Add an on-screen overdraw counter

The counter can be enabled by setting the system property called
debug.hwui.overdraw to the string "count". If the string is set
to "show", overdraw will be highlighted on screen instead of
printing out a simple counter.

Change-Id: I9a9c970d54bffab43138bbb7682f6c04bc2c40bd

7 files changed, 73 insertions, 7 deletions

diff --git a/libs/hwui/Caches.cpp b/libs/hwui/Caches.cpp
index c60848c..f08b5ca 100644
--- a/libs/hwui/Caches.cpp
+++ b/libs/hwui/Caches.cpp
@@ -152,7 +152,7 @@ bool Caches::initProperties() {
 
     if (property_get(PROPERTY_DEBUG_OVERDRAW, property, NULL) > 0) {
         INIT_LOGD("  Overdraw debug enabled: %s", property);
-        debugOverdraw = !strcmp(property, "true");
+        debugOverdraw = !strcmp(property, "show");
     } else {
         debugOverdraw = false;
     }
diff --git a/libs/hwui/OpenGLRenderer.cpp b/libs/hwui/OpenGLRenderer.cpp
index 025e9f8..1447eb7 100644
--- a/libs/hwui/OpenGLRenderer.cpp
+++ b/libs/hwui/OpenGLRenderer.cpp
@@ -21,7 +21,6 @@
 #include <sys/types.h>
 
 #include <SkCanvas.h>
-#include <SkPathMeasure.h>
 #include <SkTypeface.h>
 
 #include <utils/Log.h>
@@ -120,6 +119,7 @@ OpenGLRenderer::OpenGLRenderer():
 
     mFirstSnapshot = new Snapshot;
     mFrameStarted = false;
+    mCountOverdraw = false;
 
     mScissorOptimizationDisabled = false;
 }
@@ -222,6 +222,7 @@ status_t OpenGLRenderer::prepare(bool opaque) {
 
 status_t OpenGLRenderer::prepareDirty(float left, float top,
         float right, float bottom, bool opaque) {
+
     setupFrameState(left, top, right, bottom, opaque);
 
     // Layer renderers will start the frame immediately
@@ -253,7 +254,7 @@ void OpenGLRenderer::discardFramebuffer(float left, float top, float right, floa
 }
 
 status_t OpenGLRenderer::clear(float left, float top, float right, float bottom, bool opaque) {
-    if (!opaque) {
+    if (!opaque || mCountOverdraw) {
         mCaches.enableScissor();
         mCaches.setScissor(left, mSnapshot->height - bottom, right - left, bottom - top);
         glClear(GL_COLOR_BUFFER_BIT);
@@ -335,6 +336,10 @@ void OpenGLRenderer::finish() {
 #endif
     }
 
+    if (mCountOverdraw) {
+        countOverdraw();
+    }
+
     mFrameStarted = false;
 }
 
@@ -524,6 +529,21 @@ void OpenGLRenderer::renderOverdraw() {
     }
 }
 
+void OpenGLRenderer::countOverdraw() {
+    size_t count = mWidth * mHeight;
+    uint32_t* buffer = new uint32_t[count];
+    glReadPixels(0, 0, mWidth, mHeight, GL_RGBA, GL_UNSIGNED_BYTE, &buffer[0]);
+
+    size_t total = 0;
+    for (size_t i = 0; i < count; i++) {
+        total += buffer[i] & 0xff;
+    }
+
+    mOverdraw = total / float(count);
+
+    delete[] buffer;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // Layers
 ///////////////////////////////////////////////////////////////////////////////
@@ -1656,6 +1676,8 @@ void OpenGLRenderer::setupDraw(bool clear) {
     mDescription.hasDebugHighlight = !mCaches.debugOverdraw &&
             mCaches.debugStencilClip == Caches::kStencilShowHighlight &&
             mCaches.stencil.isTestEnabled();
+
+    mDescription.emulateStencil = mCountOverdraw;
 }
 
 void OpenGLRenderer::setupDrawWithTexture(bool isAlpha8) {
@@ -3546,6 +3568,19 @@ void OpenGLRenderer::drawAlpha8TextureMesh(float left, float top, float right, f
 
 void OpenGLRenderer::chooseBlending(bool blend, SkXfermode::Mode mode,
         ProgramDescription& description, bool swapSrcDst) {
+    if (mCountOverdraw) {
+        if (!mCaches.blend) glEnable(GL_BLEND);
+        if (mCaches.lastSrcMode != GL_ONE || mCaches.lastDstMode != GL_ONE) {
+            glBlendFunc(GL_ONE, GL_ONE);
+        }
+
+        mCaches.blend = true;
+        mCaches.lastSrcMode = GL_ONE;
+        mCaches.lastDstMode = GL_ONE;
+
+        return;
+    }
+
     blend = blend || mode != SkXfermode::kSrcOver_Mode;
 
     if (blend) {
diff --git a/libs/hwui/OpenGLRenderer.h b/libs/hwui/OpenGLRenderer.h
index 640c7db..df275d7 100644
--- a/libs/hwui/OpenGLRenderer.h
+++ b/libs/hwui/OpenGLRenderer.h
@@ -192,6 +192,14 @@ public:
      */
     virtual void resume();
 
+    ANDROID_API void setCountOverdrawEnabled(bool enabled) {
+        mCountOverdraw = enabled;
+    }
+
+    ANDROID_API float getOverdraw() {
+        return mCountOverdraw ? mOverdraw : 0.0f;
+    }
+
     ANDROID_API status_t invokeFunctors(Rect& dirty);
     ANDROID_API void detachFunctor(Functor* functor);
     ANDROID_API void attachFunctor(Functor* functor);
@@ -981,6 +989,7 @@ private:
 
     void debugOverdraw(bool enable, bool clear);
     void renderOverdraw();
+    void countOverdraw();
 
     /**
      * Should be invoked every time the glScissor is modified.
@@ -1072,6 +1081,12 @@ private:
     // No-ops start/endTiling when set
     bool mSuppressTiling;
 
+
+    // If true, this renderer will setup drawing to emulate
+    // an increment stencil buffer in the color buffer
+    bool mCountOverdraw;
+    float mOverdraw;
+
     // Optional name of the renderer
     String8 mName;
 
diff --git a/libs/hwui/Program.h b/libs/hwui/Program.h
index a252209..dd1aaa2 100644
--- a/libs/hwui/Program.h
+++ b/libs/hwui/Program.h
@@ -85,6 +85,7 @@ namespace uirenderer {
 #define PROGRAM_HAS_COLORS 42
 
 #define PROGRAM_HAS_DEBUG_HIGHLIGHT 43
+#define PROGRAM_EMULATE_STENCIL 44
 
 ///////////////////////////////////////////////////////////////////////////////
 // Types
@@ -163,6 +164,7 @@ struct ProgramDescription {
     float gamma;
 
     bool hasDebugHighlight;
+    bool emulateStencil;
 
     /**
      * Resets this description. All fields are reset back to the default
@@ -275,6 +277,7 @@ struct ProgramDescription {
         if (isSimpleGradient) key |= programid(0x1) << PROGRAM_IS_SIMPLE_GRADIENT;
         if (hasColors) key |= programid(0x1) << PROGRAM_HAS_COLORS;
         if (hasDebugHighlight) key |= programid(0x1) << PROGRAM_HAS_DEBUG_HIGHLIGHT;
+        if (emulateStencil) key |= programid(0x1) << PROGRAM_EMULATE_STENCIL;
         return key;
     }
 
diff --git a/libs/hwui/ProgramCache.cpp b/libs/hwui/ProgramCache.cpp
index 8eb85e5..367294c 100644
--- a/libs/hwui/ProgramCache.cpp
+++ b/libs/hwui/ProgramCache.cpp
@@ -342,6 +342,12 @@ const char* gFS_Main_ApplyColorOp[4] = {
 };
 const char* gFS_Main_DebugHighlight =
         "    gl_FragColor.rgb = vec3(0.0, gl_FragColor.a, 0.0);\n";
+const char* gFS_Main_EmulateStencil =
+        "    gl_FragColor.rgba = vec4(1.0 / 255.0, 1.0 / 255.0, 1.0 / 255.0, 1.0);\n"
+        "    return;\n"
+        "    /*\n";
+const char* gFS_Footer_EmulateStencil =
+        "    */\n";
 const char* gFS_Footer =
         "}\n\n";
 
@@ -603,7 +609,8 @@ String8 ProgramCache::generateFragmentShader(const ProgramDescription& descripti
     // Optimization for common cases
     if (!description.isAA && !blendFramebuffer && !description.hasColors &&
             description.colorOp == ProgramDescription::kColorNone &&
-            !description.isPoint && !description.hasDebugHighlight) {
+            !description.isPoint && !description.hasDebugHighlight &&
+            !description.emulateStencil) {
         bool fast = false;
 
         const bool noShader = !description.hasGradient && !description.hasBitmap;
@@ -683,6 +690,9 @@ String8 ProgramCache::generateFragmentShader(const ProgramDescription& descripti
 
     // Begin the shader
     shader.append(gFS_Main); {
+        if (description.emulateStencil) {
+            shader.append(gFS_Main_EmulateStencil);
+        }
         // Stores the result in fragColor directly
         if (description.hasTexture || description.hasExternalTexture) {
             if (description.hasAlpha8Texture) {
@@ -757,6 +767,9 @@ String8 ProgramCache::generateFragmentShader(const ProgramDescription& descripti
             shader.append(gFS_Main_DebugHighlight);
         }
     }
+    if (description.emulateStencil) {
+        shader.append(gFS_Footer_EmulateStencil);
+    }
     // End the shader
     shader.append(gFS_Footer);
 
diff --git a/libs/hwui/Properties.h b/libs/hwui/Properties.h
index 87ac845..7c68b5b 100644
--- a/libs/hwui/Properties.h
+++ b/libs/hwui/Properties.h
@@ -71,9 +71,9 @@ enum DebugLevel {
 
 /**
  * Used to enable/disable overdraw debugging. The accepted values are
- * "true" and "false". The default value is "false".
+ * "show", "count" and "false". The default value is "false".
  */
-#define PROPERTY_DEBUG_OVERDRAW "debug.hwui.show_overdraw"
+#define PROPERTY_DEBUG_OVERDRAW "debug.hwui.overdraw"
 
 /**
  * Used to enable/disable non-rectangular clipping debugging.
diff --git a/libs/hwui/thread/TaskManager.h b/libs/hwui/thread/TaskManager.h
index 477314b..f2a216f 100644
--- a/libs/hwui/thread/TaskManager.h
+++ b/libs/hwui/thread/TaskManager.h
@@ -43,7 +43,7 @@ public:
     /**
      * Returns true if this task  manager can run tasks,
      * false otherwise. This method will typically return
-     * true on a single CPU core device.
+     * false on a single CPU core device.
      */
     bool canRunTasks() const;