setLabelFont doesn't seem to work (crashes the app)

[mayeranalytics]

While making a little port of the 'Hello World' example on fltk.org

// http://www.fltk.org/doc-1.3/basics.html
#include <FL/Fl.H>
#include <FL/Fl_Window.H>
#include <FL/Fl_Box.H>
int main(int argc, char **argv) {
  Fl_Window *window = new Fl_Window(340,180);
  Fl_Box *box = new Fl_Box(20,40,300,100,"Hello, World!");
  box->box(FL_UP_BOX);
  box->labelfont(FL_BOLD+FL_ITALIC);
  box->labelsize(36);
  box->labeltype(FL_SHADOW_LABEL);
  window->end();
  window->show(argc, argv);
  return Fl::run();
}

I noticed that the setLabelFont doesn't seem to work. The program compiles fine, but crashes.

{-# LANGUAGE OverloadedStrings #-}
module Main where

import qualified Graphics.UI.FLTK.LowLevel.FL              as FL
import qualified Graphics.UI.FLTK.LowLevel.Fl_Enumerations as FL
import qualified Graphics.UI.FLTK.LowLevel.Fl_Types        as FL
import           Graphics.UI.FLTK.LowLevel.FLTKHS
import qualified Graphics.UI.FLTK.LowLevel.Hierarchy       as FL hiding (flush)

ui :: IO ()
ui = do
    window <- windowNew (Size (Width 340) (Height 180)) Nothing (Just "First Program")
    begin window
    let
        boxPos  = (Position (X 20) (Y 40))
        boxSize = Size (Width 300) (Height 100)
    box <- boxNewWithBoxtype FL.UpBox (Rectangle boxPos boxSize) "Hello World"
    FL.setLabeltype box (FL.ShadowLabel)
    FL.setLabelfont box (FL.Font 12)     -- remove this line to avoid crash
    end window

    showWidget window
    return ()

main :: IO ()
main = do
    ui >> FL.run >> FL.flush

I think this needs to be looked at.

I noticed that the types of the C++ and the Haskell do not quite match. In C++ there's labelfont and labelsize, which take a font type enum and a size int. In Haskell setLabelFont takes a Font type. (My guess is that setLabelFont corresponds to the C++ labelfont member function.)

[deech]

Hi, Thanks for the report! Unfortunately I am unable to reproduce the crash on my Debian box, but what I do see is a window with a blank box. The reason is that the line FL.setLabelfont box (FL.Font 12) does not map to box->labelfont(FL_BOLD+FL_ITALIC). This is why I get a blank box because FL.Font 12 maps to the symbol font which is not present on my machine. The fix is FL.setLabelfont box FL.helveticaBoldItalic.

[mayeranalytics]

Yes indeed that is it. Thank you!

[mayeranalytics]

May I ask one more thing? How do you find out (in a systematic way, i.e. not by looking at examples), what the argument to the set/get functions is, e.g. for setLabelsize? I know it is something like FontSize 36 and I got that by looking at fltkhs-fluidtohs output. From the docs or error messages I'm not able deduce that, though.

[deech]

Yes there is a way. In this case you could start with the docs for Box and click the link for Widget in the hierarchy diagram and widget functions will show that setLabelsize takes a FontSize. As to what number to use you can then consult the FLTK docs.

I wish it were less awkward but it's the best I can do.