First step of PaintInvalidator implementation

third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/paint/ObjectPaintInvalidator.h"
+
+#include "core/layout/LayoutBlockFlow.h"
+#include "core/paint/PaintInvalidator.h"
+#include "core/paint/PaintLayer.h"
+
+namespace blink {
+
+typedef HashMap<const LayoutObject*, LayoutRect> SelectionPaintInvalidationMap;
+static SelectionPaintInvalidationMap& selectionPaintInvalidationMap()
+{
+    DEFINE_STATIC_LOCAL(SelectionPaintInvalidationMap, map, ());
+    return map;
+}
+
+static void setPreviousSelectionPaintInvalidationRect(const LayoutObject& object, const LayoutRect& rect)
+{
+    if (rect.isEmpty())
+        selectionPaintInvalidationMap().remove(&object);
+    else
+        selectionPaintInvalidationMap().set(&object, rect);
+}
+
+void ObjectPaintInvalidator::objectWillBeDestroyed(const LayoutObject& object)
+{
+    selectionPaintInvalidationMap().remove(&object);
+}
+
+void ObjectPaintInvalidator::incrementallyInvalidatePaint()
+{
+    const LayoutRect& oldBounds = m_context.oldBounds;
+    const LayoutRect& newBounds = m_context.newBounds;
+
+    DCHECK(oldBounds.location() == newBounds.location());
+
+    LayoutUnit deltaRight = newBounds.maxX() - oldBounds.maxX();
+    if (deltaRight > 0) {
+        LayoutRect invalidationRect(oldBounds.maxX(), newBounds.y(), deltaRight, newBounds.height());
+        m_object.invalidatePaintUsingContainer(*m_context.paintInvalidationContainer, invalidationRect, PaintInvalidationIncremental);
+    } else if (deltaRight < 0) {
+        LayoutRect invalidationRect(newBounds.maxX(), oldBounds.y(), -deltaRight, oldBounds.height());
+        m_object.invalidatePaintUsingContainer(*m_context.paintInvalidationContainer, invalidationRect, PaintInvalidationIncremental);
+    }
+
+    LayoutUnit deltaBottom = newBounds.maxY() - oldBounds.maxY();
+    if (deltaBottom > 0) {
+        LayoutRect invalidationRect(newBounds.x(), oldBounds.maxY(), newBounds.width(), deltaBottom);
+        m_object.invalidatePaintUsingContainer(*m_context.paintInvalidationContainer, invalidationRect, PaintInvalidationIncremental);
+    } else if (deltaBottom < 0) {
+        LayoutRect invalidationRect(oldBounds.x(), newBounds.maxY(), oldBounds.width(), -deltaBottom);
+        m_object.invalidatePaintUsingContainer(*m_context.paintInvalidationContainer, invalidationRect, PaintInvalidationIncremental);
+    }
+}
+
+void ObjectPaintInvalidator::fullyInvalidatePaint(PaintInvalidationReason reason, const LayoutRect& oldBounds, const LayoutRect& newBounds)
+{
+    // The following logic avoids invalidating twice if one set of bounds contains the other.
+    if (!newBounds.contains(oldBounds)) {
+        LayoutRect invalidationRect = oldBounds;
+        m_object.invalidatePaintUsingContainer(*m_context.paintInvalidationContainer, invalidationRect, reason);
+
+        if (invalidationRect.contains(newBounds))
+            return;
+    }
+
+    m_object.invalidatePaintUsingContainer(*m_context.paintInvalidationContainer, newBounds, reason);
+}
+
+PaintInvalidationReason ObjectPaintInvalidator::computePaintInvalidationReason()
+{
+    // This is before any early return to ensure the background obscuration status is saved.
+    bool backgroundObscurationChanged = false;
+    bool backgroundObscured = m_object.backgroundIsKnownToBeObscured();
+    if (backgroundObscured != m_object.previousBackgroundObscured()) {
+        m_object.getMutableForPainting().setPreviousBackgroundObscured(backgroundObscured);
+        backgroundObscurationChanged = true;
+    }
+
+    if (m_context.forcedSubtreeInvalidationFlags & PaintInvalidatorContext::ForcedSubtreeFullInvalidation)
+        return PaintInvalidationSubtree;
+
+    if (m_object.shouldDoFullPaintInvalidation())
+        return m_object.fullPaintInvalidationReason();
+
+    if (backgroundObscurationChanged)
+        return PaintInvalidationBackgroundObscurationChange;
+
+    if (m_object.paintedOutputOfObjectHasNoEffect())
+        return PaintInvalidationNone;
+
+    const ComputedStyle& style = m_object.styleRef();
+
+    // The outline may change shape because of position change of descendants. For simplicity,
+    // just force full paint invalidation if this object is marked for checking paint invalidation
+    // for any reason.
+    // TODO(wangxianzhu): Optimize this.
+    if (style.hasOutline())
+        return PaintInvalidationOutline;
+
+    bool locationChanged = m_context.newLocation != m_context.oldLocation;
+
+    // If the bounds are the same then we know that none of the statements below
+    // can match, so we can early out.
+    if (m_context.oldBounds == m_context.newBounds)
+        return locationChanged && !m_context.oldBounds.isEmpty() ? PaintInvalidationLocationChange : PaintInvalidationNone;
+
+    // If we shifted, we don't know the exact reason so we are conservative and trigger a full invalidation. Shifting could
+    // be caused by some layout property (left / top) or some in-flow layoutObject inserted / removed before us in the tree.
+    if (m_context.newBounds.location() != m_context.oldBounds.location())
+        return PaintInvalidationBoundsChange;
+
+    // If the size is zero on one of our bounds then we know we're going to have
+    // to do a full invalidation of either old bounds or new bounds.
+    if (m_context.oldBounds.isEmpty())
+        return PaintInvalidationBecameVisible;
+    if (m_context.newBounds.isEmpty())
+        return PaintInvalidationBecameInvisible;
+
+    if (locationChanged)
+        return PaintInvalidationLocationChange;
+
+    return PaintInvalidationIncremental;
+}
+
+void ObjectPaintInvalidator::invalidateSelectionIfNeeded(PaintInvalidationReason reason)
+{
+    // Update selection rect when we are doing full invalidation (in case that the object is moved,
+    // composite status changed, etc.) or shouldInvalidationSelection is set (in case that the
+    // selection itself changed).
+    bool fullInvalidation = isFullPaintInvalidationReason(reason);
+    if (!fullInvalidation && !m_object.shouldInvalidateSelection())
+        return;
+
+    LayoutRect oldSelectionRect = selectionPaintInvalidationMap().get(&m_object);
+    LayoutRect newSelectionRect = m_object.localSelectionRect();
+    if (!newSelectionRect.isEmpty())
+        m_context.mapLocalRectToPaintInvalidationBacking(m_object, newSelectionRect);
+
+    newSelectionRect.move(m_object.scrollAdjustmentForPaintInvalidation(*m_context.paintInvalidationContainer));
+
+    setPreviousSelectionPaintInvalidationRect(m_object, newSelectionRect);
+
+    if (!fullInvalidation) {
+        fullyInvalidatePaint(PaintInvalidationSelection, oldSelectionRect, newSelectionRect);
+        m_context.paintingLayer->setNeedsRepaint();
+        m_object.invalidateDisplayItemClients(PaintInvalidationSelection);
+    }
+}
+
+PaintInvalidationReason ObjectPaintInvalidator::invalidatePaintIfNeededWithComputedReason(PaintInvalidationReason reason)
+{
+    // We need to invalidate the selection before checking for whether we are doing a full invalidation.
+    // This is because we need to update the previous selection rect regardless.
+    invalidateSelectionIfNeeded(reason);
+
+    switch (reason) {
+    case PaintInvalidationNone:
+        // TODO(trchen): Currently we don't keep track of paint offset of layout objects.
+        // There are corner cases that the display items need to be invalidated for paint offset
+        // mutation, but incurs no pixel difference (i.e. bounds stay the same) so no rect-based
+        // invalidation is issued. See crbug.com/508383 and crbug.com/515977.
+        // This is a workaround to force display items to update paint offset.
+        if (m_context.forcedSubtreeInvalidationFlags & PaintInvalidatorContext::ForcedSubtreeInvalidationChecking) {
+            reason = PaintInvalidationLocationChange;
+            break;
+        }
+        return PaintInvalidationNone;
+    case PaintInvalidationIncremental:
+        incrementallyInvalidatePaint();
+        break;
+    case PaintInvalidationDelayedFull:
+        return PaintInvalidationDelayedFull;
+    default:
+        DCHECK(isFullPaintInvalidationReason(reason));
+        fullyInvalidatePaint(reason, m_context.oldBounds, m_context.newBounds);
+    }
+
+    m_context.paintingLayer->setNeedsRepaint();
+    m_object.invalidateDisplayItemClients(reason);
+    return reason;
+}
+
+} // namespace blink