Workaround double blit failure

An issue occurs on Stingray where calling glTexSubImage2d in order to blit an
update to a texture fails silently if the texture has already been updated this
frame.

With this change, we now draw the tile off-screen to work around the issue just
before the second blit is required. This way, the second blit succeeds.

bug:6630040

Change-Id: I07213954669b0f3d3f5b87a748a591e532b097b4

3 files changed, 12 insertions, 0 deletions

diff --git a/Source/WebCore/platform/graphics/android/rendering/Surface.cpp b/Source/WebCore/platform/graphics/android/rendering/Surface.cpp
index 73466d3..1898910 100644
--- a/Source/WebCore/platform/graphics/android/rendering/Surface.cpp
+++ b/Source/WebCore/platform/graphics/android/rendering/Surface.cpp
@@ -420,6 +420,14 @@ bool Surface::blitFromContents(Tile* tile)
     if (!singleLayer() || !tile || !getFirstLayer() || !getFirstLayer()->content())
         return false;
 
+    if (tile->frontTexture() != tile->lastDrawnTexture()) {
+        // the below works around an issue where glTexSubImage2d can't update a
+        // texture that hasn't drawn yet by drawing it off screen.
+        // glFlush() and glFinish() work also, but are likely more wasteful.
+        SkRect rect = SkRect::MakeXYWH(-100, -100, 0, 0);
+        FloatRect fillPortion(0, 0, 0, 0);
+        tile->frontTexture()->drawGL(false, rect, 1.0f, 0, false, true, fillPortion);
+    }
     LayerContent* content = getFirstLayer()->content();
     // Extract the dirty rect from the region. Note that this is *NOT* constrained
     // to this tile
diff --git a/Source/WebCore/platform/graphics/android/rendering/Tile.cpp b/Source/WebCore/platform/graphics/android/rendering/Tile.cpp
index e674884..96b189a 100644
--- a/Source/WebCore/platform/graphics/android/rendering/Tile.cpp
+++ b/Source/WebCore/platform/graphics/android/rendering/Tile.cpp
@@ -52,6 +52,7 @@ Tile::Tile(bool isLayerTile)
     , m_y(-1)
     , m_frontTexture(0)
     , m_backTexture(0)
+    , m_lastDrawnTexture(0)
     , m_scale(1)
     , m_dirty(true)
     , m_repaintsPending(0)
@@ -242,6 +243,7 @@ bool Tile::drawGL(float opacity, const SkRect& rect, float scale,
 
     m_frontTexture->drawGL(isLayerTile(), rect, opacity, transform,
                            forceBlending, usePointSampling, fillPortion);
+    m_lastDrawnTexture = m_frontTexture;
     return true;
 }
 
diff --git a/Source/WebCore/platform/graphics/android/rendering/Tile.h b/Source/WebCore/platform/graphics/android/rendering/Tile.h
index 2dc5414..b045f1f 100644
--- a/Source/WebCore/platform/graphics/android/rendering/Tile.h
+++ b/Source/WebCore/platform/graphics/android/rendering/Tile.h
@@ -127,6 +127,7 @@ public:
     int y() const { return m_y; }
     TileTexture* frontTexture() { return m_frontTexture; }
     TileTexture* backTexture() { return m_backTexture; }
+    TileTexture* lastDrawnTexture() { return m_lastDrawnTexture; }
 
     // only used for prioritization - the higher, the more relevant the tile is
     unsigned long long drawCount() { return m_drawCount; }
@@ -151,6 +152,7 @@ private:
 
     TileTexture* m_frontTexture;
     TileTexture* m_backTexture;
+    TileTexture* m_lastDrawnTexture;
     float m_scale;
 
     // used to signal that the that the tile is out-of-date and needs to be