[mathgl] missing internal dep

[autoantwort]

Fixes

CMake Error at CMakeLists.txt:605 (message):
  You have to enable ZLib if you plan to use PNG export.

[jimwang118]

There is a problem with the usage of this port. Follow the usage prompt to test the compiled library and the following problems occur:

Severity	Code	Description	Project	File	Line	Suppression State
Error (active)	E1696	cannot open source file "mgl2/dllexport.h"	testmathgl.exe (testmathgl\Debug\testmathgl.exe) - x64-
Error	C1083	Cannot open include file: 'mgl2/dllexport.h': No such file or directory 	

[autoantwort]

Follow the usage prompt to test the compiled library and the following problems occur:

Was this caused by this PR or is this an existing problem?

[jimwang118]

Follow the usage prompt to test the compiled library and the following problems occur:

Was this caused by this PR or is this an existing problem?

This should be a problem that has always existed. I tested the version before the upgrade and this problem also exists.

[BillyONeal]

This should be a problem that has always existed. I tested the version before the upgrade and this problem also exists.

Then I don't think we should be requiring that @autoantwort fix it in order to fix this unrelated bug. Did you see other problems?

[jimwang118]

You can make a patch that modifies the src/CMakeLists.txt file. Add the following two lines to use it normally.

target_include_directories(mgl PUBLIC $<INSTALL_INTERFACE:include>)
target_include_directories(mgl-static PUBLIC $<INSTALL_INTERFACE:include>)

[BillyONeal]

You can make a patch that modifies the src/CMakeLists.txt file. Add the following two lines to use it normally.

target_include_directories(mgl PUBLIC $<INSTALL_INTERFACE:include>)
target_include_directories(mgl-static PUBLIC $<INSTALL_INTERFACE:include>)

I'm not sure I understand. Are you saying this fixes the preexisting usage problem? Do you already have that change in a branch somewhere?

I'm happy to smash a spot fix like that into the same PR if @autoantwort is willing but I don't want to block them over it.

[jimwang118]

You can make a patch that modifies the src/CMakeLists.txt file. Add the following two lines to use it normally.

target_include_directories(mgl PUBLIC $<INSTALL_INTERFACE:include>)
target_include_directories(mgl-static PUBLIC $<INSTALL_INTERFACE:include>)

I'm not sure I understand. Are you saying this fixes the preexisting usage problem? Do you already have that change in a branch somewhere?

I'm happy to smash a spot fix like that into the same PR if @autoantwort is willing but I don't want to block them over it.

I cloned the branch of this PR locally, and then used the above method to fix the usage issue and the local test can be used normally. If @autoantwort does not want to incorporate this usage issue in this PR, then I will submit a separate PR to fix the usage issue.

[dg0yt]

@jimwang118 I can tell you that this is broken for many of the unofficial configs added in vcpkg. You can find suspects with git grep.

[autoantwort]

@jimwang118 I have now included your patch. Thank you!