CodeMirror text editor plug-in.

- Based on the ace mode.
- Efficiently updates the DOM.
- Deals with insert and delete events.

Signed-off-by: Thaddee Tyl <thaddee.tyl@gmail.com>

src/client/cm.coffee

@@ -0,0 +1,94 @@
+# This is some utility code to connect a CodeMirror editor
+# to a sharejs document.
+# It is heavily inspired from the Ace editor hook.
+
+# Convert a CodeMirror delta into an op understood by share.js
+applyToShareJS = (editorDoc, delta, doc) ->
+  # CodeMirror deltas give a text replacement.
+  # I tuned this operation a little bit, for speed.
+  startPos = 0  # Get character position from # of chars in each line.
+  i = 0         # i goes through all lines.
+
+  while i < delta.from.line
+    startPos += editorDoc.lineInfo(i).text.length + 1   # Add 1 for '\n'
+    i++
+
+  startPos += delta.from.ch
+
+  if delta.to.line == delta.from.line &&
+     delta.to.ch == delta.from.ch # Then nothing was removed.
+    doc.insert startPos, delta.text.join '\n'
+  else
+    delLen = delta.to.ch - delta.from.ch
+    while i < delta.to.line
+      delLen += editorDoc.lineInfo(i).text.length + 1   # Add 1 for '\n'
+      i++
+    doc.del startPos, delLen
+    doc.insert startPos, delta.text.join '\n' if delta.text
+
+  applyToShareJS editorDoc, delta.next, doc if delta.next
+
+# Attach a CodeMirror editor to the document. The editor's contents are replaced
+# with the document's contents unless keepEditorContents is true. (In which case
+# the document's contents are nuked and replaced with the editor's).
+window.sharejs.Doc::attach_cm = (editor, keepEditorContents) ->
+  unless @provides.text
+    throw new Error 'Only text documents can be attached to CodeMirror2'
+
+  sharedoc = @
+  check = ->
+    window.setTimeout ->
+        editorText = editor.getValue()
+        otText = sharedoc.getText()
+
+        if editorText != otText
+          console.error "Text does not match!"
+          console.error "editor: #{editorText}"
+          console.error "ot:     #{otText}"
+          # Replace the editor text with the doc snapshot.
+          editor.setValue sharedoc.snapshot
+      , 0
+
+  if keepEditorContents
+    @del 0, sharedoc.getText().length
+    @insert 0, editor.getValue()
+  else
+    editor.setValue sharedoc.getText()
+
+  check()
+
+  # When we apply ops from sharejs, CodeMirror emits edit events.
+  # We need to ignore those to prevent an infinite typing loop.
+  suppress = false
+
+  # Listen for edits in CodeMirror.
+  editorListener = (ed, change) ->
+    return if suppress
+    applyToShareJS editor, change, sharedoc
+
+    check()
+
+  editor.setOption 'onChange',  editorListener
+
+  @on 'insert', (pos, text) ->
+    suppress = true
+    # All the primitives we need are already in CM's API.
+    editor.replaceRange text, editor.posFromIndex(pos)
+    suppress = false
+    check()
+
+  @on 'delete', (pos, text) ->
+    suppress = true
+    from = editor.posFromIndex pos
+    to = editor.posFromIndex (pos + text.length)
+    editor.replaceRange '', from, to
+    suppress = false
+    check()
+
+  @detach_ace = ->
+    # TODO: can we remove the insert and delete event callbacks?
+    editor.setOption 'onChange', null
+    delete @detach_ace
+
+  return
+