SkRasterPipeline shader adapter

(lifted from https://skia-review.googlesource.com/c/7088/)

R=mtklein@google.com,herb@google.com,reed@google.com

CQ_INCLUDE_TRYBOTS=skia.primary:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD

Change-Id: Idddb84069423c5fc535bea0a65a5b21a4d07084d
Reviewed-on: https://skia-review.googlesource.com/7615
Commit-Queue: Florin Malita <fmalita@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Reed <reed@google.com>

4 files changed, 40 insertions, 4 deletions

diff --git a/include/core/SkShader.h b/include/core/SkShader.h
index a885f0b982..30a10dcc9f 100644
--- a/include/core/SkShader.h
+++ b/include/core/SkShader.h
@@ -503,9 +503,7 @@ protected:
 
     virtual bool onAppendStages(SkRasterPipeline*, SkColorSpace*, SkArenaAlloc*,
                                 const SkMatrix&, const SkPaint&,
-                                const SkMatrix* /*local matrix*/) const {
-        return false;
-    }
+                                const SkMatrix* /*local matrix*/) const;
 
 private:
     // This is essentially const, but not officially so it can be modified in
diff --git a/src/core/SkRasterPipeline.h b/src/core/SkRasterPipeline.h
index 5143d523e4..2dd2c32a99 100644
--- a/src/core/SkRasterPipeline.h
+++ b/src/core/SkRasterPipeline.h
@@ -95,7 +95,8 @@
     M(bicubic_n3y) M(bicubic_n1y) M(bicubic_p1y) M(bicubic_p3y)  \
     M(save_xy) M(accumulate)                                     \
     M(linear_gradient_2stops)                                    \
-    M(byte_tables)
+    M(byte_tables)                                               \
+    M(shader_adapter)
 
 class SkRasterPipeline {
 public:
diff --git a/src/core/SkShader.cpp b/src/core/SkShader.cpp
index 0e03fb7112..7c93394b12 100644
--- a/src/core/SkShader.cpp
+++ b/src/core/SkShader.cpp
@@ -5,6 +5,7 @@
  * found in the LICENSE file.
  */
 
+#include "SkArenaAlloc.h"
 #include "SkAtomics.h"
 #include "SkBitmapProcShader.h"
 #include "SkColorShader.h"
@@ -13,9 +14,12 @@
 #include "SkPaint.h"
 #include "SkPicture.h"
 #include "SkPictureShader.h"
+#include "SkPM4fPriv.h"
+#include "SkRasterPipeline.h"
 #include "SkReadBuffer.h"
 #include "SkScalar.h"
 #include "SkShader.h"
+#include "SkTLazy.h"
 #include "SkWriteBuffer.h"
 
 #if SK_SUPPORT_GPU
@@ -262,6 +266,31 @@ bool SkShader::appendStages(SkRasterPipeline* pipeline,
     return this->onAppendStages(pipeline, dst, scratch, ctm, paint, nullptr);
 }
 
+bool SkShader::onAppendStages(SkRasterPipeline* p,
+                              SkColorSpace* cs,
+                              SkArenaAlloc* alloc,
+                              const SkMatrix& ctm,
+                              const SkPaint& paint,
+                              const SkMatrix* localM) const {
+    // Legacy shaders handle the paint opacity internally,
+    // but RP applies it as a separate stage.
+    SkTCopyOnFirstWrite<SkPaint> opaquePaint(paint);
+    if (paint.getAlpha() != SK_AlphaOPAQUE) {
+        opaquePaint.writable()->setAlpha(SK_AlphaOPAQUE);
+    }
+
+    ContextRec rec(*opaquePaint, ctm, localM, ContextRec::kPM4f_DstType, cs);
+    if (auto* ctx = this->createContext(rec,
+                                        alloc->makeArrayDefault<char>(this->contextSize(rec)))) {
+        p->append(SkRasterPipeline::shader_adapter, ctx);
+        // Legacy shaders aren't aware of color spaces. We can pretty
+        // safely assume they're in sRGB gamut.
+        return append_gamut_transform(p, alloc,
+                                      SkColorSpace::MakeNamed(SkColorSpace::kSRGB_Named).get(), cs);
+    }
+    return false;
+}
+
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 
 sk_sp<SkFlattenable> SkEmptyShader::CreateProc(SkReadBuffer&) {
diff --git a/src/opts/SkRasterPipeline_opts.h b/src/opts/SkRasterPipeline_opts.h
index 1b27fc25d4..dec81d990a 100644
--- a/src/opts/SkRasterPipeline_opts.h
+++ b/src/opts/SkRasterPipeline_opts.h
@@ -18,6 +18,7 @@
 #include "SkPM4f.h"
 #include "SkPM4fPriv.h"
 #include "SkRasterPipeline.h"
+#include "SkShader.h"
 #include "SkSRGB.h"
 
 namespace {
@@ -1085,6 +1086,13 @@ STAGE_CTX(byte_tables, const void*) {
     a = SkNf_from_byte(gather(tail, tables->a, SkNf_round(255.0f, a)));
 }
 
+STAGE_CTX(shader_adapter, SkShader::Context*) {
+    SkPM4f buf[N];
+    static_assert(sizeof(buf) == sizeof(r) + sizeof(g) + sizeof(b) + sizeof(a), "");
+    ctx->shadeSpan4f(x, (int)g[0], buf, N);
+    SkNf::Load4(buf, &r, &g, &b, &a);
+}
+
 SI Fn enum_to_Fn(SkRasterPipeline::StockStage st) {
     switch (st) {
     #define M(stage) case SkRasterPipeline::stage: return stage;