[SDL] using an image as mouse cursor

j_post at pacbell.net j_post at pacbell.net
Sat Jan 22 09:36:52 PST 2005



On Saturday 22 January 2005 04:47 am, Roger D. Vargas wrote:
> I didnt got any answer about how to convert a surface to cursor, so I
> tried another method I found in a demo app. I hide system cursor, then
> use mouse motion events to change image coordinates. The demo works
> smooth, but in my program for some reason the image floats slowly
> following mouse path during some time instead of behaving like the
> system cursor.
> This is the code I use (copied exactly from demo)
>
> if (event.motion.type==SDL_MOUSEMOTION) {
>                          cx=event.button.x;
>                          cy=event.button.y;
>                          cur_pos.x=cx;
>                          cur_pos.y=cy;
>                          cur_pos.w=cursor->w;
>                          cur_pos.h=cursor->h;
>
> //after closing if...
> SDL_BlitSurface(cursor,NULL, screen,&cur_pos);
>
> What Im doing wrong?

Probably responding to each mouse motion event. You'll get *lots* of them--if 
you redraw for each one, it may bog down your system.

Try saving the x & y coordinates of each event and only redraw after there 
are no more, or another event type occurs. If you're using a typical

while (SDL_PollEvent(&event))

loop, you'll catch enough mouse motion events for the cursor to move 
smoothly, but not drag down the system doing unnecessary blits.

HTH,
Jeff






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