feat: add buildDtkVersion/runtimeDtkVersion to DApplication

    buildDtkVersion: return the libdtkwidget version of build application
    runtimeDtkVersion: return the libdtkwidget version of runing application

Change-Id: I4d8053265a6bdd5fd7f78fc4a843cc491c1189f2

src/widgets/dapplication.cpp

@@ -391,6 +391,16 @@ bool DApplication::isDXcbPlatform()
     return qApp && (qApp->platformName() == DXCB_PLUGIN_KEY || qApp->property(DXCB_PLUGIN_SYMBOLIC_PROPERTY).toBool());
 }
 
+int DApplication::buildDtkVersion()
+{
+    return DtkBuildVersion::value;
+}
+
+int DApplication::runtimeDtkVersion()
+{
+    return DTK_VERSION;
+}
+
 /**
  * @brief DApplication::productName returns the product name of this application.
  *
@@ -704,4 +714,6 @@ bool DApplication::notify(QObject *obj, QEvent *event)
     return QApplication::notify(obj, event);
 }
 
+int DtkBuildVersion::value = 0;
+
 DWIDGET_END_NAMESPACE

src/widgets/dapplication.h

@@ -66,6 +66,11 @@ class LIBDTKWIDGETSHARED_EXPORT DApplication : public QApplication, public DTK_C
     static bool loadDXcbPlugin();
     static bool isDXcbPlatform();
 
+    // return the libdtkwidget version of build application
+    static int buildDtkVersion();
+    // return the libdtkwidget version of runing application
+    static int runtimeDtkVersion();
+
     // meta information that necessary to create a about dialog for the application.
     QString productName() const;
     void setProductName(const QString &productName);
@@ -132,6 +137,22 @@ class LIBDTKWIDGETSHARED_EXPORT DApplication : public QApplication, public DTK_C
     friend class DMainWindowPrivate;
 };
 
+class DtkBuildVersion {
+public:
+    static int value;
+};
+
+#ifndef LIBDTKWIDGET_LIBRARY
+class Q_DECL_HIDDEN _DtkBuildVersion {
+public:
+    _DtkBuildVersion() {
+        DtkBuildVersion::value = DTK_VERSION;
+    }
+};
+
+static _DtkBuildVersion _dtk_build_version;
+#endif
+
 DWIDGET_END_NAMESPACE
 
 #endif // DAPPLICATION_H

src/widgets/dtitlebar.cpp

@@ -474,6 +474,10 @@ DTitlebar::DTitlebar(QWidget *parent) :
     QFrame(parent),
     DObject(*new DTitlebarPrivate(this))
 {
+    if (DApplication::buildDtkVersion() < DTK_VERSION_CHECK(2, 0, 6, 1)) {
+        setBackgroundTransparent(true);
+    }
+
     DThemeManager::registerWidget(this, {"transparent"});
 
     D_D(DTitlebar);