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[muku]

I feel stupid for not being able to figure this out; even some quick googling hasn't turned anything up.

Anyway, I try to use SDL_GetRelativeMouseState to get incremental mouse input (think controlling a flight simulator with the mouse, that's rather close to my use case). It basically works, but as soon as the mouse leaves the game window, I don't get any more input. I tried to remedy that by calling SDL_WM_GrabInput(1), but that just constrains the mouse pointer to the window; as soon as it hits the border, no further relative motion in that direction is possible. So my last idea was to use SDL_WarpMouse to put the mouse cursor at the window's center every frame, but when I do that I don't get any deltas at all anymore.

So, help! I don't need a mouse pointer, I just want to know how much the user has moved the mouse in any given frame. How do I do that?

[Saint]

Well, if you warp the mouse to the center of the screen and do this *every frame* you can just call SDL_GetMouseState and your delta movement is the offset from the wanted position, like so:

Code:

//Somewhere in the gameloop
int MouseX,MouseY;
SDL_GetMouseState(&MouseX,&MouseY);
int DeltaX = MouseX - HalfScreenX;
int DeltaY = MouseY - HalfScreenY;
SDL_WarpMouse(HalfScreenX,HalfScreenY);

[muku]

Hm, good idea. Why doesn't this seem to work with SDL_GetRelativeMouseState though? From the name I would have guessed that that is exactly the function I'd want to use...

EDIT: Wait a moment... I guess SDL updates the mouse state when I poll the message queue, huh? Maybe I called WarpMouse at the wrong time and it does work after all when I do it right, will have to check...

[Ivan]

On initialization:

  SDL_ShowCursor(0);
  SDL_WM_GrabInput(SDL_GRAB_ON);

In your event update loop:

while ( SDL_PollEvent(&event) ) {
         switch (event.type) {
            case SDL_MOUSEMOTION:
             // use event.motion.xrel and event.motion.yrel

SDL_WM_GrabInput confines the mouse to the window, so you don't have to call WarpMouse every frame or anything like that.