The code in your test application doing the gf_layer_attach() specifies display_info.main_layer_index for the layer 
index.  With the iMX31 driver this value is 0 which corresponds to the Background window.   
If you wish to use the Foreground window you will need to specify a layer_index of 1.

Note the iMX31 terms Background and Foreground have nothing to do with the setting of background or foreground color.

-----Original Message-----
From: gong mingyu [mailto:community-noreply@qnx.com] 
Sent: July 29, 2009 9:21 PM
To: advanced-graphics
Subject: Re: RE: background and foreground windows problem

the lcd test code as follow:

int main() {
//device & display
gf_dev_t            gdev;
gf_dev_info_t       gdev_info;
gf_display_t        display;
gf_display_info_t   display_info;
int i;
//layer
gf_layer_t  layer;
//surface
gf_surface_t    surface;
gf_surface_info_t surface_info;
unsigned height;
unsigned width;
gf_layer_info_t layer_info;
//context
gf_context_t context;
if (gf_dev_attach(&gdev, GF_DEVICE_INDEX(0), &gdev_info) != GF_ERR_OK) {
    printf("gf_dev_attach() failed\n");
perror( "gf_dev_attach()" );
    return (-1);
}
printf("gdev_info.ndisplays: %d\n",gdev_info.ndisplays);
for (i = 0; i < gdev_info.ndisplays; i++) {
    printf("Display %d: ", i);
    if (gf_display_attach(&display, gdev, i, &display_info) == GF_ERR_OK) {
        printf("%dX%d, refresh = %dHz\n", display_info.xres,
            display_info.yres, display_info.refresh);
        printf("display_info.nlayers: %d\n", display_info.nlayers);
    } else {
        printf("gf_display_attach() failed\n");
     perror( "gf_display_attach()" );
gf_dev_detach(gdev);
    }
}
if (display != NULL) {
    if (gf_layer_attach(&layer,display,display_info.main_layer_index, 0) == GF_ERR_OK) {
printf("Attaching Layer %d to display.\n ",display_info.main_layer_index);
    }
    else {
        printf("gf_layer_attach() failed\n");
gf_dev_detach( gdev );
        return (-1);
    }
}
if((gf_layer_query(layer,0,&layer_info))==GF_ERR_OK){
printf("Layer's Format 0 : 0x%x, GF_FORMAT_PACK_RGB565: 0x%x\n",layer_info.format,GF_FORMAT_PACK_RGB565);
}
else{
printf(" gf_layer_query() failed");
    return (-1);
}
width = display_info.xres;
height = display_info.yres;
if (gf_surface_create_layer(&surface, &layer, 1, 0,
width, height, layer_info.format, NULL, 0) == GF_ERR_OK) {
printf("Succesfully created surface on top of layer\n");
        gf_layer_set_surfaces(layer, &surface, 1);
        gf_surface_get_info(surface, &surface_info);    
         printf("surface's Format: 0x%x, GF_FORMAT_PKLE_RGB565: 0x%x\n",surface_info.format,GF_FORMAT_PKLE_RGB565);
    } else {
        printf("gf_surface_create_layer() failed\n");
        return (-1);
    }
if (gf_context_create(&context) != GF_ERR_OK) {
        fprintf(stderr, "gf_context_create failed\n");
        return -1;
    }
else{
printf(" Created the context succefully\n");
}
if (gf_context_set_surface(context,surface)!= GF_ERR_OK) {
            fprintf(stderr, "gf_context_set_surface failed\n");
            return -1;
        }
 else{
        printf("Context Surface is Set Succesfully\n");
        }
int x,y;
gf_draw_begin(context);
gf_context_set_penwidth(context, 1 );
gf_context_set_bgcolor( context, 0x000000 );//white, background is not enable
gf_draw_rect( context, 0, 0, width-1, height-1 ); 
gf_draw_flush(context );
x=400; 
y=240;
gf_context_set_fgcolor( context, 0xFF0000);//red output mode 18 rgb565 
gf_draw_rect(context,(width>>1)-1-x,(height>>1)-1-y,(width>>1)-1+x,(height>>1)-1+y); 
x>>=1;
y>>=1;
gf_context_set_fgcolor( context, 0x00FF00);//green 
gf_draw_rect(context,(width>>1)-1-x,(height>>1)-1-y,(width>>1)-1+x,(height>>1)-1+y); 
x>>=1;
y>>=1;
gf_context_set_fgcolor( context, 0x0000FF);//blue...