fltk-based app snap exit with "XOpenIM() failed"

[Shuduo Sang]

It's simple FLTK-based example app. Here is the source code https://github.com/sangshuduo/fltk-hello-snap.
After be packed to snap by snapcraft and installed into 16.04 desktop, run "fltk-hello".

Expect: show fltk window with "Hello World".

Actual: the window show up and exit immediately. Output:
  XOpenIM() failed
  Unable to find fonts. Check your FontConfig configuration.

[Michael R Sweet (msweet)]

Also affects my RasterView and HTMLDOC projects:

    https://github.com/michaelrsweet/htmldoc
    https://github.com/michaelrsweet/rasterview

[Andrew Katz (akatz712)]

It affects me and I am bummed out about it, since I wrote a huge program using FLTK and now I cannot use SNAP to distribute it.

Here is my GitHub and my yaml file: https://github.com/akatz712/Magic_Designer_Emulator

name: mdesigner
base: core18 # the base snap is the execution environment for this snap
version: '1.0' # just for humans, typically '1.2+git' or '1.3.2'
summary: Extended emulation of metalic gear based toy, creates curved line designs.
description: |
  Fun artistic tool set for producing mathematically inspired designs.
  The emulator is based on a 1929 invention by Howard B. Jones of Chicago, Illinois. Originally called Hoot Nanny, the Magic Designer was marketed for about 50 years by the Northern Signal Co. of Saukville, Wisconsin. Its 6 inch diameter Center Gear meshed with two 1-inch Planetary Gears, each with a circling Peg. The Pen Arms were placed on these Gear Pegs or on fixed Stud Pegs at either side. The Left Gear was moved in a 60 degree arc by the Shift Lever. By selecting holes in the arms and a setting on the shift lever, brilliant designs could be cranked out on rotating paper discs.
  The emulator extends the capabilities of the device in a variety of ways including changing the mathematical parameters, allowing designs to be placed on a screen canvas, and instantly producing a sequence of designs which morph between two designs. There is also a rudimentary coloring in ability, the saving/loading of design specification files, as well as PDF output.

grade: devel # must be 'stable' to release into candidate/stable channels
confinement: devmode # use 'strict' once you have the right plugs and slots

apps:
  mdesigner:
    command: bin/mdesigner

parts:
  my-part:
    plugin: autotools
    source-type: tar
    source: https://sourceforge.net/projects/complexshapes/files/mdesigner-1.0.tar.gz/download
    build-packages:
      - g++
      - libfltk1.3-dev
      - libhpdf-dev
    stage-packages:
      - libx11-6
      - libxau6
      - libxcursor1
      - libxdmcp6
      - libxext6
      - libxfixes3
      - libxft2
      - libxinerama1
      - libxrender1
      - libfltk1.3
      - libfltk-images1.3
      - libfontconfig
      - libfreetype6
      - libhpdf-2.3.0
      - libjpeg9
      - libpng16-16
      - libxcb1

[Zygmunt Krynicki (zyga)]

Hello

I tried building the project but the remote part desktop/gtk3 seems to no longer exist. Could you please try updating the package to build again?

Having said that, I had a look at the interface declarations. Can you please look at https://snapcraft.io/docs/desktop-interfaces for an overview of which interfaces to use for desktop applications? I think you want the "desktop" and "x11" interfaces but I cannot try without a way to build the package first.