Sanitize display list properties

The comparisons used in the various properties setters could fail badly
in some specific conditions. The scale properties in particular did not
use the same comparisons.

This change also clamps alpha to the 0..1 range which avoids overflow
issues with lowp registers in GLSL computations.

Change-Id: I3e73b584e907a14e2c33d0865ca0d2d4d5bff31d

Author: Romain Guy

libs/hwui/DisplayListRenderer.h

@@ -170,9 +170,10 @@ class DisplayList {
     }
 
     void setAlpha(float alpha) {
+        alpha = fminf(1.0f, fmaxf(0.0f, alpha));
         if (alpha != mAlpha) {
             mAlpha = alpha;
-            mMultipliedAlpha = (int)(255 * alpha);
+            mMultipliedAlpha = (int) (255 * alpha);
         }
     }
 
@@ -184,7 +185,7 @@ class DisplayList {
         if (translationX != mTranslationX) {
             mTranslationX = translationX;
             mMatrixDirty = true;
-            if (ALMOST_EQUAL(mTranslationX, 0) && ALMOST_EQUAL(mTranslationY, 0)) {
+            if (mTranslationX == 0.0f && mTranslationY == 0.0f) {
                 mMatrixFlags &= ~TRANSLATION;
             } else {
                 mMatrixFlags |= TRANSLATION;
@@ -196,7 +197,7 @@ class DisplayList {
         if (translationY != mTranslationY) {
             mTranslationY = translationY;
             mMatrixDirty = true;
-            if (ALMOST_EQUAL(mTranslationX, 0) && ALMOST_EQUAL(mTranslationY, 0)) {
+            if (mTranslationX == 0.0f && mTranslationY == 0.0f) {
                 mMatrixFlags &= ~TRANSLATION;
             } else {
                 mMatrixFlags |= TRANSLATION;
@@ -208,7 +209,7 @@ class DisplayList {
         if (rotation != mRotation) {
             mRotation = rotation;
             mMatrixDirty = true;
-            if (ALMOST_EQUAL(mRotation, 0)) {
+            if (mRotation == 0.0f) {
                 mMatrixFlags &= ~ROTATION;
             } else {
                 mMatrixFlags |= ROTATION;
@@ -220,7 +221,7 @@ class DisplayList {
         if (rotationX != mRotationX) {
             mRotationX = rotationX;
             mMatrixDirty = true;
-            if (ALMOST_EQUAL(mRotationX, 0) && ALMOST_EQUAL(mRotationY, 0)) {
+            if (mRotationX == 0.0f && mRotationY == 0.0f) {
                 mMatrixFlags &= ~ROTATION_3D;
             } else {
                 mMatrixFlags |= ROTATION_3D;
@@ -232,7 +233,7 @@ class DisplayList {
         if (rotationY != mRotationY) {
             mRotationY = rotationY;
             mMatrixDirty = true;
-            if (ALMOST_EQUAL(mRotationX, 0) && ALMOST_EQUAL(mRotationY, 0)) {
+            if (mRotationX == 0.0f && mRotationY == 0.0f) {
                 mMatrixFlags &= ~ROTATION_3D;
             } else {
                 mMatrixFlags |= ROTATION_3D;
@@ -244,7 +245,7 @@ class DisplayList {
         if (scaleX != mScaleX) {
             mScaleX = scaleX;
             mMatrixDirty = true;
-            if (ALMOST_EQUAL(mScaleX, 1) && ALMOST_EQUAL(mScaleY, 1)) {
+            if (mScaleX == 1.0f && mScaleY == 1.0f) {
                 mMatrixFlags &= ~SCALE;
             } else {
                 mMatrixFlags |= SCALE;
@@ -267,7 +268,7 @@ class DisplayList {
     void setPivotX(float pivotX) {
         mPivotX = pivotX;
         mMatrixDirty = true;
-        if (ALMOST_EQUAL(mPivotX, 0) && ALMOST_EQUAL(mPivotY, 0)) {
+        if (mPivotX == 0.0f && mPivotY == 0.0f) {
             mMatrixFlags &= ~PIVOT;
         } else {
             mMatrixFlags |= PIVOT;
@@ -278,7 +279,7 @@ class DisplayList {
     void setPivotY(float pivotY) {
         mPivotY = pivotY;
         mMatrixDirty = true;
-        if (ALMOST_EQUAL(mPivotX, 0) && ALMOST_EQUAL(mPivotY, 0)) {
+        if (mPivotX == 0.0f && mPivotY == 0.0f) {
             mMatrixFlags &= ~PIVOT;
         } else {
             mMatrixFlags |= PIVOT;

libs/hwui/OpenGLRenderer.h

@@ -90,7 +90,7 @@ class OpenGLRenderer {
     virtual int saveLayerAlpha(float left, float top, float right, float bottom,
             int alpha, int flags);
 
-    virtual void setAlpha(float alpha) {
+    void setAlpha(float alpha) {
         mSnapshot->alpha = alpha;
     }
 

libs/hwui/utils/Compare.h

@@ -19,10 +19,6 @@
 
 #include <cmath>
 
-#define EPSILON 0.00001f
-
-#define ALMOST_EQUAL(u, v) (fabs((u) - (v)) < EPSILON)
-
 /**
  * Compare floats.
  */