GUI: reduce macOS repaint and Dock preview overhead

src/VBox/Frontends/VirtualBox/src/runtime/UIFrameBuffer.cpp

@@ -1151,6 +1151,9 @@ void UIFrameBufferPrivate::performRescale()
     switch (m_pMachineView->machineLogic()->visualStateType())
     {
         case UIVisualStateType_Scale:
+#ifdef VBOX_WS_MAC
+        case UIVisualStateType_Fullscreen:
+#endif
             m_scaledSize = scaledSize().width() == m_iWidth && scaledSize().height() == m_iHeight ? QSize() : scaledSize();
             break;
         default:
@@ -1314,14 +1317,32 @@ void UIFrameBufferPrivate::paintDefault(QPaintEvent *pEvent)
     /* Take the device-pixel-ratio into account: */
     paintRectHiDPI.moveTo(paintRectHiDPI.topLeft() * devicePixelRatio());
     paintRectHiDPI.setSize(paintRectHiDPI.size() * devicePixelRatio());
-
     /* Make sure hidpi paint rectangle is within the image boundary: */
     paintRectHiDPI &= pSourceImage->rect();
     if (paintRectHiDPI.isEmpty())
+    {
+#ifdef VBOX_WS_MAC
+        switch (m_pMachineView->visualStateType())
+        {
+            case UIVisualStateType_Normal:
+            case UIVisualStateType_Fullscreen:
+            case UIVisualStateType_Scale:
+            {
+                QPainter painter(m_pMachineView->viewport());
+                painter.setCompositionMode(QPainter::CompositionMode_Source);
+                painter.fillRect(paintRect, QColor(Qt::black));
+                painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
+                break;
+            }
+            default:
+                break;
+        }
+#endif /* VBOX_WS_MAC */
         return;
-
+    }
     /* Create painter: */
     QPainter painter(m_pMachineView->viewport());
+    bool fRestoreSourceOverComposition = false;
 
     /* Depending on visual-state type: */
     switch (m_pMachineView->visualStateType())
@@ -1331,12 +1352,17 @@ void UIFrameBufferPrivate::paintDefault(QPaintEvent *pEvent)
         case UIVisualStateType_Scale:
         {
 #ifdef VBOX_WS_MAC
-            /* On OSX for Qt5 we need to fill the backing store first: */
+            /* On macOS, make the destination explicitly opaque before drawing the guest image.
+             * The guest RGB32 backing buffer may carry transparent/undefined alpha bits for
+             * black pixels; drawing it with Source can copy those bits into the window backing
+             * store and make the boot framebuffer appear gray or washed out. */
             painter.setCompositionMode(QPainter::CompositionMode_Source);
             painter.fillRect(paintRect, QColor(Qt::black));
             painter.setCompositionMode(QPainter::CompositionMode_SourceAtop);
+            fRestoreSourceOverComposition = true;
+#else
+            /* Nothing to do. */
 #endif /* VBOX_WS_MAC */
-
             break;
         }
         case UIVisualStateType_Seamless:
@@ -1357,12 +1383,12 @@ void UIFrameBufferPrivate::paintDefault(QPaintEvent *pEvent)
             painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
             unlock();
 
-#ifdef VBOX_WITH_TRANSLUCENT_SEAMLESS
+#if defined(VBOX_WITH_TRANSLUCENT_SEAMLESS) && QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
             /* In case of translucent seamless for Qt5 we need to fill the backing store first: */
             painter.setCompositionMode(QPainter::CompositionMode_Source);
             painter.fillRect(paintRect, QColor(Qt::black));
             painter.setCompositionMode(QPainter::CompositionMode_SourceAtop);
-#endif /* VBOX_WITH_TRANSLUCENT_SEAMLESS */
+#endif /* VBOX_WITH_TRANSLUCENT_SEAMLESS && Qt < 6 */
 
             break;
         }
@@ -1374,6 +1400,8 @@ void UIFrameBufferPrivate::paintDefault(QPaintEvent *pEvent)
     drawImageRect(painter, *pSourceImage, paintRectHiDPI,
                   m_pMachineView->contentsX(), m_pMachineView->contentsY(),
                   devicePixelRatio());
+    if (fRestoreSourceOverComposition)
+        painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
 
     /* If we had to scale image for some reason: */
     if (   scaledSize().isValid()
@@ -1441,31 +1469,25 @@ void UIFrameBufferPrivate::drawImageRect(QPainter &painter, const QImage &image,
                                          int iContentsShiftX, int iContentsShiftY,
                                          double dDevicePixelRatio)
 {
-    /* Calculate offset: */
-    const size_t offset = (rect.x() + iContentsShiftX) * image.depth() / 8 +
-                          (rect.y() + iContentsShiftY) * image.bytesPerLine();
-
     /* Restrain boundaries: */
     const int iSubImageWidth = qMin(rect.width(), image.width() - rect.x() - iContentsShiftX);
     const int iSubImageHeight = qMin(rect.height(), image.height() - rect.y() - iContentsShiftY);
+    if (   iSubImageWidth <= 0
+        || iSubImageHeight <= 0)
+        return;
 
-    /* Create sub-image (no copy involved): */
-    QImage subImage = QImage(image.bits() + offset,
-                             iSubImageWidth, iSubImageHeight,
-                             image.bytesPerLine(), image.format());
-
-    /* Create sub-pixmap on the basis of sub-image above (1st copy involved): */
-    QPixmap subPixmap = QPixmap::fromImage(subImage);
-    /* Take the device-pixel-ratio into account: */
-    subPixmap.setDevicePixelRatio(dDevicePixelRatio);
-
-    /* Which point we should draw corresponding sub-pixmap? */
+    /* Which point we should draw the image at? */
     QPoint paintPoint = rect.topLeft();
     /* Take the device-pixel-ratio into account: */
     paintPoint /= dDevicePixelRatio;
 
-    /* Draw sub-pixmap: */
-    painter.drawPixmap(paintPoint, subPixmap);
+    /* Draw directly from the source image to avoid materializing a temporary pixmap for every update rectangle. */
+    const QRect sourceRect(rect.x() + iContentsShiftX, rect.y() + iContentsShiftY,
+                           iSubImageWidth, iSubImageHeight);
+    const QRectF targetRect(QPointF(paintPoint),
+                            QSizeF((double)iSubImageWidth / dDevicePixelRatio,
+                                   (double)iSubImageHeight / dDevicePixelRatio));
+    painter.drawImage(targetRect, image, sourceRect);
 }
 
 /* static */

src/VBox/Frontends/VirtualBox/src/runtime/UIMachineLogic.cpp

@@ -114,6 +114,7 @@
 
 /* Other VBox includes: */
 #include <iprt/path.h>
+#include <iprt/time.h>
 
 /* VirtualBox interface declarations: */
 #include <VBox/com/VirtualBox.h>
@@ -332,19 +333,30 @@ void UIMachineLogic::openNetworkSettingsDialogTheModalWay()
 }
 
 #ifdef VBOX_WS_MAC
+/** Minimum interval between live Dock preview frame updates. */
+static const uint64_t s_u64DockIconUpdateIntervalMs = 250;
+
 void UIMachineLogic::updateDockIcon()
 {
     if (!isMachineWindowsCreated())
         return;
 
-    if (   m_fIsDockIconEnabled
-        && m_pDockIconPreview)
-        if(UIMachineView *pView = machineWindows().at(m_DockIconPreviewMonitor)->machineView())
-            if (CGImageRef image = pView->vmContentImage())
-            {
-                m_pDockIconPreview->updateDockPreview(image);
-                CGImageRelease(image);
-            }
+    if (   !m_fIsDockIconEnabled
+        || !m_pDockIconPreview)
+        return;
+
+    const uint64_t u64NowMs = RTTimeMilliTS();
+    if (   m_u64LastDockIconUpdateMs
+        && u64NowMs - m_u64LastDockIconUpdateMs < s_u64DockIconUpdateIntervalMs)
+        return;
+
+    if (UIMachineView *pView = machineWindows().at(m_DockIconPreviewMonitor)->machineView())
+        if (CGImageRef image = pView->vmContentImage())
+        {
+            m_u64LastDockIconUpdateMs = u64NowMs;
+            m_pDockIconPreview->updateDockPreview(image);
+            CGImageRelease(image);
+        }
 }
 
 void UIMachineLogic::updateDockIconSize(int screenId, int width, int height)
@@ -790,6 +802,7 @@ UIMachineLogic::UIMachineLogic(UIMachine *pMachine)
     , m_pDockPreviewSelectMonitorGroup(0)
     , m_pDockSettingsMenuSeparator(0)
     , m_DockIconPreviewMonitor(0)
+    , m_u64LastDockIconUpdateMs(0)
     , m_pDockSettingMenuAction(0)
 #endif /* VBOX_WS_MAC */
     , m_pHostLedsState(NULL)

src/VBox/Frontends/VirtualBox/src/runtime/UIMachineLogic.h

@@ -407,6 +407,7 @@ private slots:
     QActionGroup *m_pDockPreviewSelectMonitorGroup;
     QAction *m_pDockSettingsMenuSeparator;
     int m_DockIconPreviewMonitor;
+    uint64_t m_u64LastDockIconUpdateMs;
     QAction *m_pDockSettingMenuAction;
     /* Keeps a list of machine menu actions that we add to dock menu. */
     QList<QAction*> m_dockMachineMenuActions;