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 13 namespace 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). 36 class 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
