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The reason why the image flashes is that most of our drawing processes are stored in the ondraw or onpaint function, and ondraw calls the onpaint function for screen display. When the window needs to be re-painted for any reason, the display area is always cleared with the background color before onpaint is called. The background color is often in a large contrast with the drawing content, in this way, the background color and the display image appear alternately in a short period of time, making the display window appear flashing. If you set the background to null, the duplicate drawing will not flash. Of course, this will make the display of the window messy, because during the re-painting, there is no background color to clear the original drawing, and a new image is superimposed. Some people may say that the blinking is caused by the drawing speed being too slow or the display graphics being too complex. In fact, this is not true. The influence of the display speed of the drawing on the flashing is not fundamental.
How to implement dual buffering: In ondraw (CDC * PDC:
CDC memdc; // define a display device object
Cbitmap membitmap; // defines a bitmap object.
// Create a memory display device compatible with Screen Display
Memdc. createcompatibledc (null );
// No drawing yet, because there is no place to draw ^_^
// A bitmap compatible with screen display is created below. The size of the bitmap can be set to the size of the window.
Membitmap. createcompatiblebitmap (PDC, nwidth, nheight );
// Select the bitmap to the memory display device.
// Only the memory display device with the bitmap selected can draw a local image and draw it to the specified bitmap.
Cbitmap * poldbit = memdc. SelectObject (& membitmap );
// Use the background color to clear the bitmap. Here, I use white as the background color.
// You can also use your own color
Memdc. fillsolidrect (255,255,255, nwidth, nheight, RGB ));
// Drawing
Memdc. moveTo (......);
Memdc. lineto (......);
// Copy the image in the memory to the screen for display
PDC-> bitblt (0, 0, nwidth, nheight, & memdc, 0, srccopy );
// Cleanup after drawing is complete
Membitmap. deleteobject ();
Memdc. deletedc ();
Address: http://hi.baidu.com/f234f234/blog/item/a17f4f0863710c950a7b8291.html
