Check the deferred caption button before execution.

The user may cancel the button press on a caption button by moving the mouse away before releasing.
rust-windowing · Jun 22, 2019 · e413f5a · e413f5a
1 parent b0d2d7f
commit e413f5a
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Showing 2 changed files with 25 additions and 6 deletions.
diff --git a/src/platform_impl/windows/event_loop.rs b/src/platform_impl/windows/event_loop.rs
@@ -844,6 +844,8 @@ unsafe extern "system" fn public_window_callback<T>(
                     // Discard the non-client button-down event and defer the processing until
                     // the non-client button-up event. This prevents a pause in the message loop
                     // while the user has the mouse button pressed on one of these buttons.
+                    let mut window_state = subclass_input.window_state.lock();
+                    window_state.deferred_nclbuttondown_wparam = Some(wparam);
                     0
                 },
                 _ => {
@@ -863,9 +865,18 @@ unsafe extern "system" fn public_window_callback<T>(
         },
 
         winuser::WM_NCLBUTTONUP => {
-            // Manually apply min, max, restore, and close since we discarded the button down event.
-            match wparam as isize {
-                winuser::HTMAXBUTTON => {
+            let deferred_wparam = subclass_input
+                .window_state
+                .lock()
+                .deferred_nclbuttondown_wparam
+                .filter(|deferred_wparam| *deferred_wparam == wparam)
+                .map(|wparam| wparam as isize)
+                .take();
+            // Manually apply min, max, restore, and close since we discarded the button down event,
+            // but only in the event that the user did not cancel the operation. If the user canelled
+            // the operation, WM_LBUTTONUP will fire and we'll clear the deferred state there as well.
+            match deferred_wparam {
+                Some(winuser::HTMAXBUTTON) => {
                     let window_state = subclass_input.window_state.lock();
                     let window_flags = window_state.window_flags();
                     drop(window_state);
@@ -876,11 +887,11 @@ unsafe extern "system" fn public_window_callback<T>(
                     }
                     0
                 }
-                winuser::HTMINBUTTON => {
+                Some(winuser::HTMINBUTTON) => {
                     winuser::ShowWindow(window, winuser::SW_MINIMIZE);
                     0
                 }
-                winuser::HTCLOSE => {
+                Some(winuser::HTCLOSE) => {
                     winuser::PostMessageW(window, winuser::WM_CLOSE, 0, 0);
                     0
                 }
@@ -1195,6 +1206,12 @@ unsafe extern "system" fn public_window_callback<T>(
                 ElementState::Released, MouseButton::Left, WindowEvent::MouseInput,
             };
 
+            subclass_input
+                .window_state
+                .lock()
+                .deferred_nclbuttondown_wparam
+                .take();
+
             release_mouse(&mut *subclass_input.window_state.lock());
 
             subclass_input.send_event(Event::WindowEvent {

diff --git a/src/platform_impl/windows/window_state.rs b/src/platform_impl/windows/window_state.rs
@@ -8,7 +8,7 @@ use parking_lot::MutexGuard;
 use std::{io, ptr};
 use winapi::{
     shared::{
-        minwindef::DWORD,
+        minwindef::{DWORD, WPARAM},
         windef::{HWND, RECT},
     },
     um::winuser,
@@ -30,6 +30,7 @@ pub struct WindowState {
     pub dpi_factor: f64,
 
     pub fullscreen: Option<MonitorHandle>,
+    pub deferred_nclbuttondown_wparam: Option<WPARAM>,
     window_flags: WindowFlags,
 }
 
@@ -111,6 +112,7 @@ impl WindowState {
 
             fullscreen: None,
             window_flags: WindowFlags::empty(),
+            deferred_nclbuttondown_wparam: None,
         }
     }