background drawn using bitmap from task03b_back.bmp file (as in the demonstration)
parts of the screen drawn in quarters of the window
Functionality:
left mouse button down - copy appropriate quarter of the screen (click in the left-top part of the window should copy left-top quarter of the screen etc.)
right mouse button double click - hide the window, copy whole screen, show the window
Technical requirements:
copied parts of the screen must be remembered for repainting window's content
no flickering (during window's resizing and repainting)
background bitmap should be loaded from file, if there is no file show a message box and terminate the application
you can assume that the number of colours in system doesn't change during application's lifetime