DiffEditor: Fix editor actions

The text editor widgets all need a TextEditorActionHandler that takes
care of the editor actions for them.
Each text editor needs its own context, so the editor with focus
receives the actions. This does not happen automatically for these text
editors, since the diff editor manages these itself.

Task-number: QTCREATORBUG-9445
Change-Id: Ib42f095ec23550e401e8ee9b36f3f49517a22877
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/diffeditor/sidebysidediffeditorwidget.h

@@ -30,7 +30,12 @@
 #include <QWidget>
 #include <QTextCharFormat>
 
-namespace TextEditor { class FontSettings; }
+namespace Core { class IContext; }
+
+namespace TextEditor {
+class FontSettings;
+class TextEditorWidget;
+}
 
 QT_BEGIN_NAMESPACE
 class QMenu;
@@ -52,6 +57,10 @@ class SideBySideDiffEditorWidget : public QWidget
     Q_OBJECT
 public:
     explicit SideBySideDiffEditorWidget(QWidget *parent = 0);
+    ~SideBySideDiffEditorWidget();
+
+    TextEditor::TextEditorWidget *leftEditorWidget() const;
+    TextEditor::TextEditorWidget *rightEditorWidget() const;
 
     void setDocument(DiffEditorDocument *document);
     DiffEditorDocument *diffDocument() const;
@@ -98,6 +107,8 @@ private:
     bool m_horizontalSync = false;
 
     QTextCharFormat m_spanLineFormat;
+    Core::IContext *m_leftContext;
+    Core::IContext *m_rightContext;
 };
 
 } // namespace Internal