Core: Introduce a IContext::attach() version taking a help provider

... and use it to dissolve the DesignerContext as example.

Change-Id: I0b67989050390fd9017203ec48068c144e0b8ac9
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/coreplugin/icontext.cpp

@@ -41,6 +41,15 @@ void IContext::attach(QWidget *widget, const Context &context, const HelpItem &h
     ICore::addContextObject(icontext);
 }
 
+void IContext::attach(QWidget *widget, const Context &context, const HelpProvider &helpProvider)
+{
+    auto icontext = new IContext(widget); // As QObject parent.
+    icontext->setContext(context);
+    icontext->setWidget(widget);
+    icontext->setContextHelpProvider(helpProvider);
+    ICore::addContextObject(icontext);
+}
+
 QDebug operator<<(QDebug debug, const Core::Context &context)
 {
     debug.nospace() << "Context(";

src/plugins/coreplugin/icontext.h

@@ -69,6 +69,9 @@ public:
     static void attach(QWidget *widget,
                        const Context &context,
                        const HelpItem &contextHelp = {});
+    static void attach(QWidget *widget,
+                       const Context &context,
+                       const HelpProvider &helpProvider);
 
 protected:
     Context m_context;

src/plugins/designer/formeditor.cpp

@@ -92,21 +92,6 @@ using namespace Utils;
 
 namespace Designer::Internal {
 
-class DesignerContext final : public IContext
-{
-public:
-    DesignerContext(const Context &context, QWidget *widget, QObject *parent)
-        : IContext(parent)
-    {
-        setContext(context);
-        setWidget(widget);
-        setContextHelpProvider([](const HelpCallback &callback) {
-            const QDesignerFormEditorInterface *core = designerEditor();
-            callback(core->integration()->contextHelpId());
-        });
-    }
-};
-
 /* A stub-like, read-only text editor which displays UI files as text. Could be used as a
   * read/write editor too, but due to lack of XML editor, highlighting and other such
   * functionality, editing is disabled.
@@ -443,7 +428,11 @@ void FormEditorData::fullInit()
 
     Context designerContexts = m_contexts;
     designerContexts.add(Core::Constants::C_EDITORMANAGER);
-    ICore::addContextObject(new DesignerContext(designerContexts, m_modeWidget, this));
+
+    IContext::attach(m_modeWidget, designerContexts, [](const IContext::HelpCallback &callback) {
+        const QDesignerFormEditorInterface *core = designerEditor();
+        callback(core->integration()->contextHelpId());
+    });
 
     DesignMode::registerDesignWidget(m_modeWidget,
                                      QStringList(Utils::Constants::FORM_MIMETYPE),