Fix mousereport

This patch replaces the previous one I sent.

The following changes are made in this patch:
 - Fix tracking of pressed buttons. Previously, pressing two buttons and
   then releasing one would make st think no buttons are pressed, which
   in particular broke MODE_MOUSEMOTION.
 - Always send the lowest-numbered pressed button on motion events; when
   no button is pressed for a motion event in MODE_MOUSEMANY, then send
   a release. This matches the behaviour of xterm. (Previously, st sent
   the most recently pressed button in the motion report.)
 - Remove UB (?) access to potentially inactive struct member
   e->xbutton.button of XEvent union.
 - Fix (unlikely) possibility of overflow for large button numbers.

The one discrepancy I found between st and xterm is that xterm sometimes
encodes buttons with large numbers (>5) strangely. E.g., xterm reports
presses of buttons 8 and 9 as releases, whereas st properly (?) encodes
them as presses.

1 files changed, 51 insertions, 35 deletions

diff --git a/x.c b/x.c
index 8a16faa..5f4ea73 100644
--- a/x.c
+++ b/x.c
@@ -252,7 +252,7 @@ static char *opt_line  = NULL;
 static char *opt_name  = NULL;
 static char *opt_title = NULL;
 
-static int oldbutton = 3; /* button event on startup: 3 = release */
+static uint buttons; /* bit field of pressed buttons */
 
 void
 clipcopy(const Arg *dummy)
@@ -364,61 +364,68 @@ mousesel(XEvent *e, int done)
 void
 mousereport(XEvent *e)
 {
-        int len, x = evcol(e), y = evrow(e),
-            button = e->xbutton.button, state = e->xbutton.state;
+        int len, btn, code;
+        int x = evcol(e), y = evrow(e);
+        int state = e->xbutton.state;
         char buf[40];
         static int ox, oy;
 
-        /* from urxvt */
-        if (e->xbutton.type == MotionNotify) {
+        if (e->type == MotionNotify) {
                 if (x == ox && y == oy)
                         return;
                 if (!IS_SET(MODE_MOUSEMOTION) && !IS_SET(MODE_MOUSEMANY))
                         return;
-                /* MOUSE_MOTION: no reporting if no button is pressed */
-                if (IS_SET(MODE_MOUSEMOTION) && oldbutton == 3)
+                /* MODE_MOUSEMOTION: no reporting if no button is pressed */
+                if (IS_SET(MODE_MOUSEMOTION) && buttons == 0)
                         return;
-
-                button = oldbutton + 32;
-                ox = x;
-                oy = y;
+                /* Set btn to lowest-numbered pressed button, or 12 if no
+                 * buttons are pressed. */
+                for (btn = 1; btn <= 11 && !(buttons & (1<<(btn-1))); btn++)
+                        ;
+                code = 32;
         } else {
-                if (!IS_SET(MODE_MOUSESGR) && e->xbutton.type == ButtonRelease) {
-                        button = 3;
-                } else {
-                        button -= Button1;
-                        if (button >= 7)
-                                button += 128 - 7;
-                        else if (button >= 3)
-                                button += 64 - 3;
-                }
-                if (e->xbutton.type == ButtonPress) {
-                        oldbutton = button;
-                        ox = x;
-                        oy = y;
-                } else if (e->xbutton.type == ButtonRelease) {
-                        oldbutton = 3;
+                btn = e->xbutton.button;
+                /* Only buttons 1 through 11 can be encoded */
+                if (btn < 1 || btn > 11)
+                        return;
+                if (e->type == ButtonRelease) {
                         /* MODE_MOUSEX10: no button release reporting */
                         if (IS_SET(MODE_MOUSEX10))
                                 return;
-                        if (button == 64 || button == 65)
+                        /* Don't send release events for the scroll wheel */
+                        if (btn == 4 || btn == 5)
                                 return;
                 }
+                code = 0;
         }
 
+        ox = x;
+        oy = y;
+
+        /* Encode btn into code. If no button is pressed for a motion event in
+         * MODE_MOUSEMANY, then encode it as a release. */
+        if ((!IS_SET(MODE_MOUSESGR) && e->type == ButtonRelease) || btn == 12)
+                code += 3;
+        else if (btn >= 8)
+                code += 128 + btn - 8;
+        else if (btn >= 4)
+                code += 64 + btn - 4;
+        else
+                code += btn - 1;
+
         if (!IS_SET(MODE_MOUSEX10)) {
-                button += ((state & ShiftMask  ) ? 4  : 0)
-                        + ((state & Mod4Mask   ) ? 8  : 0)
-                        + ((state & ControlMask) ? 16 : 0);
+                code += ((state & ShiftMask  ) ?  4 : 0)
+                      + ((state & Mod4Mask   ) ?  8 : 0)
+                      + ((state & ControlMask) ? 16 : 0);
         }
 
         if (IS_SET(MODE_MOUSESGR)) {
                 len = snprintf(buf, sizeof(buf), "\033[<%d;%d;%d%c",
-                                button, x+1, y+1,
-                                e->xbutton.type == ButtonRelease ? 'm' : 'M');
+                                code, x+1, y+1,
+                                e->type == ButtonRelease ? 'm' : 'M');
         } else if (x < 223 && y < 223) {
                 len = snprintf(buf, sizeof(buf), "\033[M%c%c%c",
-                                32+button, 32+x+1, 32+y+1);
+                                32+code, 32+x+1, 32+y+1);
         } else {
                 return;
         }
@@ -461,9 +468,13 @@ mouseaction(XEvent *e, uint release)
 void
 bpress(XEvent *e)
 {
+        int btn = e->xbutton.button;
         struct timespec now;
         int snap;
 
+        if (1 <= btn && btn <= 11)
+                buttons |= 1 << (btn-1);
+
         if (IS_SET(MODE_MOUSE) && !(e->xbutton.state & forcemousemod)) {
                 mousereport(e);
                 return;
@@ -472,7 +483,7 @@ bpress(XEvent *e)
         if (mouseaction(e, 0))
                 return;
 
-        if (e->xbutton.button == Button1) {
+        if (btn == Button1) {
                 /*
                  * If the user clicks below predefined timeouts specific
                  * snapping behaviour is exposed.
@@ -686,6 +697,11 @@ xsetsel(char *str)
 void
 brelease(XEvent *e)
 {
+        int btn = e->xbutton.button;
+
+        if (1 <= btn && btn <= 11)
+                buttons &= ~(1 << (btn-1));
+
         if (IS_SET(MODE_MOUSE) && !(e->xbutton.state & forcemousemod)) {
                 mousereport(e);
                 return;
@@ -693,7 +709,7 @@ brelease(XEvent *e)
 
         if (mouseaction(e, 1))
                 return;
-        if (e->xbutton.button == Button1)
+        if (btn == Button1)
                 mousesel(e, 1);
 }