Custom Gtk.CellRenderer just rendering the first row?

Question

I'm having problems to understand why my custom Gtk.CellRenderer is only rendering the first row of a Gtk.ListStore.

I've been reading many docs and trying stuff like cellrenderer.set_visible(True) but I still have no idea of why this is happening.

Here is a full example:

from gi.repository import Gtk, Gdk, cairo, Pango, PangoCairo, GObject
import time

class CellRenderer5Stars(Gtk.CellRenderer):
    __gproperties__ = {
        'rating': ( int, # type
                    "integer prop", # nick
                    "A property that contains an integer", # blurb
                    0, # min
                    5, # max
                    0, # default
                    GObject.PARAM_READWRITE # flags
                    ),
    }

    def __init__(self):
        super().__init__()
        self.font_size=15
        self.font="Sans Bold {}".format(self.font_size)
        self.rating = 5

    def do_set_property(self, pspec, value):
        setattr(self, pspec.name, value)

    def do_get_property(self, pspec):
        return getattr(self, pspec.name)

    def do_get_size(self, widget, cell_area):
        return (0, 0, self.font_size*5, self.font_size+5)

    def do_render(self, cr, widget, background_area, cell_area, flags):
        cr.translate (0, 0)
        layout = PangoCairo.create_layout(cr)
        desc = Pango.font_description_from_string (self.font)
        layout.set_font_description(desc)

        stars_var = self.rating

        for i in range(5):
            if i < stars_var:
                layout.set_text("★", -1)
            else:
                layout.set_text("☆", -1)

            cr.save()
            PangoCairo.update_layout (cr, layout)
            cr.move_to (i*(self.font_size+1), 0)
            PangoCairo.show_layout (cr, layout)
            cr.restore()

GObject.type_register(CellRenderer5Stars)


class Window(Gtk.Window):
    def __init__(self):
        Gtk.Window.__init__(self)
        self.connect('destroy', self.on_quit)

        liststore = Gtk.ListStore(int)
        liststore.append([3])
        liststore.append([2])
        liststore.append([1])

        treeview = Gtk.TreeView(liststore)

        treeviewcolumn = Gtk.TreeViewColumn("Rating")
        treeview.append_column(treeviewcolumn)
        cellrenderer = CellRenderer5Stars()
        treeviewcolumn.pack_start(cellrenderer, True)
        treeviewcolumn.add_attribute(cellrenderer, "rating", 0)

        self.add(treeview)
        self.show_all()

    def on_quit(self):
        Gtk.main_quit()

w = Window()
Gtk.main()

Answer 1

You're rendering your stars to the same place of the cairo surface for every item you pass and don't obey the cell_area you should use. Replacing

cr.move_to (i*(self.font_size+1), cell_area.y)

in your code will yield a result you'd expect. But the documentation for do_render() gives you a little more info about the spacing to use:

Invokes the virtual render function of the Gtk.CellRenderer. The three passed-in rectangles are areas in cr. Most renderers will draw within cell_area; the xalign, yalign, xpad, and ypad fields of the Gtk.CellRenderer should be honored with respect to cell_area. background_area includes the blank space around the cell, and also the area containing the tree expander; so the background_area rectangles for all cells tile to cover the entire window.

Additionally the 'destroy' signal has a window argument, so you should define on_quit(self, window) or similar instead.