Re: Any simple text rendering

[Carlo Agrusti <carlo-ag libero it>]

Frank Hrebabetzky ha scritto lo scorso 29/09/2004 15:00:
> I am working on a Program which draws diagrams on a drawing area and 
> therefore I need to draw some simple text such as 'y-Axis' or '0.00', 
> '1.00' and so on, nothing fancy, no chinese or arab, just plain english 
> monospaced text. Now how should I do that ?
>
> Label widgets? I didn't see how to get ascent and descent which I need 
> to place the text correctly. Besides that, I need to allocate each 
> label, but as the number of axis numbers depends on the size of the 
> drawing area (grid spacing), this must be done anew after each resizing 
> and labels would accumulate contiuously.
>
> Pango? No idea where to start reading. Seems a huge engine. Use this 
> just to display a few characters?
>
> So what would you guys do?

This is how I managed a similar issue - drawing a simple x-y chart; 
sorry for the comments (they are in italian). HTH.

void on_drawGraph_expose_event (GtkWidget * draw,
                                GdkEventExpose * event,
                                gpointer user_data) {
        GdkGC    * gc;
        GdkPoint * points = NULL;
        gint       i, np;
        guint      width, height, x0, y0, x1, y1;
        gchar    * buf;
        gchar    * ulabel = NULL;
        gchar      label[64];
        gsize      len;
        GIOChannel
                 * dati;
        gfloat     fx, fy;
        GdkColor * nero,
                 * grigio,
                 * rosso;
        PangoLayout
                 * pl;
        PangoFontDescription
                 * lblfont;
        GdkWChar * wlabel;

        /* Dimensioni della finestra
         */
	gdk_window_get_geometry (draw->window, NULL, NULL, & width, & height, 
NULL);

        x0 = 50;
        y0 = 10;
        x1 = width - 10;
        y1 = height - 50;

        /* Impostazione dei colori personalizzati
         */
        rosso = (GdkColor *)g_malloc (sizeof (GdkColor));
        rosso->pixel = 0;
        rosso->red   = 0xffff;
        rosso->green = 0;
        rosso->blue  = 0;
        nero = (GdkColor *)g_malloc (sizeof (GdkColor));
        nero->pixel = 0;
        nero->red   = 0;
        nero->green = 0;
        nero->blue  = 0;
        grigio = (GdkColor *)g_malloc (sizeof (GdkColor));
        grigio->pixel = 0;
        grigio->red   = 0x8fff;
        grigio->green = 0x8fff;
        grigio->blue  = 0x8fff;

        /* Ora non resta che disegnare il grafico
         */
        gc = gdk_gc_new (draw->window);

        /* ticks & labels; il grafico avrà range fissi
         * [0 < fx < 65, 550 < fy < 950] e tick prefissati
         */
        points = (GdkPoint *)g_malloc (2 * sizeof (GdkPoint));

        pl = gtk_widget_create_pango_layout (draw, " ");
        lblfont = pango_font_description_from_string ("Sans 8");
        pango_layout_set_font_description (pl, lblfont);

        /* Asse X
         */
        for (i = 0; i < 9; i ++) {
                points[0].y = y1;
                points[0].x = points[1].x = (guint)(x0 + (x1 - x0) * (i * 10)/ 65);
                points[1].y = y1 + 3;
                /* Imposta gli stili della linea e traccia le ticks
                 */
		gdk_gc_set_line_attributes (gc, 0, GDK_LINE_SOLID, GDK_CAP_ROUND, 
GDK_JOIN_ROUND);
                gdk_gc_set_rgb_fg_color (gc, nero);
                gdk_draw_lines (draw->window, gc, points, 2);

                points[0].y = y1;
                points[1].y = y0;
                /* Imposta gli stili della linea e traccia le linee di divisione
                 */
		gdk_gc_set_line_attributes (gc, 0, GDK_LINE_ON_OFF_DASH, 
GDK_CAP_ROUND, GDK_JOIN_ROUND);
                gdk_gc_set_rgb_fg_color (gc, grigio);
                gdk_draw_lines (draw->window, gc, points, 2);

                /* labels
                 */
                g_sprintf (label, "%8.1f\0", (gfloat)(i * 10));
                ulabel = g_locale_to_utf8 (label, -1, NULL, NULL, NULL);
                pango_layout_set_text (pl, ulabel, -1);
                g_free (ulabel);
                points[0].x -= 21;
                points[0].y += 10;
		gdk_draw_layout_with_colors (draw->window, gc, points[0].x, 
points[0].y, pl, grigio, NULL);
        }

        /* Asse Y
         */
        for (i = 0; i < 9; i ++) {
                points[0].x = x0 - 3;
                points[0].y = points[1].y = (guint)(y1 - (y1 - y0) * (i * 50)/ 400);
                points[1].x = x0;
                /* Imposta gli stili della linea e traccia le ticks
                 */
		gdk_gc_set_line_attributes (gc, 0, GDK_LINE_SOLID, GDK_CAP_ROUND, 
GDK_JOIN_ROUND);
                gdk_gc_set_rgb_fg_color (gc, nero);
                gdk_draw_lines (draw->window, gc, points, 2);

                points[0].x = x0;
                points[1].x = x1;
                /* Imposta gli stili della linea e traccia le linee di divisione
                 */
		gdk_gc_set_line_attributes (gc, 0, GDK_LINE_ON_OFF_DASH, 
GDK_CAP_ROUND, GDK_JOIN_ROUND);
                gdk_gc_set_rgb_fg_color (gc, grigio);
                gdk_draw_lines (draw->window, gc, points, 2);

                /* labels
                 */
                g_sprintf (label, "%d \260C\0", (i * 50 + 550));
                ulabel = g_locale_to_utf8 (label, -1, NULL, NULL, NULL);
                pango_layout_set_text (pl, ulabel, -1);
                g_free (ulabel);
                points[0].x -= 45;
                points[0].y -= 7;
		gdk_draw_layout_with_colors (draw->window, gc, points[0].x, 
points[0].y, pl, grigio, NULL);
        }

        /*
         * Risultati: legge i punti da graficare da SimulaDeb.out
         */
        dati   = g_io_channel_new_file ("SimulaDeb.out", "r", NULL);
        np     = 1;
        while (g_io_channel_read_line (dati, & buf, & len, NULL, NULL) !=
                G_IO_STATUS_EOF) {
                points = (GdkPoint *)g_realloc (points, np * sizeof (GdkPoint));
                sscanf (buf, "%f %f", & fx, & fy);
                /* I valori spazio-Temp letti devono ora essere trasformati in
                   posizioni sul gc [ 0 < fx < 65, 500 < fy < 1000]
            */
                points[np-1].x = (guint)(x0 + (x1-x0) * fx/ 65);
                points[np-1].y = (guint)(y1 - (y1-y0) * (fy - 550)/ 400);
                np ++;
                g_free (buf);
        }

        /*
         * Traccia il grafico
         *
         * Imposta il colore (rosso)
         */
        gdk_gc_set_rgb_fg_color (gc, rosso);
        /* Imposta gli stili della linea
         */
	gdk_gc_set_line_attributes (gc, 2, GDK_LINE_SOLID, GDK_CAP_ROUND, 
GDK_JOIN_ROUND);

        /* Traccia la linea
         */
        gdk_draw_lines (draw->window, gc, points, np - 1);

        /* e infine il frame-box
         */
	gdk_gc_set_line_attributes (gc, 0, GDK_LINE_SOLID, GDK_CAP_ROUND, 
GDK_JOIN_ROUND);
        gdk_gc_set_rgb_fg_color (gc, nero);
        gdk_draw_rectangle (draw->window, gc, FALSE,
                        x0, y0, x1 - x0, y1 - y0);

        /* Libera tutti
         */
        g_io_channel_shutdown (dati, FALSE, NULL);
        g_io_channel_unref (dati);
        pango_font_description_free (lblfont);
        g_object_unref (pl);
        g_free (points);
        g_free (nero);
        g_free (rosso);
        g_free (grigio);
        g_object_unref (gc);
        
}