On Windows, fix set_control_flow from `AboutToWait

ogoffart · kchibisov · commit dec45ce0ff0d · 2023-11-24T18:13:46.000+04:00
In case the AboutToWait event sets the control flow to another value it's not being used on this iteration. Fixes #3215.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -13,6 +13,7 @@ Unreleased` header.
 
 - On X11, check common alternative cursor names when loading cursor.
 - On Windows, fix so `drag_window` and `drag_resize_window` can be called from another thread.
+- On Windows, fix `set_control_flow` in `AboutToWait` not being taken in account.
 - On macOS, send a `Resized` event after each `ScaleFactorChanged` event.
 
 # 0.29.3
diff --git a/src/platform_impl/windows/event_loop.rs b/src/platform_impl/windows/event_loop.rs
@@ -356,19 +356,6 @@ impl<T: 'static> EventLoop<T> {
 
     /// Wait for one message and dispatch it, optionally with a timeout
     fn wait_and_dispatch_message(&mut self, timeout: Option<Duration>) {
-        let start = Instant::now();
-
-        let runner = &self.window_target.p.runner_shared;
-
-        let control_flow_timeout = match runner.control_flow() {
-            ControlFlow::Wait => None,
-            ControlFlow::Poll => Some(Duration::ZERO),
-            ControlFlow::WaitUntil(wait_deadline) => {
-                Some(wait_deadline.saturating_duration_since(start))
-            }
-        };
-        let timeout = min_timeout(control_flow_timeout, timeout);
-
         fn get_msg_with_timeout(msg: &mut MSG, timeout: Option<Duration>) -> PumpStatus {
             unsafe {
                 // A timeout of None means wait indefinitely (so we don't need to call SetTimer)
@@ -404,6 +391,8 @@ impl<T: 'static> EventLoop<T> {
             }
         }
 
+        let runner = &self.window_target.p.runner_shared;
+
         // We aim to be consistent with the MacOS backend which has a RunLoop
         // observer that will dispatch AboutToWait when about to wait for
         // events, and NewEvents after the RunLoop wakes up.
@@ -415,6 +404,16 @@ impl<T: 'static> EventLoop<T> {
         //
         runner.prepare_wait();
 
+        let control_flow_timeout = match runner.control_flow() {
+            ControlFlow::Wait => None,
+            ControlFlow::Poll => Some(Duration::ZERO),
+            ControlFlow::WaitUntil(wait_deadline) => {
+                let start = Instant::now();
+                Some(wait_deadline.saturating_duration_since(start))
+            }
+        };
+        let timeout = min_timeout(control_flow_timeout, timeout);
+
         // # Safety
         // The Windows API has no documented requirement for bitwise
         // initializing a `MSG` struct (it can be uninitialized memory for the C
