Re: pango_layout_get_line_count () segfault

[Behdad Esfahbod <behdad behdad org>]

On 07/31/2009 11:41 AM, emj10 vt edu wrote:
> Hey all,
>
> I am attempting to display text with modified letter spacing using an attribute
> list and a font description.  However, I'm not sure if I'm using the
> pango_attr_letter_spacing_new (), pango_layout_set_attributes (), or
> pango_layout_set_font_description () calls correctly as I am receiving a
> segmentation fault when I attempt to call pango_layout_get_line_count ().
>
> Am I using these functions incorrectly? Also, would a simple workaround to avoid
> using an attribute list be adding markup to the text when calling
> pango_layout_set_text ()?

You forgot to initialize attr_list as far as I can see.  pango_attr_list_new()

behdad


> The backtrace shows the actual segmentation fault coming from
> pango_attribute_copy (), which was called by pango_attr_list_copy (), which was
> called from pango_layout_get_line_count ().
>
> Thanks in advance,
> Eric
>
>
> static gboolean
> draw(GtkWidget *widget,
>       GdkEventConfigure *event,
>       gpointer data)
> {
>    cairo_surface_t *surface;
>    cairo_t         *cr;
>
>    surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32,128,64);
>    cr = cairo_create(surface);
>
>    switch(cairo_status(cr))
>    {
>      case CAIRO_STATUS_SUCCESS:
>      {
>        PangoLayout          *layout;
>        PangoFontDescription *desc;
>        PangoAttrList        *attr_list;
>        PangoAttribute       *spacing;
>        unsigned char        *data;
>
>        layout = pango_cairo_create_layout(cr);
>        if (!layout)
>        {
>            fprintf(stderr,"draw(): ");
>            fprintf(stderr,"Could not create pango-layout!\n");
>            break;
>        }
>
>        desc = pango_font_description_new();
>        if (!desc)
>        {
>            fprintf(stderr,"draw(): ");
>            fprintf(stderr,"Could not create pango-font-description!\n");
>            break;
>        }
>
>        spacing = pango_attr_letter_spacing_new(5);
>        pango_attr_list_change(attr_list, spacing);
>        pango_font_description_set_absolute_size(desc, 16 * PANGO_SCALE);
>        pango_font_description_set_family(desc, "Arial");
>        pango_font_description_set_weight(desc, PANGO_WEIGHT_ULTRALIGHT);
>        pango_font_description_set_style(desc, PANGO_STYLE_NORMAL);
>        pango_layout_set_attributes(layout, attr_list);
>        pango_layout_set_font_description (layout, desc);
>        pango_layout_set_text (layout, "Display some text", -1);
>
>        cairo_set_source_rgb(cr, 0.5, 0.0, 0.5);
>        cairo_move_to(cr, 10, 25);
>
>        fprintf(stderr, "layout line count:%d\n",
> pango_layout_get_line_count(layout));
>        pango_cairo_show_layout_line(cr, pango_layout_get_line(layout,0));
>
>        pango_attribute_destroy(spacing);
>        pango_attr_list_unref(attr_list);
>        pango_font_description_free (desc);
>        g_object_unref (layout);
>      }
>    }
>    cairo_destroy(cr);
>    cairo_surface_destroy(surface);
>    return FALSE;
> }
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