docs: Move documentation to inline comments: gdkpango

1 files changed, 99 insertions, 0 deletions

diff --git a/gdk/gdkpango.c b/gdk/gdkpango.c
index 20361eada9..e21175bd9a 100644
--- a/gdk/gdkpango.c
+++ b/gdk/gdkpango.c
@@ -27,6 +27,105 @@
 #include <math.h>
 #include <pango/pangocairo.h>
 
+
+/**
+ * SECTION:pango_interaction
+ * @Short_description: Using Pango in GDK
+ * @Title: Pango Interaction
+ *
+ * Pango is the text layout system used by GDK and GTK+. The functions
+ * and types in this section are used to obtain clip regions for
+ * #PangoLayouts, and to get #PangoContexts that can be used with
+ * GDK.
+ *
+ * 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 <link
+ * linkend="PANGO-SCALE-CAPS">PANGO_SCALE</link> or the PANGO_PIXELS() macro.)
+ *
+ * Rendering a Pango layout is done most simply with pango_cairo_show_layout();
+ * you can also draw pieces of the layout with pango_cairo_show_layout_line().
+ * <example id="rotated-example">
+ * <title>Draw transformed text with Pango and cairo</title>
+ * <!-- Note that this example is basically the same as
+ *      demos/gtk-demo/rotated_text.c -->
+ * <programlisting>
+ * #define RADIUS 100
+ * #define N_WORDS 10
+ * #define FONT "Sans Bold 18"
+ *
+ * PangoContext *context;
+ * PangoLayout *layout;
+ * PangoFontDescription *desc;
+ *
+ * double radius;
+ * int width, height;
+ * int i;
+ *
+ * /<!---->* 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 *<!---->/
+ *
+ * width = gdk_window_get_width (window);
+ * height = gdk_window_get_height (window);
+ * radius = MIN (width, height) / 2.;
+ *
+ * cairo_translate (cr,
+ *                  radius + (width - 2 * radius) / 2,
+ *                  radius + (height - 2 * radius) / 2);
+ *                  cairo_scale (cr, radius / RADIUS, 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++)
+ *   {
+ *     double red, green, blue;
+ *     double angle = 2 * G_PI * i / n_words;
+ *
+ *     cairo_save (cr);
+ *
+ *     /<!---->* Gradient from red at angle == 60 to blue at angle == 300 *<!---->/
+ *     red = (1 + cos (angle - 60)) / 2;
+ *     green = 0;
+ *     blue = 1 - red;
+ *
+ *     cairo_set_source_rgb (cr, red, green, blue);
+ *     cairo_rotate (cr, angle);
+ *
+ *     /<!---->* Inform Pango to re-layout the text with the new transformation matrix *<!---->/
+ *     pango_cairo_update_layout (cr, layout);
+ *
+ *     pango_layout_get_size (layout, &width, &height);
+ *
+ *     cairo_move_to (cr, - width / 2 / PANGO_SCALE, - DEFAULT_TEXT_RADIUS);
+ *     pango_cairo_show_layout (cr, layout);
+ *
+ *     cairo_restore (cr);
+ *   }
+ *
+ * g_object_unref (layout);
+ * g_object_unref (context);
+ * </programlisting>
+ * </example>
+ * <figure>
+ *   <title>Output of <xref linkend="rotated-example"/></title>
+ *   <graphic fileref="rotated-text.png" format="PNG"/>
+ * </figure>
+ */
+
 /* Get a clip region to draw only part of a layout. index_ranges
  * contains alternating range starts/stops. The region is the
  * region which contains the given ranges, i.e. if you draw with the