Add a property to disable libhwui's scissor optimization

Bug #7158326

When scissor optimization is enabled, OpenGLRenderer will attempt to
minimize the use of scissor by selectively enabling and disabling the
GL scissor test.
When the optimization is disabled, OpenGLRenderer will keep the GL
scissor test enabled and change the scissor rect as needed.
Some GPUs (for instance the SGX 540) perform better when changing
the scissor rect often than when enabling/disabling the scissor test
often.

Change-Id: Idb68862e287a23358f9188d577ae0f86161902fd

3 files changed, 85 insertions, 46 deletions

diff --git a/libs/hwui/OpenGLRenderer.cpp b/libs/hwui/OpenGLRenderer.cpp
index a4403c8..35cc716 100644
--- a/libs/hwui/OpenGLRenderer.cpp
+++ b/libs/hwui/OpenGLRenderer.cpp
@@ -34,6 +34,7 @@
 #include "OpenGLRenderer.h"
 #include "DisplayListRenderer.h"
 #include "PathRenderer.h"
+#include "Properties.h"
 #include "Vector.h"
 
 namespace android {
@@ -117,6 +118,8 @@ OpenGLRenderer::OpenGLRenderer(): mCaches(Caches::getInstance()) {
     memcpy(mMeshVertices, gMeshVertices, sizeof(gMeshVertices));
 
     mFirstSnapshot = new Snapshot;
+
+    mScissorOptimizationDisabled = false;
 }
 
 OpenGLRenderer::~OpenGLRenderer() {
@@ -124,16 +127,15 @@ OpenGLRenderer::~OpenGLRenderer() {
     // GL APIs. All GL state should be kept in Caches.h
 }
 
-///////////////////////////////////////////////////////////////////////////////
-// Debug
-///////////////////////////////////////////////////////////////////////////////
-
-void OpenGLRenderer::startMark(const char* name) const {
-    mCaches.startMark(0, name);
-}
-
-void OpenGLRenderer::endMark() const {
-    mCaches.endMark();
+void OpenGLRenderer::initProperties() {
+    char property[PROPERTY_VALUE_MAX];
+    if (property_get(PROPERTY_DISABLE_SCISSOR_OPTIMIZATION, property, "false")) {
+        mScissorOptimizationDisabled = !strcasecmp(property, "true");
+        INIT_LOGD("  Scissor optimization %s",
+                mScissorOptimizationDisabled ? "disabled" : "enabled");
+    } else {
+        INIT_LOGD("  Scissor optimization enabled");
+    }
 }
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -268,40 +270,6 @@ void OpenGLRenderer::finish() {
     }
 }
 
-void OpenGLRenderer::debugOverdraw(bool enable, bool clear) {
-    if (mCaches.debugOverdraw && getTargetFbo() == 0) {
-        if (clear) {
-            mCaches.disableScissor();
-            mCaches.stencil.clear();
-        }
-        if (enable) {
-            mCaches.stencil.enableDebugWrite();
-        } else {
-            mCaches.stencil.disable();
-        }
-    }
-}
-
-void OpenGLRenderer::renderOverdraw() {
-    if (mCaches.debugOverdraw && getTargetFbo() == 0) {
-        const Rect* clip = mTilingSnapshot->clipRect;
-
-        mCaches.enableScissor();
-        mCaches.setScissor(clip->left, mTilingSnapshot->height - clip->bottom,
-                clip->right - clip->left, clip->bottom - clip->top);
-
-        mCaches.stencil.enableDebugTest(2);
-        drawColor(0x2f0000ff, SkXfermode::kSrcOver_Mode);
-        mCaches.stencil.enableDebugTest(3);
-        drawColor(0x2f00ff00, SkXfermode::kSrcOver_Mode);
-        mCaches.stencil.enableDebugTest(4);
-        drawColor(0x3fff0000, SkXfermode::kSrcOver_Mode);
-        mCaches.stencil.enableDebugTest(4, true);
-        drawColor(0x7fff0000, SkXfermode::kSrcOver_Mode);
-        mCaches.stencil.disable();
-    }
-}
-
 void OpenGLRenderer::interrupt() {
     if (mCaches.currentProgram) {
         if (mCaches.currentProgram->isInUse()) {
@@ -439,6 +407,52 @@ status_t OpenGLRenderer::callDrawGLFunction(Functor* functor, Rect& dirty) {
 }
 
 ///////////////////////////////////////////////////////////////////////////////
+// Debug
+///////////////////////////////////////////////////////////////////////////////
+
+void OpenGLRenderer::startMark(const char* name) const {
+    mCaches.startMark(0, name);
+}
+
+void OpenGLRenderer::endMark() const {
+    mCaches.endMark();
+}
+
+void OpenGLRenderer::debugOverdraw(bool enable, bool clear) {
+    if (mCaches.debugOverdraw && getTargetFbo() == 0) {
+        if (clear) {
+            mCaches.disableScissor();
+            mCaches.stencil.clear();
+        }
+        if (enable) {
+            mCaches.stencil.enableDebugWrite();
+        } else {
+            mCaches.stencil.disable();
+        }
+    }
+}
+
+void OpenGLRenderer::renderOverdraw() {
+    if (mCaches.debugOverdraw && getTargetFbo() == 0) {
+        const Rect* clip = mTilingSnapshot->clipRect;
+
+        mCaches.enableScissor();
+        mCaches.setScissor(clip->left, mTilingSnapshot->height - clip->bottom,
+                clip->right - clip->left, clip->bottom - clip->top);
+
+        mCaches.stencil.enableDebugTest(2);
+        drawColor(0x2f0000ff, SkXfermode::kSrcOver_Mode);
+        mCaches.stencil.enableDebugTest(3);
+        drawColor(0x2f00ff00, SkXfermode::kSrcOver_Mode);
+        mCaches.stencil.enableDebugTest(4);
+        drawColor(0x3fff0000, SkXfermode::kSrcOver_Mode);
+        mCaches.stencil.enableDebugTest(4, true);
+        drawColor(0x7fff0000, SkXfermode::kSrcOver_Mode);
+        mCaches.stencil.disable();
+    }
+}
+
+///////////////////////////////////////////////////////////////////////////////
 // Layers
 ///////////////////////////////////////////////////////////////////////////////
 
@@ -1248,7 +1262,7 @@ bool OpenGLRenderer::quickReject(float left, float top, float right, float botto
 
     bool rejected = !clipRect.intersects(r);
     if (!isDeferred() && !rejected) {
-        mCaches.setScissorEnabled(!clipRect.contains(r));
+        mCaches.setScissorEnabled(mScissorOptimizationDisabled || !clipRect.contains(r));
     }
 
     return rejected;
@@ -2711,7 +2725,7 @@ status_t OpenGLRenderer::drawLayer(Layer* layer, float x, float y, SkPaint* pain
         debugLayerUpdate = mCaches.debugLayersUpdates;
     }
 
-    mCaches.setScissorEnabled(!clip.contains(transformed));
+    mCaches.setScissorEnabled(mScissorOptimizationDisabled || !clip.contains(transformed));
     mCaches.activeTexture(0);
 
     if (CC_LIKELY(!layer->region.isEmpty())) {
diff --git a/libs/hwui/OpenGLRenderer.h b/libs/hwui/OpenGLRenderer.h
index 46e66cb..c29e3fb 100644
--- a/libs/hwui/OpenGLRenderer.h
+++ b/libs/hwui/OpenGLRenderer.h
@@ -64,6 +64,12 @@ public:
     virtual ~OpenGLRenderer();
 
     /**
+     * Read externally defined properties to control the behavior
+     * of the renderer.
+     */
+    ANDROID_API void initProperties();
+
+    /**
      * Indicates whether this renderer executes drawing commands immediately.
      * If this method returns true, the drawing commands will be executed
      * later.
@@ -804,6 +810,10 @@ private:
     // Indicate whether we are drawing an opaque frame
     bool mOpaqueFrame;
 
+    // See PROPERTY_DISABLE_SCISSOR_OPTIMIZATION in
+    // Properties.h
+    bool mScissorOptimizationDisabled;
+
     friend class DisplayListRenderer;
 
 }; // class OpenGLRenderer
diff --git a/libs/hwui/Properties.h b/libs/hwui/Properties.h
index 31e60e4..1e8765b 100644
--- a/libs/hwui/Properties.h
+++ b/libs/hwui/Properties.h
@@ -67,6 +67,21 @@ enum DebugLevel {
  */
 #define PROPERTY_DEBUG_OVERDRAW "debug.hwui.show_overdraw"
 
+/**
+ * Used to enable/disable scissor optimization. The accepted values are
+ * "true" and "false". The default value is "false".
+ *
+ * When scissor optimization is enabled, OpenGLRenderer will attempt to
+ * minimize the use of scissor by selectively enabling and disabling the
+ * GL scissor test.
+ * When the optimization is disabled, OpenGLRenderer will keep the GL
+ * scissor test enabled and change the scissor rect as needed.
+ * Some GPUs (for instance the SGX 540) perform better when changing
+ * the scissor rect often than when enabling/disabling the scissor test
+ * often.
+ */
+#define PROPERTY_DISABLE_SCISSOR_OPTIMIZATION "ro.hwui.disable_scissor_opt"
+
 // These properties are defined in mega-bytes
 #define PROPERTY_TEXTURE_CACHE_SIZE "ro.hwui.texture_cache_size"
 #define PROPERTY_LAYER_CACHE_SIZE "ro.hwui.layer_cache_size"