fix: issue with QWidget painting off the main thread

the spectrogram render thread changing some bit metadata triggered a bas render thread

corrected with Qt::QueuedConnection in PreviewScrollbar

Author: hello-adam

src/hobbits-widgets/displayhandle.cpp

@@ -269,7 +269,7 @@ void DisplayHandle::checkCurrentContainer()
     disconnect(this, SLOT(containerUpdate()));
 
     if (!currentContainer().isNull()) {
-        connect(currentContainer().data(), SIGNAL(changed()), this, SLOT(containerUpdate()));
+        connect(currentContainer().data(), SIGNAL(changed()), this, SLOT(containerUpdate()), Qt::QueuedConnection);
     }
     emit currentContainerChanged();
 

src/hobbits-widgets/displaywidget.cpp

@@ -13,12 +13,12 @@ DisplayWidget::DisplayWidget(QSharedPointer<DisplayInterface> display,
     QWidget(parent),
     m_display(display),
     m_handle(handle),
-    m_redrawing(false)
+    m_repaintScheduled(false)
 {
     this->setSizePolicy(QSizePolicy::MinimumExpanding, QSizePolicy::MinimumExpanding);
     this->setMouseTracking(true);
 
-    connect(m_handle.data(), SIGNAL(containerChanged()), this, SLOT(checkFullRedraw()));
+    connect(m_handle.data(), SIGNAL(containerChanged()), this, SLOT(checkFullRedraw()), Qt::QueuedConnection);
     connect(m_handle.data(), SIGNAL(currentContainerChanged()), this, SLOT(checkNewContainer()));
 
     connect(m_handle.data(), SIGNAL(overlayRedrawRequested(DisplayInterface*)), this, SLOT(checkOverlayRedraw(DisplayInterface*)));
@@ -84,6 +84,8 @@ void DisplayWidget::paintEvent(QPaintEvent *event)
     if (!overlay.isNull()) {
         painter.drawImage(0, 0, overlay);
     }
+
+    m_repaintScheduled = false;
 }
 
 void DisplayWidget::wheelEvent(QWheelEvent *event)
@@ -152,7 +154,7 @@ void DisplayWidget::performDisplayRender()
                                         this->size(),
                                         m_displayParameters,
                                         m_displayRenderProgress);
-        connect(&m_displayRenderWatcher, &QFutureWatcher<QImage>::finished, [this]() {
+        connect(&m_displayRenderWatcher, &QFutureWatcher<QImage>::finished, this, [this]() {
             if (this->m_displayRenderWatcher.isFinished()) {
                 this->setDisplayImage(this->m_displayRenderWatcher.result());
             }
@@ -175,8 +177,9 @@ void DisplayWidget::handleDisplayRenderPreview(QString type, QVariant value)
 
 void DisplayWidget::setDisplayImage(QImage image)
 {
+    QMutexLocker lock(&m_mutex);
     m_displayImage = image;
-    update();
+    scheduleRepaint();
 }
 
 void DisplayWidget::resetRendering()
@@ -193,15 +196,8 @@ void DisplayWidget::resetRendering()
 
 void DisplayWidget::fullRedraw()
 {
-    if (m_redrawing) {
-        return;
-    }
-    m_redrawing = true;
-    disconnect(m_handle.data(), SIGNAL(containerChanged()), this, SLOT(checkFullRedraw()));
     performDisplayRender();
-    update();
-    connect(m_handle.data(), SIGNAL(containerChanged()), this, SLOT(checkFullRedraw()));
-    m_redrawing = false;
+    scheduleRepaint();
 }
 
 void DisplayWidget::showContextMenu(const QPoint &point)
@@ -443,6 +439,7 @@ void DisplayWidget::checkNewContainer()
 
 void DisplayWidget::checkFullRedraw(DisplayInterface *display)
 {
+    QMutexLocker lock(&m_mutex);
     if (!m_handle->activeDisplays().contains(this)) {
         return;
     }
@@ -454,12 +451,22 @@ void DisplayWidget::checkFullRedraw(DisplayInterface *display)
 
 void DisplayWidget::checkOverlayRedraw(DisplayInterface *display)
 {
+    QMutexLocker lock(&m_mutex);
     if (!m_handle->activeDisplays().contains(this)) {
         return;
     }
     if (display != nullptr && display != m_display.data()) {
         return;
     }
+    scheduleRepaint();
+}
+
+void DisplayWidget::scheduleRepaint()
+{
+    if (m_repaintScheduled) {
+        return;
+    }
+    m_repaintScheduled = true;
     update();
 }
 

src/hobbits-widgets/displaywidget.h

@@ -52,12 +52,15 @@ private slots:
     void checkFullRedraw(DisplayInterface* display = nullptr);
     void checkOverlayRedraw(DisplayInterface* display = nullptr);
 
+    void scheduleRepaint();
+
 private:
     QSharedPointer<DisplayInterface> m_display;
     QSharedPointer<DisplayHandle> m_handle;
     QJsonObject m_displayParameters;
     QImage m_displayImage;
-    bool m_redrawing;
+    bool m_repaintScheduled;
+    QMutex m_mutex;
 
     QFutureWatcher<QImage> m_displayRenderWatcher;
     QSharedPointer<PluginActionProgress> m_displayRenderProgress;

src/hobbits-widgets/previewscrollbar.cpp

@@ -62,7 +62,7 @@ void PreviewScrollBar::paintEvent(QPaintEvent *event)
                 }
                 m_previewImageCache.remove(containerPtr);
                 m_previewImageCache.insert(containerPtr, QImage(preview));
-                this->repaint();
+                this->update();
             }, Qt::QueuedConnection);
 
             connect(container.data(), &BitContainer::changed, this, [containerPtr, watcherRef, this]() {
@@ -74,8 +74,8 @@ void PreviewScrollBar::paintEvent(QPaintEvent *event)
                 m_imageCache.remove(containerPtr);
                 m_previewImageCache.remove(containerPtr);
                 m_renderWatchers.remove(containerPtr);
-                this->repaint();
-            });
+                this->update();
+            }, Qt::QueuedConnection);
 
             connect(actionWatcher->watcher(), &QFutureWatcher<QImage>::finished, this, [containerPtr, watcherRef, this]() {
                 auto watcher = watcherRef.toStrongRef();
@@ -90,7 +90,7 @@ void PreviewScrollBar::paintEvent(QPaintEvent *event)
                     }
                     m_renderWatchers.remove(containerPtr);
                 }
-                this->repaint();
+                this->update();
             });
 
             // clean out any deleted containers