feat: use MTK toolkit widgets in login.elf, improve login.elf draw performance

programs/src/login/main.cpp

@@ -41,8 +41,8 @@ static void initialize_login_mode(LoginState* ls) {
         ls->active_field = 0;
         montauk::strcpy(ls->username, "admin");
         ls->username_len = 5;
-        ls->username_edit.cursor = ls->username_len;
-        clear_field_selection(&ls->username_edit);
+        gui::mtk::text_input_set_cursor(ls->username_input, ls->username_len,
+                                        ls->username_len, false);
         return;
     }
 
@@ -63,10 +63,20 @@ extern "C" void _start() {
     montauk::set_mouse_bounds(ls->screen_w - 1, ls->screen_h - 1);
     load_login_wallpaper(ls);
 
+    // MTK theme (picks up the system accent). The compose buffer is only
+    // needed when the framebuffer pitch is not tightly packed; otherwise the
+    // renderer draws straight into the framebuffer back buffer.
+    ls->theme = gui::mtk::make_theme();
+    if (ls->fb.pitch() != ls->screen_w * (int)sizeof(uint32_t)) {
+        ls->compose = (uint32_t*)montauk::alloc(
+            (uint64_t)ls->screen_w * ls->screen_h * sizeof(uint32_t));
+    }
+
     maybe_run_setup_session();
     initialize_login_mode(ls);
 
     bool first_frame = true;
+    uint64_t input_serial = montauk::input_wait(0, 0);
     for (;;) {
         bool mouse_changed = false;
         bool key_changed = false;
@@ -95,9 +105,20 @@ extern "C" void _start() {
         if (first_frame || mouse_changed || key_changed) {
             draw_login_screen(ls);
             first_frame = false;
-            montauk::sleep_ms(fast_mouse_path ? 1 : 4);
-        } else {
-            montauk::sleep_ms(16);
         }
+
+        // Event-driven wait: input_wait returns the instant the mouse or
+        // keyboard ISR reports activity, so the cursor tracks the device with
+        // no fixed-timer latency. timeoutMs is only an upper bound. Matches
+        // the desktop's run loop; a plain sleep_ms() here cannot wake early
+        // and makes every gesture start ~16 ms late.
+        //
+        // The login screen has no periodic UI (no clock, no caret blink, no
+        // animation), so when idle it never needs to wake without input: pass
+        // UINT64_MAX to block indefinitely and consume 0% CPU until the next
+        // mouse/keyboard event, instead of waking ~62x/sec for nothing.
+        uint64_t wait_ms = fast_mouse_path ? 1
+                         : ((mouse_changed || key_changed) ? 4 : UINT64_MAX);
+        input_serial = montauk::input_wait(input_serial, wait_ms);
     }
 }