systray + xrdb compatibility issue ref. #429

When changing colour scheme during runtime using xrdb the systray and
icons would keep the original colours.

To work around that the systray icon windows need to be redrawn after
changing the background pixel value. Just calling XClearWindow for
each systray window results in the systray icons disappearing, they
do not automatically redraw. The solution is apparently to send an
Expose event to each window which should in principle trigger a redraw
from the application side.

One way to achieve this is to move the window out of the drawable area.
When the window is then brought back into view the X server will send
the Expose event for the window. The "easiest" way to do this is to
move the entire systray window out of view as part of the xrdb call.

It is possible to do this in the draw_systray function itself, but we
probably do not want to do this every single time the bar is drawn and
it may also cause some noticeable flickering.

This issue is isolated to using the systray without the alpha patch.

patch/bar_systray.c

@@ -94,6 +94,12 @@ draw_systray(Bar *bar, BarArg *a)
 			i->mon = bar->mon;
 	}
 
+	#if !BAR_ALPHA_PATCH
+	wa.background_pixel = scheme[SchemeNorm][ColBg].pixel;
+	XChangeWindowAttributes(dpy, systray->win, CWBackPixel, &wa);
+	XClearWindow(dpy, systray->win);
+	#endif // BAR_ALPHA_PATCH
+
 	XMoveResizeWindow(dpy, systray->win, bar->bx + a->x + lrpad / 2, (w ? bar->by + a->y + (a->h - systray->h) / 2: -systray->h), MAX(w, 1), systray->h);
 	return w;
 }

patch/xrdb.c

@@ -132,6 +132,11 @@ xrdb(const Arg *arg)
 		#endif // BAR_ALPHA_PATCH
 		ColCount
 		);
+	#if BAR_SYSTRAY_PATCH && !BAR_ALPHA_PATCH
+	if (systray) {
+		XMoveWindow(dpy, systray->win, -32000, -32000);
+	}
+	#endif // BAR_SYSTRAY_PATCH
 	arrange(NULL);
 	focus(NULL);
 }