Implement stub handlers and add focus/cursor/pointer tracking

- Implement SetInputFocus, GetInputFocus, FreeGC, ClearArea,
  QueryPointer, TranslateCoordinates, CreateGlyphCursor,
  CreateCursor, and FreeCursor handlers
- Fix QueryTree to use actual window parent/children hierarchy
- Add focused_window, cursor map, and pointer position tracking
  to Server struct with proper coordinate translation
- Update ChangeWindowAttributes to apply cursors via backend
- Track pointer position from motion/button/enter events
- Fix unused variable warnings in macOS backend
- Fix formatting issues flagged by cargo fmt
- Add XOR fill function support in macOS Swift backend

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: MagicalTux

src/backend/macos.rs

@@ -85,6 +85,7 @@ extern "C" {
         r: f32,
         g: f32,
         b: f32,
+        gc_function: i32,
     ) -> i32;
     fn macos_backend_draw_line(
         handle: BackendHandle,
@@ -726,6 +727,7 @@ impl Backend for MacOSBackend {
                 r,
                 g,
                 b,
+                gc.function as i32,
             );
 
             Ok(())
@@ -1272,8 +1274,8 @@ impl MacOSBackend {
         window_id: i32,
         x: i32,
         y: i32,
-        width: i32,
-        height: i32,
+        _width: i32,
+        _height: i32,
         keycode: i32,
         button: i32,
         state: i32,

src/server/extensions.rs

@@ -1987,7 +1987,7 @@ fn encode_xkb_get_map_reply(sequence: u16) -> Vec<u8> {
     buffer[1] = 0; // deviceID (use core keyboard)
     buffer[2..4].copy_from_slice(&write_u16_le(sequence));
     buffer[4..8].copy_from_slice(&write_u32_le(2)); // length: 8 extra bytes = 2 words
-    // Bytes 8-9: pad
+                                                    // Bytes 8-9: pad
     buffer[10] = 8; // minKeyCode (standard)
     buffer[11] = 255; // maxKeyCode (standard)
     buffer[12..14].copy_from_slice(&write_u16_le(0)); // present (no components)
@@ -1997,7 +1997,7 @@ fn encode_xkb_get_map_reply(sequence: u16) -> Vec<u8> {
     buffer[18] = 8; // firstKeySym
     buffer[19] = 0; // totalSyms (high byte)
     buffer[20] = 0; // nKeySyms
-    // Rest of the header fields are 0 (no key actions, behaviors, etc.)
+                    // Rest of the header fields are 0 (no key actions, behaviors, etc.)
     buffer
 }