How to set the background of an image?

[Frank Hrebabetzky <hreba terra com br>]

In order to rotate text by 90 degrees I want to render the text to a 
bitmap, create a GdkImage from that, read pixel by pixel, transform 
their coordinates, write them back to another image and draw that one 
finally. No I wrote a small program as an exercise, without the 
transformation part, and the problem is the black background which I 
don't see how to change. Any help?

The expose-event callback function which contains my experimental code 
is here:

void draw (GtkWidget *widget, GdkEventExpose *event, gpointer data)
{
GdkGC    * gc;
GdkColor   red;
GdkPixmap *hpixmap;
PangoLayout *layout;
GdkImage *image;
int width, height;

red.pixel = 0;
red.red = 0xffff;
red.green = 0;
red.blue = 0;
gc = gdk_gc_new (widget->window);
gdk_gc_set_rgb_fg_color (gc, &red);
gdk_draw_arc (widget->window, gc,
            FALSE, 0, 0, widget->allocation.width,
            widget->allocation.height, 0, 64*360);
hpixmap = gdk_pixmap_new (widget->window, 512, 32, -1);
layout = gtk_widget_create_pango_layout (widget, "Demo");
gdk_draw_layout (hpixmap, gc, 0, 0, layout);
pango_layout_get_pixel_size (layout, &width, &height);
image = gdk_drawable_get_image (hpixmap, 0, 0, width, height);
gdk_draw_image (widget->window, gc, image, 0, 0, 0, 0, width, height);
g_object_unref (gc);
}

--
Frank Hrebabetzky               +55 / 48 / 235 1106
Florianopolis, Brazil