[patch] EmulateWheel button press broken

[Andrew Pimlott]

As reported in two Debian bug reports [1] [2], the ability for the
EmulateWheelButton to generate button events was broken shortly before
the 6.9 release.  It is still broken in current Debian unstable package
6.9.0.dfsg.1-3, and I believe it is still broken in x.org CVS.

It was broken by version 1.15 of
xc/programs/Xserver/hw/xfree86/input/mouse/mouse.c.  The problem is the
removal of the truebuttons variable.  The wheel emulation code in
MouseDoPostEvent modifies buttons to mask out EmulateWheelButton,
therefore the if condition

    if (buttons != pMse->lastMappedButtons) {

(line 2256) was failing when the EmulateWheelButton was pressed,
therefore

    pMse->lastMappedButtons = buttons;

(line 2359) was not being run, therefore when the EmulateWheelButton was
released,

    change = buttons ^ pMse->lastMappedButtons;

(line 2162) thought there was no change, therefore the button press was
not generated.

The appended patch fixes this by restoring truebuttons (which I called
origbuttons to be slightly clearer).  The logic is very similar to
before 1.15, and it does not appear to interfere with the mapping
changes in 1.15, so I don't think it will introduce any problems that
weren't already there.  I tested that I can now generate a button press
with EmulateWheelButton.

The patch was generated against the latest Debian unstable sources, but
applies cleanly to the latest CVS.

Andrew

[1] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=320136
[2] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=346098
[3] http://cvs.freedesktop.org/xorg/xc/programs/Xserver/hw/xfree86/input/mouse/mouse.c?r1=1.14&r2=1.15


--- mouse.c.orig	2006-01-12 13:46:21.000000000 -0800
+++ mouse.c	2006-01-12 14:10:46.000000000 -0800
@@ -2076,7 +2076,7 @@
 MouseDoPostEvent(InputInfoPtr pInfo, int buttons, int dx, int dy)
 {
     MouseDevPtr pMse;
-    int emulateButtons;
+    int origbuttons, emulateButtons;
     int id, change;
     int emuWheelDelta, emuWheelButton, emuWheelButtonMask;
     int wheelButtonMask;
@@ -2084,6 +2084,8 @@
 
     pMse = pInfo->private;
 
+    origbuttons = buttons;
+
     /* Do single button double click */
     if (pMse->doubleClickSourceButtonMask) {
         if (buttons & pMse->doubleClickSourceButtonMask) {
@@ -2211,7 +2213,7 @@
     if (dx || dy)
 	xf86PostMotionEvent(pInfo->dev, 0, 0, 2, dx, dy);
 
-    if (buttons != pMse->lastMappedButtons) {
+    if (origbuttons != pMse->lastMappedButtons) {
 
 	change = buttons ^ pMse->lastMappedButtons;
 
@@ -2314,7 +2316,7 @@
 				(buttons & (1 << (id - 1))), 0, 0);
 	}
 
-        pMse->lastMappedButtons = buttons;
+        pMse->lastMappedButtons = origbuttons;
     }
 }