Re: Pango Layout Mystery

["muppet" <scott asofyet org>]

James Muir wrote:
> Can anyone explain to me why "$layout->get_pixel_size()" returns
> different values than those I'd get when I get the Gnome2:Canvas::Item
> 'text-height' and 'text-width' properties? I've looked at several other
> Layout properties (spacing, indent, justify) and they all return "0". In
> the example below, I get:
>
> text, text: Hello World!  font: Ariel Normal 10  text_height: 13
> layout_height: 17  text_width: 66  layout_width: 76

When i run it, i get text_height: 17 and layout_height: 17, but text_width: 77
and layout_height: 72.


At the end of gnome_canvas_text_set_property() i found this code:

        if (text->layout)
                pango_layout_get_pixel_size (text->layout,
                                             &text->max_width,
                                             &text->height);
        else {
                text->max_width = 0;
                text->height = 0;
        }

which appears to be the only place where the values of ->height and
->max_width are set.  Those values are used in
gnome_canvas_text_get_property() like so:


        case PROP_TEXT_WIDTH:
                g_value_set_double (value, text->max_width /
text->item.canvas->pixels_per_unit);
                break;

        case PROP_TEXT_HEIGHT:
                g_value_set_double (value, text->height / text->item.canvas->pixels_per_unit);
                break;



That is, when you do this:

> my $text_width = $text->get('text-width');
> my $text_height = $text->get('text-height');

you're essentially doing

    my ($layout_width, $layout_height) = $layout->get_pixel_size();
    $layout_width /= $text->pixels_per_unit;
    $layout_height /= $text->pixels_per_unit;



Granted, this is based on looking for about two minutes at stuff i had lying
around.


-- 
muppet <scott at asofyet dot org>