Re: Combobox on touchscreen

[Roland Koebler <rk-list simple-is-better org>]

Hi,

On Mon, Jun 26, 2017 at 10:08:36AM +0000, Rúben Rodrigues wrote:
> Following this post that didn't receive an answer 
> https://mail.gnome.org/archives/gtk-app-devel-list/2016-June/msg00030.html 
> , want to ask if someone knows this problem.
I know this problem, since I wrote this mail. But maybe I'm the only one, and
noone else cares. :(

> Sometimes combobox works, 
> but i think that is dificult to change the state of the combobox. There 
> is a workaround?
I know two workarounds:

1. Patch the library with my patch, see https://bugzilla.gnome.org/show_bug.cgi?id=333470
2. Stack a transparent button on top of the combobox.

I'm using the 2nd way, by using the following function in Python
for every combobox. It's not perfect (and only a workaround and not
a real solution), but as long as the GTK+-developers don't care,
that's all I can do.

--

def workaround_combobox_touch(widget):
    """Workaround for comboboxes for touchscreens.

    Comboboxes (and menus) do not work with touchscreens, due to a bug in
    GTK+3, bugnumber #33470.

    There are usually 2 ways to select a combobox-entry:

    1. press + move + release

       This works with touchscreens in GTK+2 and partly in GTK+3 3.4, but not
       in e.g. GTK+3 3.20: Press + move does not move the selection, but tries
       to scroll the combobox-popup.

    2. click -> popup, click -> select/popdown

       This does not work on touchscreens, since (a) some touchscreens send
       MotionNotify-events with 0 pixels movement after the press and (b)
       GTK+ closes the combobox-popup if a MotionNotify-event occurred
       during the click.

    So, this workaround stacks a transparent button above the combobox, and
    opens the combobox-popup on button-click.
    """
    container = widget.get_parent()
    left = container.child_get_property(widget, "left-attach")
    top  = container.child_get_property(widget, "top-attach")
    button = Gtk.Button()
    button.set_label("")
    button.set_opacity(0)
    button.connect("clicked", lambda w, _=None: widget.popup())
    container.remove(widget)
    container.attach(button, left, top, 1, 1)
    container.attach(widget, left, top, 1, 1)

--

Roland