quick-rejects based on xfermode, using SkPaint::nothingToDraw()

git-svn-id: http://skia.googlecode.com/svn/trunk@2402 2bbb7eff-a529-9590-31e7-b0007b416f81

4 files changed, 86 insertions, 23 deletions

diff --git a/include/core/SkPaint.h b/include/core/SkPaint.h
index 7f3f0be223..4785baa6f1 100644
--- a/include/core/SkPaint.h
+++ b/include/core/SkPaint.h
@@ -865,6 +865,10 @@ private:
     const SkRect& computeStrokeFastBounds(const SkRect& orig,
                                           SkRect* storage) const;
 
+    // returns true if the paint's settings (e.g. xfermode + alpha) resolve to
+    // mean that we need not draw at all (e.g. SrcOver + 0-alpha)
+    bool nothingToDraw() const;
+
     enum {
         kCanonicalTextSizeForPaths = 64
     };
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index 3ee29ce67e..df717f0dc7 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -53,6 +53,9 @@ static SkCanvas::EdgeType paint2EdgeType(const SkPaint* paint) {
             SkCanvas::kAA_EdgeType : SkCanvas::kBW_EdgeType;
 }
 
+#define CHECK_NOTHING_TO_DRAW(paint)    \
+    do { if ((paint).nothingToDraw()) return; } while (0)
+
 ///////////////////////////////////////////////////////////////////////////////
 
 /*  This is the record we keep for each SkDevice that the user installs.
@@ -822,6 +825,10 @@ void SkCanvas::internalDrawBitmap(const SkBitmap& bitmap, const SkIRect* srcRect
 
 void SkCanvas::drawDevice(SkDevice* device, int x, int y,
                           const SkPaint* paint) {
+    if (paint) {
+        CHECK_NOTHING_TO_DRAW(*paint);
+    }
+
     SkPaint tmp;
     if (NULL == paint) {
         tmp.setDither(true);
@@ -1206,6 +1213,8 @@ void SkCanvas::clear(SkColor color) {
 }
 
 void SkCanvas::drawPaint(const SkPaint& paint) {
+    CHECK_NOTHING_TO_DRAW(paint);
+
     LOOPER_BEGIN(paint, SkDrawFilter::kPaint_Type)
 
     while (iter.next()) {
@@ -1217,6 +1226,7 @@ void SkCanvas::drawPaint(const SkPaint& paint) {
 
 void SkCanvas::drawPoints(PointMode mode, size_t count, const SkPoint pts[],
                           const SkPaint& paint) {
+    CHECK_NOTHING_TO_DRAW(paint);
     if ((long)count <= 0) {
         return;
     }
@@ -1233,6 +1243,8 @@ void SkCanvas::drawPoints(PointMode mode, size_t count, const SkPoint pts[],
 }
 
 void SkCanvas::drawRect(const SkRect& r, const SkPaint& paint) {
+    CHECK_NOTHING_TO_DRAW(paint);
+
     if (paint.canComputeFastBounds()) {
         SkRect storage;
         if (this->quickReject(paint.computeFastBounds(r, &storage),
@@ -1251,6 +1263,8 @@ void SkCanvas::drawRect(const SkRect& r, const SkPaint& paint) {
 }
 
 void SkCanvas::drawPath(const SkPath& path, const SkPaint& paint) {
+    CHECK_NOTHING_TO_DRAW(paint);
+
     if (paint.canComputeFastBounds()) {
         SkRect storage;
         const SkRect& bounds = path.getBounds();
@@ -1273,6 +1287,10 @@ void SkCanvas::drawBitmap(const SkBitmap& bitmap, SkScalar x, SkScalar y,
                           const SkPaint* paint) {
     SkDEBUGCODE(bitmap.validate();)
 
+    if (paint) {
+        CHECK_NOTHING_TO_DRAW(*paint);
+    }
+
     if (NULL == paint || (paint->getMaskFilter() == NULL)) {
         SkRect fastBounds;
         fastBounds.set(x, y,
@@ -1338,11 +1356,17 @@ void SkCanvas::internalDrawBitmapRect(const SkBitmap& bitmap, const SkIRect* src
 void SkCanvas::drawBitmapRect(const SkBitmap& bitmap, const SkIRect* src,
                               const SkRect& dst, const SkPaint* paint) {
     SkDEBUGCODE(bitmap.validate();)
+    if (paint) {
+        CHECK_NOTHING_TO_DRAW(*paint);
+    }
     this->internalDrawBitmapRect(bitmap, src, dst, paint);
 }
 
 void SkCanvas::drawBitmapMatrix(const SkBitmap& bitmap, const SkMatrix& matrix,
                                 const SkPaint* paint) {
+    if (paint) {
+        CHECK_NOTHING_TO_DRAW(*paint);
+    }
     SkDEBUGCODE(bitmap.validate();)
     this->internalDrawBitmap(bitmap, NULL, matrix, paint);
 }
@@ -1413,6 +1437,9 @@ void SkCanvas::internalDrawBitmapNine(const SkBitmap& bitmap,
 
 void SkCanvas::drawBitmapNine(const SkBitmap& bitmap, const SkIRect& center,
                               const SkRect& dst, const SkPaint* paint) {
+    if (paint) {
+        CHECK_NOTHING_TO_DRAW(*paint);
+    }
     SkDEBUGCODE(bitmap.validate();)
 
     // Need a device entry-point, so gpu can use a mesh
@@ -1421,6 +1448,9 @@ void SkCanvas::drawBitmapNine(const SkBitmap& bitmap, const SkIRect& center,
 
 void SkCanvas::drawSprite(const SkBitmap& bitmap, int x, int y,
                           const SkPaint* paint) {
+    if (paint) {
+        CHECK_NOTHING_TO_DRAW(*paint);
+    }
     SkDEBUGCODE(bitmap.validate();)
 
     if (reject_bitmap(bitmap)) {
@@ -1536,6 +1566,8 @@ void SkCanvas::DrawTextDecorations(const SkDraw& draw, const SkPaint& paint,
 
 void SkCanvas::drawText(const void* text, size_t byteLength,
                         SkScalar x, SkScalar y, const SkPaint& paint) {
+    CHECK_NOTHING_TO_DRAW(paint);
+
     LOOPER_BEGIN(paint, SkDrawFilter::kText_Type)
 
     while (iter.next()) {
@@ -1550,6 +1582,8 @@ void SkCanvas::drawText(const void* text, size_t byteLength,
 
 void SkCanvas::drawPosText(const void* text, size_t byteLength,
                            const SkPoint pos[], const SkPaint& paint) {
+    CHECK_NOTHING_TO_DRAW(paint);
+
     LOOPER_BEGIN(paint, SkDrawFilter::kText_Type)
 
     while (iter.next()) {
@@ -1564,6 +1598,8 @@ void SkCanvas::drawPosText(const void* text, size_t byteLength,
 void SkCanvas::drawPosTextH(const void* text, size_t byteLength,
                             const SkScalar xpos[], SkScalar constY,
                             const SkPaint& paint) {
+    CHECK_NOTHING_TO_DRAW(paint);
+
     LOOPER_BEGIN(paint, SkDrawFilter::kText_Type)
 
     while (iter.next()) {
@@ -1578,6 +1614,8 @@ void SkCanvas::drawPosTextH(const void* text, size_t byteLength,
 void SkCanvas::drawTextOnPath(const void* text, size_t byteLength,
                               const SkPath& path, const SkMatrix* matrix,
                               const SkPaint& paint) {
+    CHECK_NOTHING_TO_DRAW(paint);
+
     LOOPER_BEGIN(paint, SkDrawFilter::kText_Type)
 
     while (iter.next()) {
@@ -1592,6 +1630,7 @@ void SkCanvas::drawTextOnPath(const void* text, size_t byteLength,
 void SkCanvas::drawPosTextOnPath(const void* text, size_t byteLength,
                                  const SkPoint pos[], const SkPaint& paint,
                                  const SkPath& path, const SkMatrix* matrix) {
+    CHECK_NOTHING_TO_DRAW(paint);
 
     LOOPER_BEGIN(paint, SkDrawFilter::kText_Type)
 
@@ -1609,6 +1648,8 @@ void SkCanvas::drawVertices(VertexMode vmode, int vertexCount,
                             const SkColor colors[], SkXfermode* xmode,
                             const uint16_t indices[], int indexCount,
                             const SkPaint& paint) {
+    CHECK_NOTHING_TO_DRAW(paint);
+
     LOOPER_BEGIN(paint, SkDrawFilter::kPath_Type)
 
     while (iter.next()) {
@@ -1686,6 +1727,8 @@ void SkCanvas::drawRectCoords(SkScalar left, SkScalar top,
 
 void SkCanvas::drawCircle(SkScalar cx, SkScalar cy, SkScalar radius,
                           const SkPaint& paint) {
+    CHECK_NOTHING_TO_DRAW(paint);
+
     if (radius < 0) {
         radius = 0;
     }
@@ -1708,6 +1751,8 @@ void SkCanvas::drawCircle(SkScalar cx, SkScalar cy, SkScalar radius,
 
 void SkCanvas::drawRoundRect(const SkRect& r, SkScalar rx, SkScalar ry,
                              const SkPaint& paint) {
+    CHECK_NOTHING_TO_DRAW(paint);
+
     if (rx > 0 && ry > 0) {
         if (paint.canComputeFastBounds()) {
             SkRect storage;
@@ -1726,6 +1771,8 @@ void SkCanvas::drawRoundRect(const SkRect& r, SkScalar rx, SkScalar ry,
 }
 
 void SkCanvas::drawOval(const SkRect& oval, const SkPaint& paint) {
+    CHECK_NOTHING_TO_DRAW(paint);
+
     if (paint.canComputeFastBounds()) {
         SkRect storage;
         if (this->quickReject(paint.computeFastBounds(oval, &storage),
@@ -1742,6 +1789,8 @@ void SkCanvas::drawOval(const SkRect& oval, const SkPaint& paint) {
 void SkCanvas::drawArc(const SkRect& oval, SkScalar startAngle,
                        SkScalar sweepAngle, bool useCenter,
                        const SkPaint& paint) {
+    CHECK_NOTHING_TO_DRAW(paint);
+
     if (SkScalarAbs(sweepAngle) >= SkIntToScalar(360)) {
         this->drawOval(oval, paint);
     } else {
diff --git a/src/core/SkDraw.cpp b/src/core/SkDraw.cpp
index e40c587843..1bfac70283 100644
--- a/src/core/SkDraw.cpp
+++ b/src/core/SkDraw.cpp
@@ -527,8 +527,7 @@ void SkDraw::drawPoints(SkCanvas::PointMode mode, size_t count,
     SkDEBUGCODE(this->validate();)
 
      // nothing to draw
-    if (fClip->isEmpty() ||
-        (paint.getAlpha() == 0 && paint.getXfermode() == NULL)) {
+    if (fClip->isEmpty()) {
         return;
     }
 
@@ -697,8 +696,7 @@ void SkDraw::drawRect(const SkRect& rect, const SkPaint& paint) const {
     SkDEBUGCODE(this->validate();)
 
     // nothing to draw
-    if (fClip->isEmpty() ||
-        (paint.getAlpha() == 0 && paint.getXfermode() == NULL)) {
+    if (fClip->isEmpty()) {
         return;
     }
 
@@ -881,8 +879,7 @@ void SkDraw::drawPath(const SkPath& origSrcPath, const SkPaint& origPaint,
     SkDEBUGCODE(this->validate();)
 
     // nothing to draw
-    if (fClip->isEmpty() ||
-        (origPaint.getAlpha() == 0 && origPaint.getXfermode() == NULL)) {
+    if (fClip->isEmpty()) {
         return;
     }
 
@@ -1098,8 +1095,7 @@ void SkDraw::drawBitmap(const SkBitmap& bitmap, const SkMatrix& prematrix,
     // nothing to draw
     if (fClip->isEmpty() ||
             bitmap.width() == 0 || bitmap.height() == 0 ||
-            bitmap.getConfig() == SkBitmap::kNo_Config ||
-            (origPaint.getAlpha() == 0 && origPaint.getXfermode() == NULL)) {
+            bitmap.getConfig() == SkBitmap::kNo_Config) {
         return;
     }
 
@@ -1193,8 +1189,7 @@ void SkDraw::drawSprite(const SkBitmap& bitmap, int x, int y,
     // nothing to draw
     if (fClip->isEmpty() ||
             bitmap.width() == 0 || bitmap.height() == 0 ||
-            bitmap.getConfig() == SkBitmap::kNo_Config ||
-            (origPaint.getAlpha() == 0 && origPaint.getXfermode() == NULL)) {
+            bitmap.getConfig() == SkBitmap::kNo_Config) {
         return;
     }
 
@@ -1475,9 +1470,7 @@ void SkDraw::drawText(const char text[], size_t byteLength,
     SkDEBUGCODE(this->validate();)
 
     // nothing to draw
-    if (text == NULL || byteLength == 0 ||
-        fClip->isEmpty() ||
-        (paint.getAlpha() == 0 && paint.getXfermode() == NULL)) {
+    if (text == NULL || byteLength == 0 || fClip->isEmpty()) {
         return;
     }
 
@@ -1667,9 +1660,7 @@ void SkDraw::drawPosText(const char text[], size_t byteLength,
     SkDEBUGCODE(this->validate();)
 
     // nothing to draw
-    if (text == NULL || byteLength == 0 ||
-        fClip->isEmpty() ||
-        (paint.getAlpha() == 0 && paint.getXfermode() == NULL)) {
+    if (text == NULL || byteLength == 0 || fClip->isEmpty()) {
         return;
     }
 
@@ -1875,9 +1866,7 @@ void SkDraw::drawTextOnPath(const char text[], size_t byteLength,
     SkASSERT(byteLength == 0 || text != NULL);
 
     // nothing to draw
-    if (text == NULL || byteLength == 0 ||
-        fClip->isEmpty() ||
-        (paint.getAlpha() == 0 && paint.getXfermode() == NULL)) {
+    if (text == NULL || byteLength == 0 || fClip->isEmpty()) {
         return;
     }
 
@@ -1923,8 +1912,7 @@ void SkDraw::drawPosTextOnPath(const char text[], size_t byteLength,
                                const SkPoint pos[], const SkPaint& paint,
                                const SkPath& path, const SkMatrix* matrix) const {
     // nothing to draw
-    if (text == NULL || byteLength == 0 || fClip->isEmpty() ||
-        (paint.getAlpha() == 0 && paint.getXfermode() == NULL)) {
+    if (text == NULL || byteLength == 0 || fClip->isEmpty()) {
         return;
     }
 
@@ -2222,8 +2210,7 @@ void SkDraw::drawVertices(SkCanvas::VertexMode vmode, int count,
     SkASSERT(0 == count || NULL != vertices);
 
     // abort early if there is nothing to draw
-    if (count < 3 || (indices && indexCount < 3) || fClip->isEmpty() ||
-            (paint.getAlpha() == 0 && paint.getXfermode() == NULL)) {
+    if (count < 3 || (indices && indexCount < 3) || fClip->isEmpty()) {
         return;
     }
 
diff --git a/src/core/SkPaint.cpp b/src/core/SkPaint.cpp
index b2f5d8e0e1..522d9d2003 100644
--- a/src/core/SkPaint.cpp
+++ b/src/core/SkPaint.cpp
@@ -1833,3 +1833,26 @@ const SkPath* SkTextToPathIter::next(SkScalar* xpos) {
     }
     return NULL;
 }
+
+///////////////////////////////////////////////////////////////////////////////
+
+bool SkPaint::nothingToDraw() const {
+    SkXfermode::Mode mode;
+    if (SkXfermode::AsMode(fXfermode, &mode)) {
+        switch (mode) {
+            case SkXfermode::kSrcOver_Mode:
+            case SkXfermode::kSrcATop_Mode:
+            case SkXfermode::kDstOut_Mode:
+            case SkXfermode::kDstOver_Mode:
+            case SkXfermode::kPlus_Mode:
+                return 0 == this->getAlpha();
+            case SkXfermode::kDst_Mode:
+                return true;
+            default:
+                break;
+        }
+    }
+    return false;
+}
+
+