1 files changed, 142 insertions, 0 deletions
diff --git a/demos/gtk-demo/rotated_text.c b/demos/gtk-demo/rotated_text.c
new file mode 100644
index 000000000..1c37548dd
--- /dev/null
+++ b/demos/gtk-demo/rotated_text.c
@@ -0,0 +1,142 @@
+/* Rotated Text
+ *
+ * This demo shows how to use GDK and Pango to draw rotated and transformed
+ * text. The use of GdkPangoRenderer in this example is a somewhat advanced
+ * technique; most applications can simply use gdk_draw_layout(). We use
+ * it here mostly because that allows us to work in user coordinates - that is,
+ * coordinates prior to the application of the transformation matrix, rather
+ * than device coordinates.
+ *
+ * As of GTK+-2.6, the ability to draw transformed and anti-aliased graphics
+ * as shown in this example is only present for text. With GTK+-2.8, a new
+ * graphics system called "Cairo" will be introduced that provides these
+ * capabilities and many more for all types of graphics.
+ */
+#include <math.h>
+#include <gtk/gtk.h>
+
+static GtkWidget *window = NULL;
+
+static gboolean
+rotated_text_expose_event (GtkWidget      *widget,
+			   GdkEventExpose *event,
+			   gpointer	   data)
+{
+#define RADIUS 150
+#define N_WORDS 10
+#define FONT "Sans Bold 27"
+  
+  PangoRenderer *renderer;
+  PangoMatrix matrix = PANGO_MATRIX_INIT;
+  PangoContext *context;
+  PangoLayout *layout;
+  PangoFontDescription *desc;
+
+  int width = widget->allocation.width;
+  int height = widget->allocation.height;
+  double device_radius;
+  int i;
+
+  /* Get the default renderer for the screen, and set it up for drawing  */
+  renderer = gdk_pango_renderer_get_default (gtk_widget_get_screen (widget));
+  gdk_pango_renderer_set_drawable (GDK_PANGO_RENDERER (renderer), widget->window);
+  gdk_pango_renderer_set_gc (GDK_PANGO_RENDERER (renderer), widget->style->black_gc);
+
+  /* Set up a transformation matrix so that the user space coordinates for
+   * the centered square where we draw are [-RADIUS, RADIUS], [-RADIUS, RADIUS]
+   * We first center, then change the scale */
+  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 = gtk_widget_create_pango_context (widget);
+  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);
+  
+  return FALSE;
+}
+
+GtkWidget *
+do_rotated_text (GtkWidget *do_widget)
+{
+  GtkWidget *drawing_area;
+  
+  if (!window)
+    {
+      const GdkColor white = { 0, 0xffff, 0xffff, 0xffff };
+      
+      window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+      gtk_window_set_screen (GTK_WINDOW (window),
+			     gtk_widget_get_screen (do_widget));
+      gtk_window_set_title (GTK_WINDOW (window), "Rotated Text");
+
+      g_signal_connect (window, "destroy", G_CALLBACK (gtk_widget_destroyed), &window);
+
+      drawing_area = gtk_drawing_area_new ();
+      gtk_container_add (GTK_CONTAINER (window), drawing_area);
+
+      /* This overrides the background color from the theme */
+      gtk_widget_modify_bg (drawing_area, GTK_STATE_NORMAL, &white);
+
+      g_signal_connect (drawing_area, "expose-event",
+			G_CALLBACK (rotated_text_expose_event), NULL);
+
+      gtk_window_set_default_size (GTK_WINDOW (window), 2 * RADIUS, 2 * RADIUS);
+    }
+
+  if (!GTK_WIDGET_VISIBLE (window))
+    {
+      gtk_widget_show_all (window);
+    }
+  else
+    {
+      gtk_widget_destroy (window);
+      window = NULL;
+    }
+
+  return window;
+}