sl0ppty: say which build you are talking to

The middle of the status line is empty unless the pointer is on something,
which is most of the time. It says which sl0ppty this is now.

That reads as decoration and is not. A session keeps the binary it started
with, so after a rebuild there are two versions in play: the one on disk and
the one you are attached to. This session has been dogfooding sl0ppty for a
while, and "which build is this?" has already been the answer to two bugs
that looked like something else -- once when a config reload appeared to do
nothing, and once when kitty graphics were fixed and still broken on screen.
The banner answers it without asking, and `sl0ppty --version` answers for the
binary, from the same string.

The version is baked in by the Makefile from `git describe --always --dirty`,
into a generated header that is only rewritten when the value changes -- so a
commit rebuilds and a second `make` does nothing.

It takes the hint's slot and yields to it: a hint is about what you are doing
right now, the banner is about always, and it comes back the moment the
pointer moves off. Both give way to the ends of the line, which was already
the rule for hints and is why a narrow terminal loses the middle rather than
its session name. `version_banner false` for anyone who finds it noisy; it is
a separate knob from `hints`, and the tests hold both directions of that.

4 files changed, 41 insertions, 11 deletions

diff --git a/src/app.c b/src/app.c
index c9ba927..5c6d7f4 100644
--- a/src/app.c
+++ b/src/app.c
@@ -12,6 +12,7 @@
 #include <string.h>
 
 #include "json.h"
+#include "version.h"
 #include "graphics.h"
 #include "kdl.h"
 
@@ -610,22 +611,34 @@ static void draw_status_line(app_t *a, screen_t *s) {
   if (n > (size_t)(right - x)) line[right - x] = 0;
   if (n) screen_text(s, x, y, line, STATUS_C, NO_COLOR, 0);
 
-  /* The hint sits in what is left between the two ends, centred there rather
-   * than in the row: centring it in the row would put it under the session
-   * name on a narrow screen, and a hint that overwrites what it is explaining
-   * is worse than no hint. It is simply not drawn when it does not fit. */
-  if (!CFG.hints || !a->painted) return;
-  const char *hint = hint_for(a, hit_test(&s->hits, a->ptr_x, a->ptr_y));
-  if (!hint || !a->ptr_valid) return;
+  /* What goes between the two ends: the hint for whatever the pointer is on,
+   * and when there is none, which sl0ppty this is. The hint wins because it is
+   * about right now and the banner is about always; the banner takes the slot
+   * back the moment the pointer moves off, which is most of the time.
+   *
+   * Centred in what is *left* rather than in the row: centring it in the row
+   * would put it under the session name on a narrow screen, and either of
+   * these overwriting what it sits next to is worse than not being drawn. */
+  const char *middle = NULL;
+  color_t middle_fg = HINT_C;
+  if (CFG.hints && a->painted && a->ptr_valid)
+    middle = hint_for(a, hit_test(&s->hits, a->ptr_x, a->ptr_y));
+  if (!middle && CFG.version_banner) {
+    /* Quieter than a hint: this is ambient, and a hint is an answer to
+     * something you are doing. */
+    middle = "sl0ppty " SL0PPTY_VERSION;
+    middle_fg = STATUS_C;
+  }
+  if (!middle) return;
 
   uint16_t used = (uint16_t)(x + cells(line));
   uint16_t from = (uint16_t)(used + 2);
   if (right <= from) return;
   uint16_t span = (uint16_t)(right - from);
-  uint16_t hw = cells(hint);
+  uint16_t hw = cells(middle);
   if (hw + 2 > span) return;
-  screen_text(s, (uint16_t)(from + (span - hw) / 2), y, hint, HINT_C, NO_COLOR,
-              0);
+  screen_text(s, (uint16_t)(from + (span - hw) / 2), y, middle, middle_fg,
+              NO_COLOR, 0);
 }
 
 static void draw_toasts(app_t *a, screen_t *s) {
diff --git a/src/config.c b/src/config.c
index 941d6e9..c31ca76 100644
--- a/src/config.c
+++ b/src/config.c
@@ -210,6 +210,7 @@ void config_defaults(config_t *c) {
   c->title_align = ALIGN_CENTER;
   c->title_inset = 2;
   c->hints = true;
+  c->version_banner = true;
   c->pane_buttons = true;
   snprintf(c->zoom_mark, sizeof c->zoom_mark, "#");
   snprintf(c->zoom_on_mark, sizeof c->zoom_on_mark, "*");
@@ -618,6 +619,8 @@ bool config_load(config_t *c, const char *path, char *err, size_t errcap) {
   c->title_inset =
       (uint16_t)kdl_arg_int(kdl_child(root, "title_inset"), 0, c->title_inset);
   c->hints = kdl_arg_bool(kdl_child(root, "hints"), 0, c->hints);
+  c->version_banner =
+      kdl_arg_bool(kdl_child(root, "version_banner"), 0, c->version_banner);
   c->pane_buttons =
       kdl_arg_bool(kdl_child(root, "pane_buttons"), 0, c->pane_buttons);
   const char *zm = kdl_arg(kdl_child(root, "zoom_mark"), 0, NULL);
diff --git a/src/config.h b/src/config.h
index c093f93..2f844ee 100644
--- a/src/config.h
+++ b/src/config.h
@@ -98,6 +98,12 @@ typedef struct {
    * Discoverability for a frame whose affordances are mostly one character
    * wide; off if you already know them. */
   bool hints;
+  /* What sl0ppty this is, in the middle of the status line, whenever there is
+   * no hint to put there. The slot is otherwise empty most of the time, and
+   * "which build am I attached to" is the first question when a session is
+   * behaving oddly -- a session keeps the binary it started with, so the
+   * answer is not whatever was built last. */
+  bool version_banner;
   bool pane_buttons;
   /* Marks of similar visual weight, so the even spacing between the buttons
    * reads as even: a glyph that floats in a mostly-empty cell donates its own
diff --git a/src/main.c b/src/main.c
index f898746..e2d0602 100644
--- a/src/main.c
+++ b/src/main.c
@@ -20,6 +20,7 @@
 
 #include "proto.h"
 #include "server.h"
+#include "version.h"
 
 int run_headless(const char *const argv[], uint16_t cols, uint16_t rows,
                  int idle_ms, bool script, const char *layout);
@@ -36,7 +37,8 @@ static void term_size(uint16_t *cols, uint16_t *rows) {
 }
 
 static void usage(void) {
-  fputs("usage: sl0ppty [-s NAME] [--layout FILE] [--no-reload]\n                [ls | cmd LINE | -- CMD...]\n",
+  fputs("usage: sl0ppty [-s NAME] [--layout FILE] [--no-reload]\n"
+        "                [--version] [ls | cmd LINE | -- CMD...]\n",
         stderr);
 }
 
@@ -60,6 +62,12 @@ int main(int argc, char **argv) {
     else if (strcmp(a, "-s") == 0 && i + 1 < argc) name = argv[++i];
     else if (strcmp(a, "--layout") == 0 && i + 1 < argc) layout = argv[++i];
     else if (strcmp(a, "--no-reload") == 0) watch = false;
+    else if (strcmp(a, "--version") == 0) {
+      /* The same string the status line shows, so "which build is this" has
+       * one answer whether you ask the binary or the session. */
+      printf("sl0ppty %s\n", SL0PPTY_VERSION);
+      return 0;
+    }
     else if (strcmp(a, "ls") == 0) list = true;
     else if (strcmp(a, "cmd") == 0 && i + 1 < argc) cmd_line = argv[++i];
     else if (strcmp(a, "--cols") == 0 && i + 1 < argc) cols = (uint16_t)atoi(argv[++i]);