add a callback stage to SkRasterPipeline

This lets us temporarily escape to piece of code outside
SkRasterPipeline.  We should be able to use this to replace
   - parametric_{r,g,b,a}
   - table_{r,g,b,a}
   - color_lookup_table
   - shader_adapter*

* We want to obsolete shader_adapter for other reasons anyway,
but we _could_ replace it with this if we want to.

Change-Id: I42b657b3c19c679796ed1876856cae0c8471307e
Reviewed-on: https://skia-review.googlesource.com/12102
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Herb Derby <herb@google.com>
Reviewed-by: Matt Sarett <msarett@google.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/src/opts/SkRasterPipeline_opts.h b/src/opts/SkRasterPipeline_opts.h
index 1146b3d7fb..b15ebf36d8 100644
--- a/src/opts/SkRasterPipeline_opts.h
+++ b/src/opts/SkRasterPipeline_opts.h
@@ -1098,6 +1098,11 @@ STAGE_CTX(shader_adapter, SkShader::Context*) {
     SkNf::Load4(buf, &r, &g, &b, &a);
 }
 
+STAGE_CTX(callback, const void*) {
+    auto c = (const SkJumper_CallbackCtx*)ctx;
+    c->fn(c->arg, tail ? tail : N);
+}
+
 SI Fn enum_to_Fn(SkRasterPipeline::StockStage st) {
     switch (st) {
     #define M(stage) case SkRasterPipeline::stage: return stage;