From cd96d870118d15734a61a019f69ef5f0269bbe05 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Morten=20Johan=20S=C3=B8rvig?= <morten.sorvig@qt.io>
Date: Thu, 23 Sep 2021 16:28:55 +0200
Subject: [PATCH] Move VM_DPICHANGE handling to QWindowsWindow
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We want to have as little code in the QWindowsContext
event switch as possible.

Pick-to: 6.2
Change-Id: I04d578aae81c4ee804310a70bd87ee60b2890b6a
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
---
 .../platforms/windows/qwindowscontext.cpp     | 31 ++-----------------
 .../platforms/windows/qwindowswindow.cpp      | 27 ++++++++++++++++
 .../platforms/windows/qwindowswindow.h        |  1 +
 3 files changed, 30 insertions(+), 29 deletions(-)

diff --git a/src/plugins/platforms/windows/qwindowscontext.cpp b/src/plugins/platforms/windows/qwindowscontext.cpp
index bbdf1ad692..91fb80dc28 100644
--- a/src/plugins/platforms/windows/qwindowscontext.cpp
+++ b/src/plugins/platforms/windows/qwindowscontext.cpp
@@ -1453,36 +1453,9 @@ bool QWindowsContext::windowsProc(HWND hwnd, UINT message,
         return true;
 #endif
     }   break;
-    case QtWindows::DpiChangedEvent: {
-
-        const UINT dpi = HIWORD(wParam);
-        const qreal scale = qreal(dpi) / qreal(platformWindow->savedDpi());
-        platformWindow->setSavedDpi(dpi);
-
-        // Send screen change first, so that the new sceen is set during any following resize
-        platformWindow->checkForScreenChanged(QWindowsWindow::FromDpiChange);
-
-        // Apply the suggested window geometry to the native window. This will make
-        // sure the window tracks the mouse cursor during screen change, and also
-        // that the window size is scaled according to the DPI change.
-        platformWindow->updateFullFrameMargins();
-        const auto prcNewWindow = reinterpret_cast<RECT *>(lParam);
-        SetWindowPos(hwnd, nullptr, prcNewWindow->left, prcNewWindow->top,
-                     prcNewWindow->right - prcNewWindow->left,
-                     prcNewWindow->bottom - prcNewWindow->top, SWP_NOZORDER | SWP_NOACTIVATE);
-
-        // Scale child QPlatformWindow size. Windows sends WM_DPICHANGE to top-level windows only.
-        for (QWindow *childWindow : platformWindow->window()->findChildren<QWindow *>()) {
-            QWindowsWindow *platformChildWindow = static_cast<QWindowsWindow *>(childWindow->handle());
-            if (!platformChildWindow)
-                continue;
-            QRect currentGeometry = platformChildWindow->geometry();
-            QRect scaledGeometry = QRect(currentGeometry.topLeft() * scale, currentGeometry.size() * scale);
-            platformChildWindow->setGeometry(scaledGeometry);
-        }
-
+    case QtWindows::DpiChangedEvent:
+        platformWindow->handleDpiChanged(hwnd, wParam, lParam);
         return true;
-    }
 #if QT_CONFIG(sessionmanager)
     case QtWindows::QueryEndSessionApplicationEvent: {
         QWindowsSessionManager *sessionManager = platformSessionManager();
diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index bbbf261273..3c64ae1a35 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -1833,6 +1833,33 @@ void QWindowsWindow::handleCompositionSettingsChanged()
     }
 }
 
+void QWindowsWindow::handleDpiChanged(HWND hwnd, WPARAM wParam, LPARAM lParam)
+{
+    const UINT dpi = HIWORD(wParam);
+    const qreal scale = qreal(dpi) / qreal(savedDpi());
+    setSavedDpi(dpi);
+
+    // Send screen change first, so that the new sceen is set during any following resize
+    checkForScreenChanged(QWindowsWindow::FromDpiChange);
+
+    // Apply the suggested window geometry to the native window. This will make
+    // sure the window tracks the mouse cursor during screen change, and also
+    // that the window size is scaled according to the DPI change.
+    updateFullFrameMargins();
+    const auto prcNewWindow = reinterpret_cast<RECT *>(lParam);
+    SetWindowPos(hwnd, nullptr, prcNewWindow->left, prcNewWindow->top,
+                 prcNewWindow->right - prcNewWindow->left,
+                 prcNewWindow->bottom - prcNewWindow->top, SWP_NOZORDER | SWP_NOACTIVATE);
+
+    // Scale child QPlatformWindow size. Windows sends WM_DPICHANGE to top-level windows only.
+    for (QWindow *childWindow : window()->findChildren<QWindow *>()) {
+        QWindowsWindow *platformChildWindow = static_cast<QWindowsWindow *>(childWindow->handle());
+        QRect currentGeometry = platformChildWindow->geometry();
+        QRect scaledGeometry = QRect(currentGeometry.topLeft() * scale, currentGeometry.size() * scale);
+        platformChildWindow->setGeometry(scaledGeometry);
+    }
+}
+
 static QRect normalFrameGeometry(HWND hwnd)
 {
     WINDOWPLACEMENT wp;
diff --git a/src/plugins/platforms/windows/qwindowswindow.h b/src/plugins/platforms/windows/qwindowswindow.h
index ea170aeee1..14c5f47853 100644
--- a/src/plugins/platforms/windows/qwindowswindow.h
+++ b/src/plugins/platforms/windows/qwindowswindow.h
@@ -318,6 +318,7 @@ public:
     void handleResized(int wParam);
     void handleHidden();
     void handleCompositionSettingsChanged();
+    void handleDpiChanged(HWND hwnd, WPARAM wParam, LPARAM lParam);
 
     static void displayChanged();
     static void settingsChanged();