Fix stale taskbar preview thumbnails after closing child windows.

CMakeLists.txt

@@ -853,6 +853,7 @@ target_link_libraries(gui PRIVATE
 	md4c-html
 	winmm
 	wininet
+	dwmapi
 )
 
 if(CMAKE_SIZEOF_VOID_P EQUAL 4) # x86

cmake.toml

@@ -148,6 +148,7 @@ private-link-libraries = [
     "::md4c-html",
     "winmm",
     "wininet",
+    "dwmapi"
 ]
 x86.private-link-libraries = [
     "src/gui/Src/ThirdPartyLibs/ldconvert/ldconvert_x86.lib",

src/gui/Src/main.cpp

@@ -10,6 +10,7 @@
 #include <QDebug>
 #include <QDir>
 #include "MiscUtil.h"
+#include <dwmapi.h>
 
 MyApplication::MyApplication(int & argc, char** argv)
     : QApplication(argc, argv)
@@ -28,6 +29,21 @@ bool MyApplication::globalEventFilter(void* message)
 }
 #endif
 
+static void invalidateParentThumbnail(QDialog* dialog)
+{
+    // Find the top-level parent window
+    auto parent = dialog->parentWidget();
+    while(parent && parent->parentWidget())
+    {
+        parent = parent->parentWidget();
+    }
+
+    if(parent && parent->windowHandle())
+    {
+        DwmInvalidateIconicBitmaps((HWND)parent->winId());
+    }
+}
+
 bool MyApplication::notify(QObject* receiver, QEvent* event)
 {
     bool done = true;
@@ -41,7 +57,20 @@ bool MyApplication::notify(QObject* receiver, QEvent* event)
                 MainWindow::updateDarkTitleBar(widget);
             }
         }
+
         done = QApplication::notify(receiver, event);
+
+        // Fix stale taskbar preview thumbnails after closing child windows.
+        // Windows DWM caches the preview bitmap while hovering the taskbar, but Qt
+        // doesn't notify DWM when modal dialogs close, leaving the cached thumbnail
+        // showing the now-closed dialog. Force DWM to refresh by invalidating it.
+        if(event->type() == QEvent::Hide)
+        {
+            if(auto dialog = qobject_cast<QDialog*>(receiver))
+            {
+                invalidateParentThumbnail(dialog);
+            }
+        }
     }
     catch(const std::exception & ex)
     {

src/gui/Src/main.h

@@ -33,12 +33,12 @@ extern thread_local TranslatedStringStorage TLS_TranslatedString;
 #if QT_VERSION >= QT_VERSION_CHECK(5,0,0)
 class MyEventFilter : public QAbstractNativeEventFilter
 {
-public:
-    virtual bool nativeEventFilter(const QByteArray & eventType, void* message, long* result) Q_DECL_OVERRIDE
+protected:
+    bool nativeEventFilter(const QByteArray & eventType, void* message, long* result) override
     {
         if(eventType == "windows_dispatcher_MSG")
             return DbgWinEventGlobal((MSG*)message);
-        else if(eventType == "windows_generic_MSG")
+        if(eventType == "windows_generic_MSG")
             return DbgWinEvent((MSG*)message, result);
         return false;
     }