drawbar: Don't expend effort drawing bar if it is occluded

I noticed that a non-trivial amount of dwm's work on my machine was from
drw_text, which seemed weird, because I have the bar disabled and we
only use drw_text as part of bar drawing.

Looking more closely, I realised that while we use m->showbar when
updating the monitor bar margins, but don't skip actually drawing the
bar if it is hidden. This patch skips drawing it entirely if that is the
case.

On my machine, this takes 10% of dwm's on-CPU time, primarily from
restack() and focus().

When the bar is toggled on again, the X server will generate an Expose
event, and we'll redraw the bar as normal as part of expose().

diff --git a/dwm.c b/dwm.c
index 5e4d49484e8e7bd3ff8c00b6b422af93502e5802..a96f33c1fe009c16c8ca4b2ebac5fb511437e347 100644 (file)
--- a/dwm.c
+++ b/dwm.c
@@ -702,6 +702,9 @@ drawbar(Monitor *m)
        unsigned int i, occ = 0, urg = 0;
        Client *c;
 
+       if (!m->showbar)
+               return;
+
        /* draw status first so it can be overdrawn by tags later */
        if (m == selmon) { /* status is only drawn on selected monitor */
                drw_setscheme(drw, scheme[SchemeNorm]);