Reduce redundant resize repaint passes

new_editor/app/Application.cpp

@@ -957,6 +957,7 @@ LRESULT CALLBACK Application::WndProc(HWND hwnd, UINT message, WPARAM wParam, LP
     Application* application = Host::WindowMessageDispatcher::GetApplicationFromWindow(hwnd);
     if (application != nullptr &&
         Host::WindowMessageDispatcher::TryDispatch(
+            hwnd,
             *application,
             message,
             wParam,

new_editor/app/Host/WindowMessageDispatcher.cpp

@@ -45,11 +45,23 @@ bool WindowMessageDispatcher::TryHandleNonClientCreate(
 }
 
 bool WindowMessageDispatcher::TryDispatch(
+    HWND hwnd,
     Application& application,
     UINT message,
     WPARAM wParam,
     LPARAM lParam,
     LRESULT& outResult) {
+    const auto renderAndValidateWindow = [&application, hwnd]() {
+        if (!application.m_renderReady) {
+            return;
+        }
+
+        application.RenderFrame();
+        if (hwnd != nullptr && IsWindow(hwnd)) {
+            ValidateRect(hwnd, nullptr);
+        }
+    };
+
     switch (message) {
     case WM_SETCURSOR:
         if (LOWORD(lParam) == HTCLIENT && application.ApplyCurrentCursor()) {
@@ -64,9 +76,7 @@ bool WindowMessageDispatcher::TryDispatch(
         application.OnDpiChanged(
             static_cast<UINT>(LOWORD(wParam)),
             *reinterpret_cast<const RECT*>(lParam));
-        if (application.m_renderReady) {
-            application.RenderFrame();
-        }
+        renderAndValidateWindow();
         outResult = 0;
         return true;
     case WM_ENTERSIZEMOVE:
@@ -75,9 +85,7 @@ bool WindowMessageDispatcher::TryDispatch(
         return true;
     case WM_EXITSIZEMOVE:
         application.OnExitSizeMove();
-        if (application.m_renderReady) {
-            application.RenderFrame();
-        }
+        renderAndValidateWindow();
         outResult = 0;
         return true;
     case WM_SIZE:
@@ -85,9 +93,7 @@ bool WindowMessageDispatcher::TryDispatch(
             application.OnResize(
                 static_cast<UINT>(LOWORD(lParam)),
                 static_cast<UINT>(HIWORD(lParam)));
-            if (application.m_renderReady) {
-                application.RenderFrame();
-            }
+            renderAndValidateWindow();
         }
         outResult = 0;
         return true;

new_editor/app/Host/WindowMessageDispatcher.h

@@ -21,6 +21,7 @@ public:
         LPARAM lParam,
         LRESULT& outResult);
     static bool TryDispatch(
+        HWND hwnd,
         Application& application,
         UINT message,
         WPARAM wParam,