I am trying to find the simplest example of a custom widget being written for Gtk-3.
So far the best thing I've found is this (using PyGTK), but it seems to be targeted to Gtk-2.
BTW: I don't care the language it is written in, but if we can avoid C++, much better!
Python3 Gtk3 it is, then:
from gi.repository import Gtk
class SuperSimpleWidget(Gtk.Label):
__gtype_name__ = 'SuperSimpleWidget'
Here is a non-trivial example that actually does something, namely paints its background and draws a diagonal line through it. I'm inheriting from Gtk.Misc
instead of Gtk.Widget
to save some boilerplate (see below):
class SimpleWidget(Gtk.Misc):
__gtype_name__ = 'SimpleWidget'
def __init__(self, *args, **kwds):
super().__init__(*args, **kwds)
self.set_size_request(40, 40)
def do_draw(self, cr):
# paint background
bg_color = self.get_style_context().get_background_color(Gtk.StateFlags.NORMAL)
cr.set_source_rgba(*list(bg_color))
cr.paint()
# draw a diagonal line
allocation = self.get_allocation()
fg_color = self.get_style_context().get_color(Gtk.StateFlags.NORMAL)
cr.set_source_rgba(*list(fg_color));
cr.set_line_width(2)
cr.move_to(0, 0) # top left of the widget
cr.line_to(allocation.width, allocation.height)
cr.stroke()
Finally, if you really want to derive from Gtk.Widget
then you also have to set up a drawing background. Gtk.Misc
does that for you, but Gtk.Widget
could be a container that doesn't actually draw anything itself. But inquiring minds want to know, so you could do it like so:
from gi.repository import Gdk
class ManualWidget(Gtk.Widget):
__gtype_name__ = 'ManualWidget'
def __init__(self, *args, **kwds):
# same as above
def do_draw(self, cr):
# same as above
def do_realize(self):
allocation = self.get_allocation()
attr = Gdk.WindowAttr()
attr.window_type = Gdk.WindowType.CHILD
attr.x = allocation.x
attr.y = allocation.y
attr.width = allocation.width
attr.height = allocation.height
attr.visual = self.get_visual()
attr.event_mask = self.get_events() | Gdk.EventMask.EXPOSURE_MASK
WAT = Gdk.WindowAttributesType
mask = WAT.X | WAT.Y | WAT.VISUAL
window = Gdk.Window(self.get_parent_window(), attr, mask);
self.set_window(window)
self.register_window(window)
self.set_realized(True)
window.set_background_pattern(None)
Edit and to actually use it:
w = Gtk.Window()
w.add(SimpleWidget())
w.show_all()
w.present()
import signal # enable Ctrl-C since there is no menu to quit
signal.signal(signal.SIGINT, signal.SIG_DFL)
Gtk.main()
Or, more fun, use it directly from the ipython3 REPL:
from IPython.lib.inputhook import enable_gtk3
enable_gtk3()
w = Gtk.Window()
w.add(SimpleWidget())
w.show_all()
w.present()