osc 5577: `busy`, and a sidebar that shows it (busy_mark)

A status is a line of text, and a line of text cannot say whether it is still
true. "building 3/7" reads exactly the same while it builds and ten minutes
after it stopped, which is the one thing somebody reading it from another tab
wants to know -- and the only workaround available to a program was to write
the answer into the words and keep rewriting them.

So `busy`:

    printf '\033]5577;1;status;make test\033\\'
    printf '\033]5577;1;busy;1\033\\'
    ...
    printf '\033]5577;1;busy;0\033\\'

A flag of its own rather than a field of `status`, because a status is the
*whole* payload after the verb -- `status;a;b;c` has always been the text
"a;b;c" -- so anything added to that line would change what every existing
sender means, including the five pi extensions D1 promises byte compatibility
to. Orthogonal, so a program can leave one line up and toggle the other;
anything but 0/false/no/off is on; `clear` takes both; and a pane whose program
has gone is never busy, whatever it last claimed, because a spinner turning
under a dead tab is a lie you keep looking at.

In a sidebar the row turns `tab_status_busy` -- the theme's accent, derived
like the other status colours, so no theme needs a line -- and takes a spinner
in the column `tab_bar_padding` was already holding blank, so nothing reflows
when a program starts or stops working. `busy_mark` is the frames, separated by
spaces: one frame is a static mark and costs nothing, several make it turn, and
only then does the session keep a frame clock -- via the same `animating` flag
an animated shader uses, so the cost lands only while such a row is actually
composed, and `""` drops the mark entirely and leaves the colour to say it.
The frame is a pure function of the clock, like every other pulse here, so two
clients attached to one session show the same one.

`panes` now reports `status` and `busy`, which is the scriptable half of the
same fact: what a pane says about itself, without reading its screen.

1 files changed, 18 insertions, 0 deletions

diff --git a/src/pane.c b/src/pane.c
index 47db104..b9b3f44 100644
--- a/src/pane.c
+++ b/src/pane.c
@@ -99,6 +99,12 @@ struct pane {
 
   osc_scan_t scan;
   char status[256];
+  /* Whether what the status describes is still happening. Its own flag rather
+   * than a field of the status text, because the text is the *whole* payload
+   * after the verb (`status;a;b;c` is "a;b;c") and always has been -- adding a
+   * field to it would change what every existing sender means. Orthogonal, so
+   * a program can leave one line up and toggle the other. */
+  bool busy;
   pane_button_t buttons[8];
   size_t nbuttons;
   pane_osc_fn osc_cb;
@@ -115,6 +121,7 @@ void pane_set_osc_handler(pane_t *p, pane_osc_fn fn, void *ud) {
 }
 
 const char *pane_status(const pane_t *p) { return p->status; }
+bool pane_status_busy(const pane_t *p) { return p->busy && p->alive; }
 size_t pane_buttons(const pane_t *p, const pane_button_t **out) {
   *out = p->buttons;
   return p->nbuttons;
@@ -176,10 +183,20 @@ static void on_osc5577(const char *verb, const char *payload, void *ud) {
   if (strcmp(verb, "status") == 0) {
     snprintf(p->status, sizeof p->status, "%s", payload);
     p->dirty = true;
+  } else if (strcmp(verb, "busy") == 0) {
+    /* "is this still happening?" -- the one thing a line of text cannot say
+     * about itself. Off for the spellings of no, on for everything else
+     * including an empty payload, because `busy` with nothing after it is a
+     * program saying it is busy. */
+    bool on = !(strcmp(payload, "0") == 0 || strcmp(payload, "false") == 0 ||
+                strcmp(payload, "no") == 0 || strcmp(payload, "off") == 0);
+    if (p->busy != on) p->dirty = true;
+    p->busy = on;
   } else if (strcmp(verb, "buttons") == 0) {
     parse_buttons(p, payload);
   } else if (strcmp(verb, "clear") == 0) {
     p->status[0] = 0;
+    p->busy = false;
     p->nbuttons = 0;
     p->dirty = true;
   } else if (strcmp(verb, "hello") == 0) {
@@ -690,6 +707,7 @@ bool pane_restart(pane_t *p) {
    * status line and buttons from a program that is not there describe
    * nothing, and the new run gets to say its own. */
   p->status[0] = 0;
+  p->busy = false;
   p->nbuttons = 0;
   osc_scan_reset(&p->scan);
   p->exit_known = false;