Windows QPA: Do not use QSettings to access the registry

When commenting out the warning in createOrOpenKey()
(src\corelib\io\qsettings_win.cpp:157), applications produce warnings:
QSettings: Failed to create subkey "Software\Microsoft\Windows NT\CurrentVersion\FontSubstitutes": Access is denied.
indicating that an attempt to open the registry in read/write mode fails.
Add a utility function to read out registry strings in read-only mode to
the font database and use that instead.

Change-Id: I4187344cac7ec2ba27f15b51e237575efc171853
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

src/platformsupport/fontdatabases/windows/qwindowsfontdatabase.cpp

@@ -1981,4 +1981,26 @@ int QWindowsFontDatabase::defaultVerticalDPI()
     return vDPI;
 }
 
+QString QWindowsFontDatabase::readRegistryString(HKEY parentHandle, const wchar_t *keyPath, const wchar_t *keyName)
+{
+    QString result;
+    HKEY handle = 0;
+    if (RegOpenKeyEx(parentHandle, keyPath, 0, KEY_READ, &handle) == ERROR_SUCCESS) {
+        // get the size and type of the value
+        DWORD dataType;
+        DWORD dataSize;
+        if (RegQueryValueEx(handle, keyName, 0, &dataType, 0, &dataSize) == ERROR_SUCCESS) {
+            if (dataType == REG_SZ || dataType == REG_EXPAND_SZ) {
+                dataSize += 2; // '\0' missing?
+                QVarLengthArray<unsigned char> data(dataSize);
+                data[dataSize - 2] = data[dataSize - 1] = '\0';
+                if (RegQueryValueEx(handle, keyName, 0, 0, data.data(), &dataSize) == ERROR_SUCCESS)
+                    result = QString::fromWCharArray(reinterpret_cast<const wchar_t *>(data.data()));
+            }
+        }
+        RegCloseKey(handle);
+    }
+    return result;
+}
+
 QT_END_NAMESPACE

src/platformsupport/fontdatabases/windows/qwindowsfontdatabase_p.h

@@ -130,6 +130,8 @@ public:
     static void setFontOptions(unsigned options);
     static unsigned fontOptions();
 
+    static QString readRegistryString(HKEY parentHandle, const wchar_t *keyPath, const wchar_t *keyName);
+
 private:
     void populateFamily(const QString &familyName, bool registerAlias);
     void removeApplicationFonts();

src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite.cpp

@@ -42,7 +42,6 @@
 #include "qwindowsfontenginedirectwrite_p.h"
 #include "qwindowsfontdatabase_p.h"
 
-#include <QtCore/QSettings>
 #include <QtCore/QtEndian>
 #include <QtCore/QVarLengthArray>
 #include <QtCore/QFile>
@@ -915,9 +914,11 @@ void QWindowsFontEngineDirectWrite::initFontInfo(const QFontDef &request,
 
 QString QWindowsFontEngineDirectWrite::fontNameSubstitute(const QString &familyName)
 {
-    static const char keyC[] = "HKEY_LOCAL_MACHINE\\Software\\Microsoft\\Windows NT\\CurrentVersion\\"
-                               "FontSubstitutes";
-    return QSettings(QLatin1String(keyC), QSettings::NativeFormat).value(familyName, familyName).toString();
+    const wchar_t key[] = L"Software\\Microsoft\\Windows NT\\CurrentVersion\\FontSubstitutes";
+    const QString substitute =
+        QWindowsFontDatabase::readRegistryString(HKEY_LOCAL_MACHINE, key,
+                                                 reinterpret_cast<const wchar_t *>(familyName.utf16()));
+    return substitute.isEmpty() ? familyName : substitute;
 }
 
 glyph_metrics_t QWindowsFontEngineDirectWrite::alphaMapBoundingBox(glyph_t glyph,

src/plugins/platforms/windows/accessible/qwindowsaccessibility.cpp

@@ -47,13 +47,13 @@
 #include <QtCore/qmap.h>
 #include <QtCore/qpair.h>
 #include <QtCore/qpointer.h>
-#include <QtCore/qsettings.h>
 #include <QtGui/qaccessible.h>
 #include <QtGui/private/qguiapplication_p.h>
 #include <qpa/qplatformnativeinterface.h>
 #include <qpa/qplatformintegration.h>
 #include <QtGui/qwindow.h>
 #include <QtGui/qguiapplication.h>
+#include <QtFontDatabaseSupport/private/qwindowsfontdatabase_p.h> // registry helper
 
 #include "qwindowsaccessibility.h"
 #ifdef Q_CC_MINGW
@@ -114,6 +114,14 @@ static inline QString messageBoxAlertSound(const QObject *messageBox)
     return QString();
 }
 
+static QString soundFileName(const QString &soundName)
+{
+    const QString key = QStringLiteral("AppEvents\\Schemes\\Apps\\.Default\\")
+        + soundName + QStringLiteral("\\.Current");
+    return QWindowsFontDatabase::readRegistryString(HKEY_CURRENT_USER,
+                                                    reinterpret_cast<const wchar_t *>(key.utf16()), L"");
+}
+
 void QWindowsAccessibility::notifyAccessibilityUpdate(QAccessibleEvent *event)
 {
     QString soundName;
@@ -134,17 +142,9 @@ void QWindowsAccessibility::notifyAccessibilityUpdate(QAccessibleEvent *event)
         break;
     }
 
-    if (!soundName.isEmpty()) {
-#ifndef QT_NO_SETTINGS
-        QSettings settings(QLatin1String("HKEY_CURRENT_USER\\AppEvents\\Schemes\\Apps\\.Default\\") + soundName,
-                           QSettings::NativeFormat);
-        QString file = settings.value(QLatin1String(".Current/.")).toString();
-#else
-        QString file;
-#endif
-        if (!file.isEmpty()) {
-            PlaySound(reinterpret_cast<const wchar_t *>(soundName.utf16()), 0, SND_ALIAS | SND_ASYNC | SND_NODEFAULT | SND_NOWAIT);
-        }
+    if (!soundName.isEmpty() && !soundFileName(soundName).isEmpty()) {
+        PlaySound(reinterpret_cast<const wchar_t *>(soundName.utf16()), 0,
+                  SND_ALIAS | SND_ASYNC | SND_NODEFAULT | SND_NOWAIT);
     }
 
     // An event has to be associated with a window,

src/plugins/platforms/windows/accessible/qwindowsmsaaaccessible.cpp

@@ -50,7 +50,6 @@
 #include <QtCore/qdebug.h>
 #include <QtCore/qmap.h>
 #include <QtCore/qpair.h>
-#include <QtCore/qsettings.h>
 #include <QtGui/qaccessible.h>
 #include <QtGui/qguiapplication.h>
 #include <qpa/qplatformnativeinterface.h>