Commit 874bf8650437ab7561b0a845d910abd947383160
2015-08-13T17:40:28
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.
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diff --git a/src/video/x11/SDL_x11events.c b/src/video/x11/SDL_x11events.c
index 313753d..6c8f8d4 100644
--- a/src/video/x11/SDL_x11events.c
+++ b/src/video/x11/SDL_x11events.c
@@ -167,54 +167,20 @@ static SDL_bool X11_KeyRepeat(Display *display, XEvent *event)
return d.found;
}
-static Bool X11_IsWheelCheckIfEvent(Display *display, XEvent *chkev,
- XPointer arg)
-{
- XEvent *event = (XEvent *) arg;
- /* we only handle buttons 4 and 5 - false positive avoidance */
- if (chkev->type == ButtonRelease &&
- (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)
+static SDL_bool
+X11_IsWheelEvent(Display * display,XEvent * event,int * xticks,int * yticks)
{
- XEvent relevent;
- if (X11_XPending(display)) {
- /* according to the xlib docs, no specific mouse wheel events exist.
- however, mouse wheel events trigger a button press and a button release
- immediately. thus, checking if the same button was released at the same
- 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;
- }
+ /* according to the xlib docs, no specific mouse wheel events exist.
+ However, the defacto standard is that the vertical wheel is X buttons
+ 4 (up) and 5 (down) and a horizontal wheel is 6 (left) and 7 (right). */
+
+ /* Xlib defines "Button1" through 5, so we just use literals here. */
+ switch (event->xbutton.button) {
+ case 4: *yticks = 1; return SDL_TRUE;
+ case 5: *yticks = -1; return SDL_TRUE;
+ case 6: *xticks = 1; return SDL_TRUE;
+ case 7: *xticks = -1; return SDL_TRUE;
+ default: break;
}
return SDL_FALSE;
}
@@ -1056,9 +1022,13 @@ X11_DispatchEvent(_THIS)
case ButtonRelease:{
int button = xevent.xbutton.button;
- if (button > 7) {
- /* see explanation at case ButtonPress */
- button -= (8-SDL_BUTTON_X1);
+ /* The X server sends a Release event for each Press for wheels. Ignore them. */
+ int xticks = 0, yticks = 0;
+ 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);
}