Opt-in burst mechanism for pipeline shaders

Add a dedicated virtual for shaders to select burst mode.

Enabled for linear gradients with more than 8 stops, as a start.

BUG=skia:6710

Change-Id: I1b19124f42d1d805de27a5db6a26601c386bb9ff
Reviewed-on: https://skia-review.googlesource.com/18628
Commit-Queue: Florin Malita <fmalita@chromium.org>
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/src/shaders/SkShaderBase.h b/src/shaders/SkShaderBase.h
index ee8d5c02dc..8dc9354e53 100644
--- a/src/shaders/SkShaderBase.h
+++ b/src/shaders/SkShaderBase.h
@@ -148,6 +148,15 @@ public:
      */
     Context* makeContext(const ContextRec&, SkArenaAlloc*) const;
 
+    /**
+     * Shaders may opt-in for burst mode, if they can operate
+     * significantly more efficiently in that mode.
+     *
+     * Burst mode is prioritized in SkRasterPipelineBlitter over
+     * regular (appendStages) pipeline operation.
+     */
+    Context* makeBurstPipelineContext(const ContextRec&, SkArenaAlloc*) const;
+
 #if SK_SUPPORT_GPU
     struct AsFPArgs {
         AsFPArgs() {}
@@ -240,6 +249,13 @@ protected:
         return nullptr;
     }
 
+    /**
+     * Overriden by shaders which prefer burst mode.
+     */
+    virtual Context* onMakeBurstPipelineContext(const ContextRec&, SkArenaAlloc*) const {
+        return nullptr;
+    }
+
     virtual bool onAsLuminanceColor(SkColor*) const {
         return false;
     }