Design Ideas of the Kate::TextBuffer


  • Basic idea: text stored as lines
  • Lines hold text and additional data (like for highlighting)
  • Advanced Concept: Stores lines in blocks of xxx lines, to have better performance

Cursor Support

  • They will move on editing
  • Cursors can be combined to ranges
  • KateTextCursor will be stored in the buffer blocks


  • Each edit action must be encapsuled in a transaction
  • startEdit/endEdit will do this
  • Signals for starting and ending this transactions


  • After loading, buffer has revision 0
  • Each edit action which is no nop will lead to increment in revision number
  • Successful saving will reset revision back to 0

Editing Operations (only 4 different editing primitives)

  • Insert Text (inside one line)
  • Remove Text (inside one line)
  • Wrap Line (wrap a line at given position, create a new line with content behind wrap position)
  • Unwrap Line (unites the line with its predecessor)
  • Signals for all of these actions, containing the change (to allow to layer undo/swap file support/…) on top of the buffer

Load/Save & Encodings

  • Loading will try to use given codec, if that doesn’t work, try to detect the codec by the BOM at start of file or use fallback codec, if that again doesn’t work, given codec will be used again, and errors reported
  • Saving will just use the given codec

Unit Tests

  • Each of the above implementation details will be covered by unit tests
  • KateTextBuffer (+KateTextLine and Cursor) must therefor be usable without other components
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