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.

3 files changed, 23 insertions, 0 deletions

diff --git a/include/app_internal.h b/include/app_internal.h
index 7948b13..1af9163 100644
--- a/include/app_internal.h
+++ b/include/app_internal.h
@@ -412,6 +412,7 @@ extern config_t CFG;
 #define TAB_COUNT (CFG.tab_count)
 #define TAB_STATUS_FG (CFG.tab_status_fg)
 #define TAB_STATUS_BG (CFG.tab_status_bg)
+#define TAB_STATUS_BUSY (CFG.tab_status_busy)
 #define TAB_STATUS_STRIPE (CFG.tab_status_stripe)
 #define STATUS_C (CFG.status)
 #define STATUS_STATE (CFG.status_state)
diff --git a/include/config.h b/include/config.h
index 47e48a7..40a5ace 100644
--- a/include/config.h
+++ b/include/config.h
@@ -235,6 +235,17 @@ typedef struct {
    * terminals while chrome here is booked as one — so the default is narrow
    * and anyone who knows their terminal can say otherwise. */
   char bell_mark[32];
+  /* What a pane that says it is *busy* looks like in the sidebar: the frames
+   * of a spinner, 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 -- and only while such a row is actually on screen. Empty
+   * draws no mark at all and leaves the colour to say it. */
+  char busy_mark[64];
+  /* Milliseconds a spinner frame is held. Its own knob rather than anim_ms,
+   * which is how often the session repaints while something animates: this is
+   * how fast the thing being repainted moves, and a spinner stepping at the
+   * repaint rate is a blur. */
+  uint16_t busy_ms;
   /* Which dead panes stay, showing what they printed and offering to run
    * again, and which just go.
    *
@@ -530,6 +541,12 @@ typedef struct {
    * none leaves the terminal's own background alone, which is what a
    * translucent one wants. */
   color_t tab_status_fg, tab_status_bg;
+  /* A status whose program says it is still happening. Brighter than the
+   * ambient one, because "running" and "finished" are the two states worth
+   * telling apart from another tab, and the difference between them should
+   * not be something you have to read the words to work out. Derived from the
+   * theme, like tab_status_fg. */
+  color_t tab_status_busy;
   /* The other stripe. With wrapped statuses, where one pane's rows end and
    * the next one's begin is no longer obvious from the shape -- both are
    * just italic text down the same column -- so alternate panes sit on
diff --git a/include/slosh.h b/include/slosh.h
index beec697..b8c8849 100644
--- a/include/slosh.h
+++ b/include/slosh.h
@@ -313,6 +313,11 @@ const char *pane_name(const pane_t *p);
 /* "" clears the name and gives the pane back to the program's title. */
 void pane_set_name(pane_t *p, const char *name);
 const char *pane_status(const pane_t *p);
+/* Whether the program says what its status describes is still happening
+ * (`busy` over OSC 5577). Never true of a pane whose program has gone: a
+ * status left behind by something that exited is a description of the past,
+ * whatever it last claimed. */
+bool pane_status_busy(const pane_t *p);
 size_t pane_buttons(const pane_t *p, const pane_button_t **out);
 void pane_click_button(pane_t *p, const char *id);
 void pane_set_osc_handler(pane_t *p, pane_osc_fn fn, void *ud);