Introduce dynamic pipeline state

Adds a DynamicState struct to GrPipeline that has a field for the
scissor rect. Eventually this should become the only way to specify a
scissor rectangle and may grow to contain more fields. Adds an array of
DynamicStates to GrGpuCommandBuffer::draw and implements support in GL
and Vulkan.

Bug: skia:
Change-Id: If5aebbf9da5d192acf7e68e7def4674ffc7ec310
Reviewed-on: https://skia-review.googlesource.com/18510
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>

1 files changed, 18 insertions, 3 deletions

diff --git a/src/gpu/GrPipeline.h b/src/gpu/GrPipeline.h
index 078cb68437..3fd518985d 100644
--- a/src/gpu/GrPipeline.h
+++ b/src/gpu/GrPipeline.h
@@ -68,6 +68,11 @@ public:
         return flags;
     }
 
+    enum ScissorState : bool {
+        kEnabled = true,
+        kDisabled = false
+    };
+
     struct InitArgs {
         uint32_t fFlags = 0;
         const GrProcessorSet* fProcessors = nullptr;  // Must be finalized
@@ -80,16 +85,26 @@ public:
     };
 
     /**
+     *  Graphics state that can change dynamically without creating a new pipeline.
+     **/
+    struct DynamicState {
+        // Overrides the scissor rectangle (if scissor is enabled in the pipeline).
+        // TODO: eventually this should be the only way to specify a scissor rectangle, as is the
+        // case with the simple constructor.
+        SkIRect fScissorRect;
+    };
+
+    /**
      * A Default constructed pipeline is unusable until init() is called.
      **/
     GrPipeline() = default;
 
     /**
      * Creates a simple pipeline with default settings and no processors. The provided blend mode
-     * must be "Porter Duff" (<= kLastCoeffMode). This pipeline is initialized without requiring
-     * a call to init().
+     * must be "Porter Duff" (<= kLastCoeffMode). If using ScissorState::kEnabled, the caller must
+     * specify a scissor rectangle through the DynamicState struct.
      **/
-    GrPipeline(GrRenderTarget*, SkBlendMode);
+    GrPipeline(GrRenderTarget*, ScissorState, SkBlendMode);
 
     GrPipeline(const InitArgs& args) { this->init(args); }