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[pango-render] Keep a reference to the first line to detect layout changes

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In order to cope with the situation where an application renders with
a PangoLayout, makes some changes and then renders again with the same
layout, CoglPangoRenderer needs to detect that the changes have
occured so that it can recreate the display list. This is acheived by
keeping a reference to the first line of the layout. When the layout
is changed Pango will clear the layout pointer in the first line and
create a new line. So if the layout pointer in the line becomes NULL
then we know the layout has changed. This trick was suggested by
Behdad Esfahbod in this email:

http://mail.gnome.org/archives/gtk-i18n-list/2009-May/msg00019.html
This commit is contained in:
Neil Roberts 2009-05-21 12:17:12 +01:00
parent 085be4cebc
commit 3fc64dfaa7
1 changed files with 67 additions and 14 deletions
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81
clutter/pango/cogl-pango-render.c
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@ -65,6 +65,19 @@ struct _CoglPangoRendererClass
PangoRendererClass class_instance;
};
typedef struct _CoglPangoRendererQdata CoglPangoRendererQdata;
/* An instance of this struct gets attached to each PangoLayout to
cache the VBO and to detect changes to the layout */
struct _CoglPangoRendererQdata
{
/* The cache of the geometry for the layout */
CoglPangoDisplayList *display_list;
/* A reference to the first line of the layout. This is just used to
detect changes */
PangoLayoutLine *first_line;
};
static void
cogl_pango_renderer_draw_glyph (CoglPangoRenderer *priv,
CoglPangoGlyphCacheValue *cache_value,
@ -192,7 +205,7 @@ cogl_pango_get_renderer_from_context (PangoContext *context)
}
static GQuark
cogl_pango_render_get_display_list_key (void)
cogl_pango_render_get_qdata_key (void)
{
static GQuark key = 0;
@ -202,6 +215,16 @@ cogl_pango_render_get_display_list_key (void)
return key;
}
static void
cogl_pango_render_qdata_destroy (CoglPangoRendererQdata *qdata)
{
if (qdata->display_list)
_cogl_pango_display_list_free (qdata->display_list);
if (qdata->first_line)
pango_layout_line_unref (qdata->first_line);
g_slice_free (CoglPangoRendererQdata, qdata);
}
/**
* cogl_pango_render_layout_subpixel:
* @layout: a #PangoLayout
@ -221,37 +244,67 @@ cogl_pango_render_layout_subpixel (PangoLayout *layout,
const CoglColor *color,
int flags)
{
PangoContext *context;
CoglPangoRenderer *priv;
CoglPangoDisplayList *display_list;
PangoContext *context;
CoglPangoRenderer *priv;
CoglPangoRendererQdata *qdata;
context = pango_layout_get_context (layout);
priv = cogl_pango_get_renderer_from_context (context);
if (G_UNLIKELY (!priv))
return;
display_list = g_object_get_qdata (G_OBJECT (layout),
cogl_pango_render_get_display_list_key ());
qdata = g_object_get_qdata (G_OBJECT (layout),
cogl_pango_render_get_qdata_key ());
if (display_list == NULL)
if (qdata == NULL)
{
priv->display_list = display_list =_cogl_pango_display_list_new ();
priv->color = *color;
qdata = g_slice_new0 (CoglPangoRendererQdata);
g_object_set_qdata_full (G_OBJECT (layout),
cogl_pango_render_get_display_list_key (),
display_list,
(GDestroyNotify) _cogl_pango_display_list_free);
pango_renderer_draw_layout (PANGO_RENDERER (priv), layout, 0, 0);
cogl_pango_render_get_qdata_key (),
qdata,
(GDestroyNotify)
cogl_pango_render_qdata_destroy);
}
/* Check if the layout has changed since the last build of the
display list. This trick was suggested by Behdad Esfahbod here:
http://mail.gnome.org/archives/gtk-i18n-list/2009-May/msg00019.html */
if (qdata->display_list && qdata->first_line
&& qdata->first_line->layout != layout)
{
_cogl_pango_display_list_free (qdata->display_list);
qdata->display_list = NULL;
}
if (qdata->display_list == NULL)
{
qdata->display_list = _cogl_pango_display_list_new ();
priv->color = *color;
priv->display_list = qdata->display_list;
pango_renderer_draw_layout (PANGO_RENDERER (priv), layout, 0, 0);
priv->display_list = NULL;
}
cogl_push_matrix ();
cogl_translate (x / (gfloat) PANGO_SCALE, y / (gfloat) PANGO_SCALE, 0);
_cogl_pango_display_list_render (display_list,
_cogl_pango_display_list_render (qdata->display_list,
priv->glyph_material,
priv->solid_material);
cogl_pop_matrix ();
/* Keep a reference to the first line of the layout so we can detect
changes */
if (qdata->first_line)
{
pango_layout_line_unref (qdata->first_line);
qdata->first_line = NULL;
}
if (pango_layout_get_line_count (layout) > 0)
{
qdata->first_line = pango_layout_get_line (layout, 0);
pango_layout_line_ref (qdata->first_line);
}
}
/**