Don't support GrCubicEffect if float != fp32

Otherwise the cubic math is too unstable.

Bug: skia:
Change-Id: I2c8d8d9abcae517d42dd3eddb5bf455c7c7487dd
Reviewed-on: https://skia-review.googlesource.com/121709
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>

2 files changed, 17 insertions, 0 deletions

diff --git a/gm/beziereffects.cpp b/gm/beziereffects.cpp
index ebcd27bb49..57caa46410 100644
--- a/gm/beziereffects.cpp
+++ b/gm/beziereffects.cpp
@@ -8,6 +8,7 @@
 // This test only works with the GPU backend.
 
 #include "gm.h"
+#include "sk_tool_utils.h"
 
 #if SK_SUPPORT_GPU
 
@@ -135,6 +136,17 @@ protected:
             return;
         }
 
+        if (!context->caps()->shaderCaps()->floatIs32Bits()) {
+            SkPaint paint;
+            sk_tool_utils::set_portable_typeface(&paint);
+            paint.setAntiAlias(true);
+            paint.setTextSize(20);
+
+            canvas->clear(SK_ColorWHITE);
+            canvas->drawString("float != fp32", 20, 40, paint);
+            return;
+        }
+
         struct Vertex {
             SkPoint fPosition;
             float   fKLM[4]; // The last value is ignored. The effect expects a vec4f.
diff --git a/src/gpu/effects/GrBezierEffect.h b/src/gpu/effects/GrBezierEffect.h
index 267259e634..174470410c 100644
--- a/src/gpu/effects/GrBezierEffect.h
+++ b/src/gpu/effects/GrBezierEffect.h
@@ -229,6 +229,11 @@ public:
                                            bool flipKL,
                                            const GrClipEdgeType edgeType,
                                            const GrCaps& caps) {
+        if (!caps.shaderCaps()->floatIs32Bits()) {
+            // Cubic math will be too unstable if the hardware doesn't support full fp32.
+            return nullptr;
+        }
+
         // Map KLM to something that operates in device space.
         SkMatrix devKLM;
         if (!viewMatrix.invert(&devKLM)) {