- 1 year ago
How to read content of WM_PAINT message?
In Windows, you typically don't read the content of the WM_PAINT
message directly. Instead, you handle the WM_PAINT
message in your window procedure and use the device context (HDC
) provided by the message to draw or update the contents of your window.
The WM_PAINT
message is sent to a window whenever it needs to be redrawn, such as when it is first created, when it is resized, or when it is covered and then uncovered by other windows. When your window receives a WM_PAINT
message, you should call the BeginPaint
function to get the device context for drawing, and then perform your drawing operations. After you are done, you should call the EndPaint
function to release the device context.
Here's an example of how you can handle the WM_PAINT
message in your window procedure:
cLRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {
switch (message) {
case WM_PAINT: {
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
// Perform your drawing operations here using the hdc
EndPaint(hWnd, &ps);
return 0;
}
// Handle other messages here...
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
}
In this example, when the window receives a WM_PAINT
message, it calls BeginPaint
to get the device context and EndPaint
to release the device context after drawing is complete. You can use the hdc
provided by BeginPaint
to draw directly on the window's client area using various GDI functions.
Note that the WM_PAINT
message can be sent very frequently, so it's important to make your drawing operations as efficient as possible to avoid performance issues. If you have a complex or time-consuming drawing operation, you may consider using double buffering techniques to reduce flickering and improve performance.