lines.py

import math
from gi.repository import Gdk, Gtk, Pango

WIDTH = 150
HEIGHT = 207
CSS = '''
.frame { border: 1px solid red; }
'''

class FixedSize(Gtk.Frame):
    def __init__(self, **props):
        Gtk.Frame.__init__(self, **props)
        
    def do_get_request_mode(self):
        return Gtk.SizeRequestMode.CONSTANT_SIZE

    def do_get_preferred_width(self):
        return WIDTH, WIDTH
   
    def do_get_preferred_height(self):
        return HEIGHT, HEIGHT

class AdaptiveLabel(Gtk.Label):
    def __init__(self, **props):
        Gtk.Label.__init__(self, **props)
        
    def do_size_allocate(self, alloc):
        Gtk.Label.do_size_allocate(self, alloc)
        layout = self.create_pango_layout('0')
        ink_rect, logical_rect = layout.get_pixel_extents()
        lines = int(math.floor(alloc.height / logical_rect.height))
        self.props.lines = lines

provider = Gtk.CssProvider()
provider.load_from_data(CSS)
Gtk.StyleContext.add_provider_for_screen(Gdk.Screen.get_default(), provider,
    Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION)

win = Gtk.Window()
card = FixedSize(expand=False, halign=Gtk.Align.START, valign=Gtk.Align.START)
text = AdaptiveLabel(label='Drive the road / to your surrender / time comes '
    'around / out of my hands / Small boats / on the beach at dead of night / '
    'Come and go / before first light / First light / Leave me running / into '
    'the wind / King of the world / How do you feel / What is there to feel',
    wrap=True, wrap_mode=Pango.WrapMode.WORD_CHAR,
    ellipsize=Pango.EllipsizeMode.END, lines=15)
card.add(text)
win.add(card)
win.show_all()
win.connect('destroy', Gtk.main_quit)
Gtk.main()