Opentoonz tcomposer env variable is broken on Ubuntu linux

[Sam2much96]

Test device: HP 255g4 with Ubuntu OS 22.04

Ubuntu, which uses a custom package manager for software download/installs called snap, breaks the default env variable for RenderChan and so renderchan requires an update to point to tcomposer binary at $/snap/opentoonz/147/bin/tcomposer

Tcomposer can also be called directly on command line via
$opentoonz.tcomposer

[Sam2much96]

The fix is :

1. to edit the systems environment variables to point to $renderchan/env/linux using the instructions here
2. create a linx folder in the env folder and copy tcomposer.txt from the windows directory to this new linux directory
3. edit tcomposer.txt to renderchan/env/linux/opentoonz-app-image-binary

This will fix the module load error for opentoonz tcomposer

[morevnaproject]

Hi! I can make RenderChan always look into "env" directory, regardless of the fact if RENDERCHAN_ENVDIR set or not. :)
In this case we will eliminate step 1 of fix.

Also, I think we can ship default "tcomposer.txt" in linux package, which will have several possible variants where to look for TComposer, i.e.:

/usr/bin/tcomposer
/usr/local/bin/tcomposer
/snap/bin/opentoonz.tcomposer

This should simplify setup in the future.

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Related information about RENDERCHAN_ENVDIR variable:

• a84c6be
• https://github.com/morevnaproject-org/RenderChan/pull/71/files

[Sam2much96]

I made a quick Pull Request that uses an app image binary for opentoonz rendering instead of snap opentoonz. Also, i modified the README.md to include Linux instructions for adding RENDERCHAN_ENVDIR system wide.