Fix:pinning-induced window position drift on Windows

examples/mainwindow/mainwindow.cpp

@@ -26,6 +26,10 @@
 
 #include <QWKWidgets/widgetwindowagent.h>
 
+#ifdef Q_OS_WIN
+#  include <QtCore/qt_windows.h>
+#endif
+
 #include <widgetframe/windowbar.h>
 #include <widgetframe/windowbutton.h>
 
@@ -128,6 +132,14 @@ bool MainWindow::event(QEvent *event) {
             break;
         }
 
+#ifdef Q_OS_WINDOWS
+        case QEvent::WinIdChange:
+            if (!applyingStayOnTop) {
+                setStayOnTop(stayOnTop);
+            }
+            break;
+#endif
+
         default:
             break;
     }
@@ -432,11 +444,14 @@ void MainWindow::installWindowAgent() {
 #ifndef Q_OS_MAC
     connect(windowBar, &QWK::WindowBar::pinRequested, this, [this, pinButton](bool pin) {
         if (isHidden() || isMinimized() || isMaximized() || isFullScreen()) {
+            pinButton->setChecked(stayOnTop);
             return;
         }
-        setWindowFlag(Qt::WindowStaysOnTopHint, pin);
-        show();
-        pinButton->setChecked(pin);
+        if (setStayOnTop(pin)) {
+            pinButton->setChecked(pin);
+        } else {
+            pinButton->setChecked(stayOnTop);
+        }
     });
     connect(windowBar, &QWK::WindowBar::minimizeRequested, this, &QWidget::showMinimized);
     connect(windowBar, &QWK::WindowBar::maximizeRequested, this, [this, maxButton](bool max) {
@@ -455,6 +470,46 @@ void MainWindow::installWindowAgent() {
 #endif
 }
 
+bool MainWindow::setStayOnTop(bool enabled) {
+#ifdef Q_OS_WINDOWS
+    if (applyingStayOnTop) {
+        return false;
+    }
+
+    const auto hwnd = reinterpret_cast<HWND>(internalWinId());
+    if (!hwnd) {
+        return false;
+    }
+
+    applyingStayOnTop = true;
+    const bool success = ::SetWindowPos(hwnd, enabled ? HWND_TOPMOST : HWND_NOTOPMOST,
+                                        0, 0, 0, 0,
+                                        SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE |
+                                            SWP_NOOWNERZORDER) != FALSE;
+    applyingStayOnTop = false;
+    if (success) {
+        stayOnTop = enabled;
+    }
+    return success;
+#else
+    if (windowFlags().testFlag(Qt::WindowStaysOnTopHint) == enabled) {
+        stayOnTop = enabled;
+        return true;
+    }
+
+    const bool visible = isVisible();
+    const QPoint frameTopLeft = frameGeometry().topLeft();
+    setWindowFlag(Qt::WindowStaysOnTopHint, enabled);
+    if (visible) {
+        show();
+        const QPoint clientOffset = geometry().topLeft() - frameGeometry().topLeft();
+        move(frameTopLeft + clientOffset);
+    }
+    stayOnTop = enabled;
+    return true;
+#endif
+}
+
 void MainWindow::loadStyleSheet(Theme theme) {
     if (!styleSheet().isEmpty() && theme == currentTheme)
         return;

examples/mainwindow/mainwindow.h

@@ -33,8 +33,11 @@ class MainWindow : public QMainWindow {
 private:
     void installWindowAgent();
     void loadStyleSheet(Theme theme);
+    bool setStayOnTop(bool stayOnTop);
 
     Theme currentTheme{};
+    bool stayOnTop{false};
+    bool applyingStayOnTop{false};
 
     QWK::WidgetWindowAgent *windowAgent;
 };