LibGUI: Implement Vim motion system

This patch implements Vim motions.  The VimMotion class will accept
keycodes from the editing engine to build up a motion, and will
signal when a motion is complete via VimMotion::is_complete().  The
editing engine can then call VimMotion::get_range() to obtain a
TextRange object which can be used to perform operations on the text,
or VimMotion::get_position() to obtain a TextPosition which is the
new position of the cursor after the motion.

Currently, the following motions are supported:

- h/j/k/l, regular Vim line and character movements
- 0/^/$, start/end of line and start of non-blank
- w/e/b/ge, word-related movements
- W/E/B/gE, WORD (anything non-blank) versions of the above motions
- gg/G, document related movements
- t/f, to/find character

All motions except gg/G accept a number prefix to repeat the motion that
many times.

This patch updates insert, normal and visual modes to use this motion
system for movement.

1 files changed, 6 insertions, 0 deletions

diff --git a/Userland/Libraries/LibGUI/EditingEngine.h b/Userland/Libraries/LibGUI/EditingEngine.h
index c718bfe6a1..83c89ca124 100644
--- a/Userland/Libraries/LibGUI/EditingEngine.h
+++ b/Userland/Libraries/LibGUI/EditingEngine.h
@@ -29,6 +29,12 @@ public:
     void attach(TextEditor& editor);
     void detach();
 
+    TextEditor& editor()
+    {
+        VERIFY(!m_editor.is_null());
+        return *m_editor.unsafe_ptr();
+    }
+
     virtual bool on_key(const KeyEvent& event);
 
 protected: