CCPR: Process quadratic flat edges without soft msaa

The artifacts previously thought to require msaa can be handled by
(1) converting near-linear quadratics into lines, and (2) ensuring all
quadratic segments are monotonic with respect to the vector of their
closing edge [P2 -> P0].

No. 1 was already in effect.

No. 2 is implemented by this change.

Now we only fall back on soft msaa for the two corner pixels.

This change also does some generic housekeeping in the quadratic
processor.

Bug: skia:
Change-Id: Ib3309c2ed86d3d8bec5f451125a69326e82eeb1c
Reviewed-on: https://skia-review.googlesource.com/29721
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>

1 files changed, 22 insertions, 11 deletions

diff --git a/samplecode/SampleCCPRGeometry.cpp b/samplecode/SampleCCPRGeometry.cpp
index a6a71af792..d1cb2b5b57 100644
--- a/samplecode/SampleCCPRGeometry.cpp
+++ b/samplecode/SampleCCPRGeometry.cpp
@@ -10,6 +10,7 @@
 #if SK_SUPPORT_GPU
 
 #include "GrContextPriv.h"
+#include "GrPathUtils.h"
 #include "GrRenderTargetContext.h"
 #include "GrRenderTargetContextPriv.h"
 #include "GrResourceProvider.h"
@@ -155,7 +156,6 @@ void CCPRGeometryView::onDrawContent(SkCanvas* canvas) {
 
 void CCPRGeometryView::updateGpuData() {
     int vertexCount = num_points(fMode);
-    int instanceCount = 1;
 
     fGpuPoints.reset();
     fGpuInstances.reset();
@@ -171,7 +171,7 @@ void CCPRGeometryView::updateGpuData() {
             }
         }
 
-        instanceCount = chops.count() + 1;
+        int instanceCount = chops.count() + 1;
         SkPoint chopped[10];
         SkChopCubicAt(fPoints, chopped, chops.begin(), chops.count());
 
@@ -196,22 +196,33 @@ void CCPRGeometryView::updateGpuData() {
         if (fMode >= Mode::kLoopInsets && SkCubicType::kLoop != type) {
             fMode = (Mode) ((int) fMode - 2);
         }
-    } else {
-        // Endpoints.
-        fGpuPoints.push_back(fPoints[0]);
-        fGpuPoints.push_back(fPoints[3]);
-        // Control points.
-        fGpuPoints.push_back(fPoints[1]);
-    }
 
-    if (4 == vertexCount) {
         int controlPointsIdx = instanceCount + 1;
         for (int i = 0; i < instanceCount; ++i) {
             fGpuInstances.push_back().fCubicData = {controlPointsIdx + i * 4, i};
         }
     } else if (is_curve(fMode)) {
-        fGpuInstances.push_back().fQuadraticData = {2, 0};
+        SkPoint P[3] = {fPoints[0], fPoints[1], fPoints[3]};
+        SkPoint chopped[5];
+        fGpuPoints.push_back(P[0]);
+        if (GrPathUtils::chopMonotonicQuads(P, chopped)) {
+            // Endpoints.
+            fGpuPoints.push_back(chopped[2]);
+            fGpuPoints.push_back(chopped[4]);
+            // Control points.
+            fGpuPoints.push_back(chopped[1]);
+            fGpuPoints.push_back(chopped[3]);
+            fGpuInstances.push_back().fQuadraticData = {3, 0};
+            fGpuInstances.push_back().fQuadraticData = {4, 1};
+        } else {
+            fGpuPoints.push_back(P[2]);
+            fGpuPoints.push_back(P[1]);
+            fGpuInstances.push_back().fQuadraticData = {2, 0};
+        }
     } else {
+        fGpuPoints.push_back(fPoints[0]);
+        fGpuPoints.push_back(fPoints[3]);
+        fGpuPoints.push_back(fPoints[1]);
         fGpuInstances.push_back().fTriangleData = {0, 2, 1}; // Texel buffer has endpoints first.
     }