slosh: greet an attach with the logo, wearing a random shader

logo.txt is the source of truth; the Makefile bakes it into
build/logo.h the way version.h is baked. When a client attaches
(MSG_HELLO turning a connection into the display), the logo appears
centered over everything for splash_ms (900, 0 for never), on a
cleared backdrop, in the accent -- and one of six effects runs over
its rect through the ordinary shader pass: a diagonal sheen, plasma,
rings, sparkle, a left-to-right reveal, a breathe. Which one is picked
by the splash's own timestamp, so every attach looks a little
different without anybody keeping a counter.

Every effect reads the clock, so the frame clock runs only while the
splash is up (note_animation, same as any animated chain), and `since`
in a splash context is milliseconds since it appeared, so one-shot
effects sweep exactly once. Any key or click ends it and still lands
where it was aimed: a greeting is not a modal. A screen the box does
not fit on gets no greeting rather than a cropped one.

Headless and scripted sessions never attach, so the whole fast suite
never sees it; {"cmd":"splash"} triggers it on demand, which is what
makes it testable from a scripted session -- and lets you replay the
greeting whenever you like.

3 files changed, 14 insertions, 1 deletions

diff --git a/include/app.h b/include/app.h
index 2a3435e..7901d33 100644
--- a/include/app.h
+++ b/include/app.h
@@ -66,6 +66,9 @@ size_t app_fds(app_t *a, int *out, size_t max);
 void app_reap(app_t *a);
 
 void app_compose(app_t *a, screen_t *s);
+/* Show the logo splash for splash_ms, centered over everything, wearing a
+ * different shader effect each time. Called on attach; any input ends it. */
+void app_splash(app_t *a);
 /* Bytes straight into the focused pane's pty (the harness's `raw`). */
 void app_write_focused(app_t *a, const void *buf, size_t len);
 bool app_should_quit(const app_t *a);
diff --git a/include/app_internal.h b/include/app_internal.h
index bc94408..441bbd4 100644
--- a/include/app_internal.h
+++ b/include/app_internal.h
@@ -261,6 +261,11 @@ struct app {
    * remembering "this session animates" would keep a clock running for a pulse
    * that was hung off a state no pane is in any more. */
   bool animating;
+
+  /* The logo splash: shown until this instant, 0 for not at all. Set when a
+   * client attaches (app_splash), ended early by any key or click. The
+   * timestamp doubles as the seed that picks which effect this one wears. */
+  int64_t splash_until;
 };
 
 /* One config per process, owned by app.c (ensure_config/app_reload_config
@@ -366,6 +371,8 @@ void purpose_begin(app_t *a, uint32_t id);
 void rename_begin(app_t *a, uint32_t id);
 void rename_tab_begin(app_t *a, uint32_t id);
 
+void draw_splash(app_t *a, screen_t *s);
+
 /* round two */
 void drop_pane_on_strip(app_t *a);
 void focus_next(app_t *a);
diff --git a/include/config.h b/include/config.h
index ce4d5b0..5aefd01 100644
--- a/include/config.h
+++ b/include/config.h
@@ -194,7 +194,10 @@ typedef struct {
    * and a silently wrapped limit is worse than a refused one. */
   size_t scrollback;
   size_t scrollback_bytes;
-  uint16_t toast_ms;        /* how long an announcement stays up */
+  uint16_t toast_ms; /* how long an announcement stays up */
+  /* How long the logo splash stays over a freshly attached screen, 0 for
+   * never. Attach-only: a headless or scripted session has nobody to greet. */
+  uint16_t splash_ms;
   uint16_t hover_delay_ms;  /* how long the pointer must rest to arm a guide */
   uint16_t double_click_ms; /* how close two clicks must be to be a double */
   /* What a double-click's word stops at, listed as *separators* rather than as