aura: Draw drop shadows under browsers and menus.

ui/aura/image_grid.h

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UI_AURA_IMAGE_GRID_H_
+#define UI_AURA_IMAGE_GRID_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/gtest_prod_util.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/gfx/compositor/layer.h"
+#include "ui/gfx/compositor/layer_delegate.h"
+#include "ui/gfx/rect.h"
+#include "ui/gfx/size.h"
+
+namespace gfx {
+class Image;
+}  // namespace gfx
+
+namespace aura {
+namespace internal {
+
+// An ImageGrid is a 3x3 array of ui::Layers, each containing an image.
+//
+// As the grid is resized, its images fill the requested space:
+// - corner images are not scaled
+// - top and bottom images are scaled horizontally
+// - left and right images are scaled vertically
+// - the center image is scaled in both directions
+//
+// If one of the non-center images is smaller than the largest images in its
+// row or column, it will be aligned with the outside of the grid.  For
+// example, given 4x4 top-left and top-right images and a 1x2 top images:
+//
+//   +--------+---------------------+--------+
+//   |        |         top         |        |
+//   | top-   +---------------------+  top-  +
+//   | left   |                     | right  |
+//   +----+---+                     +---+----+
+//   |    |                             |    |
+//   ...
+//
+// This may seem odd at first, but it lets ImageGrid be used to draw shadows
+// with curved corners that extend inwards beyond a window's borders.  In the
+// below example, the top-left corner image is overlaid on top of the window's
+// top-left corner:
+//
+//   +---------+-----------------------
+//   |    ..xxx|XXXXXXXXXXXXXXXXXX
+//   |  .xXXXXX|XXXXXXXXXXXXXXXXXX_____
+//   | .xXX    |                    ^ window's top edge
+//   | .xXX    |
+//   +---------+
+//   | xXX|
+//   | xXX|< window's left edge
+//   | xXX|
+//   ...
+//
+class ImageGrid {
+ public:
+  // Helper class for use by tests.
+  class TestAPI {
+   public:
+    TestAPI(ImageGrid* grid) : grid_(grid) {}
+    ui::Layer* top_left_layer() const { return grid_->top_left_layer_.get(); }
+    ui::Layer* top_layer() const { return grid_->top_layer_.get(); }
+    ui::Layer* top_right_layer() const { return grid_->top_right_layer_.get(); }
+    ui::Layer* left_layer() const { return grid_->left_layer_.get(); }
+    ui::Layer* center_layer() const { return grid_->center_layer_.get(); }
+    ui::Layer* right_layer() const { return grid_->right_layer_.get(); }
+    ui::Layer* bottom_left_layer() const {
+      return grid_->bottom_left_layer_.get();
+    }
+    ui::Layer* bottom_layer() const { return grid_->bottom_layer_.get(); }
+    ui::Layer* bottom_right_layer() const {
+      return grid_->bottom_right_layer_.get();
+    }
+
+    // Returns |layer|'s bounds after applying the layer's current transform.
+    gfx::Rect GetTransformedLayerBounds(const ui::Layer& layer);
+
+   private:
+    ImageGrid* grid_;  // not owned
+
+    DISALLOW_COPY_AND_ASSIGN(TestAPI);
+  };
+
+  ImageGrid();
+  ~ImageGrid();
+
+  ui::Layer* layer() { return layer_.get(); }
+  int top_image_height() const { return top_image_height_; }
+  int bottom_image_height() const { return bottom_image_height_; }
+  int left_image_width() const { return left_image_width_; }
+  int right_image_width() const { return right_image_width_; }
+
+  // Initializes the grid to display the passed-in images (any of which can be
+  // NULL).  Ownership of the images remains with the caller.
+  void Init(const gfx::Image* top_left_image,
+            const gfx::Image* top_image,
+            const gfx::Image* top_right_image,
+            const gfx::Image* left_image,
+            const gfx::Image* center_image,
+            const gfx::Image* right_image,
+            const gfx::Image* bottom_left_image,
+            const gfx::Image* bottom_image,
+            const gfx::Image* bottom_right_image);
+
+  void SetSize(const gfx::Size& size);
+
+ private:
+  // Delegate responsible for painting a specific image on a layer.
+  class ImagePainter : public ui::LayerDelegate {
+   public:
+    ImagePainter(const gfx::Image* image) : image_(image) {}
+    virtual ~ImagePainter() {}
+
+    // ui::LayerDelegate implementation:
+    virtual void OnPaintLayer(gfx::Canvas* canvas) OVERRIDE;
+
+   private:
+    const gfx::Image* image_;  // not owned
+
+    DISALLOW_COPY_AND_ASSIGN(ImagePainter);
+  };
+
+  // Returns the dimensions of |image| if non-NULL or gfx::Size(0, 0) otherwise.
+  static gfx::Size GetImageSize(const gfx::Image* image);
+
+  // Initializes |layer_ptr| and |painter_ptr| to display |image|.
+  // Also adds the passed-in layer to |layer_|.
+  void InitImage(const gfx::Image* image,
+                 scoped_ptr<ui::Layer>* layer_ptr,
+                 scoped_ptr<ImagePainter>* painter_ptr);
+
+  // Layer that contains all of the image layers.
+  scoped_ptr<ui::Layer> layer_;
+
+  // The grid's dimensions.
+  gfx::Size size_;
+
+  // Heights and widths of the images displayed by |top_layer_|,
+  // |bottom_layer_|, |left_layer_|, and |right_layer_|.
+  int top_image_height_;
+  int bottom_image_height_;
+  int left_image_width_;
+  int right_image_width_;
+
+  // Heights of the tallest images in the top and bottom rows and the widest
+  // images in the left and right columns.
+  int top_row_height_;
+  int bottom_row_height_;
+  int left_column_width_;
+  int right_column_width_;
+
+  // Layers used to display the various images.  Children of |layer_|.
+  // Positions for which no images were supplied are NULL.
+  scoped_ptr<ui::Layer> top_left_layer_;
+  scoped_ptr<ui::Layer> top_layer_;
+  scoped_ptr<ui::Layer> top_right_layer_;
+  scoped_ptr<ui::Layer> left_layer_;
+  scoped_ptr<ui::Layer> center_layer_;
+  scoped_ptr<ui::Layer> right_layer_;
+  scoped_ptr<ui::Layer> bottom_left_layer_;
+  scoped_ptr<ui::Layer> bottom_layer_;
+  scoped_ptr<ui::Layer> bottom_right_layer_;
+
+  // Delegates responsible for painting the above layers.
+  // Positions for which no images were supplied are NULL.
+  scoped_ptr<ImagePainter> top_left_painter_;
+  scoped_ptr<ImagePainter> top_painter_;
+  scoped_ptr<ImagePainter> top_right_painter_;
+  scoped_ptr<ImagePainter> left_painter_;
+  scoped_ptr<ImagePainter> center_painter_;
+  scoped_ptr<ImagePainter> right_painter_;
+  scoped_ptr<ImagePainter> bottom_left_painter_;
+  scoped_ptr<ImagePainter> bottom_painter_;
+  scoped_ptr<ImagePainter> bottom_right_painter_;
+
+  DISALLOW_COPY_AND_ASSIGN(ImageGrid);
+};
+
+}  // namespace internal
+}  // namespace aura
+
+#endif  // UI_AURA_IMAGE_GRID_H_