PyGObject: Drag and Drop with ToolPalette

Platform Language bindings
1

I have been able to get drag and drop working from a Gtk.ToolPalette, but only when setting Gtk.ToolButton.set_use_drag_window(True) . However when clicking on a ToolButton to drag and drop it, it does not result in the button actually being visually clicked. I understand this is because set_use_drag_window causes all events (even button clicks) to be intercepted as a drag event.

The docs say that the easiest way to use drag and drop with Gtk.ToolPalette is to call Gtk.ToolPalette.add_drag_dest() with the desired drag source palette and the desired drag target widget. This is kind of the opposite of what I need based on the complexity of the GUI app, since I need to setup the ToolPalette and then add a callback to the drag source after the DrawingArea is created.

I have inherited from the Gtk.TooPalette , created a Gtk.ToolItemGroup for each section of the palette, and then I am creating the buttons:

def toolbox_button(self, action_name, stock_id):
    button = Gtk.ToolButton.new_from_stock(stock_id)
    button.action_name = action_name
    button.set_use_drag_window(True)

    # Enable Drag and Drop
    button.drag_source_set(
        Gdk.ModifierType.BUTTON1_MASK,
        self.DND_TARGETS,
        Gdk.DragAction.COPY | Gdk.DragAction.LINK,
    )
    button.drag_source_set_icon_stock(stock_id)
    button.connect("drag-data-get", self._button_drag_data_get)

    return button

On the DrawingArea I am then making it a drag dest:

    view.drag_dest_set(
        Gtk.DestDefaults.MOTION,
        DiagramPage.VIEW_DND_TARGETS,
        Gdk.DragAction.MOVE | Gdk.DragAction.COPY | Gdk.DragAction.LINK,
    )

Is there a way to get drag and drop to work with the ToolPalette while still allowing the buttons to work normally?

2

My fellow contributor dug in to the GTK source code and figured out that the Gtk.ToggleToolButton actually has a child button which isn’t currently documented. Drag and drop works if you set the drag source to this “inner button”.

def toolbox_button(action_name, stock_id, label, shortcut):
    button = Gtk.ToggleToolButton.new()
    button.set_icon_name(stock_id)
    button.action_name = action_name
    if label:
        button.set_tooltip_text("%s (%s)" % (label, shortcut))

    # Enable Drag and Drop
    inner_button = button.get_children()[0]
    inner_button.drag_source_set(
        Gdk.ModifierType.BUTTON1_MASK | Gdk.ModifierType.BUTTON3_MASK,
        self.DND_TARGETS,
        Gdk.DragAction.COPY | Gdk.DragAction.LINK,
    )
    inner_button.drag_source_set_icon_stock(stock_id)
    inner_button.connect(
        "drag-data-get", self._button_drag_data_get, action_name
    )

    return button

What would be the best way to resolve this? I have never contributed to GTK before, would a PR be welcome to improve the C documentation?

3

So, does Gtk.ToolPalette.add_drag_dest do what you need, except that it requires you to specify the destination widget? If so, you should be able to use Gtk.ToolPalette.set_drag_source when you make the palette, and then call Gtk.Widget.drag_dest_set on the DrawingArea. That is what Gtk.ToolPalette.add_drag_dest does internally.

4

That works good. Tried it out. Not sure of a different way of going about it.

Eric

import gi
gi.require_version("Gtk", "3.0")
from gi.repository import Gtk, Gdk

class MainWindow(Gtk.Window):
    def __init__(self):
        Gtk.Window.__init__(self, title="Drag and Drop")
        self.set_position(Gtk.WindowPosition.CENTER)
        self.set_default_size(300, 200)

        #Just change a color with dnd.
        self.color = 0

        self.button = Gtk.ToolButton.new(label = "Click or Drag")
        self.button.set_hexpand(True)
        '''
        self.button.set_use_drag_window(True)
        self.button.drag_source_set(Gdk.ModifierType.BUTTON1_MASK, [], Gdk.DragAction.MOVE)
        self.button.drag_source_set_target_list(None)
        self.button.drag_source_add_text_targets()
        self.button.connect("drag-data-get", self.on_drag_data_get)
        '''
        self.button.connect("clicked", self.button_down)
        
        self.inner_button = self.button.get_children()[0]
        self.inner_button.drag_source_set(Gdk.ModifierType.BUTTON1_MASK, [], Gdk.DragAction.MOVE)
        self.inner_button.drag_source_set_target_list(None)
        self.inner_button.drag_source_add_text_targets()
        self.inner_button.connect("drag-data-get", self.on_drag_data_get)
        
        self.da = Gtk.DrawingArea()
        self.da.set_hexpand(True)
        self.da.set_vexpand(True)
        self.da.connect("draw", self.da_draw)      
        self.da.drag_dest_set(Gtk.DestDefaults.ALL, [], Gdk.DragAction.MOVE)
        self.da.drag_dest_set_target_list(None)
        self.da.drag_dest_add_text_targets()  
        self.da.connect("drag-data-received", self.on_drag_data_received)

        self.grid = Gtk.Grid()
        self.grid.attach(self.button, 0, 0, 1, 1)
        self.grid.attach(self.da, 0, 1, 1, 1)
        self.add(self.grid)

    def button_down(self, args):
        print("Button Clicked")
       
    def on_drag_data_get(self, widget, drag_context, data, info, time):
        print("Data Get")
        if(self.color == 0): 
            self.color = 1
        else:
            self.color = 0
        data.set_text("Button Dragged", -1)
        self.da.queue_draw()

    def on_drag_data_received(self, widget, drag_context, x, y, data, info, time):
        print("Data Received " + data.get_text())

    def da_draw(self, wid, cr):
        if(self.color == 0):
            cr.set_source_rgb(0.0 , 0.0 , 1.0)
        else:
            cr.set_source_rgb(0.0 , 1.0 , 0.0)
        cr.paint()
                     
win = MainWindow()
win.connect("delete-event", Gtk.main_quit)
win.show_all()
Gtk.main()
5

I will see if I can try to make that work, I definitely haven’t had success so far, but I will give it another shot.

@cecashon It looks like you made use of the inner button as well to get it to work. Thanks for providing an example!

6

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