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Fixed bug #1056 (Frequent crashes in Touch events by simply touching the screen)

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Joseba García Echebarria      2010-12-15 01:55:22 PST

I believe the crash is caused by a check not being performed on wether an
SDL_Touch element is NULL before using it in the SDL_SendTouchMotion function
in src/events/SDL_touch.c around line 400.
Judging from the rest of the code, there's a missing

    if (!touch) {
        return 0;
    }

before using "touch" as SDL_GetFinger(), SDL_GetFingerIndexId() use
touch->num_fingers without checking.

I can attach a patch if you like. It seems pretty straightforward, though.

I have yet to discover why touch is being returned as NULL as this error is
only triggered when an actual gesture has been performed, maybe something
related to SDL_AddTouch()?
This commit is contained in:
Sam Lantinga 2011-01-28 10:21:58 -08:00
parent c3daf0f0cd
commit e64d0e8d85
1 changed files with 10 additions and 6 deletions
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16
src/events/SDL_touch.c
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@ -397,15 +397,16 @@ SDL_SendTouchMotion(SDL_TouchID id, SDL_FingerID fingerid, int relative,
float xin, float yin, float pressurein) float xin, float yin, float pressurein)
{ {
int index = SDL_GetTouchIndexId(id); int index = SDL_GetTouchIndexId(id);
SDL_Touch *touch = SDL_GetTouch(id); SDL_Touch *touch;
SDL_Finger *finger = SDL_GetFinger(touch,fingerid); SDL_Finger *finger;
int posted; int posted;
Sint16 xrel, yrel; Sint16 xrel, yrel;
float x_max = 0, y_max = 0; float x_max = 0, y_max = 0;
Uint16 x; Uint16 x;
Uint16 y; Uint16 y;
Uint16 pressure; Uint16 pressure;
touch = SDL_GetTouch(id);
if (!touch) { if (!touch) {
return SDL_TouchNotFoundError(id); return SDL_TouchNotFoundError(id);
} }
@ -418,6 +419,7 @@ SDL_SendTouchMotion(SDL_TouchID id, SDL_FingerID fingerid, int relative,
return 0; return 0;
} }
finger = SDL_GetFinger(touch,fingerid);
if(finger == NULL || !finger->down) { if(finger == NULL || !finger->down) {
return SDL_SendFingerDown(id,fingerid,SDL_TRUE,xin,yin,pressurein); return SDL_SendFingerDown(id,fingerid,SDL_TRUE,xin,yin,pressurein);
} else { } else {
@ -496,14 +498,16 @@ SDL_SendTouchMotion(SDL_TouchID id, SDL_FingerID fingerid, int relative,
return posted; return posted;
} }
} }
int int
SDL_SendTouchButton(SDL_TouchID id, Uint8 state, Uint8 button) SDL_SendTouchButton(SDL_TouchID id, Uint8 state, Uint8 button)
{ {
SDL_Touch *touch = SDL_GetTouch(id); SDL_Touch *touch;
int posted; int posted;
Uint32 type; Uint32 type;
touch = SDL_GetTouch(id);
if (!touch) { if (!touch) {
return SDL_TouchNotFoundError(id); return SDL_TouchNotFoundError(id);
} }