Windows: Fix drag mouse position for parented windows (bugfix) - take 2

src/platform/win/drop_target.rs

@@ -66,7 +66,14 @@ impl DropTarget {
     }
 
     fn parse_coordinates(&self, pt: POINTL) {
-        let Ok(phy_point) = self.hwnd.screen_to_client(PhysicalPosition::new(pt.x, pt.y)) else {
+        let Some(window_state) = self.window_state.upgrade() else {
+            return;
+        };
+
+        let dpi_aware = !window_state.shared.dpi_scaling_strategy.get().assume_96_dpi;
+        let Ok(phy_point) =
+            self.hwnd.screen_to_client(PhysicalPosition::new(pt.x, pt.y), dpi_aware)
+        else {
             return;
         };
 

src/wrappers/win32/window/handle.rs

@@ -15,7 +15,10 @@ use windows_sys::Win32::Graphics::Gdi::{
     MONITOR_DEFAULTTOPRIMARY,
 };
 use windows_sys::Win32::System::Ole::{RegisterDragDrop, RevokeDragDrop};
-use windows_sys::Win32::UI::HiDpi::{DPI_HOSTING_BEHAVIOR_MIXED, MDT_DEFAULT};
+use windows_sys::Win32::UI::HiDpi::{
+    LogicalToPhysicalPointForPerMonitorDPI, PhysicalToLogicalPointForPerMonitorDPI,
+    DPI_HOSTING_BEHAVIOR_MIXED, MDT_DEFAULT,
+};
 use windows_sys::Win32::UI::Input::KeyboardAndMouse::{
     GetFocus, ReleaseCapture, SetCapture, SetFocus, TrackMouseEvent, TME_LEAVE, TRACKMOUSEEVENT,
 };
@@ -298,11 +301,26 @@ impl HWnd {
         }
     }
 
-    pub fn screen_to_client(&self, pt: PhysicalPosition<i32>) -> Result<PhysicalPosition<i32>> {
+    /// Converts screen coordinates to client coordinates.
+    ///
+    /// For DPI-aware windows, OLE screen points can disagree with what
+    /// [`ScreenToClient`] expects, so we convert to logical space first and then back to physical.
+    pub fn screen_to_client(
+        &self, pt: PhysicalPosition<i32>, dpi_aware: bool,
+    ) -> Result<PhysicalPosition<i32>> {
         let mut pt = POINT { x: pt.x, y: pt.y };
-        let result = unsafe { ScreenToClient(self.as_raw(), &mut pt as *mut POINT) };
 
-        if result == 0 {
+        if dpi_aware && unsafe { PhysicalToLogicalPointForPerMonitorDPI(null_mut(), &mut pt) } == 0
+        {
+            return Err(Error::from_thread());
+        }
+
+        if unsafe { ScreenToClient(self.as_raw(), &mut pt) } == 0 {
+            return Err(Error::from_thread());
+        }
+
+        if dpi_aware && unsafe { LogicalToPhysicalPointForPerMonitorDPI(null_mut(), &mut pt) } == 0
+        {
             return Err(Error::from_thread());
         }