Add support for instanced draws

Adds an instance buffer to GrMesh and instance attribs to
GrPrimitiveProcessor. Implements support in GL and Vulkan. Adds unit
tests for instanced rendering with GrMesh.

Bug: skia:
Change-Id: If1a9920feb9366f346b8c37cf914713c49129b3a
Reviewed-on: https://skia-review.googlesource.com/16200
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>

1 files changed, 11 insertions, 1 deletions

diff --git a/src/gpu/gl/GrGLVertexArray.cpp b/src/gpu/gl/GrGLVertexArray.cpp
index 74e609e9b8..59f2be9831 100644
--- a/src/gpu/gl/GrGLVertexArray.cpp
+++ b/src/gpu/gl/GrGLVertexArray.cpp
@@ -53,8 +53,10 @@ void GrGLAttribArrayState::set(GrGLGpu* gpu,
                                const GrBuffer* vertexBuffer,
                                GrVertexAttribType type,
                                GrGLsizei stride,
-                               size_t offsetInBytes) {
+                               size_t offsetInBytes,
+                               int divisor) {
     SkASSERT(index >= 0 && index < fAttribArrayStates.count());
+    SkASSERT(0 == divisor || gpu->caps()->instanceAttribSupport());
     AttribArrayState* array = &fAttribArrayStates[index];
     if (array->fVertexBufferUniqueID != vertexBuffer->uniqueID() ||
         array->fType != type ||
@@ -84,10 +86,18 @@ void GrGLAttribArrayState::set(GrGLGpu* gpu,
         array->fStride = stride;
         array->fOffset = offsetInBytes;
     }
+    if (gpu->caps()->instanceAttribSupport() && array->fDivisor != divisor) {
+        SkASSERT(0 == divisor || 1 == divisor); // not necessarily a requirement but what we expect.
+        GR_GL_CALL(gpu->glInterface(), VertexAttribDivisor(index, divisor));
+        array->fDivisor = divisor;
+    }
 }
 
 void GrGLAttribArrayState::enableVertexArrays(const GrGLGpu* gpu, int enabledCount) {
     SkASSERT(enabledCount <= fAttribArrayStates.count());
+    if (fEnabledCountIsValid && enabledCount == fNumEnabledArrays) {
+        return;
+    }
 
     int firstIdxToEnable = fEnabledCountIsValid ? fNumEnabledArrays : 0;
     for (int i = firstIdxToEnable; i < enabledCount; ++i) {