From f9e678d6964bc5a6c2b38edbc36d9f23cf96c37f Mon Sep 17 00:00:00 2001
From: Jim Van Verth <jvanverth@google.com>
Date: Wed, 15 Feb 2017 15:46:52 -0500
Subject: Use SDF path miplevels based on the original path's size

Should produce sharper results than arbitrary fixed sizes.
Adds a new test to pathfill GM.

Was: https://skia-review.googlesource.com/c/8328/

BUG=chromium:682918, skia:6238

Change-Id: Ia62ea5ce6b4a5ac2b8b51d06d57dc951d6c340b8
Reviewed-on: https://skia-review.googlesource.com/8384
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
---
 src/gpu/ops/GrAADistanceFieldPathRenderer.cpp | 53 +++++++++++++++------------
 1 file changed, 30 insertions(+), 23 deletions(-)

(limited to 'src/gpu/ops')

diff --git a/src/gpu/ops/GrAADistanceFieldPathRenderer.cpp b/src/gpu/ops/GrAADistanceFieldPathRenderer.cpp
index a72f7dc40f..7131e18a46 100644
--- a/src/gpu/ops/GrAADistanceFieldPathRenderer.cpp
+++ b/src/gpu/ops/GrAADistanceFieldPathRenderer.cpp
@@ -10,6 +10,7 @@
 
 #include "GrBuffer.h"
 #include "GrContext.h"
+#include "GrDistanceFieldGenFromVector.h"
 #include "GrDrawOpTest.h"
 #include "GrOpFlushState.h"
 #include "GrPipelineBuilder.h"
@@ -20,10 +21,9 @@
 #include "effects/GrDistanceFieldGeoProc.h"
 #include "ops/GrMeshDrawOp.h"
 
-#include "SkPathOps.h"
 #include "SkAutoMalloc.h"
 #include "SkDistanceFieldGen.h"
-#include "GrDistanceFieldGenFromVector.h"
+#include "SkPathOps.h"
 
 #define ATLAS_TEXTURE_WIDTH 2048
 #define ATLAS_TEXTURE_HEIGHT 2048
@@ -39,9 +39,11 @@ static int g_NumFreedShapes = 0;
 #endif
 
 // mip levels
-static const int kSmallMIP = 32;
-static const int kMediumMIP = 73;
-static const int kLargeMIP = 162;
+static const SkScalar kMaxMIP = 162;
+
+static const SkScalar kMaxDim = 73;
+static const SkScalar kMinSize = 8;
+static const SkScalar kMaxSize = 2*kMaxMIP;
 
 // Callback to clear out internal path cache when eviction occurs
 void GrAADistanceFieldPathRenderer::HandleEviction(GrDrawOpAtlas::AtlasID id, void* pr) {
@@ -107,14 +109,20 @@ bool GrAADistanceFieldPathRenderer::onCanDrawPath(const CanDrawPathArgs& args) c
         return false;
     }
 
-    // Only support paths with bounds within kMediumMIP by kMediumMIP,
-    // scaled to have bounds within 2.0f*kLargeMIP by 2.0f*kLargeMIP.
+    // Only support paths with bounds within kMaxDim by kMaxDim,
+    // scaled to have bounds within kMaxSize by kMaxSize.
     // The goal is to accelerate rendering of lots of small paths that may be scaling.
-    SkScalar maxScale = args.fViewMatrix->getMaxScale();
+    SkScalar scaleFactors[2];
+    if (!args.fViewMatrix->getMinMaxScales(scaleFactors)) {
+        return false;
+    }
     SkRect bounds = args.fShape->styledBounds();
+    SkScalar minDim = SkMinScalar(bounds.width(), bounds.height());
     SkScalar maxDim = SkMaxScalar(bounds.width(), bounds.height());
+    SkScalar minSize = minDim * scaleFactors[0];
+    SkScalar maxSize = maxDim * scaleFactors[1];
 
-    return maxDim <= kMediumMIP && maxDim * maxScale <= 2.0f*kLargeMIP;
+    return maxDim <= kMaxDim && kMinSize <= minSize && maxSize <= kMaxSize;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -240,23 +248,22 @@ private:
             SkScalar maxScale = this->viewMatrix().getMaxScale();
             const SkRect& bounds = args.fShape.bounds();
             SkScalar maxDim = SkMaxScalar(bounds.width(), bounds.height());
-            SkScalar size = maxScale * maxDim;
-            SkScalar desiredDimension;
-            // For minimizing (or the common case of identity) transforms, we try to
-            // create the DF at the appropriately sized native src-space path resolution.
+            // We try to create the DF at a power of two scaled path resolution (1/2, 1, 2, 4, etc)
             // In the majority of cases this will yield a crisper rendering.
-            if (size <= maxDim && maxDim < kSmallMIP) {
-                desiredDimension = maxDim;
-            } else if (size <= kSmallMIP) {
-                desiredDimension = kSmallMIP;
-            } else if (size <= maxDim) {
-                desiredDimension = maxDim;
-            } else if (size <= kMediumMIP) {
-                desiredDimension = kMediumMIP;
-            } else {
-                desiredDimension = kLargeMIP;
+            SkScalar mipScale = 1.0f;
+            // Our mipscale is the maxScale clamped to the next highest power of 2
+            if (maxScale < SK_ScalarHalf) {
+                SkScalar log = SkScalarFloorToScalar(SkScalarLog2(SkScalarInvert(maxScale)));
+                mipScale = SkScalarPow(2, -log);
+            } else if (maxScale > SK_Scalar1) {
+                SkScalar log = SkScalarCeilToScalar(SkScalarLog2(maxScale));
+                mipScale = SkScalarPow(2, log);
             }
 
+            SkScalar mipSize = mipScale*maxDim;
+            SkASSERT(maxScale * maxDim <= mipSize);
+            SkScalar desiredDimension = SkTMin(mipSize, kMaxMIP);
+
             // check to see if path is cached
             ShapeData::Key key(args.fShape, SkScalarCeilToInt(desiredDimension));
             ShapeData* shapeData = fShapeCache->find(key);
-- 
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