-            m_pWidget->swapBuffers();
-            m_dirty = false;
-        }
         m_pWidget->paintGL();
     }
 }
@@ -44,7 +38,6 @@ void OpenGLWindow::resizeGL(int w, int h) {
         // QGLWidget::resizeGL has devicePixelRatio applied, so we mimic the same behaviour
         m_pWidget->resizeGL(static_cast<int>(static_cast<float>(w) * devicePixelRatio()),
                 static_cast<int>(static_cast<float>(h) * devicePixelRatio()));
-        m_dirty = true;
         m_pWidget->doneCurrent();
     }
 }
@@ -62,6 +55,11 @@ bool OpenGLWindow::event(QEvent* pEv) {
     // this recursion.
     const auto t = pEv->type();
 
+    if (t == QEvent::Expose && m_pWidget->useExplicitPaintAndSwap()) {
+        // Avoid updates for windows that use explicit swaps
+        return false;
+    }
+
     bool result = QOpenGLWindow::event(pEv);
 
     if (m_pWidget) {

src/widget/openglwindow.h

@@ -22,5 +22,4 @@ class OpenGLWindow : public QOpenGLWindow {
     bool event(QEvent* pEv) override;
 
     WGLWidget* m_pWidget;
-    bool m_dirty;
 };

src/widget/wglwidgetqopengl.cpp

@@ -1,3 +1,4 @@
+#include <QDebug>
 #include <QResizeEvent>
 
 #include "widget/openglwindow.h"
@@ -8,12 +9,15 @@ WGLWidget::WGLWidget(QWidget* pParent)
         : QWidget(pParent),
           m_pOpenGLWindow(nullptr),
           m_pContainerWidget(nullptr),
-          m_pTrackDropTarget(nullptr) {
+          m_pTrackDropTarget(nullptr),
+          m_useExplicitPaintAndSwap(true) {
     // When the widget is resized or moved, the QOpenGLWindow visibly resizes
     // or moves before the widgets do. This can be solved by calling
     //   setAttribute(Qt::WA_PaintOnScreen);
     // here, but this comes with a clear performance penalty and drop in
     // frame rate.
+
+    setAutoFillBackground(true);
 }
 
 WGLWidget::~WGLWidget() {
@@ -42,13 +46,16 @@ void WGLWidget::showEvent(QShowEvent* event) {
         m_pContainerWidget = createWindowContainer(m_pOpenGLWindow, this);
         m_pContainerWidget->resize(size());
         m_pContainerWidget->show();
-        m_pContainerWidget->setAutoFillBackground(true);
     }
     QWidget::showEvent(event);
 }
 
 void WGLWidget::resizeEvent(QResizeEvent* event) {
-    if (m_pContainerWidget) {
+    // For widgets that are being used with swapBuffers, post-pone
+    // the resize of the containerWidget and this of the OpenGLWindow
+    // to the swapBuffers call to avoid flickering,
+    if (m_pContainerWidget && !m_useExplicitPaintAndSwap) {
+        // Otherwise do it here.
         m_pContainerWidget->resize(event->size());
     }
     QWidget::resizeEvent(event);
@@ -71,7 +78,8 @@ void WGLWidget::doneCurrent() {
 }
 
 void WGLWidget::paintGL() {
-    // to be implemented in derived widgets if needed
+    // to be implemented in derived widgets if needed,
+    // only called on widgets with setUseExplicitSwap(false)
 }
 
 void WGLWidget::initializeGL() {
@@ -86,6 +94,9 @@ void WGLWidget::resizeGL(int w, int h) {
 
 void WGLWidget::swapBuffers() {
     if (shouldRender()) {
+        if (size() != m_pContainerWidget->size()) {
+            m_pContainerWidget->resize(size());
+        }
         m_pOpenGLWindow->context()->swapBuffers(m_pOpenGLWindow->context()->surface());
     }
 }

src/widget/wglwidgetqopengl.h

@@ -40,6 +40,13 @@ class WGLWidget : public QWidget {
 
     QOpenGLWindow* getOpenGLWindow() const;
 
+    bool useExplicitPaintAndSwap() const {
+        return m_useExplicitPaintAndSwap;
+    }
+    void setUseExplicitPaintAndSwap(bool value) {
+        m_useExplicitPaintAndSwap = value;
+    }
+
   protected:
     void showEvent(QShowEvent* event) override;
     void resizeEvent(QResizeEvent* event) override;
@@ -50,4 +57,5 @@ class WGLWidget : public QWidget {
     OpenGLWindow* m_pOpenGLWindow;
     QWidget* m_pContainerWidget;
     TrackDropTarget* m_pTrackDropTarget;
+    bool m_useExplicitPaintAndSwap;
 };

src/widget/winitialglwidget.cpp

@@ -6,6 +6,7 @@
 
 WInitialGLWidget::WInitialGLWidget(QWidget* pParent)
         : WGLWidget(pParent) {
+    setUseExplicitPaintAndSwap(false);
 }
 
 void WInitialGLWidget::paintGL() {