Don't increment the paint's generation ID when drawing bitmaps

When the renderer draws a bitmap as part of a display list with an
alpha < 1.0f, the paint is temporarily modified to alter the opacity
of the bitmap. This has the side effect of increasing the paint's
generation ID counter which can break paint caching.

Change-Id: I5055d059ad1639829fa50af3d946e296c4dab877
diff --git a/libs/hwui/DisplayListOp.h b/libs/hwui/DisplayListOp.h
index 97812d4..9db8fe8 100644
--- a/libs/hwui/DisplayListOp.h
+++ b/libs/hwui/DisplayListOp.h
@@ -176,8 +176,8 @@
      */
     DeferredDisplayState state;
 protected:
-    SkPaint* getPaint(OpenGLRenderer& renderer) {
-        return renderer.filterPaint(mPaint);
+    SkPaint* getPaint(OpenGLRenderer& renderer, bool alwaysCopy = false) {
+        return renderer.filterPaint(mPaint, alwaysCopy);
     }
 
     SkPaint* mPaint; // should be accessed via getPaint() when applying
@@ -643,16 +643,13 @@
 
     virtual status_t applyDraw(OpenGLRenderer& renderer, Rect& dirty, uint32_t level,
             bool caching, int multipliedAlpha) {
-        SkPaint* paint = getPaint(renderer);
-        int oldAlpha = -1;
-        if (caching && multipliedAlpha < 255) {
-            oldAlpha = paint->getAlpha();
+        bool makeCopy = caching && multipliedAlpha < 255;
+        SkPaint* paint = getPaint(renderer, makeCopy);
+        if (makeCopy) {
+            // The paint is safe to modify since we're working on a copy
             paint->setAlpha(multipliedAlpha);
         }
         status_t ret = renderer.drawBitmap(mBitmap, mLocalBounds.left, mLocalBounds.top, paint);
-        if (oldAlpha >= 0) {
-            paint->setAlpha(oldAlpha);
-        }
         return ret;
     }
 
diff --git a/libs/hwui/OpenGLRenderer.cpp b/libs/hwui/OpenGLRenderer.cpp
index 34d1c98..9df0c58 100644
--- a/libs/hwui/OpenGLRenderer.cpp
+++ b/libs/hwui/OpenGLRenderer.cpp
@@ -2942,8 +2942,14 @@
     mDrawModifiers.mPaintFilterSetBits = setBits & SkPaint::kAllFlags;
 }
 
-SkPaint* OpenGLRenderer::filterPaint(SkPaint* paint) {
-    if (CC_LIKELY(!mDrawModifiers.mHasDrawFilter || !paint)) return paint;
+SkPaint* OpenGLRenderer::filterPaint(SkPaint* paint, bool alwaysCopy) {
+    if (CC_LIKELY(!mDrawModifiers.mHasDrawFilter || !paint)) {
+        if (CC_UNLIKELY(alwaysCopy)) {
+            mFilteredPaint = *paint;
+            return &mFilteredPaint;
+        }
+        return paint;
+    }
 
     uint32_t flags = paint->getFlags();
 
diff --git a/libs/hwui/OpenGLRenderer.h b/libs/hwui/OpenGLRenderer.h
index 80f2081..9144a33 100644
--- a/libs/hwui/OpenGLRenderer.h
+++ b/libs/hwui/OpenGLRenderer.h
@@ -259,7 +259,7 @@
     virtual void resetPaintFilter();
     virtual void setupPaintFilter(int clearBits, int setBits);
 
-    SkPaint* filterPaint(SkPaint* paint);
+    SkPaint* filterPaint(SkPaint* paint, bool alwaysCopy = false);
 
     bool disallowDeferral() {
         // returns true if the OpenGLRenderer's state can be completely represented by