Override the paint
signal of
ClutterText and use the CoglPango API to paint the
PangoLayout of the actor with the color of the
shadow at a given offset.
The ClutterText class provides an actor that transforms the PangoLayout object into an element of the Clutter scene graph. The underlying layout is painted, though, through a subset of the Cogl API, called CoglPango.
It is possible to paint PangoLayout created by a
ClutterText by invoking
cogl_pango_render_layout()
:
void cogl_pango_render_layout (PangoLayout *layout, int x_offset, int y_offset, CoglColor *text_color, int flags);
This function will paint the layout at the given offsets using the provided color.
Warning
The cogl_pango_render_layout()
function will only work with PangoLayouts created by
Clutter.
Since the shadow of the text is literally the same text but painted
with a different color and at an offset, we can use the
paint
signal of ClutterText to paint
the shadow, and then let ClutterText paint its contents on
top:
static void _text_paint_cb (ClutterActor *actor) { ClutterText *text = CLUTTER_TEXT (actor); /* Get the PangoLayout that the Text actor is going to paint... */ PangoLayout *layout; layout = clutter_text_get_layout (text); /* ... Create the color of the shadow... */ /* ... Finally, render the Text layout at a given * offset using the color of the shadow */ cogl_pango_render_layout (layout, SHADOW_X_OFFSET, SHADOW_Y_OFFSET, &color, 0); }
Note that we are using the PangoLayout of the
ClutterText because the ClutterText actor
always keeps an updated layout internally. It is, however, possible for
any ClutterActor to create a PangoLayout using
clutter_actor_create_pango_layout()
, and then paint
that layout using cogl_pango_render_layout()
in
their implementation of the paint
virtual
function.
Example 6.1. Creating a shadow of a text
#include <stdlib.h> #include <cogl/cogl.h> #include <cogl-pango/cogl-pango.h> #include <clutter/clutter.h> #define SHADOW_X_OFFSET 3 #define SHADOW_Y_OFFSET 3 static void _text_paint_cb (ClutterActor *actor) { PangoLayout *layout; guint8 real_opacity; CoglColor color; ClutterText *text = CLUTTER_TEXT (actor); ClutterColor text_color = { 0, }; /* Get the PangoLayout that the Text actor is going to paint */ layout = clutter_text_get_layout (text); /* Get the color of the text, to extract the alpha component */ clutter_text_get_color (text, &text_color); /* Composite the opacity so that the shadow is correctly blended */ real_opacity = clutter_actor_get_paint_opacity (actor) * text_color.alpha / 255; /* Create a #ccc color and premultiply it */ cogl_color_init_from_4ub (&color, 0xcc, 0xcc, 0xcc, real_opacity); cogl_color_premultiply (&color); /* Finally, render the Text layout at a given offset using the color */ cogl_pango_render_layout (layout, SHADOW_X_OFFSET, SHADOW_Y_OFFSET, &color, 0); } int main (int argc, char *argv[]) { ClutterActor *stage; ClutterActor *text; if (clutter_init (&argc, &argv) != CLUTTER_INIT_SUCCESS) return 1; stage = clutter_stage_new (); clutter_stage_set_title (CLUTTER_STAGE (stage), "Text shadow"); g_signal_connect (stage, "destroy", G_CALLBACK (clutter_main_quit), NULL); text = clutter_text_new (); clutter_text_set_text (CLUTTER_TEXT (text), "Hello, World!"); clutter_text_set_font_name (CLUTTER_TEXT (text), "Sans 64px"); clutter_actor_add_constraint (text, clutter_align_constraint_new (stage, CLUTTER_ALIGN_X_AXIS, 0.5)); clutter_actor_add_constraint (text, clutter_align_constraint_new (stage, CLUTTER_ALIGN_Y_AXIS, 0.5)); g_signal_connect (text, "paint", G_CALLBACK (_text_paint_cb), NULL); clutter_container_add (CLUTTER_CONTAINER (stage), text, NULL); clutter_actor_show (stage); clutter_main (); return EXIT_SUCCESS; }