From 226604cb186589023de2b088915fc660adf80f35 Mon Sep 17 00:00:00 2001
From: "Ngo Iok Ui (Wu Yu Wei)" <wusyong9104@gmail.com>
Date: Fri, 1 Jul 2022 05:11:46 +0800
Subject: [PATCH] Revert "Remove most RedrawWindow to event target window
 (#427)"

This reverts commit 5ca39af1117677b469f92a8094769610c01419ad.
---
 src/platform_impl/windows/event_loop.rs       | 44 +++++++++----------
 .../windows/event_loop/runner.rs              | 23 +++-------
 2 files changed, 26 insertions(+), 41 deletions(-)

diff --git a/src/platform_impl/windows/event_loop.rs b/src/platform_impl/windows/event_loop.rs
index 747018818..fb87d64f7 100644
--- a/src/platform_impl/windows/event_loop.rs
+++ b/src/platform_impl/windows/event_loop.rs
@@ -2051,10 +2051,8 @@ unsafe extern "system" fn thread_event_target_callback<T: 'static>(
 ) -> LRESULT {
   let subclass_input = Box::from_raw(subclass_input_ptr as *mut ThreadMsgTargetSubclassInput<T>);
 
-  // Calling RedrawWindow will cause other window busy waiting. So we handle clear event directly
-  // as long as there's a thread event target message.
   if msg != WM_PAINT {
-    handle_clear_event(&subclass_input.event_loop_runner, window);
+    RedrawWindow(window, ptr::null(), HRGN::default(), RDW_INTERNALPAINT);
   }
 
   let mut subclass_removed = false;
@@ -2072,8 +2070,25 @@ unsafe extern "system" fn thread_event_target_callback<T: 'static>(
     // when the event queue has been emptied. See `process_event` for more details.
     win32wm::WM_PAINT => {
       ValidateRect(window, ptr::null());
-
-      handle_clear_event(&subclass_input.event_loop_runner, window);
+      // If the WM_PAINT handler in `public_window_callback` has already flushed the redraw
+      // events, `handling_events` will return false and we won't emit a second
+      // `RedrawEventsCleared` event.
+      if subclass_input.event_loop_runner.handling_events() {
+        if subclass_input.event_loop_runner.should_buffer() {
+          // This branch can be triggered when a nested win32 event loop is triggered
+          // inside of the `event_handler` callback.
+          RedrawWindow(window, ptr::null(), HRGN::default(), RDW_INTERNALPAINT);
+        } else {
+          // This WM_PAINT handler will never be re-entrant because `flush_paint_messages`
+          // doesn't call WM_PAINT for the thread event target (i.e. this window).
+          assert!(flush_paint_messages(
+            None,
+            &subclass_input.event_loop_runner
+          ));
+          subclass_input.event_loop_runner.redraw_events_cleared();
+          process_control_flow(&subclass_input.event_loop_runner);
+        }
+      }
 
       // Default WM_PAINT behaviour. This makes sure modals and popups are shown immediatly when opening them.
       DefSubclassProc(window, msg, wparam, lparam)
@@ -2341,22 +2356,3 @@ unsafe fn handle_raw_input<T: 'static>(
     });
   }
 }
-
-unsafe fn handle_clear_event<T: 'static>(event_loop_runner: &EventLoopRunner<T>, window: HWND) {
-  // If the WM_PAINT handler in `public_window_callback` has already flushed the redraw
-  // events, `handling_events` will return false and we won't emit a second
-  // `RedrawEventsCleared` event.
-  if event_loop_runner.handling_events() {
-    if event_loop_runner.should_buffer() {
-      // This branch can be triggered when a nested win32 event loop is triggered
-      // inside of the `event_handler` callback.
-      RedrawWindow(window, ptr::null(), HRGN::default(), RDW_INTERNALPAINT);
-    } else {
-      // This WM_PAINT handler will never be re-entrant because `flush_paint_messages`
-      // doesn't call WM_PAINT for the thread event target (i.e. this window).
-      assert!(flush_paint_messages(None, &event_loop_runner));
-      event_loop_runner.redraw_events_cleared();
-      process_control_flow(&event_loop_runner);
-    }
-  }
-}
diff --git a/src/platform_impl/windows/event_loop/runner.rs b/src/platform_impl/windows/event_loop/runner.rs
index cce59f3b1..a5eb983ce 100644
--- a/src/platform_impl/windows/event_loop/runner.rs
+++ b/src/platform_impl/windows/event_loop/runner.rs
@@ -196,13 +196,6 @@ impl<T> EventLoopRunner<T> {
     owned_windows.extend(&new_owned_windows);
     self.owned_windows.set(owned_windows);
   }
-
-  pub fn no_owned_windows(&self) -> bool {
-    let owned_windows = self.owned_windows.take();
-    let result = owned_windows.is_empty();
-    self.owned_windows.set(owned_windows);
-    result
-  }
 }
 
 /// Event dispatch functions.
@@ -401,16 +394,12 @@ impl<T> EventLoopRunner<T> {
     };
     self.call_event_handler(Event::NewEvents(start_cause));
     self.dispatch_buffered_events();
-    // Calling RedrawWindow will cause other window busy waiting. So we only call it when
-    // there's no window.
-    if self.no_owned_windows() {
-      RedrawWindow(
-        self.thread_msg_target,
-        ptr::null(),
-        HRGN::default(),
-        RDW_INTERNALPAINT,
-      );
-    }
+    RedrawWindow(
+      self.thread_msg_target,
+      ptr::null(),
+      HRGN::default(),
+      RDW_INTERNALPAINT,
+    );
   }
 
   unsafe fn call_redraw_events_cleared(&self) {