From 15d5fb5382d4c234fc738d425b6ff28836afe713 Mon Sep 17 00:00:00 2001
From: kleuter <support@crystalidea.com>
Date: Mon, 17 Mar 2025 17:22:31 +0100
Subject: [PATCH] turn off directwrite fonts on Windows prior to Windows 10
 (issue https://github.com/crystalidea/qt6windows7/issues/33)

---
 .../platforms/windows/qwindowsintegration.cpp | 38 ++++---------------
 1 file changed, 8 insertions(+), 30 deletions(-)

diff --git a/qtbase/src/plugins/platforms/windows/qwindowsintegration.cpp b/qtbase/src/plugins/platforms/windows/qwindowsintegration.cpp
index 547ca57d..b96715f1 100644
--- a/qtbase/src/plugins/platforms/windows/qwindowsintegration.cpp
+++ b/qtbase/src/plugins/platforms/windows/qwindowsintegration.cpp
@@ -134,29 +134,6 @@ bool parseIntOption(const QString &parameter,const QLatin1StringView &option,
 using DarkModeHandlingFlag = QNativeInterface::Private::QWindowsApplication::DarkModeHandlingFlag;
 using DarkModeHandling = QNativeInterface::Private::QWindowsApplication::DarkModeHandling;
 
-typedef LONG (WINAPI *RtlGetVersionPtr)(PRTL_OSVERSIONINFOW);
-
-bool isWindows81() {
-    HMODULE hNtdll = GetModuleHandleA("ntdll.dll");
-    if (!hNtdll) {
-        return false; // Failed to load ntdll.dll
-    }
-
-    RtlGetVersionPtr RtlGetVersion = (RtlGetVersionPtr)GetProcAddress(hNtdll, "RtlGetVersion");
-    if (!RtlGetVersion) {
-        return false; // Failed to get RtlGetVersion
-    }
-
-    RTL_OSVERSIONINFOW rovi = {0};
-    rovi.dwOSVersionInfoSize = sizeof(rovi);
-
-    if (RtlGetVersion(&rovi) == 0) { // STATUS_SUCCESS
-        return (rovi.dwMajorVersion == 6 && rovi.dwMinorVersion == 3);
-    }
-
-    return false; // Unknown version
-}
-
 static inline unsigned parseOptions(const QStringList &paramList,
                                     int *tabletAbsoluteRange,
                                     QtWindows::DpiAwareness *dpiAwareness,
@@ -164,12 +141,6 @@ static inline unsigned parseOptions(const QStringList &paramList,
 {
     unsigned options = 0;
 
-    // for some reason DirectWrite fonts don't work on Windows 8.1
-    // https://github.com/crystalidea/qt6windows7/issues/26
-
-    if (isWindows81())
-        options |= QWindowsIntegration::DontUseDirectWriteFonts;
-
     for (const QString &param : paramList) {
         if (param.startsWith(u"fontengine=")) {
             if (param.endsWith(u"gdi")) {
@@ -515,7 +486,14 @@ QPlatformFontDatabase *QWindowsIntegration::fontDatabase() const
         else
 #endif // QT_NO_FREETYPE
 #if QT_CONFIG(directwrite3)
-        if (!(d->m_options & (QWindowsIntegration::FontDatabaseGDI | QWindowsIntegration::DontUseDirectWriteFonts)))
+
+        /* IDWriteFontFace3 is only reportedly available starting with Windows 10. This change is necessary starting
+        with Qt 6.8, where DirectWrite is used by default to populate the font database. 
+        More info: https://github.com/videolan/vlc/blob/master/contrib/src/qt/0001-Use-DirectWrite-font-database-only-with-Windows-10-a.patch
+        */
+
+        if (QOperatingSystemVersion::current() >= QOperatingSystemVersion::Windows10 &&
+            !(d->m_options & (QWindowsIntegration::FontDatabaseGDI | QWindowsIntegration::DontUseDirectWriteFonts)))
             d->m_fontDatabase = new QWindowsDirectWriteFontDatabase;
         else
 #endif