test dont-clip-layer

depends on fix from https://codereview.chromium.org/2309623002/

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2296703003

Review-Url: https://codereview.chromium.org/2296703003

gm/aaclip.cpp

@@ -9,6 +9,47 @@
 #include "SkCanvas.h"
 #include "SkPath.h"
 
+static void do_draw(SkCanvas* canvas, const SkRect& r) {
+    SkPaint paint;
+    paint.setXfermodeMode(SkXfermode::kSrc_Mode);
+    paint.setColor(0x800000FF);
+    canvas->drawRect(r, paint);
+}
+
+/**
+ *  Exercise kDontClipToLayer_Legacy_SaveLayerFlag flag, which does not limit the clip to the
+ *  layer's bounds. Thus when a draw occurs, it can (depending on "where" it is) draw into the layer
+ *  and/or draw onto the surrounding portions of the canvas, or both.
+ *
+ *  This GM has a 100x100 rectangle (r), which its going to draw. However first it creates a layer
+ *  with this flag covering 1/2 of the rectangle (upper half). Then it draws the rect in SRC mode.
+ *
+ *  The portion of the draw that intersects the layer should see the SRC draw, apply it to the layer
+ *  and then during restore, it will SRC_OVER that layer onto the canvas (SRC_OVER since the layer
+ *  has no paint, so it gets the default xfermode during restore).
+ *
+ *  The portion of the draw below the layer draws directly into the canvas. Since it is in SRC mode,
+ *  it will wrote 0x80 to the canvas' alpha, making it appear darker when shown in the window.
+ *  The portion in the layer, will end up SRC_OVERing the 0x80 layer pixels onto the canvas, so
+ *  they will appear lighter (since the canvas was erased to white initially).
+ *
+ *  Thus the expected result is the upper half to be light-blue w/ 0xFF for its alpha, and
+ *  the lower half to be darker blue with 0x80 for its alpha.
+ */
+DEF_SIMPLE_GM(dont_clip_to_layer, canvas, 120, 120) {
+    SkRect r { 10, 10, 110, 110 };
+    SkRect r0 = SkRect::MakeXYWH(r.left(), r.top(), r.width(), r.height()/2);
+
+    SkCanvas::SaveLayerRec rec;
+    rec.fPaint = nullptr;
+    rec.fBounds = &r0;
+    rec.fBackdrop = nullptr;
+    rec.fSaveLayerFlags = 1 << 31;//SkCanvas::kDontClipToLayer_Legacy_SaveLayerFlag;
+    canvas->saveLayer(rec);
+    do_draw(canvas, r);
+    canvas->restore();
+}
+
 /** Draw a 2px border around the target, then red behind the target;
     set the clip to match the target, then draw >> the target in blue.
 */

src/core/SkCanvas.cpp

@@ -314,6 +314,11 @@ public:
     }
 };
 
+static SkIRect compute_device_bounds(SkBaseDevice* device) {
+    return SkIRect::MakeXYWH(device->getOrigin().x(), device->getOrigin().y(),
+                             device->width(), device->height());
+}
+
 class SkDrawIter : public SkDraw {
 public:
     SkDrawIter(SkCanvas* canvas) {
@@ -322,9 +327,27 @@ public:
 
         fClipStack = canvas->fClipStack;
         fCurrLayer = canvas->fMCRec->fTopLayer;
+
+        fMultiDeviceCS = nullptr;
+        if (fCurrLayer->fNext) {
+            fMultiDeviceCS = canvas->fClipStack;
+            fMultiDeviceCS->save();
+        }
+    }
+
+    ~SkDrawIter() {
+        if (fMultiDeviceCS) {
+            fMultiDeviceCS->restore();
+        }
     }
 
     bool next() {
+        if (fMultiDeviceCS && fDevice) {
+            // remove the previous device's bounds
+            fMultiDeviceCS->clipDevRect(compute_device_bounds(fDevice),
+                                        SkRegion::kDifference_Op);
+        }
+
         // skip over recs with empty clips
         while (fCurrLayer && fCurrLayer->fClip.isEmpty()) {
             fCurrLayer = fCurrLayer->fNext;
@@ -360,6 +383,7 @@ public:
 private:
     const DeviceCM* fCurrLayer;
     const SkPaint*  fPaint;     // May be null.
+    SkClipStack*    fMultiDeviceCS;
 
     typedef SkDraw INHERITED;
 };
@@ -1047,11 +1071,7 @@ void SkCanvas::internalSave() {
 }
 
 bool SkCanvas::BoundsAffectsClip(SaveLayerFlags saveLayerFlags) {
-#ifdef SK_SUPPORT_LEGACY_CLIPTOLAYERFLAG
     return !(saveLayerFlags & SkCanvas::kDontClipToLayer_PrivateSaveLayerFlag);
-#else
-    return true;
-#endif
 }
 
 bool SkCanvas::clipRectBounds(const SkRect* bounds, SaveLayerFlags saveLayerFlags,
@@ -1168,10 +1188,6 @@ void SkCanvas::internalSaveLayer(const SaveLayerRec& rec, SaveLayerStrategy stra
     const SkPaint* paint = rec.fPaint;
     SaveLayerFlags saveLayerFlags = rec.fSaveLayerFlags;
 
-#ifndef SK_SUPPORT_LEGACY_CLIPTOLAYERFLAG
-    saveLayerFlags &= ~kDontClipToLayer_PrivateSaveLayerFlag;
-#endif
-
     SkLazyPaint lazyP;
     SkImageFilter* imageFilter = paint ? paint->getImageFilter() : NULL;
     SkMatrix stashedMatrix = fMCRec->fMatrix;