text: // Copyright (c) 2012 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.
  
  #include "ui/base/dragdrop/drag_utils.h"
  
  #include "base/file_util.h"
  #include "base/logging.h"
  #include "base/strings/utf_string_conversions.h"
  #include "ui/base/dragdrop/os_exchange_data.h"
  #include "ui/gfx/canvas.h"
  #include "ui/gfx/font_list.h"
  #include "ui/gfx/geometry/point.h"
  #include "ui/gfx/geometry/rect.h"
  #include "ui/gfx/geometry/size.h"
  #include "ui/gfx/image/canvas_image_source.h"
  #include "url/gurl.h"
  
  namespace drag_utils {
  
  namespace {
  
  // Maximum width of the link drag image in pixels.
  static const int kLinkDragImageVPadding = 3;
  
  // File dragging pixel measurements
  static const int kFileDragImageMaxWidth = 200;
  static const SkColor kFileDragImageTextColor = SK_ColorBLACK;
  
  class FileDragImageSource : public gfx::CanvasImageSource {
   public:
    FileDragImageSource(const base::FilePath& file_name,
                        const gfx::ImageSkia& icon)
        : CanvasImageSource(CalculateSize(icon), false),
          file_name_(file_name),
          icon_(icon) {
    }
  
    virtual ~FileDragImageSource() {
    }
  
    // Overridden from gfx::CanvasImageSource.
    virtual void Draw(gfx::Canvas* canvas) OVERRIDE {
      // Paint the icon.
      canvas->DrawImageInt(icon_, (size().width() - icon_.width()) / 2, 0);
  
      base::string16 name = file_name_.BaseName().LossyDisplayName();
      const int flags = gfx::Canvas::TEXT_ALIGN_CENTER;
      const gfx::FontList font_list;
  #if defined(OS_WIN)
      // Paint the file name. We inset it one pixel to allow room for the halo.
      const gfx::Rect rect(1, icon_.height() + kLinkDragImageVPadding + 1,
                           size().width() - 2, font_list.GetHeight());
      canvas->DrawStringRectWithHalo(name, font_list, kFileDragImageTextColor,
                                     SK_ColorWHITE, rect, flags);
  #else
      // NO_SUBPIXEL_RENDERING is required when drawing to a non-opaque canvas.
      const gfx::Rect rect(0, icon_.height() + kLinkDragImageVPadding,
                           size().width(), font_list.GetHeight());
      canvas->DrawStringRectWithFlags(name, font_list, kFileDragImageTextColor,
                                      rect,
                                      flags | gfx::Canvas::NO_SUBPIXEL_RENDERING);
  #endif
    }
  
   private:
    gfx::Size CalculateSize(const gfx::ImageSkia& icon) const {
      const int width = kFileDragImageMaxWidth;
      // Add +2 here to allow room for the halo.
      const int height = gfx::FontList().GetHeight() + icon.height() +
                         kLinkDragImageVPadding + 2;
      return gfx::Size(width, height);
    }
  
    const base::FilePath file_name_;
    const gfx::ImageSkia icon_;
  
    DISALLOW_COPY_AND_ASSIGN(FileDragImageSource);
  };
  
  }  // namespace
  
  void CreateDragImageForFile(const base::FilePath& file_name,
                              const gfx::ImageSkia* icon,
                              ui::OSExchangeData* data_object) {
    DCHECK(icon);
    DCHECK(data_object);
    gfx::CanvasImageSource* source = new FileDragImageSource(file_name, *icon);
    gfx::Size size = source->size();
    // ImageSkia takes ownership of |source|.
    gfx::ImageSkia image = gfx::ImageSkia(source, size);
  
    gfx::Vector2d cursor_offset(size.width() / 2, kLinkDragImageVPadding);
    SetDragImageOnDataObject(image, size, cursor_offset, data_object);
  }
  
  void SetDragImageOnDataObject(const gfx::Canvas& canvas,
                                const gfx::Size& size,
                                const gfx::Vector2d& cursor_offset,
                                ui::OSExchangeData* data_object) {
    gfx::ImageSkia image = gfx::ImageSkia(canvas.ExtractImageRep());
    SetDragImageOnDataObject(image, size, cursor_offset, data_object);
  }
  
  }  // namespace drag_utils
  