From 67f00588b4927271cb8b89f1d0c10db3c9727093 Mon Sep 17 00:00:00 2001
From: Lucas Fernandes Nogueira <lucas@tauri.app>
Date: Sat, 3 May 2025 14:32:00 -0300
Subject: [PATCH] fix(macos): check monitor from window initial position to
 determine size (#1110)

---
 .github/fix-window-size.md        |  5 +++++
 src/platform_impl/macos/window.rs | 31 +++++++++++++++++++++++++++++--
 2 files changed, 34 insertions(+), 2 deletions(-)
 create mode 100644 .github/fix-window-size.md

diff --git a/.github/fix-window-size.md b/.github/fix-window-size.md
new file mode 100644
index 00000000..d75ff04b
--- /dev/null
+++ b/.github/fix-window-size.md
@@ -0,0 +1,5 @@
+---
+"tao": patch
+---
+
+Properly check target monitor from window initial position to determine its size with the proper scale factor on macOS.
diff --git a/src/platform_impl/macos/window.rs b/src/platform_impl/macos/window.rs
index 6959d51c..197bc980 100644
--- a/src/platform_impl/macos/window.rs
+++ b/src/platform_impl/macos/window.rs
@@ -174,13 +174,21 @@ fn create_window(
         let monitor_screen = monitor.ns_screen();
         Some(monitor_screen.unwrap_or_else(|| appkit::NSScreen::mainScreen(mtm).unwrap()))
       }
-      Some(Fullscreen::Borderless(None)) => Some(appkit::NSScreen::mainScreen(mtm).unwrap()),
+      Some(Fullscreen::Borderless(None)) => Some(
+        attrs
+          .position
+          .and_then(screen_from_position)
+          .unwrap_or_else(|| appkit::NSScreen::mainScreen(mtm).unwrap()),
+      ),
       None => None,
     };
     let frame = match &screen {
       Some(screen) => NSScreen::frame(screen),
       None => {
-        let screen = NSScreen::mainScreen(mtm).unwrap();
+        let screen = attrs
+          .position
+          .and_then(screen_from_position)
+          .unwrap_or_else(|| appkit::NSScreen::mainScreen(mtm).unwrap());
         let scale_factor = NSScreen::backingScaleFactor(&screen) as f64;
         let desired_size = attrs
           .inner_size
@@ -323,6 +331,25 @@ fn create_window(
   }
 }
 
+fn screen_from_position(position: Position) -> Option<Retained<NSScreen>> {
+  for m in monitor::available_monitors() {
+    let monitor_pos = m.position();
+    let monitor_size = m.size();
+
+    // type annotations required for 32bit targets.
+    let window_position = position.to_physical::<i32>(m.scale_factor());
+
+    let is_in_monitor = monitor_pos.x <= window_position.x
+      && window_position.x < monitor_pos.x + monitor_size.width as i32
+      && monitor_pos.y <= window_position.y
+      && window_position.y < monitor_pos.y + monitor_size.height as i32;
+    if is_in_monitor {
+      return m.ns_screen();
+    }
+  }
+  None
+}
+
 pub(super) fn get_ns_theme() -> Theme {
   unsafe {
     let appearances: Vec<Retained<NSString>> = vec![