Windows: Fix set_cursor delay (#660)

CHANGELOG.md

@@ -7,6 +7,7 @@
 - Updated window manager hints under X11 to v1.5 of [Extended Window Manager Hints](https://specifications.freedesktop.org/wm-spec/wm-spec-1.5.html#idm140200472629520).
 - Added `WindowBuilderExt::with_gtk_theme_variant` to X11-specific `WindowBuilder` functions.
 - Fixed UTF8 handling bug in X11 `set_title` function.
+- On Windows, `Window::set_cursor` now applies immediately instead of requiring specific events to occur first.
 
 # Version 0.17.2 (2018-08-19)
 

src/platform/windows/mod.rs

@@ -18,7 +18,7 @@ unsafe impl Send for PlatformSpecificWindowBuilderAttributes {}
 unsafe impl Sync for PlatformSpecificWindowBuilderAttributes {}
 
 // Cursor name in UTF-16. Used to set cursor in `WM_SETCURSOR`.
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Copy)]
 pub struct Cursor(pub *const winapi::ctypes::wchar_t);
 unsafe impl Send for Cursor {}
 unsafe impl Sync for Cursor {}

src/platform/windows/window.rs

@@ -301,7 +301,7 @@ impl Window {
 
     #[inline]
     pub fn set_cursor(&self, cursor: MouseCursor) {
-        let cursor_id = match cursor {
+        let cursor_id = Cursor(match cursor {
             MouseCursor::Arrow | MouseCursor::Default => winuser::IDC_ARROW,
             MouseCursor::Hand => winuser::IDC_HAND,
             MouseCursor::Crosshair => winuser::IDC_CROSS,
@@ -321,10 +321,15 @@ impl Window {
             MouseCursor::Progress => winuser::IDC_APPSTARTING,
             MouseCursor::Help => winuser::IDC_HELP,
             _ => winuser::IDC_ARROW, // use arrow for the missing cases.
-        };
-
-        let mut cur = self.window_state.lock().unwrap();
-        cur.cursor = Cursor(cursor_id);
+        });
+        self.window_state.lock().unwrap().cursor = cursor_id;
+        self.events_loop_proxy.execute_in_thread(move |_| unsafe {
+            let cursor = winuser::LoadCursorW(
+                ptr::null_mut(),
+                cursor_id.0,
+            );
+            winuser::SetCursor(cursor);
+        });
     }
 
     unsafe fn cursor_is_grabbed(&self) -> Result<bool, String> {