TextEditors: Separate away methods that actually work on a document

Introduces ITextEditorDocument. This is part of a more general "use
documents instead of editors whereever possible". It will allow to move
to e.g. ITextEditor::openedTextDocumentContents() instead of
ITextEditor::openedTextEditorsContents().

Change-Id: I5ebceaa257a0d2c3e8ac4ac51b9b08b6faa42487
Reviewed-by: David Schulz <david.schulz@digia.com>

src/plugins/texteditor/basetextdocument.cpp

@@ -31,6 +31,7 @@
 
 #include "basetextdocumentlayout.h"
 #include "basetexteditor.h"
+#include "convenience.h"
 #include "typingsettings.h"
 #include "storagesettings.h"
 #include "tabsettings.h"
@@ -90,6 +91,21 @@ BaseTextDocument::~BaseTextDocument()
     delete d;
 }
 
+QString BaseTextDocument::contents() const
+{
+    return document()->toPlainText();
+}
+
+QString BaseTextDocument::textAt(int pos, int length) const
+{
+    return Convenience::textAt(QTextCursor(document()), pos, length);
+}
+
+QChar BaseTextDocument::characterAt(int pos) const
+{
+    return document()->characterAt(pos);
+}
+
 QString BaseTextDocument::mimeType() const
 {
     return d->m_mimeType;