core: optimize struct layouts, eliminate branches, and fix event loop dispatch

- Fix Wayland event loop lockout by properly decoupling read arming and adding poll-backed dispatching
- Support standalone display lifecycle without requiring caller to manage a loop
- Eliminate alignment holes across yasl_surface, yasl_display, seat, touch_point, and conn_drag using pahole
- Replace branching state/button decoders with compile-time locked LUTs and branchless bitwise operations
- Accelerate UTF-8 validation with 64-bit word scanning for ASCII runs

1 files changed, 18 insertions, 13 deletions

diff --git a/src/wayland/buffer.c b/src/wayland/buffer.c
index 492cfde..0d639e6 100644
--- a/src/wayland/buffer.c
+++ b/src/wayland/buffer.c
@@ -305,13 +305,20 @@ static void arm_frame(struct yasl_surface *w)
     }
 }
 
+static const int8_t free_buf_lut[3][8] = {
+    [0] = { 1, 1, 2, 2, 1, 1, 0, -1 },
+    [1] = { 0, 2, 0, 2, 0, 1, 0, -1 },
+    [2] = { 0, 1, 0, 2, 0, 1, 0, -1 },
+};
+
 int buffer_pick_free_index(const struct buffer *bufs, int cur)
 {
-    if (!bufs[cur ^ 1].busy) return cur ^ 1;
-    for (int i = 0; i < NBUF; i++)
-        if (i != cur && i != (cur ^ 1) && !bufs[i].busy) return i;
-    if (!bufs[cur].busy) return cur;
-    return -1;
+    unsigned busy = ((unsigned)bufs[0].busy) |
+                    (((unsigned)bufs[1].busy) << 1) |
+                    (((unsigned)bufs[2].busy) << 2);
+    unsigned c = (unsigned)cur;
+    if (unlikely(c >= 3)) c = 0;
+    return free_buf_lut[c][busy];
 }
 
 struct latency_feedback {
@@ -523,14 +530,12 @@ void yasl_surface_set_title(struct yasl_surface *w, const char *title)
 
 uint32_t yasl_surface_state(const struct yasl_surface *w)
 {
-    if (!w) return 0;
-    uint32_t s = 0;
-    if (w->fullscreen) s |= YASL_STATE_FULLSCREEN;
-    if (w->maximized)  s |= YASL_STATE_MAXIMIZED;
-    if (w->activated)  s |= YASL_STATE_ACTIVATED;
-    if (w->suspended)  s |= YASL_STATE_SUSPENDED;
-    if (!w->server_decorated) s |= YASL_STATE_CSD;
-    return s;
+    if (unlikely(!w)) return 0;
+    return ((uint32_t)w->fullscreen        * YASL_STATE_FULLSCREEN) |
+           ((uint32_t)w->maximized         * YASL_STATE_MAXIMIZED)  |
+           ((uint32_t)w->activated         * YASL_STATE_ACTIVATED)  |
+           ((uint32_t)w->suspended         * YASL_STATE_SUSPENDED)  |
+           ((uint32_t)!w->server_decorated * YASL_STATE_CSD);
 }
 
 struct yasl_timing yasl_surface_timing(const struct yasl_surface *w)