I believe he needs to make his own button function for this to work.
for example let's say you have a bitmap with the sizes 50x100. and it is positioned at x = 100 and y = 100.
You could check in a loop if the mouse pointer is inside the bitmap (your button) with something like:
If mouse position x is bigger than the bitmap position x but less than its position x+size x, same for the y component, then it's inside the button.
if( (mouse_pos.x > bitmap.x) && (mouse_pos.x < bitmap.x + bitmap.size_x) &&
(mouse_pos.y > bitmap.y) && (mouse_pos.y < bitmap.y + bitmap.size_y) )
{
if(mouse_left) button_clicked(); //a way to make it clickable
}
with the given dimensions above the code, 50, 100 and position 100, 100, the if would look like this:
if mouse_pos.x > 100 but less than 100+50 and if mouse_pos.y > 100 but less than 100+100, then it's inside the panel/bitmap.
I believe something like this would work in your case. Basicly make your own button function, atleast you have full control over it and your button can now also call functions with parameters
