Reconnect to a restarted Wayland compositor

Windows now outlive the compositor. On connection loss YASL sends
DISPLAY_LOST instead of closing every window, retries the connection on
a loop timer, rebuilds each toplevel with its title, size, state and GL
context, and sends DISPLAY_RESTORED. CPU windows keep their pixels;
GPU renderers drop Vulkan surfaces and GL objects on loss and rebuild
them on restore.

- Free the dead connection's objects on the next wait, after the
  application has released GPU objects built on them.
- Report a lost connection as an event rather than a failed wait.
- Refuse window and Vulkan surface creation while offline with the new
  YASL_ERROR_DISCONNECTED.
- Close popups, cancel drags and fail pending clipboard requests on loss.
- Print only protocol errors, not ordinary disconnects.
- Examples survive a restart; game.c rebinds its GL context.
- Add an end-to-end test that kills Weston under CPU, GL and Vulkan
  windows and requires them to recover.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

4 files changed, 13 insertions, 12 deletions

diff --git a/examples/game.c b/examples/game.c
index 79beb7c..0be4461 100644
--- a/examples/game.c
+++ b/examples/game.c
@@ -29,15 +29,20 @@ int main(int argc, char **argv)
     }
     yasl_gl_swap_interval(s, 1);
     int result = 0, frames = 0;
+    bool online = true;
     for (bool running = true; running;) {
+        /* Drain events before each frame; while the display is gone, block until it returns. */
         yasl_event e;
-        int n;
-        while ((n = yasl_wait_event(&e, 0)) > 0) {
-            if (e.type == YASL_EVENT_CLOSE || e.type == YASL_EVENT_QUIT ||
-                (e.type == YASL_EVENT_KEY && e.key.key == YASL_KEY_ESCAPE)) running = false;
-            if (e.type == YASL_EVENT_DISPLAY_LOST) { result = 1; running = false; }
-        }
+        int n = yasl_wait_event(&e, online ? 0 : -1);
         if (n < 0) { result = 1; break; }
+        if (e.type == YASL_EVENT_CLOSE || e.type == YASL_EVENT_QUIT ||
+            (e.type == YASL_EVENT_KEY && e.key.key == YASL_KEY_ESCAPE)) running = false;
+        if (e.type == YASL_EVENT_DISPLAY_LOST) online = false;
+        if (e.type == YASL_EVENT_DISPLAY_RESTORED) {
+            /* The context is new: bind it again and restore GL state here. */
+            online = yasl_gl_make_current(s) && yasl_gl_swap_interval(s, 1);
+        }
+        if (n > 0 || !online || !running) continue;
         int w, h;
         yasl_surface_get_framebuffer_size(s, &w, &h);
         viewport(0, 0, w, h);
diff --git a/examples/notepad.c b/examples/notepad.c
index 92b9d44..9134653 100644
--- a/examples/notepad.c
+++ b/examples/notepad.c
@@ -1464,10 +1464,6 @@ static void on_event(struct editor *ed, const yasl_event *ev)
         ed->running = false; return;
     case YASL_EVENT_QUIT:
         ed->running = false; return;
-    case YASL_EVENT_DISPLAY_LOST:
-        ed->failed = true;
-        ed->running = false;
-        return;
 
     case YASL_EVENT_WINDOW:
         ed->surface_scale = ev->window.scale;
diff --git a/examples/simple_window.c b/examples/simple_window.c
index 114bfbf..cb12db1 100644
--- a/examples/simple_window.c
+++ b/examples/simple_window.c
@@ -14,7 +14,7 @@ int main(int argc, char **argv)
     yasl_event e;
     for (;;) {
         int n = yasl_wait_event(&e, smoke ? 20 : -1);
-        if (n < 0 || e.type == YASL_EVENT_DISPLAY_LOST) break;
+        if (n < 0) break;
         if (e.type == YASL_EVENT_CLOSE || e.type == YASL_EVENT_QUIT ||
             (e.type == YASL_EVENT_KEY && e.key.key == YASL_KEY_ESCAPE)) { result = 0; break; }
         if (e.type == YASL_EVENT_POINTER) {
diff --git a/examples/tablet.c b/examples/tablet.c
index dad4b30..176a82b 100644
--- a/examples/tablet.c
+++ b/examples/tablet.c
@@ -55,7 +55,7 @@ int main(int argc, char **argv)
     yasl_event e;
     for (;;) {
         int n = yasl_wait_event(&e, smoke ? 20 : -1);
-        if (n < 0 || e.type == YASL_EVENT_DISPLAY_LOST) break;
+        if (n < 0) break;
         if (smoke && frames && n == 0) { result = 0; break; }
         bool escape = e.type == YASL_EVENT_KEY && e.key.action == YASL_KEY_PRESS && e.key.key == YASL_KEY_ESCAPE;
         if (e.type == YASL_EVENT_CLOSE || e.type == YASL_EVENT_QUIT || escape) { result = 0; break; }