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.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/server.c b/src/server.c
index 578ffff..4635e3b 100644
--- a/src/server.c
+++ b/src/server.c
@@ -428,6 +428,9 @@ int server_run(const char *name, const char *const argv[], uint16_t cols,
                 break;
               }
             s.conns[ci].display = true;
+            /* Someone is now looking, which is the one moment a greeting
+             * makes sense: a headless or scripted session never gets here. */
+            app_splash(s.app);
           }
           if (m.len >= 4 && s.conns[ci].display) {
             uint16_t c = (uint16_t)(m.data[0] << 8 | m.data[1]);