This message is posted when the user releases the stylus from the touch screen while the stylus is pressed to the touch screen in the client area of a window or when the user releases the left mouse button while the cursor is located within the client area of a window. If another window does not capture the stylus or mouse input, the OS posts the message to the window that contains the stylus tip or cursor. If another window captures the stylus or mouse input, the OS posts the message to the window that has the capture.
WM_LBUTTONUP fwKeys = wParam; xPos = LOWORD(lParam); yPos = HIWORD(lParam);
Indicates the mouse buttons and keys that the user pressed. The following table shows the possible values, which can be combined.
The user pressed the CTRL key.
The user pressed the SHIFT key.
Value of the low-order word of lParam. Specifies the x-coordinate of the cursor, relative to the upper-left corner of the client area.
Value of the high-order word of lParam. Specifies the y-coordinate of the cursor, relative to the upper-left corner of the client area.