取消 Gtk.TreeView 中某些特定项目的拖放

Question

我在Gtk.TreeView这里 大多数但不是所有的项目都应该能够拖放。在这个例子中，第一个项目应该不能被拖放，但它应该是可选择的。

我怎么能意识到这一点？也许我必须使用drag-begin信号并停止在那里的拖动。但我不知道怎么做。

#!/usr/bin/env python3

import gi

gi.require_version('Gtk', '3.0')

from gi.repository import Gtk

from gi.repository import Gdk

class MainWindow(Gtk.Window):

    def __init__(self):

        Gtk.Window.__init__(self, title="TreeView Drag and Drop")

        self.connect("delete-event", Gtk.main_quit)

        self.set_default_size(400, 300)

        # "model" with dummy data

        self.store = Gtk.TreeStore(str)

        self.store.append(None, ['do not drag this'])

        self.store.append(None, ['drag this'])

        self.view = Gtk.TreeView(model=self.store)

        self.add(self.view)

        # build columsn

        colA = Gtk.TreeViewColumn('Col A', Gtk.CellRendererText(), text=0)

        self.view.append_column(colA)

        # DnD events

        self.view.connect("drag-data-received", self.drag_data_received)

        self.view.connect("drag-data-get", self.drag_data_get)

        self.view.connect("drag-begin", self.drag_begin)

        target_entry = Gtk.TargetEntry.new('text/plain', 2, 0)

        self.view.enable_model_drag_source(

                Gdk.ModifierType.BUTTON1_MASK,[target_entry], 

                Gdk.DragAction.DEFAULT|Gdk.DragAction.MOVE

        )

        self.view.enable_model_drag_dest(

                [target_entry],

                Gdk.DragAction.DEFAULT|Gdk.DragAction.MOVE

        )

    def drag_data_get (self, treeview, drag_context, data, info, time):

        model, path = treeview.get_selection().get_selected_rows()

        print('dd-get\tpath: {}'.format(path))

        data.set_text(str(path[0]), -1)

    def drag_data_received (self, treeview, drag_context, x,y, data,info, time):

        print('dd-received')

        store = treeview.get_model()

        source_iter = store.get_iter(data.get_text())

        dest_path, drop_pos = self.view.get_dest_row_at_pos(x, y)

        print('path: {} pos: {}'.format(dest_path, drop_pos))