[hackers] [dwm][PATCH] Sort screens by horizontal origin

From: Sebastian Sareyko <sl_AT_setq.dk>
Date: Fri, 27 Sep 2019 15:28:39 +0200

Doing a multi-head setup using other means than Xinerama may lead to
XineramaQueryScreens() returning the screens in an order that does not
actually represent the actual screen layout. This in turn may result
in dwm using the "wrong" monitor in monitor related
functions (focusmon(), tagmon(), applying rules, ...).

This change sorts the list of unique screens by their horizontal
origin to alleviate this problem.
The change does not solve (and may even provoke) the described issue
when screens are not only placed next to each other in a horizontal
way but also vertically.

---
 dwm.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
diff --git a/dwm.c b/dwm.c
index 4465af1..a8e9467 100644
--- a/dwm.c
+++ b/dwm.c
_AT_@ -1847,6 +1847,24 @@ updateclientlist()
 				(unsigned char *) &(c->win), 1);
 }
 
+#ifdef XINERAMA
+void
+sortscreens(XineramaScreenInfo *screens, int n)
+{
+	int i, j;
+	XineramaScreenInfo *screen = ecalloc(1, sizeof(XineramaScreenInfo));
+
+	for (i = 0; i < n; i++)
+		for (j = i + 1; j < n; j++)
+			if (screens[i].x_org > screens[j].x_org) {
+				memcpy(&screen[0], &screens[i], sizeof(XineramaScreenInfo));
+				memcpy(&screens[i], &screens[j], sizeof(XineramaScreenInfo));
+				memcpy(&screens[j], &screen[0], sizeof(XineramaScreenInfo));
+			}
+	XFree(screen);
+}
+#endif /* XINERAMA */
+
 int
 updategeom(void)
 {
_AT_@ -1868,6 +1886,7 @@ updategeom(void)
 				memcpy(&unique[j++], &info[i], sizeof(XineramaScreenInfo));
 		XFree(info);
 		nn = j;
+		sortscreens(unique, nn);
 		if (n <= nn) { /* new monitors available */
 			for (i = 0; i < (nn - n); i++) {
 				for (m = mons; m && m->next; m = m->next);
-- 
2.21.0

Received on Fri Sep 27 2019 - 15:28:39 CEST