Add option to use system-installed ImGui and ImPlot dependencies

[jeongseok-meta]

Hello, I'm working on adding this package to a package manager (like vsg-dev/VulkanSceneGraph#1375). One issue with it is that vsgImGui uses its dependencies (imgui and implot) via git submodules and assumes specific locations of them when including the dependency headers:

vsgImGui/src/vsgImGui/RenderImGui.cpp

Line 27 in d393985

#include "../imgui/backends/imgui_impl_vulkan.h"

However, building with their dependencies in this way (vendoring) is not recommended, as it can lead to conflicts when the package's dependencies and the vendored ones are different.

I guess the submodule was chosen because it's convenient in many ways, but would you accept PRs that enable vsgImGui to use system-installed dependencies optionally? Here's what I'm thinking of:

option(VSG_IMGUI_USE_SYSTEM_IMGUI "Use system installed ImGui" OFF)
if(VSG_IMGUI_USE_SYSTEM_IMGUI)
  find_package(ImGui CONFIG REQUIRED)
else()
  # the current logic but the header include is the same as when the dependency is installed system-wide
endif()

[robertosfield]

I have been considering dropping the submodule approach now like ImGui and ImPlot are better supported in 3rd party package managers, making it optional would be a good first step.

[jeongseok-meta]

Good to know that! Feel free to review #73 when you have a chance. I've drafted a minimal change for this.

[uebian]

Hi, I wanted to check if there are any updates on this issue. I'm preparing to release Project Chrono as a conda package, which depends on the vsgImGui conda package. The outcome of this decision will directly affect our package build pipeline, so I'm eager to hear any updates.

[robertosfield]

Unfortunately I've been very busy for the months so am a bit behind on reviewing submissions.

As a quick look I've merged @jeongseok-meta's PR #73 as a jeongseok-meta-option_use_system_deps branch.

Building VSG, vsgXchange, vsgImGui in sequence works fine without errors, but the vsgimui_example in vsgExamples fails to compile. I other critical work to tackle right now so can't investigate. I let vsgImGui build with defaults.

In file included from /home/robert/dev/vsgExamples/examples/ui/vsgimgui_example/vsgimgui_example.cpp:1:
/home/robert/install/include/vsgImGui/RenderImGui.h:34:10: fatal error: imgui.h: No such file or directory
   34 | #include <imgui.h>
      |          ^~~~~~~~~
compilation terminated.
gmake[2]: *** [examples/ui/vsgimgui_example/CMakeFiles/vsgimgui_example.dir/build.make:76: examples/ui/vsgimgui_example/CMakeFiles/vsgimgui_example.dir/vsgimgui_example.cpp.o] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:3969: examples/ui/vsgimgui_example/CMakeFiles/vsgimgui_example.dir/all] Error 2
gmake[1]: *** Waiting for unfinished jobs....
In file included from /home/robert/dev/vsgExamples/examples/state/vsgdynamicstate/vsgdynamicstate.cpp:8:
/home/robert/install/include/vsgImGui/RenderImGui.h:34:10: fatal error: imgui.h: No such file or directory
   34 | #include <imgui.h>
      |          ^~~~~~~~~
compilation terminated.

[rserban]

Any updates? It would help us greatly to have this resolved.

[robertosfield]

I haven't seen any fixes for the vsgimgui build issue so the jeongseok-meta-option_use_system_deps remains incomplete.