got rid of compile time xidx, grabbing the mouse pointer instead, falling back to screen 0 if no pointer available

config.h

@@ -6,9 +6,4 @@ static const char *normbgcolor = "#cccccc";
 static const char *normfgcolor = "#000000";
 static const char *selbgcolor  = "#0066ff";
 static const char *selfgcolor  = "#ffffff";
-
 static unsigned int spaceitem  = 30; /* px between menu items */
-
-#ifdef XINERAMA
-static unsigned int xidx       = 0;  /* Xinerama screen index to use */
-#endif

dmenu.c

@@ -17,6 +17,7 @@
 
 /* macros */
 #define CLEANMASK(mask)         (mask & ~(numlockmask | LockMask))
+#define INRECT(X,Y,RX,RY,RW,RH) ((X) >= (RX) && (X) < (RX) + (RW) && (Y) >= (RY) && (Y) < (RY) + (RH))
 
 /* enums */
 enum { ColFG, ColBG, ColLast };
@@ -585,7 +586,7 @@ run(void) {
 
 void
 setup(Bool topbar) {
-	int i, j, x, y;
+	int i, j, n, x, y;
 	XModifierKeymap *modmap;
 	XSetWindowAttributes wa;
 #if XINERAMA
@@ -618,10 +619,20 @@ setup(Bool topbar) {
 	mh = dc.font.height + 2;
 #if XINERAMA
 	if(XineramaIsActive(dpy)) {
-		info = XineramaQueryScreens(dpy, &i);
+		i = 0;
-		x = info[xidx].x_org;
+		info = XineramaQueryScreens(dpy, &n);
-		y = topbar ? info[xidx].y_org : info[xidx].y_org + info[xidx].height - mh;
+		if(n > 1) {
-		mw = info[xidx].width;
+			int di;
+			unsigned int dui;
+			Window dummy;
+			if(XQueryPointer(dpy, root, &dummy, &dummy, &x, &y, &di, &di, &dui))
+				for(i = 0; i < n; i++)
+					if(INRECT(x, y, info[i].x_org, info[i].y_org, info[i].width, info[i].height))
+						break;
+		}
+		x = info[i].x_org;
+		y = topbar ? info[i].y_org : info[i].y_org + info[i].height - mh;
+		mw = info[i].width;
 		XFree(info);
 	}
 	else