Zooming In on a Selection: Step 3

In the MainWndProc function, add some new local variables to support the GDI functions. You can add the following code to the existing variable declarations at the beginning of the function:

/* Local variables used with GDI functions on WM_MOUSEMOVE */
HGDIOBJ SavedPen, SavedBrush; 
int DisplayMode;
HDC ThisWindowDC;