Initial picture shader implementation

src/core/SkPictureShader.cpp

Index: src/core/SkPictureShader.cpp
diff --git a/src/core/SkPictureShader.cpp b/src/core/SkPictureShader.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..15df3a37a587f253f0634558517a09e141bce63a
--- /dev/null
+++ b/src/core/SkPictureShader.cpp
@@ -0,0 +1,185 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkPictureShader.h"
+
+#include "SkBitmap.h"
+#include "SkBitmapProcShader.h"
+#include "SkCanvas.h"
+#include "SkMatrixUtils.h"
+#include "SkPicture.h"
+#include "SkReadBuffer.h"
+
+#if SK_SUPPORT_GPU
+#include "GrContext.h"
+#endif
+
+SkPictureShader::SkPictureShader(SkPicture* picture, TileMode tmx, TileMode tmy)
+    : fPicture(picture)
+    , fTmx(tmx)
+    , fTmy(tmy) {
+    SkSafeRef(fPicture);
+}
+
+SkPictureShader::SkPictureShader(SkReadBuffer& buffer)
+        : INHERITED(buffer) {
+    fTmx = static_cast<SkShader::TileMode>(buffer.read32());
+    fTmy = static_cast<SkShader::TileMode>(buffer.read32());
+    if (buffer.readBool()) {
+        fPicture = SkPicture::CreateFromBuffer(buffer);
+    } else {
+        fPicture = NULL;
+    }
+}
+
+SkPictureShader::~SkPictureShader() {
+    SkSafeUnref(fPicture);
+}
+
+SkPictureShader* SkPictureShader::Create(SkPicture* picture, TileMode tmx, TileMode tmy) {
+    return SkNEW_ARGS(SkPictureShader, (picture, tmx, tmy));
+}
+
+void SkPictureShader::flatten(SkWriteBuffer& buffer) const {
+    this->INHERITED::flatten(buffer);
+
+    buffer.write32(fTmx);
+    buffer.write32(fTmy);
+    buffer.writeBool(NULL != fPicture);
+    if (fPicture) {
+        fPicture->flatten(buffer);
+    }
+}
+
+bool SkPictureShader::buildBitmapShader(const SkMatrix& matrix) const {
+    if (!fPicture || (0 == fPicture->width() && 0 == fPicture->height())) {

[scroggo, 2014/04/11 15:23:15]

It appears that if the picture is NULL or it has zero width/height, this shader
never does anything. What if the factory just returned NULL in that case? Then
we can skip these checks (possibly replacing them with asserts).

[f(malita), 2014/04/11 16:05:18]

Good point. After making the constructor private, there's no need to keep these
checks around.

+        return false;
+    }
+
+    SkMatrix m;
+    if (this->hasLocalMatrix()) {
+        m.setConcat(matrix, this->getLocalMatrix());
+    } else {
+        m = matrix;
+    }
+
+    // Use a rotation-invariant scale
+    SkPoint scale;
+    if (!SkDecomposeUpper2x2(m, NULL, &scale, NULL)) {
+        // Decomposition failed, use an approximation.
+        scale.set(SkScalarSqrt(m.getScaleX() * m.getScaleX() + m.getSkewX() * m.getSkewX()),
+                  SkScalarSqrt(m.getScaleY() * m.getScaleY() + m.getSkewY() * m.getSkewY()));
+    }
+    SkSize scaledSize = SkSize::Make(scale.x() * fPicture->width(), scale.y() * fPicture->height());
+
+    SkISize tileSize = scaledSize.toRound();
+    if (tileSize.isEmpty()) {
+        return false;
+    }
+
+    // The actual scale, compensating for rounding.
+    SkSize tileScale = SkSize::Make(SkIntToScalar(tileSize.width()) / fPicture->width(),
+                                    SkIntToScalar(tileSize.height()) / fPicture->height());
+
+    if (!fCachedShader || tileScale != fCachedTileScale) {
+        SkBitmap bm;
+        if (!bm.allocN32Pixels(tileSize.width(), tileSize.height())) {
+            return false;
+        }
+        bm.eraseColor(SK_ColorTRANSPARENT);
+
+        SkCanvas canvas(bm);
+        canvas.scale(tileScale.width(), tileScale.height());
+        canvas.drawPicture(*fPicture);
+
+        fCachedShader.reset(CreateBitmapShader(bm, fTmx, fTmy));
+        fCachedTileScale = tileScale;
+    }
+
+    SkMatrix shaderMatrix = this->getLocalMatrix();
+    shaderMatrix.preScale(1 / tileScale.width(), 1 / tileScale.height());
+    fCachedShader->setLocalMatrix(shaderMatrix);
+
+    return true;
+}
+
+bool SkPictureShader::setContext(const SkBitmap& device,
+                                 const SkPaint& paint,
+                                 const SkMatrix& matrix) {
+    if (!this->buildBitmapShader(matrix)) {
+        return false;
+    }
+
+    if (!this->INHERITED::setContext(device, paint, matrix)) {
+        return false;
+    }
+
+    SkASSERT(fCachedShader);
+    if (!fCachedShader->setContext(device, paint, matrix)) {
+        this->INHERITED::endContext();
+        return false;
+    }
+
+    return true;
+}
+
+void SkPictureShader::endContext() {
+    SkASSERT(fCachedShader);
+    fCachedShader->endContext();
+
+    this->INHERITED::endContext();
+}
+
+uint32_t SkPictureShader::getFlags() {
+    if (NULL != fCachedShader) {
+        return fCachedShader->getFlags();
+    }
+    return 0;
+}
+
+SkShader::ShadeProc SkPictureShader::asAShadeProc(void** ctx) {
+    if (fCachedShader) {
+        return fCachedShader->asAShadeProc(ctx);
+    }
+    return NULL;
+}
+
+void SkPictureShader::shadeSpan(int x, int y, SkPMColor dstC[], int count) {
+    SkASSERT(fCachedShader);
+    fCachedShader->shadeSpan(x, y, dstC, count);
+}
+
+void SkPictureShader::shadeSpan16(int x, int y, uint16_t dstC[], int count) {
+    SkASSERT(fCachedShader);
+    fCachedShader->shadeSpan16(x, y, dstC, count);
+}
+
+#ifndef SK_IGNORE_TO_STRING
+void SkPictureShader::toString(SkString* str) const {
+    static const char* gTileModeName[SkShader::kTileModeCount] = {
+        "clamp", "repeat", "mirror"
+    };
+
+    str->appendf("PictureShader: [%d:%d] ",
+                 fPicture ? fPicture->width() : 0,
+                 fPicture ? fPicture->height() : 0);
+
+    str->appendf("(%s, %s)", gTileModeName[fTmx], gTileModeName[fTmy]);
+
+    this->INHERITED::toString(str);
+}
+#endif
+
+#if SK_SUPPORT_GPU
+GrEffectRef* SkPictureShader::asNewEffect(GrContext* context, const SkPaint& paint) const {
+    if (!this->buildBitmapShader(context->getMatrix())) {
+        return NULL;
+    }
+    SkASSERT(fCachedShader);
+    return fCachedShader->asNewEffect(context, paint);
+}
+#endif