1. When the customer area text is overwritten, the default operation of the system is invisible to invalid window. The window will be filled with the Window process unless the WM_PAINT message notification window is sent.
2. A WM_PAINT message does not do not correspond to a "invalid rectangle", which can correspond to multiple, the operating system will be calculated, incorporate the newly added "invalid window" into the original "invalid window", get a new inclusion current all "Invalid Window" window collection.
3. GetUpdateect can get the "Handle of Invalid Window" at any time.
4. ValidateRect will enable any zone of the client to "Valid Window" if ValidateRect is valid for all windows of the current client area, and all WM_PAINT messages in the Windows Message queue will be cleared.
5. The window will accept the "wm_paint" message only when the customer goes to fail.
6. Device Description Table is actually the data structure saved inside the GDI. When the program requires a drawing, it must first obtain the device description table handle. When the program is completed in the client area, the device description table must be released. The program must obtain and release the handle during processing a single message, and other devices cannot be saved between the two messages.
7. When processing the WM_PAINT message, BeginPaint and Endpaint must appear. Windows does not make this zone valid if you do not call BeginPaint and Endpaint.
