WM_PAINT:
Windows call various events
by sending message (arguments) in the application message queue or sending
message to the appropriate window procedure. Window procedure paints the window
by sending message WM_PAINT message.
The WM_PAINT message:
The windows program calls
the Update Window before entering the message loop. Windows procedure takes it
as first WM_PAINT message. This message informs the window procedure that the
client area must be painted or updated. Thereafter the windows procedure should be ready
to repaint the window if necessary.
A window procedure receives
a WM_PAINT message whenever following event occurs:-
1. The
user re-sizes the window.
2. The
client area is scrolled. (Scrolled Window)
3. Previously
hidden area of the window is brought into view. (Uncover Window)
In few cases windows always
save an area of display, it overwrites and restores it when –
1. Mouse
cursor is moved across the client control area.
2. An
icon is dragged across the client area.
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