Document tray initialization better.

This commit removes an unnecessary fallback to the first output's name as
this name ("first") will only be used to see whether "tray_output none"
has been specified, anyway.

We also add documentation that clearly states when we want to initialize
the tray and when we don't want to do the same.

relates to #2220

diff --git a/i3bar/src/xcb.c b/i3bar/src/xcb.c
index 1c2134f485ef93ea47bb580ae2d0a6a4cb05d1d1..496035c22e0eaca3787ac1e13b430127288e8be0 100644 (file)
--- a/i3bar/src/xcb.c
+++ b/i3bar/src/xcb.c
@@ -1761,16 +1761,35 @@ void reconfig_windows(bool redraw_bars) {
             }
 
             /* Unless "tray_output none" was specified, we need to initialize the tray. */
-            const char *first = (TAILQ_EMPTY(&(config.tray_outputs))) ? SLIST_FIRST(outputs)->name : TAILQ_FIRST(&(config.tray_outputs))->output;
-            if (!tray_configured && strcasecmp(first, "none") != 0) {
-                /* We do a sanity check here to ensure that this i3bar instance actually handles
-                 * the output on which the tray should appear. For example,
-                 * consider tray_output == [VGA-1], but output == [HDMI-1]. */
+            bool no_tray = false;
+            if (!(TAILQ_EMPTY(&(config.tray_outputs)))) {
+                no_tray = strcasecmp(TAILQ_FIRST(&(config.tray_outputs))->output, "none") == 0;
+            }
 
+            /*
+             * There are three scenarios in which we need to initialize the tray:
+             *   1. A specific output was listed in tray_outputs which is also
+             *      in the list of outputs managed by this bar.
+             *   2. No tray_output directive was specified. In this case, we
+             *      use the first available output.
+             *   3. 'tray_output primary' was specified. In this case we use the
+             *      primary output.
+             *
+             * Three scenarios in which we specifically don't want to
+             * initialize the tray are:
+             *   1. 'tray_output none' was specified.
+             *   2. A specific output was listed as a tray_output, but is not
+             *      one of the outputs managed by this bar. For example, consider
+             *      tray_outputs == [VGA-1], but outputs == [HDMI-1].
+             *   3. 'tray_output primary' was specified and no output in the list
+             *      is primary.
+             */
+            if (!tray_configured && !no_tray) {
                 /* If no tray_output was specified, we go ahead and initialize the tray as
                  * we will be using the first available output. */
-                if (TAILQ_EMPTY(&(config.tray_outputs)))
+                if (TAILQ_EMPTY(&(config.tray_outputs))) {
                     init_tray();
+                }
 
                 /* If one or more tray_output assignments were specified, we ensure that at least one of
                  * them is actually an output managed by this instance. */