1// Copyright (c) 2011 The Chromium Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5#ifndef UI_GFX_CANVAS_PAINT_WIN_H_ 6#define UI_GFX_CANVAS_PAINT_WIN_H_ 7 8#include "skia/ext/platform_canvas.h" 9#include "ui/base/win/dpi.h" 10#include "ui/gfx/canvas.h" 11#include "ui/gfx/size.h" 12 13namespace gfx { 14 15// A class designed to help with WM_PAINT operations on Windows. It will create 16// the bitmap and canvas with the correct size and transform for the dirty rect. 17// The bitmap will be automatically painted to the screen on destruction. 18// 19// You MUST call isEmpty before painting to determine if anything needs 20// painting. Sometimes the dirty rect can actually be empty, and this makes 21// the bitmap functions we call unhappy. The caller should not paint in this 22// case. 23// 24// Therefore, all you need to do is: 25// case WM_PAINT: { 26// PAINTSTRUCT ps; 27// HDC hdc = BeginPaint(hwnd, &ps); 28// gfx::CanvasSkiaPaint canvas(hwnd, hdc, ps); 29// if (!canvas.isEmpty()) { 30// ... paint to the canvas ... 31// } 32// EndPaint(hwnd, &ps); 33// return 0; 34// } 35// Note: The created context is always inialized to (0, 0, 0, 0). 36class UI_EXPORT CanvasSkiaPaint : public Canvas { 37 public: 38 // This constructor assumes the canvas is opaque. 39 CanvasSkiaPaint(HWND hwnd, HDC dc, const PAINTSTRUCT& ps); 40 virtual ~CanvasSkiaPaint(); 41 42 // Creates a CanvasSkiaPaint for the specified region that paints to the 43 // specified dc. 44 CanvasSkiaPaint(HDC dc, bool opaque, int x, int y, int w, int h); 45 46 // Returns the rectangle that is invalid. 47 virtual gfx::Rect GetInvalidRect() const; 48 49 // Returns true if the invalid region is empty. The caller should call this 50 // function to determine if anything needs painting. 51 bool is_empty() const { 52 return ps_.rcPaint.right - ps_.rcPaint.left == 0 || 53 ps_.rcPaint.bottom - ps_.rcPaint.top == 0; 54 }; 55 56 // Use to access the Windows painting parameters, especially useful for 57 // getting the bounding rect for painting: paintstruct().rcPaint 58 const PAINTSTRUCT& paint_struct() const { return ps_; } 59 60 // Returns the DC that will be painted to 61 HDC paint_dc() const { return paint_dc_; } 62 63 private: 64 void Init(bool opaque); 65 66 HWND hwnd_; 67 HDC paint_dc_; 68 PAINTSTRUCT ps_; 69 70 // Disallow copy and assign. 71 DISALLOW_COPY_AND_ASSIGN(CanvasSkiaPaint); 72}; 73 74} // namespace gfx 75 76#endif // UI_GFX_CANVAS_PAINT_WIN_H_ 77