QWindowsXP/VistaStyle: Move the Vista treeview handling to QWindowsXPStylePrivate.

QWindowsXPStylePrivate maintains a list of theme handles for various
style items. The derived class QWindowsVistaStylePrivate had logic
to use a special helper window with the "explorer" window theme set to
obtain the correct treeview arrow branch indicator (arrow shape for Vista as
opposed to '+'/'-' on Windows XP) when creating the "TREEVIEW" theme.
This required calling the helper function
QWindowsVistaStylePrivate::initTreeViewTheming() before
QWindowsXPStylePrivate::createTheme(), which is prone to errors and
initialization order issues.

This could be solved by making QWindowsXPStylePrivate::createTheme()
virtual or similar, but since it the fate of QWindowsXPStylePrivate is most likely
to be merged into QWindowsVistaStylePrivate; it was decided to move
the entire special handling of the Vista treeviews into
QWindowsXPStylePrivate. The existing enumeration value
QWindowsXPStylePrivate::TreeViewTheme is renamed to
QWindowsXPStylePrivate::XpTreeViewTheme and a new value
QWindowsXPStylePrivate::VistaTreeViewTheme is added for which
QWindowsXPStylePrivate::createTheme() invokes the special handling.
This also removes the need to destroy the helper window in unpolish(),
which should save some initializations.

Task-number: QTBUG-52230
Change-Id: I0492ecf38fb3e5eabc4ecbdef70f0bf05e82e104
Reviewed-by: Adam Light <aclight@gmail.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>

src/widgets/styles/qwindowsvistastyle.cpp

@@ -420,9 +420,9 @@ void QWindowsVistaStyle::drawPrimitive(PrimitiveElement element, const QStyleOpt
 
     case PE_IndicatorBranch:
         {
-            XPThemeData theme(widget, painter, QWindowsXPStylePrivate::TreeViewTheme);
+            XPThemeData theme(widget, painter, QWindowsXPStylePrivate::VistaTreeViewTheme);
             static int decoration_size = 0;
-            if (!decoration_size && d->initTreeViewTheming() && theme.isValid()) {
+            if (!decoration_size && theme.isValid()) {
                 XPThemeData themeSize = theme;
                 themeSize.partId = TVP_HOTGLYPH;
                 themeSize.stateId = GLPS_OPENED;
@@ -722,9 +722,9 @@ void QWindowsVistaStyle::drawPrimitive(PrimitiveElement element, const QStyleOpt
 
                             QPainter pixmapPainter(&pixmap);
                             XPThemeData theme(widget, &pixmapPainter,
-                                              QWindowsXPStylePrivate::TreeViewTheme,
+                                              QWindowsXPStylePrivate::VistaTreeViewTheme,
                                 LVP_LISTITEM, state, QRect(0, 0, sectionSize.width(), sectionSize.height()));
-                            if (d->initTreeViewTheming() && theme.isValid()) {
+                            if (theme.isValid()) {
                                 d->drawBackground(theme);
                             } else {
                                 QWindowsXPStyle::drawPrimitive(PE_PanelItemViewItem, option, painter, widget);
@@ -2351,10 +2351,6 @@ void QWindowsVistaStyle::unpolish(QWidget *widget)
     QWindowsXPStyle::unpolish(widget);
 
     QWindowsVistaStylePrivate *d = d_func();
-    // Delete the tree view helper in case the XP style cleaned the
-    // theme handle map due to a theme or QStyle change (QProxyStyle).
-    if (!QWindowsXPStylePrivate::hasTheme(QWindowsXPStylePrivate::TreeViewTheme))
-        d->cleanupTreeViewTheming();
 
     d->stopAnimation(widget);
 
@@ -2420,15 +2416,10 @@ QPixmap QWindowsVistaStyle::standardPixmap(StandardPixmap standardPixmap, const
 }
 
 QWindowsVistaStylePrivate::QWindowsVistaStylePrivate() :
-    QWindowsXPStylePrivate(), m_treeViewHelper(0)
+    QWindowsXPStylePrivate()
 {
 }
 
-QWindowsVistaStylePrivate::~QWindowsVistaStylePrivate()
-{
-    cleanupTreeViewTheming();
-}
-
 bool QWindowsVistaStylePrivate::transitionsEnabled() const
 {
     BOOL animEnabled = false;
@@ -2440,58 +2431,6 @@ bool QWindowsVistaStylePrivate::transitionsEnabled() const
     return false;
 }
 
-/*
- * We need to set the windows "explorer" theme explicitly on a native
- * window and open the "TREEVIEW" theme handle passing its window handle
- * in order to get Vista-style item view themes (particulary drawBackground()
- * for selected items needs this).
- * We invoke a service of the native Windows interface to create
- * a non-visible window handle, open the theme on it and insert it into
- * the cache so that it is found by XPThemeData::handle() first.
- */
-
-static inline HWND createTreeViewHelperWindow()
-{
-    if (QPlatformNativeInterface *ni = QGuiApplication::platformNativeInterface()) {
-        void *hwnd = 0;
-        void *wndProc = reinterpret_cast<void *>(DefWindowProc);
-        if (QMetaObject::invokeMethod(ni, "createMessageWindow", Qt::DirectConnection,
-                                  Q_RETURN_ARG(void *, hwnd),
-                                  Q_ARG(QString, QStringLiteral("QTreeViewThemeHelperWindowClass")),
-                                  Q_ARG(QString, QStringLiteral("QTreeViewThemeHelperWindow")),
-                                  Q_ARG(void *, wndProc)) && hwnd) {
-            return reinterpret_cast<HWND>(hwnd);
-        }
-    }
-    return 0;
-}
-
-bool QWindowsVistaStylePrivate::initTreeViewTheming()
-{
-    if (m_treeViewHelper)
-        return true;
-
-    m_treeViewHelper = createTreeViewHelperWindow();
-    if (!m_treeViewHelper) {
-        qWarning("Unable to create the treeview helper window.");
-        return false;
-    }
-    const HRESULT hr = QWindowsXPStylePrivate::pSetWindowTheme(m_treeViewHelper, L"explorer", NULL);
-    if (hr != S_OK) {
-        qErrnoWarning("SetWindowTheme() failed.");
-        return false;
-    }
-    return QWindowsXPStylePrivate::createTheme(QWindowsXPStylePrivate::TreeViewTheme, m_treeViewHelper);
-}
-
-void QWindowsVistaStylePrivate::cleanupTreeViewTheming()
-{
-    if (m_treeViewHelper) {
-        DestroyWindow(m_treeViewHelper);
-        m_treeViewHelper = 0;
-    }
-}
-
 /*!
 \reimp
 */

src/widgets/styles/qwindowsvistastyle_p_p.h

@@ -162,16 +162,10 @@ class QWindowsVistaStylePrivate :  public QWindowsXPStylePrivate
 
 public:
     QWindowsVistaStylePrivate();
-    ~QWindowsVistaStylePrivate();
+
     static int fixedPixelMetric(QStyle::PixelMetric pm);
     static inline bool useVista();
     bool transitionsEnabled() const;
-
-private:
-    bool initTreeViewTheming();
-    void cleanupTreeViewTheming();
-
-    HWND m_treeViewHelper;
 };
 
 QT_END_NAMESPACE

src/widgets/styles/qwindowsxpstyle.cpp

@@ -48,6 +48,8 @@
 #include <qbackingstore.h>
 #include <qapplication.h>
 #include <qpixmapcache.h>
+#include <private/qapplication_p.h>
+#include <qpa/qplatformnativeinterface.h>
 
 #include <qdesktopwidget.h>
 #include <qtoolbutton.h>
@@ -157,7 +159,7 @@ static const wchar_t *themeNames[QWindowsXPStylePrivate::NThemes] =
     L"BUTTON",   L"COMBOBOX",   L"EDIT",    L"HEADER",    L"LISTVIEW",
     L"MENU",     L"PROGRESS",   L"REBAR",   L"SCROLLBAR", L"SPIN",
     L"TAB",      L"TASKDIALOG", L"TOOLBAR", L"TOOLTIP",   L"TRACKBAR",
-    L"TREEVIEW", L"WINDOW",     L"STATUS"
+    L"TREEVIEW", L"WINDOW",     L"STATUS",  L"TREEVIEW"
 };
 
 static inline QBackingStore *backingStoreForWidget(const QWidget *widget)
@@ -238,6 +240,7 @@ HRGN XPThemeData::mask(QWidget *widget)
 // QWindowsXPStylePrivate -------------------------------------------------------------------------
 // Static initializations
 QPixmap *QWindowsXPStylePrivate::tabbody = 0;
+HWND QWindowsXPStylePrivate::m_vistaTreeViewHelper = 0;
 HTHEME QWindowsXPStylePrivate::m_themes[NThemes];
 bool QWindowsXPStylePrivate::use_xp = false;
 QBasicAtomicInt QWindowsXPStylePrivate::ref = Q_BASIC_ATOMIC_INITIALIZER(-1); // -1 based refcounting
@@ -321,6 +324,58 @@ void QWindowsXPStylePrivate::cleanup(bool force)
     tabbody = 0;
 }
 
+/* In order to obtain the correct VistaTreeViewTheme (arrows for PE_IndicatorBranch),
+ * we need to set the windows "explorer" theme explicitly on a native
+ * window and open the "TREEVIEW" theme handle passing its window handle
+ * in order to get Vista-style item view themes (particulary drawBackground()
+ * for selected items needs this).
+ * We invoke a service of the native Windows interface to create
+ * a non-visible window handle, open the theme on it and insert it into
+ * the cache so that it is found by XPThemeData::handle() first.
+ */
+
+static inline HWND createTreeViewHelperWindow()
+{
+    if (QPlatformNativeInterface *ni = QGuiApplication::platformNativeInterface()) {
+        void *hwnd = 0;
+        void *wndProc = reinterpret_cast<void *>(DefWindowProc);
+        if (QMetaObject::invokeMethod(ni, "createMessageWindow", Qt::DirectConnection,
+                                  Q_RETURN_ARG(void *, hwnd),
+                                  Q_ARG(QString, QStringLiteral("QTreeViewThemeHelperWindowClass")),
+                                  Q_ARG(QString, QStringLiteral("QTreeViewThemeHelperWindow")),
+                                  Q_ARG(void *, wndProc)) && hwnd) {
+            return reinterpret_cast<HWND>(hwnd);
+        }
+    }
+    return 0;
+}
+
+bool QWindowsXPStylePrivate::initVistaTreeViewTheming()
+{
+    if (m_vistaTreeViewHelper)
+        return true;
+
+    m_vistaTreeViewHelper = createTreeViewHelperWindow();
+    if (!m_vistaTreeViewHelper) {
+        qWarning("Unable to create the treeview helper window.");
+        return false;
+    }
+    if (FAILED(QWindowsXPStylePrivate::pSetWindowTheme(m_vistaTreeViewHelper, L"explorer", NULL))) {
+        qErrnoWarning("SetWindowTheme() failed.");
+        cleanupVistaTreeViewTheming();
+        return false;
+    }
+    return true;
+}
+
+void QWindowsXPStylePrivate::cleanupVistaTreeViewTheming()
+{
+    if (m_vistaTreeViewHelper) {
+        DestroyWindow(m_vistaTreeViewHelper);
+        m_vistaTreeViewHelper = 0;
+    }
+}
+
 /* \internal
     Closes all open theme data handles to ensure that we don't leak
     resources, and that we don't refere to old handles when for
@@ -333,6 +388,7 @@ void QWindowsXPStylePrivate::cleanupHandleMap()
             pCloseThemeData(m_themes[i]);
             m_themes[i] = 0;
         }
+    QWindowsXPStylePrivate::cleanupVistaTreeViewTheming();
 }
 
 HTHEME QWindowsXPStylePrivate::createTheme(int theme, HWND hwnd)
@@ -343,6 +399,8 @@ HTHEME QWindowsXPStylePrivate::createTheme(int theme, HWND hwnd)
     }
     if (!m_themes[theme]) {
         const wchar_t *name = themeNames[theme];
+        if (theme == VistaTreeViewTheme && QWindowsXPStylePrivate::initVistaTreeViewTheming())
+            hwnd = QWindowsXPStylePrivate::m_vistaTreeViewHelper;
         m_themes[theme] = pOpenThemeData(hwnd, name);
         if (!m_themes[theme])
             qErrnoWarning("OpenThemeData() failed for theme %d (%s).",
@@ -1947,7 +2005,7 @@ case PE_Frame:
                 bef_v -= delta;
                 aft_h += delta;
                 aft_v += delta;
-                XPThemeData theme(0, p, QWindowsXPStylePrivate::TreeViewTheme);
+                XPThemeData theme(0, p, QWindowsXPStylePrivate::XpTreeViewTheme);
                 theme.rect = QRect(bef_h, bef_v, decoration_size, decoration_size);
                 theme.partId = TVP_GLYPH;
                 theme.stateId = flags & QStyle::State_Open ? GLPS_OPENED : GLPS_CLOSED;

src/widgets/styles/qwindowsxpstyle_p_p.h

@@ -350,9 +350,10 @@ public:
         ToolBarTheme,
         ToolTipTheme,
         TrackBarTheme,
-        TreeViewTheme,
+        XpTreeViewTheme, // '+'/'-' shape treeview indicators (XP)
         WindowTheme,
         StatusTheme,
+        VistaTreeViewTheme, // arrow shape treeview indicators (Vista) obtained from "explorer" theme.
         NThemes
     };
 
@@ -413,6 +414,9 @@ private:
     void showProperties(XPThemeData &themeData);
 #endif
 
+    static bool initVistaTreeViewTheming();
+    static void cleanupVistaTreeViewTheming();
+
     static QBasicAtomicInt ref;
     static bool use_xp;
     static QPixmap *tabbody;
@@ -424,6 +428,7 @@ private:
     uchar *bufferPixels;
     int bufferW, bufferH;
 
+    static HWND m_vistaTreeViewHelper;
     static HTHEME m_themes[NThemes];
 };