Add option to enable opengl support in QCustomPlot

[DonOregano]

Specify library name and version: qcustomplot/2.1.0

This PR adds an option to enable opengl support in the QCustomPlot recipe. In the current recipe there is a TODO that this should be done, and this PR fixes that TODO. The default is to have opengl support disabled, so as to not change the behaviour for current users.

• I've read the guidelines for contributing.
• I've followed the PEP8 style guides for Python code in the recipes.
• I've used the latest Conan client version.
• I've tried at least one configuration locally with the conan-center hook activated.

[CLAassistant]

All committers have signed the CLA.

[DonOregano]

Something broke in the Visual Studio build. Will close and reopen this PR to trigger CI rebuild. (This is what I was told to do in another recipe I was working on).

[DonOregano]

@SpaceIm, looking at the history for qcustomplot conanfile it looks like you have been involved in the creation of this recipe. Can you help me understand what is going wrong here? There is something about a missing dependency in one of the visual studio builds.

[SpaceIm]

I guess it's not directly related to qcustomplot but to a new transitive dependency in qt dependency graph.

[SpaceIm]

/ping @jgsogo, qt5 recipe has been updated recently (#11531), and I don't see any other PR afterwards which could change its package ids, so maybe few binaries have not been uploaded to artifactory?

I see on https://conan.io/center/qt?version=5.15.3&tab=dependencies&os=Windows that several Visual Studio configurations are missing. qt recipes raises for MT & shared, so for each Visual Studio version, we should see 6 configurations (4 for static, 2 for shared), but I see only 4 package id for Visual Studio 2017 & 3 for Visual Studio 2019.

[DonOregano]

Thanks for looking into this! It did seem like something out of my control...

[SpaceIm]

You should check in validate() that opengl option of qt recipe is not no.

[DonOregano]

You should check in validate() that opengl option of qt recipe is not no.

Okay, I can do that. I do however have questions about how to handle opengl32 linking on windows specifically. I have been reading https://doc.qt.io/qt-6/windows-graphics.html, and from what I understand, unless the code uses QOpenGLFunctions (which QCustomPlot does not) I have to link to OpenGL32.lib on Windows to get things to work. Another alternative would be to require that opengl in Qt is desktop, which I believe would have the same result.

To summarize the Qt opengl thing I believe it works this way: If you specify "dynamic" you have to call opengl stuff through the QOpenGLFunctions class, and Qt will magically use the appropriate opengl library. If you specify "desktop" you will get linked to OpenGL32 (through QtX::OpenGL). If you specify "dynamic" you can still add linking to OpenGL32.lib explicitly, but I think this means exactly the same thing as using "desktop".

I would appreciate guidance on how to do this in the conan recipe, in a way that provides the fewest surprises to users and is maintainable...

Another solution would be to patch QCustomPlot according to this forum post https://www.qcustomplot.com/index.php/support/forum/1281, to make "dynamic" work, but that does seem a bit too invasive.

Edit: Tried to set qt:opengl to desktop, but still get linkage errors.

[DonOregano]

Since I didn't hear anything about my comment above I chose to just improve my initial implementation to get a reaction :-D

[DonOregano]

@spacelm, what do you think of the current state of this PR?

[jgsogo]

About ERROR: Missing binary: qt/5.15.3:f32f0b09ede8c1a7d8421f05eaf42852912db16a. I can see the package is available in Artifactory with:

conan search qt/5.15.3@ --table=table.html -r=conancenter

The most simple explanation is a race condition: a new recipe revision of Qt was being merged into the central repository while your PR was running... Conan was able to find the recipe (it is uploaded first) but not the package (we copy/move packages one by one and it takes some time). I've triggered this PR manually again, let's see if we find the same error.

[conan-center-bot]

All green in build 11 (a80b85dc6126ce4710f25c8f3d37d48ef30a73cc):

• qcustomplot/2.1.0@:
  All packages built successfully! (All logs)

  🔸 Informative: This recipe is not ready for Conan v2

  _{We have started the migration process to Conan v2 and exporting recipes successfully will be required in the future.
  This is just an informative note to gain awareness about the process, no need to take any action. The plan is to enforce smaller steps that are easier to fix and, eventually, this conan export step will work.
  See the recipe migration guide to know more about the changes required.}

  ERROR: Error loading conanfile at '/home/conan/w/prod_cci_PR-11591/recipes/qcustomplot/all/conanfile.py': Unable to load conanfile in /home/conan/w/prod_cci_PR-11591/recipes/qcustomplot/all/conanfile.py
    File "<frozen importlib._bootstrap_external>", line 728, in exec_module
    File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
    File "/home/conan/w/prod_cci_PR-11591/recipes/qcustomplot/all/conanfile.py", line 1, in <module>
      from conans import ConanFile, CMake, tools
  ImportError: cannot import name 'ConanFile' from 'conans' (/opt/pyenv/versions/3.7.13/lib/python3.7/site-packages/conans/__init__.py)
  

• qcustomplot/1.3.2@:
  All packages built successfully! (All logs)

  🔸 Informative: This recipe is not ready for Conan v2

  _{We have started the migration process to Conan v2 and exporting recipes successfully will be required in the future.
  This is just an informative note to gain awareness about the process, no need to take any action. The plan is to enforce smaller steps that are easier to fix and, eventually, this conan export step will work.
  See the recipe migration guide to know more about the changes required.}

  ERROR: Error loading conanfile at '/home/conan/w/prod_cci_PR-11591/recipes/qcustomplot/all/conanfile.py': Unable to load conanfile in /home/conan/w/prod_cci_PR-11591/recipes/qcustomplot/all/conanfile.py
    File "<frozen importlib._bootstrap_external>", line 728, in exec_module
    File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
    File "/home/conan/w/prod_cci_PR-11591/recipes/qcustomplot/all/conanfile.py", line 1, in <module>
      from conans import ConanFile, CMake, tools
  ImportError: cannot import name 'ConanFile' from 'conans' (/opt/pyenv/versions/3.7.13/lib/python3.7/site-packages/conans/__init__.py)
  

[jgsogo]

👍 It looks like that was the issue. Now build has passed. Time for reviews!

Thanks!