pango_layout_get_line_count () segfault

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pango_layout_get_line_count () segfault

by emj10 :: Rate this Message:

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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 ()?

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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Re: pango_layout_get_line_count () segfault

by Behdad Esfahbod-3 :: Rate this Message:

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On 07/31/2009 11:41 AM, emj10@... 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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> gtk-i18n-list@...
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>

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