Add device space "nudge" to gpu draws

samplecode/SampleClipDrawMatch.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SampleCode.h"
 #include "SkCanvas.h"
 #include "SkInterpolator.h"
 #include "SkTime.h"
 
 // This slide tests out the match up between BW clipping and rendering. It can
 // draw a large rect through some clip geometry and draw the same geometry
 // normally. Which one is drawn first can be toggled. The pair of objects is translated
 // fractionally (via an animator) to expose snapping bugs. The key bindings are:
 //      1-9: the different geometries
 //      t:   toggle which is drawn first the clip or the normal geometry
+//      f:   flip-flops which corner the bottom AA clip rect occupies in the complex clip cases
 
 // The possible geometric combinations to test
 enum Geometry {
     kRect_Geometry,
     kRRect_Geometry,
     kCircle_Geometry,
     kConvexPath_Geometry,
     kConcavePath_Geometry,
     kRectAndRect_Geometry,
     kRectAndRRect_Geometry,
     kRectAndConvex_Geometry,
     kRectAndConcave_Geometry
 };
 
 // The basic rect used is [kMin,kMin]..[kMax,kMax]
 static const float kMin = 100.5f;
 static const float kMid = 200.0f;
 static const float kMax = 299.5f;
 
+// The translation applied to the base AA rect  in the combination cases
+// (i.e., kRectAndRect through kRectAndConcave)
+static const float kXlate = 100.0f;
+
 SkRect create_rect(const SkPoint& offset) {
     SkRect r = SkRect::MakeLTRB(kMin, kMin, kMax, kMax);
     r.offset(offset);
     return r;
 }
 
 SkRRect create_rrect(const SkPoint& offset) {
     SkRRect rrect;
     rrect.setRectXY(create_rect(offset), 10, 10);
     return rrect;
@@ skipping 24 matching lines @@
     concavePath.lineTo(kMax, kMax);
     concavePath.lineTo(kMid, 295.0f);
     concavePath.lineTo(kMin, kMax);
     concavePath.lineTo(105.0f, kMid);
     concavePath.close();
 
     concavePath.offset(offset.fX, offset.fY);
     return concavePath;
 }
 
-static void draw_clipped_geom(SkCanvas* canvas, const SkPoint& offset, int geom, bool useAA) {
-
-    int count = canvas->save();
-
-    switch (geom) {
-    case kRect_Geometry:
-        canvas->clipRect(create_rect(offset), SkRegion::kReplace_Op, useAA);
-        break;
-    case kRRect_Geometry:
-        canvas->clipRRect(create_rrect(offset), SkRegion::kReplace_Op, useAA);
-        break;
-    case kCircle_Geometry:
-        canvas->clipRRect(create_circle(offset), SkRegion::kReplace_Op, useAA);
-        break;
-    case kConvexPath_Geometry:
-        canvas->clipPath(create_convex_path(offset), SkRegion::kReplace_Op, useAA);
-        break;
-    case kConcavePath_Geometry:
-        canvas->clipPath(create_concave_path(offset), SkRegion::kReplace_Op, useAA);
-        break;
-    case kRectAndRect_Geometry: {
-        SkRect r = create_rect(offset);
-        r.offset(-100.0f, -100.0f);
-        canvas->clipRect(r, SkRegion::kReplace_Op, true); // AA here forces shader clips
-        canvas->clipRect(create_rect(offset), SkRegion::kIntersect_Op, useAA);
-        } break;
-    case kRectAndRRect_Geometry: {
-        SkRect r = create_rect(offset);
-        r.offset(-100.0f, -100.0f);
-        canvas->clipRect(r, SkRegion::kReplace_Op, true); // AA here forces shader clips
-        canvas->clipRRect(create_rrect(offset), SkRegion::kIntersect_Op, useAA);
-        } break;
-    case kRectAndConvex_Geometry: {
-        SkRect r = create_rect(offset);
-        r.offset(-100.0f, -100.0f);
-        canvas->clipRect(r, SkRegion::kReplace_Op, true); // AA here forces shader clips
-        canvas->clipPath(create_convex_path(offset), SkRegion::kIntersect_Op, useAA);
-        } break;
-    case kRectAndConcave_Geometry: {
-        SkRect r = create_rect(offset);
-        r.offset(-100.0f, -100.0f);
-        canvas->clipRect(r, SkRegion::kReplace_Op, true); // AA here forces shader clips
-        canvas->clipPath(create_concave_path(offset), SkRegion::kIntersect_Op, useAA);
-        } break;
-    } 
-
-    SkISize size = canvas->getDeviceSize();
-    SkRect bigR = SkRect::MakeWH(SkIntToScalar(size.width()), SkIntToScalar(size.height()));
-
-    SkPaint p;
-    p.setColor(SK_ColorRED);
-
-    canvas->drawRect(bigR, p);
-    canvas->restoreToCount(count);
-}
-
 static void draw_normal_geom(SkCanvas* canvas, const SkPoint& offset, int geom, bool useAA) {
     SkPaint p;
     p.setAntiAlias(useAA);
     p.setColor(SK_ColorBLACK);
 
     switch (geom) {
     case kRect_Geometry:                // fall thru
     case kRectAndRect_Geometry:
         canvas->drawRect(create_rect(offset), p);
         break;
@@ skipping 10 matching lines @@
         break;
     case kConcavePath_Geometry:         // fall thru
     case kRectAndConcave_Geometry:
         canvas->drawPath(create_concave_path(offset), p);
         break;
     } 
 }
 
 class ClipDrawMatchView : public SampleView {
 public:
-    ClipDrawMatchView() : fTrans(2, 5), fGeom(kRect_Geometry), fClipFirst(true) {
+    ClipDrawMatchView() : fTrans(2, 5), fGeom(kRect_Geometry), fClipFirst(true), fSign(1) {
         SkScalar values[2];
 
         fTrans.setRepeatCount(999);
         values[0] = values[1] = 0;
         fTrans.setKeyFrame(0, SkTime::GetMSecs() + 1000, values);
         values[1] = 1;
         fTrans.setKeyFrame(1, SkTime::GetMSecs() + 2000, values);
         values[0] = values[1] = 1;
         fTrans.setKeyFrame(2, SkTime::GetMSecs() + 3000, values);
         values[1] = 0;
@@ skipping 13 matching lines @@
             switch (uni) {
                 case '1': fGeom = kRect_Geometry; this->inval(NULL); return true;
                 case '2': fGeom = kRRect_Geometry; this->inval(NULL); return true;
                 case '3': fGeom = kCircle_Geometry; this->inval(NULL); return true;
                 case '4': fGeom = kConvexPath_Geometry; this->inval(NULL); return true;
                 case '5': fGeom = kConcavePath_Geometry; this->inval(NULL); return true;
                 case '6': fGeom = kRectAndRect_Geometry; this->inval(NULL); return true;
                 case '7': fGeom = kRectAndRRect_Geometry; this->inval(NULL); return true;
                 case '8': fGeom = kRectAndConvex_Geometry; this->inval(NULL); return true;
                 case '9': fGeom = kRectAndConcave_Geometry; this->inval(NULL); return true;
+                case 'f': fSign = -fSign; this->inval(NULL); return true;
                 case 't': fClipFirst = !fClipFirst; this->inval(NULL); return true;
                 default: break;
             }
         }
         return this->INHERITED::onQuery(evt);
     }
 
+    void drawClippedGeom(SkCanvas* canvas, const SkPoint& offset, bool useAA) {
+
+        int count = canvas->save();
+
+        switch (fGeom) {
+        case kRect_Geometry:
+            canvas->clipRect(create_rect(offset), SkRegion::kReplace_Op, useAA);
+            break;
+        case kRRect_Geometry:
+            canvas->clipRRect(create_rrect(offset), SkRegion::kReplace_Op, useAA);
+            break;
+        case kCircle_Geometry:
+            canvas->clipRRect(create_circle(offset), SkRegion::kReplace_Op, useAA);
+            break;
+        case kConvexPath_Geometry:
+            canvas->clipPath(create_convex_path(offset), SkRegion::kReplace_Op, useAA);
+            break;
+        case kConcavePath_Geometry:
+            canvas->clipPath(create_concave_path(offset), SkRegion::kReplace_Op, useAA);
+            break;
+        case kRectAndRect_Geometry: {
+            SkRect r = create_rect(offset);
+            r.offset(fSign * kXlate, fSign * kXlate);
+            canvas->clipRect(r, SkRegion::kReplace_Op, true); // AA here forces shader clips
+            canvas->clipRect(create_rect(offset), SkRegion::kIntersect_Op, useAA);
+            } break;
+        case kRectAndRRect_Geometry: {
+            SkRect r = create_rect(offset);
+            r.offset(fSign * kXlate, fSign * kXlate);
+            canvas->clipRect(r, SkRegion::kReplace_Op, true); // AA here forces shader clips
+            canvas->clipRRect(create_rrect(offset), SkRegion::kIntersect_Op, useAA);
+            } break;
+        case kRectAndConvex_Geometry: {
+            SkRect r = create_rect(offset);
+            r.offset(fSign * kXlate, fSign * kXlate);
+            canvas->clipRect(r, SkRegion::kReplace_Op, true); // AA here forces shader clips
+            canvas->clipPath(create_convex_path(offset), SkRegion::kIntersect_Op, useAA);
+            } break;
+        case kRectAndConcave_Geometry: {
+            SkRect r = create_rect(offset);
+            r.offset(fSign * kXlate, fSign * kXlate);
+            canvas->clipRect(r, SkRegion::kReplace_Op, true); // AA here forces shader clips
+            canvas->clipPath(create_concave_path(offset), SkRegion::kIntersect_Op, useAA);
+            } break;
+        } 
+
+        SkISize size = canvas->getDeviceSize();
+        SkRect bigR = SkRect::MakeWH(SkIntToScalar(size.width()), SkIntToScalar(size.height()));
+
+        SkPaint p;
+        p.setColor(SK_ColorRED);
+
+        canvas->drawRect(bigR, p);
+        canvas->restoreToCount(count);
+    }
+
     // Draw a big red rect through some clip geometry and also draw that same
     // geometry in black. The order in which they are drawn can be swapped.
     // This tests whether the clip and normally drawn geometry match up.
     void drawGeometry(SkCanvas* canvas, const SkPoint& offset, bool useAA) {
         if (fClipFirst) {
-            draw_clipped_geom(canvas, offset, fGeom, useAA);
+            this->drawClippedGeom(canvas, offset, useAA);
         }
 
         draw_normal_geom(canvas, offset, fGeom, useAA);
 
         if (!fClipFirst) {
-            draw_clipped_geom(canvas, offset, fGeom, useAA);
+            this->drawClippedGeom(canvas, offset, useAA);
         }
     }
 
     void onDrawContent(SkCanvas* canvas) SK_OVERRIDE {
         SkScalar trans[2];
         fTrans.timeToValues(SkTime::GetMSecs(), trans);
 
         SkPoint offset;
         offset.set(trans[0], trans[1]);
 
         int saveCount = canvas->save();
         this->drawGeometry(canvas, offset, false);
         canvas->restoreToCount(saveCount);
 
         this->inval(NULL);
     }
 
 private:
     SkInterpolator  fTrans;
     Geometry        fGeom;
     bool            fClipFirst;
+    int             fSign;
 
     typedef SampleView INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 static SkView* MyFactory() { return new ClipDrawMatchView; }
 static SkViewRegister reg(MyFactory);