MaterialX's cmake config should find_dependency its own OpenGL and X11 dependencies

[spiffmon]

Hi, please have a look at OpenUSD Issue 3648, which is a proposed fix to USD's cmake to work around the lack in MaterialX, when building USD with MaterialX. It would be nice if we didn't need to intuit the transitive dependencies ourselves, and wonder if other MaterialX users haven't run into this?

Thanks!
--spiff

[qbisi]

materialX should propagate opengl/x11 conditionally when target MaterialXRenderGlsl is linked against. I would suggest the following patch to materialX cmake config file:

# Always-available components
set(_MaterialX_known_components
  Core
  ...
  RenderGlsl
)

# Validate components
foreach(comp IN LISTS MaterialX_FIND_COMPONENTS)
  if(NOT comp IN_LIST _MaterialX_known_components)
    set(MaterialX_FOUND FALSE)
    set(MaterialX_NOT_FOUND_MESSAGE
      "Unknown MaterialX component: ${comp}")
    return()
  endif()
endforeach()

# Only GLSL requires OpenGL/X11
if("RenderGlsl" IN_LIST MaterialX_FIND_COMPONENTS)
  find_dependency(OpenGL)
  if(UNIX AND NOT APPLE)
    find_dependency(X11)
  endif()
endif()

Then downstream openusd can use find_dependency(MaterialX REQUIRED COMPONENTS RenderGlsl) in their cmake config file.