Design mode: Give IEditor a 'preferred mode'.

... and switch to it in EditorManager::activateEditor.
There no longer is a need for special currentEditorChanged()
handling in the editor that use a special mode.

QmlDesigner receives an additional setting specifying the
desired edit mode. QmlJSEditor detects whether QmlDesigner
is present by checking the registered mimetypes of the
Design mode and retrieves the settings via keys.

Remove some obsolete code and clean up includes
on qmldesignerconstants.h

Reviewed-by: con

src/plugins/qmljseditor/qmljseditor.cpp

@@ -45,6 +45,9 @@
 
 #include <coreplugin/actionmanager/actionmanager.h>
 #include <coreplugin/icore.h>
+#include <coreplugin/coreconstants.h>
+#include <coreplugin/modemanager.h>
+#include <coreplugin/designmode.h>
 #include <coreplugin/mimedatabase.h>
 #include <coreplugin/uniqueidmanager.h>
 #include <extensionsystem/pluginmanager.h>
@@ -53,7 +56,7 @@
 #include <texteditor/textblockiterator.h>
 #include <texteditor/texteditorconstants.h>
 #include <texteditor/texteditorsettings.h>
-
+#include <qmldesigner/qmldesignerconstants.h>
 #include <utils/changeset.h>
 #include <utils/uncommentselection.h>
 
@@ -574,6 +577,36 @@ QmlJSEditorEditable::QmlJSEditorEditable(QmlJSTextEditor *editor)
     m_context << uidm->uniqueIdentifier(TextEditor::Constants::C_TEXTEDITOR);
 }
 
+// Use preferred mode from Bauhaus settings
+static bool openInDesignMode()
+{
+    static bool bauhausDetected = false;
+    static bool bauhausPresent = false;
+    // Check if Bauhaus is loaded, that is, a Design mode widget is
+    // registered for the QML mime type.
+    if (!bauhausDetected) {
+        if (const Core::IMode *dm = Core::ModeManager::instance()->mode(QLatin1String(Core::Constants::MODE_DESIGN)))
+            if (const Core::DesignMode *designMode = qobject_cast<const Core::DesignMode *>(dm))
+                bauhausPresent = designMode->registeredMimeTypes().contains(QLatin1String(QmlJSEditor::Constants::QML_MIMETYPE));
+        bauhausDetected =  true;
+    }
+    if (!bauhausPresent)
+        return false;
+    // Query the bauhaus setting if it wants to be opened in Design mode.
+    const QString settingsKey = QLatin1String(QmlDesigner::Constants::QML_SETTINGS_GROUP)
+                                + QLatin1Char('/') + QLatin1String(QmlDesigner::Constants::QML_DESIGNER_SETTINGS_GROUP)
+                                + QLatin1Char('/') + QLatin1String(QmlDesigner::Constants::QML_OPENDESIGNMODE_SETTINGS_KEY);
+    const QVariant openDesignMode = Core::ICore::instance()->settings()->value(settingsKey);
+    return openDesignMode.isValid() ? openDesignMode.toBool() : bool(QmlDesigner::Constants::QML_OPENDESIGNMODE_DEFAULT);
+}
+
+QString QmlJSEditorEditable::preferredMode() const
+{
+    if (openInDesignMode())
+        return QLatin1String(Core::Constants::MODE_DESIGN);
+    return QString();
+}
+
 QmlJSTextEditor::QmlJSTextEditor(QWidget *parent) :
     TextEditor::BaseTextEditor(parent),
     m_methodCombo(0),