Enhanced GTK+3 TextBuffer

This post shows an enhanced version of GTK+3 TextBuffer which provides Undo(Ctrl-Z) and Redo(Ctrl-Y) functions.

1. Define a class encTextBuffer based on Gtk.DrawingTextBuffer.
2. Add the event handler insert-text. This handler will be activated whenever text are added to the buffer.
3. Add the event handler delete-range. This handler will be activated whenever text are deleted from the buffer.
4. Define two stacks, UndoStack and RedoStack, to keep the operations and data for undo and redo respectively.
5. Define two methods, undo and redo, which can be called externally by other classes.
6. The textview can include this enhanced textbuffer by:
   self.txtBuffer = encTextBuffer()
self.txtEditor = Gtk.TextView(buffer=self.txtBuffer)
7. The textview containing this encTextBuffer should add a handler key-press-event that can capture the keys Ctrl-Z and Ctrl-Y for calling the Undo and Redo operations. See the following line:
   self.txtEditor.connect("key-press-event", self.keyCapture)

Source Code

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#!/usr/bin/env python3 # Title : Enhanced textbuffer # Author : Michael Mui # Date : 19/04/2022 # Version : 0.1 # Remarks : With Undo & Redo operations import gi gi.require_version('Gtk', '3.0') from gi.repository import Gtk, Gdk from gi.repository.GdkPixbuf import Pixbuf, InterpType, PixbufLoader # Enhanced TextBuffer with Undo & Redo functions class encTextBuffer(Gtk.TextBuffer): UNDO_STACK_SIZE = 20 # maximum no. of undo def __init__(self): self.undoStack = [] self.redoStack = [] self.skipUndo = False Gtk.TextBuffer.__init__(self) self.connect('insert-text',self.insText) self.connect('delete-range',self.delText) def insText(self, widget, start, text, length): if self.skipUndo: return mCurrOffset = self.get_property('cursor-position') if len(self.undoStack)==0 or \ self.undoStack[-1][0]!='ins': mv1 = ('ins', mCurrOffset, length, text) self.undoStack.append(mv1) self.redoStack.clear() if len(self.undoStack) > self.UNDO_STACK_SIZE: self.undoStack.pop(0) return if length==1 and mCurrOffset== \ self.undoStack[-1][1]+self.undoStack[-1][2]: # group all insertions of consecutive # single characters into a single # insertion mv = self.undoStack.pop() mv1 = (mv[0], mv[1], mv[2]+1, mv[3]+text) else: mv1 = ('ins', mCurrOffset, length, text) self.undoStack.append(mv1) self.redoStack.clear() if len(self.undoStack) > self.UNDO_STACK_SIZE: self.undoStack.pop(0) def delText(self, widget, start, end): if self.skipUndo: return mtext = self.get_text(start, end, False) # get current cursor position mCurrOffset = self.get_property('cursor-position') # remember the start position of the deletion self.place_cursor(start) mOffset = self.get_property('cursor-position') # remember the end position of the deletion self.place_cursor(end) mOffsetEnd = self.get_property('cursor-position') mlength = mOffsetEnd-mOffset if mCurrOffset==mOffset: # 'Del' is pressed if len(self.undoStack)==0 or \ self.undoStack[-1][0]!='del': mv1 = ('del', mOffset, mOffsetEnd, mtext) self.undoStack.append(mv1) self.redoStack.clear() if len(self.undoStack) > self.UNDO_STACK_SIZE: self.undoStack.pop(0) return elif mlength==1 and self.undoStack[-1][0]=='del' \ and mCurrOffset==self.undoStack[-1][1]: # group all deletions of single characters # into a single deletion mv = self.undoStack.pop() mv1 = (mv[0], mv[1], mv[2]+1, mv[3]+mtext) else: mv1 = ('del', mOffset, mOffsetEnd, mtext) else: # 'Backspace' is pressed if len(self.undoStack)==0 or \ self.undoStack[-1][0]!='back': mv1 = ('back', mOffset, mOffsetEnd, mtext) self.undoStack.append(mv1) if len(self.undoStack) > self.UNDO_STACK_SIZE: self.undoStack.pop(0) return elif mlength==1 and self.undoStack[-1][0]=='back' \ and mCurrOffset==self.undoStack[-1][1]: # group all deletions of single characters # into a single deletion mv = self.undoStack.pop() mv1 = (mv[0], mv[1]-1, mv[2], mtext+mv[3]) else: mv1 = ('back', mOffset, mOffsetEnd, mtext) self.undoStack.append(mv1) self.redoStack.clear() if len(self.undoStack) > self.UNDO_STACK_SIZE: self.undoStack.pop(0) print(self.undoStack) def undo(self): if len(self.undoStack)<=0: return None mv = self.undoStack.pop() self.redoStack.append(mv) if mv[0]=='ins': mOffset = mv[1] mlen = mv[2] miter1 = self.get_iter_at_offset(mOffset) miter2 = self.get_iter_at_offset(mOffset+mlen) self.skipUndo = True self.delete(miter1,miter2) self.skipUndo = False mretIter = self.get_iter_at_offset(mOffset) elif mv[0]=='del' or mv[0]=='back': mOffset = mv[1] mOffsetEnd = mv[2] mtext = mv[3] miter1 = self.get_iter_at_offset(mOffset) self.place_cursor(miter1) self.skipUndo = True self.insert_at_cursor(mtext,-1) self.skipUndo = False mretIter = self.get_iter_at_offset(mOffsetEnd) self.place_cursor(mretIter) mUndoPos = self.create_mark(None,mretIter,False) return mUndoPos def redo(self): if len(self.redoStack)<=0: return None mv = self.redoStack.pop() self.undoStack.append(mv) if mv[0]=='ins': mOffset = mv[1] mlen = mv[2] mtext = mv[3] miter1 = self.get_iter_at_offset(mOffset) self.place_cursor(miter1) self.skipUndo = True self.insert_at_cursor(mtext,-1) self.skipUndo = False mretIter = self.get_iter_at_offset(mOffset+mlen) elif mv[0]=='del' or mv[0]=='back': mOffset = mv[1] mOffsetEnd = mv[2] miter1 = self.get_iter_at_offset(mOffset) miter2 = self.get_iter_at_offset(mOffsetEnd) self.skipUndo = True self.delete(miter1,miter2) self.skipUndo = False mretIter = self.get_iter_at_offset(mOffset) self.place_cursor(mretIter) mUndoPos = self.create_mark(None,mretIter,False) return mUndoPos # --- end of Enhanced TextBuffer with Undo & Redo functions # GUI gAppTitle = 'Enhanced Textbuffer' class Base: def __init__(self): self.win = Gtk.Window() self.win.set_title(gAppTitle) self.win.set_default_size(width=640, height=800) self.win.set_border_width(4) self.win.connect("delete-event", self.appWinDelete_event) # # vbox holding all controls mBox = Gtk.VBox(homogeneous=False, spacing=4) self.win.add(mBox) mlab1 = Gtk.Label() ms = "<b>Textbuffer with Undo (Ctrl-Z) and Redo (Ctrl-Y)</b>" mlab1.set_markup(ms) mlab1.set_halign(Gtk.Align.START) mBox.pack_start(mlab1,False,True,2) # textbuffer of the editor self.txtBuffer = encTextBuffer() # self.txtEditor = Gtk.TextView(buffer=self.txtBuffer) self.txtEditor.connect("key-press-event",self.keyCapture) self.txtEditor.set_wrap_mode(Gtk.WrapMode.WORD) mscwin = Gtk.ScrolledWindow() mscwin.set_policy(Gtk.PolicyType.NEVER, Gtk.PolicyType.AUTOMATIC) mscwin.add(self.txtEditor) mBox.pack_start(mscwin,True,True,2) # self.win.show_all() # Event Handlers # --------------------------------------------------------- # app windows delete event def appWinDelete_event(self, event, data=None): Gtk.main_quit() return False # key events def keyCapture(self, window, event): mkv = event.keyval mlab = Gtk.accelerator_get_label(mkv,event.state) if mlab=='Ctrl+Z': mCursorPos = self.txtBuffer.undo() if mCursorPos != None: self.txtEditor.scroll_to_mark(mCursorPos,0,True,0,0.25) elif mlab=='Ctrl+Y': mCursorPos = self.txtBuffer.redo() if mCursorPos != None: self.txtEditor.scroll_to_mark(mCursorPos,0,True,0,0.25) def main(): Gtk.main() if __name__ == "__main__": base = Base() main()