Update libezgl external subtree

[samehattia]

Description

Update libezgl subtree to the latest version. The latest version adds some bug fixes and functionality (scaling and justification options), and most importantly, uses the left mouse button for panning instead of the middle mouse button.

Related Issue

Motivation and Context

Panning with the left mouse button is easier than the middle button with touchpads. It is also more common.

How Has This Been Tested?

The graphics are tested using the -disp on option. The update does not require any modifications to the VTR code.

Types of changes

• Bug fix (change which fixes an issue)
• New feature (change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

[vaughnbetz]

Thanks @samehattia . I have some suggestions for readability / commenting / variable naming in a few places that I think would be good to incorporate.

[vaughnbetz]

Looks like all the runs on kokoro failed due to a build error -- a missing gtk function. The githhub actions completed though, so that implies there is some difference in what gtk version is installed / downloaded on kokoro vs. the github action runners. I'm no expert on where those setup configurations are set -- @MohamedElgammal and @kgugala : do you know where those are set / how to align them?

Consolidate compiler generated dependencies of target ezgl
[ 72%] Building CXX object libs/EXTERNAL/libezgl/CMakeFiles/ezgl.dir/src/application.cpp.o
/tmpfs/src/github/vtr-verilog-to-routing/libs/EXTERNAL/libezgl/src/application.cpp: In member function ‘void ezgl::application::create_button(const char*, int, int, int, int, ezgl::button_callback_fn)’:
/tmpfs/src/github/vtr-verilog-to-routing/libs/EXTERNAL/libezgl/src/application.cpp:328:50: error: ‘gtk_widget_set_focus_on_click’ was not declared in this scope
   gtk_widget_set_focus_on_click(new_button, false);
                                                  ^
libs/EXTERNAL/libezgl/CMakeFiles/ezgl.dir/build.make:75: recipe for target 'libs/EXTERNAL/libezgl/CMakeFiles/ezgl.dir/src/application.cpp.o' failed
make[3]: *** [libs/EXTERNAL/libezgl/CMakeFiles/ezgl.dir/src/application.cpp.o] Error 1
CMakeFiles/Makefile2:1211: recipe for target 'libs/EXTERNAL/libezgl/CMakeFiles/ezgl.dir/all' failed
make[2]: *** [libs/EXTERNAL/libezgl/CMakeFiles/ezgl.dir/all] Error 2
Makefile:145: recipe for target 'all' failed
make[1]: *** [all] Error 2
Makefile:71: recipe for target 'all' failed
make: *** [all] Error 2

[vaughnbetz]

@samehattia : it would also be good for you to make sure you run the UI (can run the vtr quick start example with --disp on), and click on everything (see the graphics documentation on the vtr documenation page) and confirm that everything works, panning works, etc. Once you've done that, please note that you've done it in this PR for posterity.

[vaughnbetz]

Looks like the problem function is gtk_widget_set_focus_on_click() which was added after version 3.18.9 and at or before 3.20.0 (see https://abi-laboratory.pro/?view=compat_report&l=gtk+&v1=3.18.9&v2=3.20.0&obj=fa019&kind=abi)
kokoro must have a version of Linux installed with an older version of gtk3. The kokoro setup does
sudo apt-get install -y
with libgtk-3-dev as one of the parameters.
The github runners do almost the same thing but use:
sudo apt install -y
with libgtk-3-dev as one of the parameters

See vtr-verilog-to-routing/.github/scripts/install_dependencies.sh vs. vtr-verilog-to-routing/.github/kokoro/steps/hostsetup.sh

The apt vs. apt-get difference shouldn't matter.
I am not sure why we're getting an older version of gtk on kokoro than github runners; @samehattia : any ideas? I would have thought it would always get the latest version, but perhaps it doesn't change the package if a version is already installed?

[samehattia]

@vaughnbetz You are right. kokoro is using Ubunutu 16.04 repos in which the default gtk version is 3.18. The problem function is supported in 3.20+. Two solutions I can think of:

1. Update Kokoro to use a newer Ubuntu version. Not sure if that is possible (and easy) or not.
2. Wrap the function call in a #define block with the gtk version.

[mithro]

Longer term, we are working on replacing Kokoro with GitHub Actions runners.

[mithro]

FYI - @QuantamHD

[vaughnbetz]

@samehattia : I suggest guarding the call with an #ifdef for now, unless @mithro or a delegate can update kokoro in the near future. I am not sure how easy it is to upgrade kokoro.
There may be some value to the #ifdef anyway, as it will avoid compilation errors on older OS's (assuming the functionality it guards isn't that important, which I don't think it is).

[samehattia]

@vaughnbetz I've included your suggestions. I've also tested the UI using the VTR quick start example with --disp on, and everything looks fine.

[vaughnbetz]

Thanks Sameh!