Pango Interaction Using Pango in GDK Pango is the text layout system used by GDK and GTK+. The functions and types in this section are used to render Pango objects to GDK. drawables, and also extend the set of Pango attributes to include stippling and embossing. Creating a #PangoLayout object is the first step in rendering text, and requires getting a handle to a #PangoContext. For GTK+ programs, you'll usually want to use gtk_widget_get_pango_context(), or gtk_widget_create_pango_layout(), rather than using the lowlevel gdk_pango_context_get_for_screen(). Once you have a #PangoLayout, you can set the text and attributes of it with Pango functions like pango_layout_set_text() and get its size with pango_layout_get_size(). (Note that Pango uses a fixed point system internally, so converting between Pango units and pixels using PANGO_SCALE or the PANGO_PIXELS() macro.) Rendering a Pango layout is done most simply with gdk_draw_layout(); you can also draw pieces of the layout with gdk_draw_layout() or gdk_draw_glyphs(). #GdkPangoRenderer is a subclass of #PangoRenderer that is used internally to implement these functions. Using it directly or subclassing it can be useful in some cases. See the #GdkPangoRenderer documentation for details. Using #GdkPangoRenderer to draw transformed text #define RADIUS 100 #define N_WORDS 10 #define FONT "Sans Bold 18" GdkScreen *screen = gdk_drawable_get_screen (drawable); PangoRenderer *renderer; GdkGC *gc; PangoMatrix matrix = PANGO_MATRIX_INIT; PangoContext *context; PangoLayout *layout; PangoFontDescription *desc; double device_radius; int width, height; int i; /* Get the default renderer for the screen, and set it up for drawing */ renderer = gdk_pango_renderer_get_default (screen); gdk_pango_renderer_set_drawable (GDK_PANGO_RENDERER (renderer), drawable); gc = gdk_gc_new (drawable); gdk_pango_renderer_set_gc (GDK_PANGO_RENDERER (renderer), gc); /* Set up a transformation matrix so that the user space coordinates for * where we are drawing are [-RADIUS, RADIUS], [-RADIUS, RADIUS] * We first center, then change the scale */ gdk_drawable_get_size (drawable, &width, &height); device_radius = MIN (width, height) / 2.; pango_matrix_translate (&matrix, device_radius + (width - 2 * device_radius) / 2, device_radius + (height - 2 * device_radius) / 2); pango_matrix_scale (&matrix, device_radius / RADIUS, device_radius / RADIUS); /* Create a PangoLayout, set the font and text */ context = gdk_pango_context_get_for_screen (screen); layout = pango_layout_new (context); pango_layout_set_text (layout, "Text", -1); desc = pango_font_description_from_string (FONT); pango_layout_set_font_description (layout, desc); pango_font_description_free (desc); /* Draw the layout N_WORDS times in a circle */ for (i = 0; i < N_WORDS; i++) { GdkColor color; PangoMatrix rotated_matrix = matrix; int width, height; double angle = (360. * i) / N_WORDS; /* Gradient from red at angle == 60 to blue at angle == 300 */ color.red = 65535 * (1 + cos ((angle - 60) * M_PI / 180.)) / 2; color.green = 0; color.blue = 65535 - color.red; gdk_pango_renderer_set_override_color (GDK_PANGO_RENDERER (renderer), PANGO_RENDER_PART_FOREGROUND, &color); pango_matrix_rotate (&rotated_matrix, angle); pango_context_set_matrix (context, &rotated_matrix); /* Inform Pango to re-layout the text with the new transformation matrix */ pango_layout_context_changed (layout); pango_layout_get_size (layout, &width, &height); pango_renderer_draw_layout (renderer, layout, - width / 2, - RADIUS * PANGO_SCALE); } /* Clean up default renderer, since it is shared */ gdk_pango_renderer_set_override_color (GDK_PANGO_RENDERER (renderer), PANGO_RENDER_PART_FOREGROUND, NULL); gdk_pango_renderer_set_drawable (GDK_PANGO_RENDERER (renderer), NULL); gdk_pango_renderer_set_gc (GDK_PANGO_RENDERER (renderer), NULL); /* free the objects we created */ g_object_unref (layout); g_object_unref (context); g_object_unref (gc);
Output of <xref linkend="rotated-example"/>
@screen: @Returns: @screen: @Returns: @gdk_renderer: @drawable: @gdk_renderer: @gc: @gdk_renderer: @part: @stipple: @gdk_renderer: @part: @color: @Returns: @screen: @Returns: @context: @colormap: A Pango text attribute containing a embossed bitmap to be used when rendering the text. @attr: the #PangoAttribute. @embossed: the embossed bitmap. A Pango text attribute specifying the color to emboss text with. @attr: the #PangoAttribute @color: the color A Pango text attribute containing a stipple bitmap to be used when rendering the text. @attr: the #PangoAttribute. @stipple: the stipple bitmap. @color: @Returns: @embossed: @Returns: @stipple: @Returns: @layout: @x_origin: @y_origin: @index_ranges: @n_ranges: @Returns: @line: @x_origin: @y_origin: @index_ranges: @n_ranges: @Returns: