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Function 50 - Set Window Form

Regular windows are rectangles. With this function, the window can be given an arbitrary shape. The form is defined by a set of points inside the framing rectangle belonging to the window. Position and the sizes of the framing rectangle are set by function 0 and change by function 67.

Data Setup with Form Information

Options:

· eax = 50 - function number

· ebx = 0 - number of subfunction

· ecx = pointer to the form data (byte array 0/1)

Return value:

· function does not return value

Scaling form data

Options:

· eax = 50 - function number

· ebx = 1 - number of subfunction

· ecx sets the scale: each data byte defines (2 ^ scale) * (2 ^ scale) pixels

Return value:

· function does not return value

Remarks:

· The default scale is 0 (scaling factor 1). If in the form data one byte corresponds to one pixel, then the scale can be not set.

· Denote xsize = window width (in pixels), ysize = height; note that they are one more than those set by functions 0, 67.

· By defining the scale, xsize and ysize should be divided by 2 ^ scale.

· The data byte at offset a must be 0/1 and determines that the window has a square with a side of 2 ^ scale (with scale = 0 we get a pixel) and coordinates of the upper left corner (a mod (xsize shr scale), a div (xsize shr scale))

· Data size: (xsize shr scale) * (ysize shr scale).

· Data must be present in the memory and not change after setting the form.

· The system views the form data every time the window is redrawn with function 0.

· Calling subfunction 0 with a null pointer results in a return to a rectangular shape.

Constants for registers:

eax - SF_SET_WINDOW_SHAPE (50)