Fltk Boxtypes

FL_NO_BOX means nothing is drawn at all, so whatever is already on the screen remains. The FRAME types only draw their edges, leaving the center unchanged. In the above diagram the blue color is the area that is not drawn by the box.

It may be useful to know: FL_NO_BOX==0. "down" versions of "up" boxes can be achieved by adding 1 to the box id. "frame" versions of boxes can be achieved by adding 2 to the box id.

Many of the boxtype symbols are macros that call a function, this was done so that they are not linked in if not used. Linking in unused box types may be a problem if large numbers of them are added to fltk. See Enumerations.H.

void fl_draw_box(Fl_Boxtype b,int x,int y,int w,int h,Fl_Color) ;

This function, declared in <FL/fl_draw.H>, draws boxtype b in the given bounding box and with color c.

int Fl::box_dx(Fl_Boxtype);
int Fl::box_dy(Fl_Boxtype);
int Fl::box_dw(Fl_Boxtype);
int Fl::box_dh(Fl_Boxtype);

Returns amounts to add to the x and y of a box, and to subtract from the width and height, to get the "inside". These values are used by some widgets to draw their contents.

Making your own Boxtypes

You can define your own boxtypes by making a small function that draws the box and adding a pointer to it to a table of boxtypes. Or you can replace existing boxtypes, replacing FL_UP_BOX, FL_DOWN_BOX, and FL_FLAT_BOX will allow you to completely change the appearance of your program. You can make the bevels thicker or thinner, change the colors of them, or use pixmaps or maybe GL gourand shanding to make nifty shiny buttons.

typedef void (Fl_Box_Draw_F)(int, int, int, int, Fl_Color);

This is the form of a boxtype function. It takes a bounding box and the color() of the widget. You can ignore the color() if you want.

Here is the actual code for the FL_UP_FRAME and FL_UP_BOX types. See <FL/fl_draw.H> for the available drawing functions if you want your boxtype to be portable:

void fl_up_frame(int x, int y, int w, int h, Fl_Color) {
  if (w >= 3 && h >= 3) {
    fl_color(FL_LIGHT3); fl_xyline(x+1, y+1, x+w-2);
    fl_color(FL_LIGHT2); fl_yxline(x+1, y+h-2, y+2, x+w-3);
    fl_color(FL_LIGHT1); fl_yxline(x+2, y+h-3, y+3/*, x+w-3*/);
    fl_color(FL_DARK1); fl_xyline(x+2, y+h-3, x+w-3, y+3);
    fl_color(FL_DARK2); fl_xyline(x+1, y+h-2, x+w-2, y+2);
  }
  fl_color(FL_GRAY0); fl_rect(x,y,w,h);
}

void fl_up_box(int x, int y, int w, int h, Fl_Color c) {
  fl_up_frame(x,y,w,h,c);
  fl_color(c); fl_rectf(x+3,y+3,w-6,h-6);
}

void Fl::set_boxtype(Fl_Boxtype n, Fl_Box_Draw_F*, uchar dx, uchar dy, uchar dw, uchar dh);

Replace the function and the deltas for boxtype n.

Fl::set_boxtype(Fl_Boxtype n, Fl_Boxtype from);

Copy one boxtype to another. This copies the deltas as well as the function. If you like thin edges this will globally replace them:

Fl::set_boxtype(FL_UP_BOX,FL_THIN_UP_BOX);
Fl::set_boxtype(FL_DOWN_BOX,FL_THIN_DOWN_BOX);
Fl::set_boxtype(FL_UP_FRAME,FL_THIN_UP_FRAME);
Fl::set_boxtype(FL_DOWN_FRAME,FL_THIN_DOWN_FRAME);

(back to contents)