GL pad painter crashes displaying `symbols.ttf` font when build with `-Dbuiltin_ftgl=OFF`

[linev]

Check duplicate issues.

• Checked for duplicates

Description

When GL canvas is selected, ROOT crashes trying to display text with symbols font.

Seems to be in FTGLFont character map is ignored or used incorrectly.

Builtin version of libftgl is working, but has many differences to external libftgl making very difficult to track problem.

Reproducer

[root] gStyle->SetCanvasPreferGL(true);
[root] .x $ROOTSYS/tutorials/visualisation/graphics/latex.C

ROOT version

All ROOT versions

Installation method

Build from source

Operating system

Linux

Additional context

Seems to be, ROOT crashes only when external libftgl is used

[ferdymercury]

Stack trace:

#11 0x0000777782fe2436 in FTGlyphContainer::BBox(unsigned int) const () from /lib/x86_64-linux-gnu/libftgl.so.2
#12 0x0000777782fea8fc in ?? () from /lib/x86_64-linux-gnu/libftgl.so.2
#13 0x0000777782feaaf0 in FTFont::BBox(char const*, int, FTPoint, FTPoint) () from /lib/x86_64-linux-gnu/libftgl.so.2
#14 0x0000777773c5913b in FTFont::BBox (this=0x5ac2d5ac2bc0, string=0x5ac2d4e35020 <incomplete sequence 362>, llx=
0x7ffe13cbacdc: 0, lly=
0x7ffe13cbace0: 0, llz=
0x7ffe13cbace4: 0, urx=
0x7ffe13cbace8: 0, ury=
0x7ffe13cbacec: 0, urz=
0x7ffe13cbacf0: 0) at /usr/include/FTGL/FTFont.h:255
#15 0x0000777773c564a6 in TGLFont::BBox (this=0x5ac2d5303db8, txt=0x5ac2d4e35020 <incomplete sequence 362>, llx=
0x7ffe13cbacdc: 0, lly=
0x7ffe13cbace0: 0, llz=
0x7ffe13cbace4: 0, urx=
0x7ffe13cbace8: 0, ury=
0x7ffe13cbacec: 0, urz=
0x7ffe13cbacf0: 0) at /opt/root_src/graf3d/gl/src/TGLFontManager.cxx:158
#16 0x0000777773c599dd in TGLFont::RenderHelper<char> (this=0x5ac2d5303db8, txt=0x5ac2d4e35020 <incomplete sequence 362>, x=242, y=449, angle=0) at /opt/root_src/graf3d/gl/src/TGLFontManager.cxx:184
#17 0x0000777773c565cb in TGLFont::Render (this=0x5ac2d5303db8, txt=0x5ac2d4e35020 <incomplete sequence 362>, x=242, y=449, angle=0, mgn=1) at /opt/root_src/graf3d/gl/src/TGLFontManager.cxx:252
#18 0x0000777773ca7a62 in TGLPadPainter::DrawTextHelper<char> (this=0x5ac2d5303c60, x=0.40428093600781467, y=0.66448779585798823, text=0x5ac2d4e35020 <incomplete sequence 362>) at /opt/root_src/graf3d/gl/src/TGLPadPainter.cxx:819
#19 0x0000777773ca2eb6 in TGLPadPainter::DrawText (this=0x5ac2d5303c60, x=0.40428093600781467, y=0.66448779585798823, text=0x5ac2d4e35020 <incomplete sequence 362>, mode=TVirtualPadPainter::kClear) at /opt/root_src/graf3d/gl/src/TGLPadPainter.cxx:840
#20 0x00007777781869e7 in TPad::PaintText (this=0x5ac2d359db30, x=0.40428093600781467, y=0.66448779585798823, text=0x5ac2d4e35020 <incomplete sequence 362>) at /opt/root_src/graf2d/gpad/src/TPad.cxx:4553
#21 0x00007777775362b2 in TLatex::Analyse (this=0x5ac2d4cca6c0, x=241.75999973267318, y=226.80625000000001, spec=..., t=0x7ffe13cbc020 <incomplete sequence 362>, length=1) at /opt/root_src/graf2d/graf/src/TLatex.cxx:1974

Maybe related frankheckenbach/ftgl@4c82e10

[ferdymercury]

and frankheckenbach/ftgl@778b8f2

[dpiparo]

on mac26

root [0] gStyle->SetCanvasPreferGL(true);
root [1] .x $ROOTSYS/tutorials/visualisation/graphics/latex.C
Assertion failed: (fSelectedDrawable > fPimpl->GetRootWindowID() && "ClearWindow, fSelectedDrawable is invalid"), function ClearWindow, file TGCocoa.mm, line 772.

[ferdymercury]

I'd propose the following way forward, in case it's really an libftgl problem (coming due to a newer or older version wrt our own builtin) and it can't be fixed with a patch/workaround ifdef FTGL_VERSION < XX on ROOT's side:

• we identify what libftgl external versions are leading to this crash, compared to the (outdated) 2.1 version in our repo, or we identify which upstream commit is making things worse wrt our local version
• we fork the repo https://github.com/frankheckenbach/ftgl and backport a fix there, and bump the version to 2.4.1 (Release v2.4.1? frankheckenbach/ftgl#8)
• we signal the change of URL to debian maintainers (New maintainer wanted frankheckenbach/ftgl#10)
• we finally change find_package(FGTL) to find_package(FTGL 2.4.1) within ROOT. This is the same as requiring builtin_ftgl for the near future as no distribution has this package yet
• it's a bit the same path that I am suggesting for [civetweb] download from GIT instead of bundle, bump from 1.16+ to latest master, and define proper CMake target #21947, requiring a minimum unreleased version to ensure we are getting the latest fixes and not an outdated system package
• it's a bit cleaner than just turning builtin=ON forever
• it follows the same builtin phillosophy of downloading externally and/or will be supported by debian packagers without much hassle.

[linev]

On my OpenSUSE libftgl 2.4.0 is installed.
Seems to be it is relatively fresh.

I suspect that in ROOT builtin version of libftgl special modifications for symbols.ttf were done.
It is very special font file and has different coding table as all other fonts.
But source code is very much different between external and builtin ftgl.

[ferdymercury]

ROOT builtin version is exactly 2.1.2
so ancient...

[dpiparo]

The strategy above is well structured. Maybe I do not fully get it, but isn't it suggesting that ROOT becomes the maintainer of FTGL for Debian?