aura: Draw shadows around tooltip windows.

ui/aura_shell/image_grid.cc

Index: ui/aura_shell/image_grid.cc
diff --git a/ui/aura_shell/image_grid.cc b/ui/aura_shell/image_grid.cc
index 14d69ce83a2d8e88d1d303101ad12890bef24029..99f8d90a299c6967cd7fa1f87a68901a2c68e3cf 100644
--- a/ui/aura_shell/image_grid.cc
+++ b/ui/aura_shell/image_grid.cc
@@ -13,6 +13,7 @@
 #include "third_party/skia/include/core/SkXfermode.h"
 
 using std::max;
+using std::min;
 
 namespace aura_shell {
 namespace internal {
@@ -92,45 +93,81 @@ void ImageGrid::SetSize(const gfx::Size& size) {
   float center_height = size.height() - top_row_height_ - bottom_row_height_;
 
   if (top_layer_.get()) {
-    ui::Transform transform;
-    transform.SetScaleX(center_width / top_layer_->bounds().width());
-    transform.ConcatTranslate(left_column_width_, 0);
-    top_layer_->SetTransform(transform);
+    if (center_width > 0) {
+      ui::Transform transform;
+      transform.SetScaleX(center_width / top_layer_->bounds().width());
+      transform.ConcatTranslate(left_column_width_, 0);
+      top_layer_->SetTransform(transform);
+    }
+    top_layer_->SetVisible(center_width > 0);
   }
   if (bottom_layer_.get()) {
-    ui::Transform transform;
-    transform.SetScaleX(center_width / bottom_layer_->bounds().width());
-    transform.ConcatTranslate(
-        left_column_width_, size.height() - bottom_layer_->bounds().height());
-    bottom_layer_->SetTransform(transform);
+    if (center_width > 0) {
+      ui::Transform transform;
+      transform.SetScaleX(center_width / bottom_layer_->bounds().width());
+      transform.ConcatTranslate(
+          left_column_width_, size.height() - bottom_layer_->bounds().height());
+      bottom_layer_->SetTransform(transform);
+    }
+    bottom_layer_->SetVisible(center_width > 0);
   }
   if (left_layer_.get()) {
-    ui::Transform transform;
-    transform.SetScaleY(center_height / left_layer_->bounds().height());
-    transform.ConcatTranslate(0, top_row_height_);
-    left_layer_->SetTransform(transform);
+    if (center_height > 0) {
+      ui::Transform transform;
+      transform.SetScaleY(center_height / left_layer_->bounds().height());
+      transform.ConcatTranslate(0, top_row_height_);
+      left_layer_->SetTransform(transform);
+    }
+    left_layer_->SetVisible(center_height > 0);
   }
   if (right_layer_.get()) {
-    ui::Transform transform;
-    transform.SetScaleY(center_height / right_layer_->bounds().height());
-    transform.ConcatTranslate(
-        size.width() - right_layer_->bounds().width(), top_row_height_);
-    right_layer_->SetTransform(transform);
+    if (center_height > 0) {
+      ui::Transform transform;
+      transform.SetScaleY(center_height / right_layer_->bounds().height());
+      transform.ConcatTranslate(
+          size.width() - right_layer_->bounds().width(), top_row_height_);
+      right_layer_->SetTransform(transform);
+    }
+    right_layer_->SetVisible(center_height > 0);
   }
 
+  // Calculate the available amount of space for corner images on all sides of
+  // the grid.  If the images don't fit, we need to clip them.
+  const int left = min(left_column_width_, size_.width() / 2);
+  const int right = min(right_column_width_, size_.width() - left);
+  const int top = min(top_row_height_, size_.height() / 2);
+  const int bottom = min(bottom_row_height_, size_.height() - top);
+
   if (top_left_layer_.get()) {
     // No transformation needed; it should be at (0, 0) and unscaled.
+    top_left_painter_->SetClipRect(
+        LayerExceedsSize(top_left_layer_.get(), gfx::Size(left, top)) ?
+            gfx::Rect(gfx::Rect(0, 0, left, top)) :
+            gfx::Rect(),
+        top_left_layer_.get());
   }
   if (top_right_layer_.get()) {
     ui::Transform transform;
     transform.SetTranslateX(size.width() - top_right_layer_->bounds().width());
     top_right_layer_->SetTransform(transform);
+    top_right_painter_->SetClipRect(
+        LayerExceedsSize(top_right_layer_.get(), gfx::Size(right, top)) ?
+            gfx::Rect(top_right_layer_->bounds().width() - right, 0,
+                      right, top) :
+            gfx::Rect(),
+        top_right_layer_.get());
   }
   if (bottom_left_layer_.get()) {
     ui::Transform transform;
     transform.SetTranslateY(
         size.height() - bottom_left_layer_->bounds().height());
     bottom_left_layer_->SetTransform(transform);
+    bottom_left_painter_->SetClipRect(
+        LayerExceedsSize(bottom_left_layer_.get(), gfx::Size(left, bottom)) ?
+            gfx::Rect(0, bottom_left_layer_->bounds().height() - bottom,
+                      left, bottom) :
+            gfx::Rect(),
+        bottom_left_layer_.get());
   }
   if (bottom_right_layer_.get()) {
     ui::Transform transform;
@@ -138,18 +175,38 @@ void ImageGrid::SetSize(const gfx::Size& size) {
         size.width() - bottom_right_layer_->bounds().width(),
         size.height() - bottom_right_layer_->bounds().height());
     bottom_right_layer_->SetTransform(transform);
+    bottom_right_painter_->SetClipRect(
+        LayerExceedsSize(bottom_right_layer_.get(), gfx::Size(right, bottom)) ?
+            gfx::Rect(bottom_right_layer_->bounds().width() - right,
+                      bottom_right_layer_->bounds().height() - bottom,
+                      right, bottom) :
+            gfx::Rect(),
+        bottom_right_layer_.get());
   }
 
   if (center_layer_.get()) {
-    ui::Transform transform;
-    transform.SetScale(center_width / center_layer_->bounds().width(),
-                       center_height / center_layer_->bounds().height());
-    transform.ConcatTranslate(left_column_width_, top_row_height_);
-    center_layer_->SetTransform(transform);
+    if (center_width > 0 && center_height > 0) {
+      ui::Transform transform;
+      transform.SetScale(center_width / center_layer_->bounds().width(),
+                         center_height / center_layer_->bounds().height());
+      transform.ConcatTranslate(left_column_width_, top_row_height_);
+      center_layer_->SetTransform(transform);
+    }
+    center_layer_->SetVisible(center_width > 0 && center_height > 0);
+  }
+}
+
+void ImageGrid::ImagePainter::SetClipRect(const gfx::Rect& clip_rect,
+                                          ui::Layer* layer) {
+  if (clip_rect != clip_rect_) {
+    clip_rect_ = clip_rect;
+    layer->ScheduleDraw();
   }
 }
 
 void ImageGrid::ImagePainter::OnPaintLayer(gfx::Canvas* canvas) {
+  if (!clip_rect_.IsEmpty())
+    canvas->ClipRect(clip_rect_);
   canvas->DrawBitmapInt(*(image_->ToSkBitmap()), 0, 0);
 }
 
@@ -160,6 +217,13 @@ gfx::Size ImageGrid::GetImageSize(const gfx::Image* image) {
       gfx::Size();
 }
 
+// static
+bool ImageGrid::LayerExceedsSize(const ui::Layer* layer,
+                                 const gfx::Size& size) {
+  return layer->bounds().width() > size.width() ||
+      layer->bounds().height() > size.height();
+}
+
 void ImageGrid::InitImage(const gfx::Image* image,
                           scoped_ptr<ui::Layer>* layer_ptr,
                           scoped_ptr<ImagePainter>* painter_ptr) {