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/* 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) * G_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;
}
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