Broaden fast inval path

Bug: 6445600
Clip fast partial invals to the screen instead of an arbitrary size
limit

Change-Id: Iafcbcb427566db87420b8bfc54eb9148530913ce

3 files changed, 41 insertions, 32 deletions

diff --git a/Source/WebCore/platform/graphics/android/layers/LayerAndroid.cpp b/Source/WebCore/platform/graphics/android/layers/LayerAndroid.cpp
index 535d211..a0cf61d 100644
--- a/Source/WebCore/platform/graphics/android/layers/LayerAndroid.cpp
+++ b/Source/WebCore/platform/graphics/android/layers/LayerAndroid.cpp
@@ -529,7 +529,10 @@ bool LayerAndroid::canUpdateWithBlit()
 {
     if (!m_content || !m_scale)
         return false;
-    PrerenderedInval* prerendered = m_content->prerenderForRect(m_dirtyRegion.getBounds());
+    IntRect clip = clippedRect();
+    IntRect dirty = m_dirtyRegion.getBounds();
+    dirty.intersect(clip);
+    PrerenderedInval* prerendered = m_content->prerenderForRect(dirty);
     if (!prerendered)
         return false;
     // Check that the scales are "close enough" to produce the same rects
diff --git a/Source/WebCore/platform/graphics/android/rendering/Surface.cpp b/Source/WebCore/platform/graphics/android/rendering/Surface.cpp
index 437b8ff..c8dfd13 100644
--- a/Source/WebCore/platform/graphics/android/rendering/Surface.cpp
+++ b/Source/WebCore/platform/graphics/android/rendering/Surface.cpp
@@ -216,13 +216,11 @@ void Surface::prepareGL(bool layerTilesDisabled, bool updateWithBlit)
         m_surfaceBacking->prepareGL(getFirstLayer()->state(), allowZoom,
                                     prepareArea, fullArea,
                                     this, useAggressiveRendering(), updateWithBlit);
-        if (updateWithBlit) {
-            for (size_t i = 0; i < m_layers.size(); i++) {
-                LayerContent* content = m_layers[i]->content();
-                if (content)
-                    content->clearPrerenders();
-            }
-        }
+    }
+    for (size_t i = 0; i < m_layers.size(); i++) {
+        LayerContent* content = m_layers[i]->content();
+        if (content)
+            content->clearPrerenders();
     }
 }
 
@@ -397,6 +395,13 @@ bool Surface::blitFromContents(Tile* tile)
     // Extract the dirty rect from the region. Note that this is *NOT* constrained
     // to this tile
     IntRect dirtyRect = tile->dirtyArea().getBounds();
+    IntRect tileRect = IntRect(tile->x() * TilesManager::tileWidth(),
+                               tile->y() * TilesManager::tileHeight(),
+                               TilesManager::tileWidth(),
+                               TilesManager::tileHeight());
+    FloatRect tileRectInDoc = tileRect;
+    tileRectInDoc.scale(1 / tile->scale());
+    dirtyRect.intersect(enclosingIntRect(tileRectInDoc));
     PrerenderedInval* prerenderedInval = content->prerenderForRect(dirtyRect);
     if (!prerenderedInval || prerenderedInval->bitmap.isNull())
         return false;
@@ -406,10 +411,6 @@ bool Surface::blitFromContents(Tile* tile)
     FloatRect screenDirty = dirtyRect;
     screenDirty.scale(tile->scale());
     IntRect enclosingScreenDirty = enclosingIntRect(screenDirty);
-    IntRect tileRect = IntRect(tile->x() * TilesManager::tileWidth(),
-                               tile->y() * TilesManager::tileHeight(),
-                               TilesManager::tileWidth(),
-                               TilesManager::tileHeight());
     enclosingScreenDirty.intersect(tileRect);
     if (enclosingScreenDirty.isEmpty())
         return false;
diff --git a/Source/WebKit/android/jni/WebViewCore.cpp b/Source/WebKit/android/jni/WebViewCore.cpp
index 34740a8..58341bb 100644
--- a/Source/WebKit/android/jni/WebViewCore.cpp
+++ b/Source/WebKit/android/jni/WebViewCore.cpp
@@ -123,6 +123,7 @@
 #include "SkUtils.h"
 #include "Text.h"
 #include "TextIterator.h"
+#include "TilesManager.h"
 #include "TypingCommand.h"
 #include "WebCache.h"
 #include "WebCoreFrameBridge.h"
@@ -732,38 +733,42 @@ void WebViewCore::paintContents(WebCore::GraphicsContext* gc, WebCore::IntRect&
 
 SkCanvas* WebViewCore::createPrerenderCanvas(PrerenderedInval* prerendered)
 {
-    IntRect screen(m_scrollOffsetX, m_scrollOffsetY, m_screenWidth, m_screenHeight);
-    if (prerendered->area.isEmpty() || !prerendered->area.intersects(screen))
+    if (prerendered->area.isEmpty())
         return 0;
+    FloatRect scaleTemp(m_scrollOffsetX, m_scrollOffsetY, m_screenWidth, m_screenHeight);
+    scaleTemp.scale(m_scale);
+    IntRect visibleTileClip = enclosingIntRect(scaleTemp);
     FloatRect scaledArea = prerendered->area;
     scaledArea.scale(m_scale);
     IntRect enclosingScaledArea = enclosingIntRect(scaledArea);
     if (enclosingScaledArea.isEmpty())
         return 0;
+    // "round out" the screen to tile boundaries so that we can clip yet still
+    // cover any visible tiles with the prerender
+    int tw = TilesManager::tileWidth();
+    int th = TilesManager::tileHeight();
+    float left = tw * (int) (visibleTileClip.x() / tw);
+    float top = th * (int) (visibleTileClip.y() / th);
+    float right = tw * (int) ceilf(visibleTileClip.maxX() / (float) tw);
+    float bottom = th * (int) ceilf(visibleTileClip.maxY() / (float) th);
+    visibleTileClip = IntRect(left, top, right - left, bottom - top);
+    enclosingScaledArea.intersect(visibleTileClip);
+    if (enclosingScaledArea.isEmpty())
+        return 0;
     prerendered->screenArea = enclosingScaledArea;
     FloatRect enclosingDocArea(enclosingScaledArea);
     enclosingDocArea.scale(1 / m_scale);
     prerendered->area = enclosingIntRect(enclosingDocArea);
     if (prerendered->area.isEmpty())
         return 0;
-    // TODO: We need a better heuristic for this. We should change this to:
-    // 1) Limit by area, not width/height (as we care more about the RAM than size)
-    // 2) Clip by the screen, but "round out" to make sure we cover partially
-    // visible tiles
-    int maxWidth = ceilf(m_screenWidth * m_scale);
-    int maxHeight = ceilf(m_screenHeight * m_scale);
-    if (enclosingScaledArea.width() <= maxWidth
-            && enclosingScaledArea.height() <= maxHeight) {
-        prerendered->bitmap.setConfig(SkBitmap::kARGB_8888_Config,
-                                      enclosingScaledArea.width(),
-                                      enclosingScaledArea.height());
-        prerendered->bitmap.allocPixels();
-        SkCanvas* bitmapCanvas = new SkCanvas(prerendered->bitmap);
-        bitmapCanvas->scale(m_scale, m_scale);
-        bitmapCanvas->translate(-enclosingDocArea.x(), -enclosingDocArea.y());
-        return bitmapCanvas;
-    }
-    return 0;
+    prerendered->bitmap.setConfig(SkBitmap::kARGB_8888_Config,
+                                  enclosingScaledArea.width(),
+                                  enclosingScaledArea.height());
+    prerendered->bitmap.allocPixels();
+    SkCanvas* bitmapCanvas = new SkCanvas(prerendered->bitmap);
+    bitmapCanvas->scale(m_scale, m_scale);
+    bitmapCanvas->translate(-enclosingDocArea.x(), -enclosingDocArea.y());
+    return bitmapCanvas;
 }
 
 void WebViewCore::notifyAnimationStarted()