demos/gtk-demo/fontrendering.c

/* Pango/Font rendering
 *
 * Demonstrates various aspects of font rendering.
 */

#include <gtk/gtk.h>

static GtkWidget *window = NULL;
static GtkWidget *font_button = NULL;
static GtkWidget *entry = NULL;
static GtkWidget *image = NULL;
static GtkWidget *hinting = NULL;
static GtkWidget *hint_metrics = NULL;
static GtkWidget *up_button = NULL;
static GtkWidget *down_button = NULL;
static GtkWidget *text_radio = NULL;
static GtkWidget *show_grid = NULL;
static GtkWidget *show_extents = NULL;

static PangoContext *context;

static int scale = 10;

static void
on_destroy (gpointer data)
{
  window = NULL;
}

static void
update_image (void)
{
  const char *text;
  PangoFontDescription *desc;
  PangoLayout *layout;
  PangoRectangle ink, pink, logical;
  int baseline;
  cairo_surface_t *surface;
  cairo_t *cr;
  GdkPixbuf *pixbuf;
  GdkPixbuf *pixbuf2;
  const char *hint;
  cairo_font_options_t *fopt;
  cairo_hint_style_t hintstyle;
  cairo_hint_metrics_t hintmetrics;
  int i;

  if (!context)
    context = gtk_widget_create_pango_context (image);

  text = gtk_editable_get_text (GTK_EDITABLE (entry));
  desc = gtk_font_chooser_get_font_desc (GTK_FONT_CHOOSER (font_button));

  fopt = cairo_font_options_copy (pango_cairo_context_get_font_options (context));

  hint = gtk_combo_box_get_active_id (GTK_COMBO_BOX (hinting));
  if (strcmp (hint, "none") == 0)
    hintstyle = CAIRO_HINT_STYLE_NONE;
  else if (strcmp (hint, "slight") == 0)
    hintstyle = CAIRO_HINT_STYLE_SLIGHT;
  else if (strcmp (hint, "medium") == 0)
    hintstyle = CAIRO_HINT_STYLE_MEDIUM;
  else if (strcmp (hint, "full") == 0)
    hintstyle = CAIRO_HINT_STYLE_FULL;
  else
    hintstyle = CAIRO_HINT_STYLE_DEFAULT;
  cairo_font_options_set_hint_style (fopt, hintstyle);

  if (gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (hint_metrics)))
    hintmetrics = CAIRO_HINT_METRICS_ON;
  else
    hintmetrics = CAIRO_HINT_METRICS_OFF;
  cairo_font_options_set_hint_metrics (fopt, hintmetrics);

  pango_cairo_context_set_font_options (context, fopt);
  cairo_font_options_destroy (fopt);
  pango_context_changed (context);

  if (gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (text_radio)))
    {
      layout = pango_layout_new (context);
      pango_layout_set_font_description (layout, desc);
      pango_layout_set_text (layout, text, -1);
      pango_layout_get_extents (layout, &ink, &logical);
      pink = ink;
      baseline = pango_layout_get_baseline (layout);

      pango_extents_to_pixels (&ink, NULL);

      surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, ink.width + 20, ink.height + 20);
      cr = cairo_create (surface);
      cairo_set_source_rgb (cr, 1, 1, 1);
      cairo_paint (cr);

      cairo_set_source_rgb (cr, 0, 0, 0);
      cairo_move_to (cr, 10, 10);
      pango_cairo_show_layout (cr, layout);

      cairo_destroy (cr);
      g_object_unref (layout);

      pixbuf = gdk_pixbuf_get_from_surface (surface, 0, 0, cairo_image_surface_get_width (surface), cairo_image_surface_get_height (surface));
      pixbuf2 = gdk_pixbuf_scale_simple (pixbuf, gdk_pixbuf_get_width (pixbuf) * scale, gdk_pixbuf_get_height (pixbuf) * scale, GDK_INTERP_NEAREST);

      g_object_unref (pixbuf);
      cairo_surface_destroy (surface);

      surface = cairo_image_surface_create_for_data (gdk_pixbuf_get_pixels (pixbuf2),
                                                     CAIRO_FORMAT_ARGB32,
                                                     gdk_pixbuf_get_width (pixbuf2),
                                                     gdk_pixbuf_get_height (pixbuf2),
                                                     gdk_pixbuf_get_rowstride (pixbuf2));

      cr = cairo_create (surface);
      cairo_set_line_width (cr, 1);

      if (gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (show_grid)))
        {
          cairo_set_source_rgba (cr, 0.2, 0, 0, 0.2);
          for (i = 1; i < ink.height + 20; i++)
            {
              cairo_move_to (cr, 0, scale * i - 0.5);
              cairo_line_to (cr, scale * (ink.width + 20), scale * i - 0.5);
              cairo_stroke (cr);
            }
          for (i = 1; i < ink.width + 20; i++)
            {
              cairo_move_to (cr, scale * i - 0.5, 0);
              cairo_line_to (cr, scale * i - 0.5, scale * (ink.height + 20));
              cairo_stroke (cr);
            }
        }

      if (gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (show_extents)))
        {
          cairo_set_source_rgba (cr, 0, 0, 1, 1);

          cairo_rectangle (cr,
                           scale * (10 + pango_units_to_double (logical.x)) - 0.5,
                           scale * (10 + pango_units_to_double (logical.y)) - 0.5,
                           scale * pango_units_to_double (logical.width) + 1,
                           scale * pango_units_to_double (logical.height) + 1);
          cairo_stroke (cr);
          cairo_move_to (cr, scale * (10 + pango_units_to_double (logical.x)) - 0.5,
                             scale * (10 + pango_units_to_double (baseline)) - 0.5);
          cairo_line_to (cr, scale * (10 + pango_units_to_double (logical.x + logical.width)) + 1,
                             scale * (10 + pango_units_to_double (baseline)) - 0.5);
          cairo_stroke (cr);
          cairo_set_source_rgba (cr, 1, 0, 0, 1);
          cairo_rectangle (cr,
                           scale * (10 + pango_units_to_double (pink.x)) + 0.5,
                           scale * (10 + pango_units_to_double (pink.y)) + 0.5,
                           scale * pango_units_to_double (pink.width) - 1,
                           scale * pango_units_to_double (pink.height) - 1);
          cairo_stroke (cr);
        }

      cairo_surface_destroy (surface);
      cairo_destroy (cr);
    }
  else
    {
      PangoLayoutIter *iter;
      PangoLayoutRun *run;
      PangoGlyphInfo *g;
      int i, j;

      layout = pango_layout_new (context);
      pango_layout_set_font_description (layout, desc);
      pango_layout_set_text (layout, "aaaa", -1);
      pango_layout_get_extents (layout, &ink, &logical);
      pango_extents_to_pixels (&logical, NULL);

      surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, logical.width * 3 / 2, 4*logical.height);
      cr = cairo_create (surface);
      cairo_set_source_rgb (cr, 1, 1, 1);
      cairo_paint (cr);

      iter = pango_layout_get_iter (layout);
      run = pango_layout_iter_get_run (iter);

      cairo_set_source_rgb (cr, 0, 0, 0);
      for (i = 0; i < 4; i++)
        {
          g = &(run->glyphs->glyphs[i]);
          g->geometry.width = PANGO_UNITS_ROUND (g->geometry.width * 3 / 2);
        }

      for (j = 0; j < 4; j++)
        {
          for (i = 0; i < 4; i++)
            {
              g = &(run->glyphs->glyphs[i]);
              g->geometry.x_offset = i * (PANGO_SCALE / 4);
              g->geometry.y_offset = j * (PANGO_SCALE / 4);
            }

          cairo_move_to (cr, 0, j * logical.height);
          pango_cairo_show_layout (cr, layout);
        }

      cairo_destroy (cr);
      pango_layout_iter_free (iter);
      g_object_unref (layout);

      pixbuf = gdk_pixbuf_get_from_surface (surface, 0, 0, cairo_image_surface_get_width (surface), cairo_image_surface_get_height (surface));
      pixbuf2 = gdk_pixbuf_scale_simple (pixbuf, gdk_pixbuf_get_width (pixbuf) * scale, gdk_pixbuf_get_height (pixbuf) * scale, GDK_INTERP_NEAREST);
      g_object_unref (pixbuf);
      cairo_surface_destroy (surface);
    }


  gtk_picture_set_pixbuf (GTK_PICTURE (image), pixbuf2);

  g_object_unref (pixbuf2);

  pango_font_description_free (desc);
}

static void
update_buttons (void)
{
  gtk_widget_set_sensitive (up_button, scale < 32);
  gtk_widget_set_sensitive (down_button, scale > 1);
}

static void
scale_up (void)
{
  scale += 1;
  update_buttons ();
  update_image ();
}

static void
scale_down (void)
{
  scale -= 1;
  update_buttons ();
  update_image ();
}

GtkWidget *
do_fontrendering (GtkWidget *do_widget)
{
  if (!window)
    {
      GtkBuilder *builder;

      builder = gtk_builder_new_from_resource ("/fontrendering/fontrendering.ui");
      window = GTK_WIDGET (gtk_builder_get_object (builder, "window"));
      gtk_window_set_display (GTK_WINDOW (window),
                              gtk_widget_get_display (do_widget));
      g_signal_connect (window, "destroy",
                        G_CALLBACK (on_destroy), NULL);
      g_object_set_data_full (G_OBJECT (window), "builder", builder, g_object_unref);
      font_button = GTK_WIDGET (gtk_builder_get_object (builder, "font_button"));
      up_button = GTK_WIDGET (gtk_builder_get_object (builder, "up_button"));
      down_button = GTK_WIDGET (gtk_builder_get_object (builder, "down_button"));
      entry = GTK_WIDGET (gtk_builder_get_object (builder, "entry"));
      image = GTK_WIDGET (gtk_builder_get_object (builder, "image"));
      hinting = GTK_WIDGET (gtk_builder_get_object (builder, "hinting"));
      hint_metrics = GTK_WIDGET (gtk_builder_get_object (builder, "hint_metrics"));
      text_radio = GTK_WIDGET (gtk_builder_get_object (builder, "text_radio"));
      show_grid = GTK_WIDGET (gtk_builder_get_object (builder, "show_grid"));
      show_extents = GTK_WIDGET (gtk_builder_get_object (builder, "show_extents"));

      g_signal_connect (up_button, "clicked", G_CALLBACK (scale_up), NULL);
      g_signal_connect (down_button, "clicked", G_CALLBACK (scale_down), NULL);
      g_signal_connect (entry, "notify::text", G_CALLBACK (update_image), NULL);
      g_signal_connect (font_button, "notify::font-desc", G_CALLBACK (update_image), NULL);
      g_signal_connect (hinting, "notify::active", G_CALLBACK (update_image), NULL);
      g_signal_connect (hint_metrics, "notify::active", G_CALLBACK (update_image), NULL);
      g_signal_connect (text_radio, "notify::active", G_CALLBACK (update_image), NULL);
      g_signal_connect (show_grid, "notify::active", G_CALLBACK (update_image), NULL);
      g_signal_connect (show_extents, "notify::active", G_CALLBACK (update_image), NULL);

      update_image ();
    }

  if (!gtk_widget_get_visible (window))
    gtk_widget_show (window);
  else
    gtk_widget_destroy (window);

  return window;
}