context.h exceptions should be documented and caught

[mwestphal]

Describe the bug
context.h can throw exceptions, however they are not documented and not caugth, relying on main.cxx catch all to not segfault, this should be fixed.

To Reproduce
Steps to reproduce the behavior:

1. comment main.cxx catch all
2. ctest -R WGL
3. segfault

[saneck2150]

Hi, i would like to work on this issue, if is still relevant

[mwestphal]

It is! Do you know guidance ?

[saneck2150]

No, I'm just starting to figure out the project, where can I get documentation? I thought it is a good issue to get started with

[mwestphal]

where can I get documentation?

https://f3d.app

https://discord.f3d.app

I thought it is a good issue to get started with

It is! But I wrote it a bit fast, I can add more context

[mwestphal]

Do you need any help moving forward @saneck2150 ?

[saneck2150]

Hello, yes, I had problems with running the program, I asked tech support to help with solving it in your discord, but in the end nothing worked out. So I can't work with this project, sorry :(

[mwestphal]

No worries @saneck2150 , thanks for the feedback.

[exbluesbreaker]

I would like to try to work on this issue.

[mwestphal]

Sure!

[exbluesbreaker]

First of all, this comment took my attention from VTK Doxygen:

vtkDynamicLoader provides a portable interface to loading dynamic libraries into a process.

See also:
A more portable and lightweight solution is kwsys::DynamicLoader

The second, I wanted to clarify a scope of this task. I see there are loading_exception and symbol_exception thrown by context itself. Does it mean we need to rework those 2, or task is about handling other possible causes of exception in context.cxx - loading/getting symbols for different OpenGL wrappers (egl,glx etc.)?

[mwestphal]

I see there are loading_exception and symbol_exception thrown by context itself. Does it mean we need to rework those 2, or task is about handling other possible causes of exception in context.cxx - loading/getting symbols for different OpenGL wrappers (egl,glx etc.)?

Actually, not at all.

The point of this task is to catch loading_exception and symbol_exception in the application in a proper way in order to handle erroring out cleanly.

The catch all in main.cxx is a last resort and not suposed to be reachable.

The modification should be in the application.

eg in F3DStarter.cxx there are calls for createGLX(). These create* methods are documented as:

   * Throws a context::loading_exception if a needed graphic library cannot be loaded
   * Throws a context::symbol_exception if a needed symbol cannot be found in graphic library
   * Throws a engine::no_window_exception if the window cannot be created for another reason
   * Throws a engine::cache_exception if the default cache directory cannot be used

But in F3DStarter we never catch these exceptions. They should be cached, logged and handled properly.

[exbluesbreaker]

I have initial version of commit prepared, but I need to find out how to test last 3 exceptions.

[exbluesbreaker]

I made #2064 but will need to find a way to test all 4 exceptions