Win32: Consolidate registry code

Add a RAII class for registry keys and use it throughout
the code base.

Change-Id: I666b2fbb790f83436443101d6bc1e3c0525e78df
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

2 files changed, 15 insertions, 38 deletions

diff --git a/src/plugins/platforms/windows/qwindowscontext.cpp b/src/plugins/platforms/windows/qwindowscontext.cpp
index bb349f08a7..f7d04b667d 100644
--- a/src/plugins/platforms/windows/qwindowscontext.cpp
+++ b/src/plugins/platforms/windows/qwindowscontext.cpp
@@ -79,6 +79,7 @@
 #include <QtCore/qscopedpointer.h>
 #include <QtCore/quuid.h>
 #include <QtCore/private/qsystemlibrary_p.h>
+#include <QtCore/private/qwinregistry_p.h>
 
 #include <QtEventDispatcherSupport/private/qwindowsguieventdispatcher_p.h>
 
@@ -1518,28 +1519,13 @@ QTouchDevice *QWindowsContext::touchDevice() const
         d->m_pointerHandler.touchDevice() : d->m_mouseHandler.touchDevice();
 }
 
-static DWORD readDwordRegistrySetting(const wchar_t *regKey, const wchar_t *subKey, DWORD defaultValue)
-{
-    DWORD result = defaultValue;
-    HKEY handle;
-    if (RegOpenKeyEx(HKEY_CURRENT_USER, regKey, 0, KEY_READ, &handle) == ERROR_SUCCESS) {
-        DWORD type;
-        if (RegQueryValueEx(handle, subKey, nullptr, &type, nullptr, nullptr) == ERROR_SUCCESS
-            && type == REG_DWORD) {
-            DWORD value;
-            DWORD size = sizeof(result);
-            if (RegQueryValueEx(handle, subKey, nullptr, nullptr, reinterpret_cast<unsigned char *>(&value), &size) == ERROR_SUCCESS)
-                result = value;
-        }
-        RegCloseKey(handle);
-    }
-    return result;
-}
-
 DWORD QWindowsContext::readAdvancedExplorerSettings(const wchar_t *subKey, DWORD defaultValue)
 {
-    return readDwordRegistrySetting(L"Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\Advanced",
-                                    subKey, defaultValue);
+    const auto value =
+        QWinRegistryKey(HKEY_CURRENT_USER,
+                        LR"(Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced)")
+                       .dwordValue(subKey);
+    return value.second ? value.first : defaultValue;
 }
 
 static inline bool isEmptyRect(const RECT &rect)
diff --git a/src/plugins/platforms/windows/qwindowsservices.cpp b/src/plugins/platforms/windows/qwindowsservices.cpp
index b2b1dee232..83b052bb49 100644
--- a/src/plugins/platforms/windows/qwindowsservices.cpp
+++ b/src/plugins/platforms/windows/qwindowsservices.cpp
@@ -45,6 +45,8 @@
 #include <QtCore/qdebug.h>
 #include <QtCore/qdir.h>
 
+#include <QtCore/private/qwinregistry_p.h>
+
 #include <shlobj.h>
 #include <intshcut.h>
 
@@ -78,35 +80,24 @@ static inline QString mailCommand()
 
     const wchar_t mailUserKey[] = L"Software\\Microsoft\\Windows\\Shell\\Associations\\UrlAssociations\\mailto\\UserChoice";
 
-    wchar_t command[MAX_PATH] = {0};
     // Check if user has set preference, otherwise use default.
-    HKEY handle;
-    QString keyName;
-    if (!RegOpenKeyEx(HKEY_CURRENT_USER, mailUserKey, 0, KEY_READ, &handle)) {
-        DWORD bufferSize = BufferSize;
-        if (!RegQueryValueEx(handle, L"Progid", nullptr, nullptr, reinterpret_cast<unsigned char*>(command), &bufferSize))
-            keyName = QString::fromWCharArray(command);
-        RegCloseKey(handle);
-    }
+    QString keyName = QWinRegistryKey(HKEY_CURRENT_USER, mailUserKey)
+                      .stringValue( L"Progid");
     const QLatin1String mailto = keyName.isEmpty() ? QLatin1String("mailto") : QLatin1String();
     keyName += mailto + QLatin1String("\\Shell\\Open\\Command");
     if (debug)
         qDebug() << __FUNCTION__ << "keyName=" << keyName;
-    command[0] = 0;
-    if (!RegOpenKeyExW(HKEY_CLASSES_ROOT, reinterpret_cast<const wchar_t*>(keyName.utf16()), 0, KEY_READ, &handle)) {
-        DWORD bufferSize = BufferSize;
-        RegQueryValueEx(handle, L"", nullptr, nullptr, reinterpret_cast<unsigned char*>(command), &bufferSize);
-        RegCloseKey(handle);
-    }
+    const QString command = QWinRegistryKey(HKEY_CLASSES_ROOT, keyName).stringValue(L"");
     // QTBUG-57816: As of Windows 10, if there is no mail client installed, an entry like
     // "rundll32.exe .. url.dll,MailToProtocolHandler %l" is returned. Launching it
     // silently fails or brings up a broken dialog after a long time, so exclude it and
     // fall back to ShellExecute() which brings up the URL assocation dialog.
-    if (!command[0] || wcsstr(command, L",MailToProtocolHandler") != nullptr)
+    if (command.isEmpty() || command.contains(QLatin1String(",MailToProtocolHandler")))
         return QString();
     wchar_t expandedCommand[MAX_PATH] = {0};
-    return ExpandEnvironmentStrings(command, expandedCommand, MAX_PATH) ?
-           QString::fromWCharArray(expandedCommand) : QString::fromWCharArray(command);
+    return ExpandEnvironmentStrings(reinterpret_cast<const wchar_t *>(command.utf16()),
+                                    expandedCommand, MAX_PATH)
+        ? QString::fromWCharArray(expandedCommand) : command;
 }
 
 static inline bool launchMail(const QUrl &url)