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X11: Simplified mousewheel event handling. 

Under load, this would race and report an incorrect mouse button event instead
of a wheel event.

Fixes Bugzilla #2987.
This commit is contained in:
Ryan C. Gordon 2015-08-13 17:40:28 -04:00
parent da6f2221e3
commit 874bf86504
1 changed files with 19 additions and 49 deletions
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68
src/video/x11/SDL_x11events.c
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@ -167,54 +167,20 @@ static SDL_bool X11_KeyRepeat(Display *display, XEvent *event)
return d.found; return d.found;
} }
static Bool X11_IsWheelCheckIfEvent(Display *display, XEvent *chkev, static SDL_bool
XPointer arg) X11_IsWheelEvent(Display * display,XEvent * event,int * xticks,int * yticks)
{ {
XEvent *event = (XEvent *) arg; /* according to the xlib docs, no specific mouse wheel events exist.
/* we only handle buttons 4 and 5 - false positive avoidance */ However, the defacto standard is that the vertical wheel is X buttons
if (chkev->type == ButtonRelease && 4 (up) and 5 (down) and a horizontal wheel is 6 (left) and 7 (right). */
(event->xbutton.button == Button4 || event->xbutton.button == Button5 ||
event->xbutton.button == 6 || event->xbutton.button == 7) &&
chkev->xbutton.button == event->xbutton.button &&
chkev->xbutton.time == event->xbutton.time)
return True;
return False;
}
static SDL_bool X11_IsWheelEvent(Display * display,XEvent * event,int * xticks,int * yticks) /* Xlib defines "Button1" through 5, so we just use literals here. */
{ switch (event->xbutton.button) {
XEvent relevent; case 4: *yticks = 1; return SDL_TRUE;
if (X11_XPending(display)) { case 5: *yticks = -1; return SDL_TRUE;
/* according to the xlib docs, no specific mouse wheel events exist. case 6: *xticks = 1; return SDL_TRUE;
however, mouse wheel events trigger a button press and a button release case 7: *xticks = -1; return SDL_TRUE;
immediately. thus, checking if the same button was released at the same default: break;
time as it was pressed, should be an adequate hack to derive a mouse
wheel event.
However, there is broken and unusual hardware out there...
- False positive: a button for which a release event is
generated (or synthesised) immediately.
- False negative: a wheel which, when rolled, doesn't have
a release event generated immediately. */
if (X11_XCheckIfEvent(display, &relevent, X11_IsWheelCheckIfEvent,
(XPointer) event)) {
/* by default, X11 only knows 5 buttons. on most 3 button + wheel mouse,
Button4 maps to (vertical) wheel up, Button5 maps to wheel down.
Horizontal scrolling usually maps to 6 and 7 which have no name */
if (event->xbutton.button == Button4) {
*yticks = 1;
}
else if (event->xbutton.button == Button5) {
*yticks = -1;
}
else if (event->xbutton.button == 6) {
*xticks = 1;
}
else if (event->xbutton.button == 7) {
*xticks = -1;
}
return SDL_TRUE;
}
} }
return SDL_FALSE; return SDL_FALSE;
} }
@ -1056,9 +1022,13 @@ X11_DispatchEvent(_THIS)
case ButtonRelease:{ case ButtonRelease:{
int button = xevent.xbutton.button; int button = xevent.xbutton.button;
if (button > 7) { /* The X server sends a Release event for each Press for wheels. Ignore them. */
/* see explanation at case ButtonPress */ int xticks = 0, yticks = 0;
button -= (8-SDL_BUTTON_X1); if (!X11_IsWheelEvent(display,&xevent,&xticks, &yticks)) {
if (button > 7) {
/* see explanation at case ButtonPress */
button -= (8-SDL_BUTTON_X1);
}
} }
SDL_SendMouseButton(data->window, 0, SDL_RELEASED, button); SDL_SendMouseButton(data->window, 0, SDL_RELEASED, button);
} }