Banish SkShaderBase::isRasterPipelineOnly()

Keeping related heuristics in sync with actual shader capabilities is somewhat tricky,
and overall fragile.

So how about this: instead of an explicit opt-in mechanism, try to instantiate a legacy
shader context and fall back to raster pipeline on failure (null Context => implicit
opt-in for raster pipeline).  Shaders can still choose not to draw by returning both a
null Context and failing appendStages().

BUG=skia:7772
Change-Id: I2e76f51af7064853a6cb851b4c30c82eba3ee828
Reviewed-on: https://skia-review.googlesource.com/118383
Commit-Queue: Florin Malita <fmalita@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Reed <reed@google.com>

1 files changed, 19 insertions, 31 deletions

diff --git a/src/shaders/SkImageShader.cpp b/src/shaders/SkImageShader.cpp
index c3e6931baf..cdd9413ace 100644
--- a/src/shaders/SkImageShader.cpp
+++ b/src/shaders/SkImageShader.cpp
@@ -69,14 +69,8 @@ bool SkImageShader::isOpaque() const {
     return fImage->isOpaque() && fTileModeX != kDecal_TileMode && fTileModeY != kDecal_TileMode;
 }
 
-static bool legacy_shader_can_handle(const SkMatrix& a, const SkMatrix& b) {
-    SkMatrix m = SkMatrix::Concat(a, b);
-    if (!m.isScaleTranslate()) {
-        return false;
-    }
-
-    SkMatrix inv;
-    if (!m.invert(&inv)) {
+static bool legacy_shader_can_handle(const SkMatrix& inv) {
+    if (!inv.isScaleTranslate()) {
         return false;
     }
 
@@ -97,37 +91,31 @@ static bool legacy_shader_can_handle(const SkMatrix& a, const SkMatrix& b) {
     return true;
 }
 
-bool SkImageShader::IsRasterPipelineOnly(const SkMatrix& ctm, SkColorType ct, SkAlphaType at,
-                                         SkShader::TileMode tx, SkShader::TileMode ty,
-                                         const SkMatrix& localM) {
-    if (ct != kN32_SkColorType) {
-        return true;
+SkShaderBase::Context* SkImageShader::onMakeContext(const ContextRec& rec,
+                                                    SkArenaAlloc* alloc) const {
+    const auto info = as_IB(fImage)->onImageInfo();
+
+    if (info.colorType() != kN32_SkColorType) {
+        return nullptr;
     }
-    if (at == kUnpremul_SkAlphaType) {
-        return true;
+    if (info.alphaType() == kUnpremul_SkAlphaType) {
+        return nullptr;
     }
 #ifndef SK_SUPPORT_LEGACY_TILED_BITMAPS
-    if (tx != ty) {
-        return true;
+    if (fTileModeX != fTileModeY) {
+        return nullptr;
     }
 #endif
-    if (tx == kDecal_TileMode || ty == kDecal_TileMode) {
-        return true;
-    }
-    if (!legacy_shader_can_handle(ctm, localM)) {
-        return true;
+    if (fTileModeX == kDecal_TileMode || fTileModeY == kDecal_TileMode) {
+        return nullptr;
     }
-    return false;
-}
 
-bool SkImageShader::onIsRasterPipelineOnly(const SkMatrix& ctm) const {
-    SkBitmapProvider provider(fImage.get(), nullptr);
-    return IsRasterPipelineOnly(ctm, provider.info().colorType(), provider.info().alphaType(),
-                                fTileModeX, fTileModeY, this->getLocalMatrix());
-}
+    SkMatrix inv;
+    if (!this->computeTotalInverse(*rec.fMatrix, rec.fLocalMatrix, &inv) ||
+        !legacy_shader_can_handle(inv)) {
+        return nullptr;
+    }
 
-SkShaderBase::Context* SkImageShader::onMakeContext(const ContextRec& rec,
-                                                    SkArenaAlloc* alloc) const {
     return SkBitmapProcLegacyShader::MakeContext(*this, fTileModeX, fTileModeY,
                                                  SkBitmapProvider(fImage.get(), rec.fDstColorSpace),
                                                  rec, alloc);