Fix selection buffer crash on resize

[iche033]

Signed-off-by: Ian Chen ichen@osrfoundation.org

🦟 Bug fix

related ign-rendering PR: gazebosim/gz-rendering#378
related issue: gazebosim/gz-rendering#362

Summary

If a window resize and mouse click happens in the same frame, the gui will crash with a backtrace pointing to the selection buffer in ign-rendering. This is more of a workaround - adding a render call ensures that the ogre resources are ready before they are used by the selection buffer (for mouse picking).

Note: we need to merge this PR before the one in ign-rendering: gazebosim/gz-rendering#378

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

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[codecov]

Codecov Report

Merging #969 (98146d5) into ign-gazebo4 (2105ae3) will decrease coverage by 0.59%.
The diff coverage is 0.00%.

@@               Coverage Diff               @@
##           ign-gazebo4     #969      +/-   ##
===============================================
- Coverage        66.08%   65.48%   -0.60%     
===============================================
  Files              242      243       +1     
  Lines            18078    20798    +2720     
===============================================
+ Hits             11946    13619    +1673     
- Misses            6132     7179    +1047     

Impacted Files	Coverage Δ
src/gui/plugins/scene3d/Scene3D.cc	10.63% <0.00%> (+0.68%)	⬆️
src/gui/plugins/scene3d/Scene3D.hh	60.00% <0.00%> (-6.67%)	⬇️
src/ServerConfig.cc	89.08% <0.00%> (-0.61%)	⬇️
src/systems/imu/Imu.hh	100.00% <0.00%> (ø)
src/systems/contact/Contact.hh	100.00% <0.00%> (ø)
src/systems/physics/Physics.hh	100.00% <0.00%> (ø)
src/systems/altimeter/Altimeter.hh	100.00% <0.00%> (ø)
src/systems/breadcrumbs/Breadcrumbs.hh	100.00% <0.00%> (ø)
src/systems/air_pressure/AirPressure.hh	100.00% <0.00%> (ø)
src/systems/wind_effects/WindEffects.hh	100.00% <0.00%> (ø)
... and 21 more

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