implement drawAtlas natively on gpu-device

BUG=skia:

Review URL: https://codereview.chromium.org/1216433002

samplecode/SampleAtlas.cpp

@@ -68,11 +68,13 @@ class DrawAtlasDrawable : public SkDrawable {
                 fVelocity.fX = -fVelocity.fX;
             }
             if (fCenter.fY > bounds.bottom()) {
-                SkASSERT(fVelocity.fY > 0);
-                fVelocity.fY = -fVelocity.fY;
+                if (fVelocity.fY > 0) {
+                    fVelocity.fY = -fVelocity.fY;
+                }
             } else if (fCenter.fY < bounds.top()) {
-                SkASSERT(fVelocity.fY < 0);
-                fVelocity.fY = -fVelocity.fY;
+                if (fVelocity.fY < 0) {
+                    fVelocity.fY = -fVelocity.fY;
+                }
             }
 
             fScale += fDScale;

src/core/SkMatrix.cpp

@@ -1844,11 +1844,26 @@ bool SkDecomposeUpper2x2(const SkMatrix& matrix,
 //////////////////////////////////////////////////////////////////////////////////////////////////
 
 void SkRSXform::toQuad(SkScalar width, SkScalar height, SkPoint quad[4]) const {
+#if 0
+    // This is the slow way, but it documents what we're doing
     quad[0].set(0, 0);
     quad[1].set(width, 0);
     quad[2].set(width, height);
     quad[3].set(0, height);
     SkMatrix m;
     m.setRSXform(*this).mapPoints(quad, quad, 4);
+#else
+    const SkScalar m00 = fSCos;
+    const SkScalar m01 = -fSSin;
+    const SkScalar m02 = fTx;
+    const SkScalar m10 = -m01;
+    const SkScalar m11 = m00;
+    const SkScalar m12 = fTy;
+
+    quad[0].set(m02, m12);
+    quad[1].set(m00 * width + m02, m10 * width + m12);
+    quad[2].set(m00 * width + m01 * height + m02, m10 * width + m11 * height + m12);
+    quad[3].set(m01 * height + m02, m11 * height + m12);
+#endif
 }
 

src/gpu/SkGpuDevice.cpp

@@ -1639,6 +1639,50 @@ void SkGpuDevice::drawVertices(const SkDraw& draw, SkCanvas::VertexMode vmode,
 
 ///////////////////////////////////////////////////////////////////////////////
 
+static void append_quad_indices(uint16_t indices[], int quadIndex) {
+    int i = quadIndex * 4;
+    indices[0] = i + 0; indices[1] = i + 1; indices[2] = i + 2;
+    indices[3] = i + 2; indices[4] = i + 3; indices[5] = i + 0;
+}
+
+void SkGpuDevice::drawAtlas(const SkDraw& d, const SkImage* atlas, const SkRSXform xform[],
+                            const SkRect texRect[], const SkColor colors[], int count,
+                            SkXfermode::Mode mode, const SkPaint& paint) {
+    if (paint.isAntiAlias()) {
+        this->INHERITED::drawAtlas(d, atlas, xform, texRect, colors, count, mode, paint);
+        return;
+    }
+
+    SkPaint p(paint);
+    p.setShader(atlas->newShader(SkShader::kClamp_TileMode, SkShader::kClamp_TileMode))->unref();
+
+    const int vertCount = count * 4;
+    const int indexCount = count * 6;
+    SkAutoTMalloc<SkPoint> vertStorage(vertCount * 2);
+    SkPoint* verts = vertStorage.get();
+    SkPoint* texs = verts + vertCount;
+    SkAutoTMalloc<uint16_t> indexStorage(indexCount);
+    uint16_t* indices = indexStorage.get();
+    SkAutoTUnref<SkXfermode> xfer(SkXfermode::Create(mode));
+
+    for (int i = 0; i < count; ++i) {
+        xform[i].toQuad(texRect[i].width(), texRect[i].height(), verts);
+        texRect[i].toQuad(texs);
+        append_quad_indices(indices, i);
+        verts += 4;
+        texs += 4;
+        indices += 6;
+    }
+
+    verts = vertStorage.get();
+    texs = verts + vertCount;
+    indices = indexStorage.get();
+    this->drawVertices(d, SkCanvas::kTriangles_VertexMode, vertCount, verts, texs, colors, xfer,
+                       indices, indexCount, p);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
 void SkGpuDevice::drawText(const SkDraw& draw, const void* text,
                            size_t byteLength, SkScalar x, SkScalar y,
                            const SkPaint& paint) {

src/gpu/SkGpuDevice.h

@@ -111,6 +111,8 @@ public:
                               const SkColor colors[], SkXfermode* xmode,
                               const uint16_t indices[], int indexCount,
                               const SkPaint&) override;
+    void drawAtlas(const SkDraw&, const SkImage* atlas, const SkRSXform[], const SkRect[],
+                       const SkColor[], int count, SkXfermode::Mode, const SkPaint&) override;
     virtual void drawDevice(const SkDraw&, SkBaseDevice*, int x, int y,
                             const SkPaint&) override;
     void drawImage(const SkDraw&, const SkImage*, SkScalar x, SkScalar y, const SkPaint&) override;