Massive re-factoring of Graphics View's update mechanism.

This is work-in-progress, so don't expect everything to work perfectly.
Most of the auto-test pass and examples and demos seem to run fine.

Unfortunately I'm too tired to write about the actual update mehanism
now, but it's faster than the old approach (if that helps:)). There's
more to optimize, but I'll come back to that later. I need some sleep now :)

To be continued.

1 files changed, 36 insertions, 158 deletions

diff --git a/src/gui/graphicsview/qgraphicsview.cpp b/src/gui/graphicsview/qgraphicsview.cpp
index 1994675..acf26e1 100644
--- a/src/gui/graphicsview/qgraphicsview.cpp
+++ b/src/gui/graphicsview/qgraphicsview.cpp
@@ -329,8 +329,6 @@ QGraphicsViewPrivate::QGraphicsViewPrivate()
 #endif
       lastDragDropEvent(0),
       fullUpdatePending(true),
-      dirtyRectCount(0),
-      updatingLater(false),
       updateSceneSlotReimplementedChecked(false)
 {
     styleOptions.reserve(QGRAPHICSVIEW_PREALLOC_STYLE_OPTIONS);
@@ -804,125 +802,28 @@ static inline QRectF adjustedItemBoundingRect(const QGraphicsItem *item)
     return boundingRect;
 }
 
-/*!
-    \internal
-*/
-void QGraphicsViewPrivate::itemUpdated(QGraphicsItem *item, const QRectF &rect)
+void QGraphicsViewPrivate::processPendingUpdates()
 {
-    if (fullUpdatePending || viewportUpdateMode == QGraphicsView::NoViewportUpdate)
-        return;
-    if (item->d_ptr->dirty)
-        updateLater();
-
-    QRectF updateRect = rect;
-    if ((item->d_ptr->flags & QGraphicsItem::ItemClipsChildrenToShape) || item->d_ptr->children.isEmpty()) {
-        updateRect &= adjustedItemBoundingRect(item);
-        if (updateRect.isEmpty())
-            return;
-    }
-
-    QGraphicsItem *clipItem = item;
-    if (item->d_ptr->ancestorFlags & QGraphicsItemPrivate::AncestorClipsChildren) {
-        // Minimize unnecessary redraw.
-        QGraphicsItem *parent = item;
-        while ((parent = parent->d_ptr->parent)) {
-            if (parent->d_ptr->flags & QGraphicsItem::ItemClipsChildrenToShape) {
-                // Map update rect to the current parent and itersect with its bounding rect.
-                updateRect = clipItem->itemTransform(parent).mapRect(updateRect)
-                             & adjustedItemBoundingRect(parent);
-                if (updateRect.isEmpty())
-                    return;
-                clipItem = parent;
-            }
-
-            if (!(parent->d_ptr->ancestorFlags & QGraphicsItemPrivate::AncestorClipsChildren))
-                break;
-        }
-    }
-
-    // Map update rect from clipItem coordinates to view coordinates.
-    Q_ASSERT(clipItem);
-    if (!item->d_ptr->hasBoundingRegionGranularity)
-        this->updateRect(mapToViewRect(clipItem, updateRect) & viewport->rect());
-    else
-        updateRegion(mapToViewRegion(clipItem, updateRect) & viewport->rect());
-}
-
-void QGraphicsViewPrivate::updateLater()
-{
-    Q_Q(QGraphicsView);
-    if (updatingLater)
-        return;
-    updatingLater = true;
-    QMetaObject::invokeMethod(q, "_q_updateLaterSlot", Qt::QueuedConnection);
-}
-
-void QGraphicsViewPrivate::_q_updateLaterSlot()
-{
-    Q_Q(QGraphicsView);
     if (!scene)
         return;
 
-    QRect vr = viewport->rect();
-    QTransform viewTransform = q->viewportTransform();
-    const QList<QGraphicsItem *> &dirtyItems = scene->d_func()->dirtyItems;
-    for (int i = 0; i < dirtyItems.size(); ++i) {
-        const QGraphicsItem *item = dirtyItems.at(i);
-        if (item->d_ptr->discardUpdateRequest(/*ignoreClipping=*/false,
-                                              /*ignoreVisibleBit=*/false,
-                                              /*ignoreDirtyBit=*/true)) {
-            continue;
-        }
-        QTransform x = item->sceneTransform() * viewTransform;
-        updateRect(x.mapRect(item->boundingRect()).toAlignedRect() & vr);
+    if (fullUpdatePending) { // We have already called viewport->update()
+        dirtyBoundingRect = QRect();
+        dirtyRegion = QRegion();
+        return;
     }
 
-    dirtyRectCount += dirtyRects.size();
-
-    bool noUpdate = !fullUpdatePending && viewportUpdateMode == QGraphicsView::FullViewportUpdate;
-    if ((dirtyRectCount > 0 || !dirtyBoundingRect.isEmpty()) && !fullUpdatePending && !noUpdate) {
-        if (viewportUpdateMode == QGraphicsView::BoundingRectViewportUpdate
-            || (viewportUpdateMode == QGraphicsView::SmartViewportUpdate
-                && dirtyRectCount >= QGRAPHICSVIEW_REGION_RECT_THRESHOLD)) {
-            if (!(optimizationFlags & QGraphicsView::DontAdjustForAntialiasing)) {
-                viewport->update(dirtyBoundingRect.adjusted(-2, -2, 2, 2));
-            } else {
-                viewport->update(dirtyBoundingRect);
-            }
-        } else {
-            // ### Improve this block, which is very slow for complex regions. We
-            // need to strike the balance between having an accurate update
-            // region, and running fast. The below approach is the simplest way to
-            // create a region from a bunch of rects, but we might want to use
-            // other approaches; e.g., a grid of a fixed size representing
-            // quadrants of the viewport, which we mark as dirty depending on the
-            // rectangles in the list. Perhaps this should go into a
-            // QRegion::fromRects(rects, how) function.
-            QRegion region;
-            if (!(optimizationFlags & QGraphicsView::DontAdjustForAntialiasing)) {
-                for (int i = 0; i < dirtyRegions.size(); ++i) {
-                    QVector<QRect> rects = dirtyRegions.at(i).rects();
-                    for (int j = 0; j < rects.size(); ++j)
-                        region += rects.at(j).adjusted(-2, -2, 2, 2);
-                }
-                for (int i = 0; i < dirtyRects.size(); ++i)
-                    region += dirtyRects.at(i).adjusted(-2, -2, 2, 2);
-            } else {
-                for (int i = 0; i < dirtyRegions.size(); ++i)
-                    region += dirtyRegions.at(i);
-                for (int i = 0; i < dirtyRects.size(); ++i)
-                    region += dirtyRects.at(i);
-            }
-
-            viewport->update(region);
-        }
+    if (viewportUpdateMode == QGraphicsView::BoundingRectViewportUpdate) {
+        if (optimizationFlags & QGraphicsView::DontAdjustForAntialiasing)
+            viewport->update(dirtyBoundingRect);
+        else
+            viewport->update(dirtyBoundingRect.adjusted(-2, -2, 2, 2));
+    } else {
+        viewport->update(dirtyRegion); // Already adjusted in updateRect/Region.
     }
 
-    dirtyRegions.clear();
-    dirtyRects.clear();
-    dirtyRectCount = 0;
     dirtyBoundingRect = QRect();
-    updatingLater = false;
+    dirtyRegion = QRegion();
 }
 
 void QGraphicsViewPrivate::updateAll()
@@ -930,14 +831,13 @@ void QGraphicsViewPrivate::updateAll()
     Q_Q(QGraphicsView);
     q->viewport()->update();
     fullUpdatePending = true;
-    dirtyRectCount = 0;
     dirtyBoundingRect = QRect();
-    updatingLater = false;
+    dirtyRegion = QRegion();
 }
 
 void QGraphicsViewPrivate::updateRegion(const QRegion &r)
 {
-    if (r.isEmpty())
+    if (r.isEmpty() || fullUpdatePending)
         return;
 
     Q_Q(QGraphicsView);
@@ -950,45 +850,30 @@ void QGraphicsViewPrivate::updateRegion(const QRegion &r)
         break;
     case QGraphicsView::BoundingRectViewportUpdate:
         dirtyBoundingRect |= r.boundingRect();
-        if (dirtyBoundingRect == q->viewport()->rect()) {
+        if (dirtyBoundingRect.contains(q->viewport()->rect())) {
             fullUpdatePending = true;
             q->viewport()->update();
-        } else {
-            updateLater();
         }
         break;
-    case QGraphicsView::SmartViewportUpdate:
-        dirtyBoundingRect |= r.boundingRect();
-        if ((dirtyRectCount + r.numRects()) < QGRAPHICSVIEW_REGION_RECT_THRESHOLD)
-            dirtyRegions << r;
-        dirtyRectCount += r.numRects();
-        updateLater();
-        break;
+    case QGraphicsView::SmartViewportUpdate: // ### DEPRECATE
     case QGraphicsView::MinimalViewportUpdate:
-        dirtyRegions << r;
-        dirtyRectCount += r.numRects();
-        updateLater();
+        if (optimizationFlags & QGraphicsView::DontAdjustForAntialiasing) {
+            dirtyRegion += r;
+        } else {
+            const QVector<QRect> &rects = r.rects();
+            for (int i = 0; i < rects.size(); ++i)
+                dirtyRegion += rects.at(i).adjusted(-2, -2, 2, 2);
+        }
         break;
     case QGraphicsView::NoViewportUpdate:
         // Unreachable
         break;
     }
-
-    // Compress the regions...
-    if (dirtyRectCount > QGRAPHICSVIEW_REGION_RECT_THRESHOLD && dirtyRegions.size() > 1) {
-        QRegion masterRegion;
-        for (int i=0; i<dirtyRegions.size(); ++i) {
-            masterRegion |= dirtyRegions.at(i);
-        }
-        dirtyRectCount = masterRegion.numRects();
-        dirtyRegions.clear();
-        dirtyRegions << masterRegion;
-    }
 }
 
 void QGraphicsViewPrivate::updateRect(const QRect &r)
 {
-    if (r.isEmpty())
+    if (r.isEmpty() || fullUpdatePending)
         return;
 
     Q_Q(QGraphicsView);
@@ -1001,22 +886,17 @@ void QGraphicsViewPrivate::updateRect(const QRect &r)
         break;
     case QGraphicsView::BoundingRectViewportUpdate:
         dirtyBoundingRect |= r;
-        if (dirtyBoundingRect == q->viewport()->rect()) {
+        if (dirtyBoundingRect.contains(q->viewport()->rect())) {
             fullUpdatePending = true;
             q->viewport()->update();
-        } else {
-            updateLater();
         }
         break;
-    case QGraphicsView::SmartViewportUpdate:
-        dirtyBoundingRect |= r;
-        if ((dirtyRectCount + dirtyRects.size()) < QGRAPHICSVIEW_REGION_RECT_THRESHOLD)
-            dirtyRects << r;
-        updateLater();
-        break;
+    case QGraphicsView::SmartViewportUpdate: // ### DEPRECATE
     case QGraphicsView::MinimalViewportUpdate:
-        dirtyRects << r;
-        updateLater();
+        if (optimizationFlags & QGraphicsView::DontAdjustForAntialiasing)
+            dirtyRegion += r;
+        else
+            dirtyRegion += r.adjusted(-2, -2, 2, 2);
         break;
     case QGraphicsView::NoViewportUpdate:
         // Unreachable
@@ -2613,9 +2493,10 @@ void QGraphicsView::updateScene(const QList<QRectF> &rects)
 
     // Extract and reset dirty scene rect info.
     QVector<QRect> dirtyViewportRects;
-    for (int i = 0; i < d->dirtyRegions.size(); ++i)
-        dirtyViewportRects += d->dirtyRegions.at(i).rects();
-    d->dirtyRegions.clear();
+    const QVector<QRect> &dirtyRects = d->dirtyRegion.rects();
+    for (int i = 0; i < dirtyRects.size(); ++i)
+        dirtyViewportRects += dirtyRects.at(i);
+    d->dirtyRegion = QRegion();
 
     bool fullUpdate = !d->accelerateScrolling || d->viewportUpdateMode == QGraphicsView::FullViewportUpdate;
     bool boundingRectUpdate = (d->viewportUpdateMode == QGraphicsView::BoundingRectViewportUpdate)
@@ -3544,10 +3425,7 @@ void QGraphicsView::scrollContentsBy(int dx, int dy)
 
     if (d->viewportUpdateMode != QGraphicsView::NoViewportUpdate) {
         if (d->viewportUpdateMode != QGraphicsView::FullViewportUpdate) {
-            for (int i = 0; i < d->dirtyRects.size(); ++i)
-                d->dirtyRects[i].translate(dx, dy);
-            for (int i = 0; i < d->dirtyRegions.size(); ++i)
-                d->dirtyRegions[i].translate(dx, dy);
+            d->dirtyRegion.translate(dx, dy);
             if (d->accelerateScrolling) {
 #ifndef QT_NO_RUBBERBAND
                 // Update new and old rubberband regions