Mac: Fix drawing when the device's transform has a scaling part.

This currently never happens in practice, but I have a patch which uses the PaintAt IPC, which doesn't work without this fix. Without this, the clip rect is scaled down too, which means if I send a PaintAt IPC that draws the renderer at 800x600 into a 400x300 pixmap, the clip rect is 200x150, because render_view sets the scale t0 0.5 and the clip rect to 400x300.

BUG=none
TEST=Everything still paints correctly.

Review URL: http://codereview.chromium.org/3033005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@52712 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 11 insertions, 8 deletions

diff --git a/skia/ext/bitmap_platform_device_mac.cc b/skia/ext/bitmap_platform_device_mac.cc
index 8a46736..feb192b 100644
--- a/skia/ext/bitmap_platform_device_mac.cc
+++ b/skia/ext/bitmap_platform_device_mac.cc
@@ -160,9 +160,6 @@ void BitmapPlatformDevice::BitmapPlatformDeviceData::LoadConfig() {
     return;  // Nothing to do.
   config_dirty_ = false;
 
-  // Transform.
-  SkMatrix t(transform_);
-
   // We must restore and then save the state of the graphics context since the
   // calls to Load the clipping region to the context are strictly cummulative,
   // i.e., you can't replace a clip rect, other than with a save/restore.
@@ -171,10 +168,8 @@ void BitmapPlatformDevice::BitmapPlatformDeviceData::LoadConfig() {
   // calls in LoadClippingRegionToCGContext() with an image mask instead.
   CGContextRestoreGState(bitmap_context_);
   CGContextSaveGState(bitmap_context_);
-  LoadTransformToCGContext(bitmap_context_, t);
-  t.setTranslateX(-t.getTranslateX());
-  t.setTranslateY(-t.getTranslateY());
-  LoadClippingRegionToCGContext(bitmap_context_, clip_region_, t);
+  LoadTransformToCGContext(bitmap_context_, transform_);
+  LoadClippingRegionToCGContext(bitmap_context_, clip_region_, transform_);
 }
 
 
diff --git a/skia/ext/platform_device_mac.cc b/skia/ext/platform_device_mac.cc
index ae9228e..42927cc 100644
--- a/skia/ext/platform_device_mac.cc
+++ b/skia/ext/platform_device_mac.cc
@@ -128,10 +128,18 @@ void PlatformDevice::LoadClippingRegionToCGContext(
     rect.setEmpty();
     CGContextClipToRect(context, gfx::SkRectToCGRect(rect));
   } else if (region.isRect()) {
+    // CoreGraphics applies the current transform to clip rects, which is
+    // unwanted. Inverse-transform the rect before sending it to CG. This only
+    // works for translations and scaling, but not for rotations (but the
+    // viewport is never rotated anyway).
+    SkMatrix t;
+    bool did_invert = transformation.invert(&t);
+    if (!did_invert)
+      t.reset();
     // Do the transformation.
     SkRect rect;
     rect.set(region.getBounds());
-    transformation.mapRect(&rect);
+    t.mapRect(&rect);
     SkIRect irect;
     rect.round(&irect);
     CGContextClipToRect(context, gfx::SkIRectToCGRect(irect));