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// 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_GFX_CANVAS_PAINT_WIN_H_
#define UI_GFX_CANVAS_PAINT_WIN_H_
#include "skia/ext/platform_canvas.h"
#include "ui/base/win/dpi.h"
#include "ui/gfx/canvas.h"
#include "ui/gfx/size.h"
namespace gfx {
// A class designed to help with WM_PAINT operations on Windows. It will create
// the bitmap and canvas with the correct size and transform for the dirty rect.
// The bitmap will be automatically painted to the screen on destruction.
//
// You MUST call isEmpty before painting to determine if anything needs
// painting. Sometimes the dirty rect can actually be empty, and this makes
// the bitmap functions we call unhappy. The caller should not paint in this
// case.
//
// Therefore, all you need to do is:
// case WM_PAINT: {
// PAINTSTRUCT ps;
// HDC hdc = BeginPaint(hwnd, &ps);
// gfx::CanvasSkiaPaint canvas(hwnd, hdc, ps);
// if (!canvas.isEmpty()) {
// ... paint to the canvas ...
// }
// EndPaint(hwnd, &ps);
// return 0;
// }
// Note: The created context is always inialized to (0, 0, 0, 0).
class UI_EXPORT CanvasSkiaPaint : public Canvas {
public:
// This constructor assumes the canvas is opaque.
CanvasSkiaPaint(HWND hwnd, HDC dc, const PAINTSTRUCT& ps);
virtual ~CanvasSkiaPaint();
// Creates a CanvasSkiaPaint for the specified region that paints to the
// specified dc.
CanvasSkiaPaint(HDC dc, bool opaque, int x, int y, int w, int h);
// Returns the rectangle that is invalid.
virtual gfx::Rect GetInvalidRect() const;
// Returns true if the invalid region is empty. The caller should call this
// function to determine if anything needs painting.
bool is_empty() const {
return ps_.rcPaint.right - ps_.rcPaint.left == 0 ||
ps_.rcPaint.bottom - ps_.rcPaint.top == 0;
};
// Use to access the Windows painting parameters, especially useful for
// getting the bounding rect for painting: paintstruct().rcPaint
const PAINTSTRUCT& paint_struct() const { return ps_; }
// Returns the DC that will be painted to
HDC paint_dc() const { return paint_dc_; }
private:
void Init(bool opaque);
HWND hwnd_;
HDC paint_dc_;
PAINTSTRUCT ps_;
// Disallow copy and assign.
DISALLOW_COPY_AND_ASSIGN(CanvasSkiaPaint);
};
} // namespace gfx
#endif // UI_GFX_CANVAS_PAINT_WIN_H_
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