From 9da5b4451365e33c4f561d74a99ad5c17ff20fed Mon Sep 17 00:00:00 2001
From: Roger Peppe <rogpeppe@gmail.com>
Date: Sat, 29 Mar 2025 13:10:49 +0000
Subject: cmd/devdraw: avoid use of X button state field

This bug is an intermittent annoyance and does not seem likely to be
fixed soon. It means that every so often my acme becomes unusable
because it behaves as if a mouse button is permanently set.

Avoid that issue by keeping track of mouse button state directly.

While we're about it, fix another annoying issue: under Linux the
FocusOut event reset the kstate field but not the kbuttons field,
meaning that the buttons state could inappropriately persist. This
happened occasionally by accident, but was easy to reproduce: with the
mouse button held down, drag outside the window and click Alt-Tab to
switch away from the window. We see a KeyDown event followed by FocusOut
but no KeyUp event.

Change-Id: I3708316478c80c41806d7157ae9929c6cd84b662
---
 src/cmd/devdraw/x11-screen.c | 63 +++++++++-----------------------------------
 1 file changed, 12 insertions(+), 51 deletions(-)

(limited to 'src')

diff --git a/src/cmd/devdraw/x11-screen.c b/src/cmd/devdraw/x11-screen.c
index f4aa1ce9..df7cca46 100644
--- a/src/cmd/devdraw/x11-screen.c
+++ b/src/cmd/devdraw/x11-screen.c
@@ -502,6 +502,7 @@ runxevent(XEvent *xev)
 		 * so clear out the keyboard state when we lose the focus.
 		 */
 		_x.kstate = 0;
+		_x.kbuttons = 0;
 		_x.altdown = 0;
 		gfx_abortcompose(w->client);
 		break;
@@ -1275,10 +1276,18 @@ _xtoplan9kbd(XEvent *e)
 	return k+0;
 }
 
+int
+_xtoplan9buttons(unsigned int b)
+{
+	if(b == 0){
+		return 0;
+	}
+	return 1<<(b-1);
+}
+
 static int
 _xtoplan9mouse(Xwin *w, XEvent *e, Mouse *m)
 {
-	int s;
 	XButtonEvent *be;
 	XMotionEvent *me;
 
@@ -1307,54 +1316,18 @@ _xtoplan9mouse(Xwin *w, XEvent *e, Mouse *m)
 		/* BUG? on mac need to inherit these from elsewhere? */
 		m->xy.x = be->x;
 		m->xy.y = be->y;
-		s = be->state;
 		m->msec = be->time;
-		switch(be->button){
-		case 1:
-			s |= Button1Mask;
-			break;
-		case 2:
-			s |= Button2Mask;
-			break;
-		case 3:
-			s |= Button3Mask;
-			break;
-		case 4:
-			s |= Button4Mask;
-			break;
-		case 5:
-			s |= Button5Mask;
-			break;
-		}
+		m->buttons |= _xtoplan9buttons(be->button);
 		break;
 	case ButtonRelease:
 		be = (XButtonEvent*)e;
 		m->xy.x = be->x;
 		m->xy.y = be->y;
-		s = be->state;
 		m->msec = be->time;
-		switch(be->button){
-		case 1:
-			s &= ~Button1Mask;
-			break;
-		case 2:
-			s &= ~Button2Mask;
-			break;
-		case 3:
-			s &= ~Button3Mask;
-			break;
-		case 4:
-			s &= ~Button4Mask;
-			break;
-		case 5:
-			s &= ~Button5Mask;
-			break;
-		}
-		break;
+		m->buttons &= ~_xtoplan9buttons(be->button);
 
 	case MotionNotify:
 		me = (XMotionEvent*)e;
-		s = me->state;
 		m->xy.x = me->x;
 		m->xy.y = me->y;
 		m->msec = me->time;
@@ -1363,18 +1336,6 @@ _xtoplan9mouse(Xwin *w, XEvent *e, Mouse *m)
 	default:
 		return -1;
 	}
-
-	m->buttons = 0;
-	if(s & Button1Mask)
-		m->buttons |= 1;
-	if(s & Button2Mask)
-		m->buttons |= 2;
-	if(s & Button3Mask)
-		m->buttons |= 4;
-	if(s & Button4Mask)
-		m->buttons |= 8;
-	if(s & Button5Mask)
-		m->buttons |= 16;
 	return 0;
 }
 
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