TODOs for the stupid annoying Emscripten -s<SPACE>WHATEVER flags.

modules/FindMagnum.cmake

@@ -1042,6 +1042,10 @@ if(CORRADE_TARGET_EMSCRIPTEN)
     # IN_LIST as an operator since 3.1 (Emscripten needs at least 3.7), but
     # it's behind a policy, so enable that one as well.
     cmake_policy(SET CMP0057 NEW)
+    # TODO since 1.39.19 it's possible to use `-sUSE_WEBGL2=1`, which can be
+    #   then passed via target_link_libraries() etc. without requiring CMake
+    #   3.13: https://github.com/emscripten-core/emscripten/blob/main/ChangeLog.md#13919-07072020
+    #   -- change to that once we drop support for older Emscripten versions
     if(CMAKE_VERSION VERSION_LESS 3.13 AND GL IN_LIST Magnum_FIND_COMPONENTS AND NOT MAGNUM_TARGET_GLES2 AND NOT CMAKE_EXE_LINKER_FLAGS MATCHES "-s USE_WEBGL2=1")
         set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -s USE_WEBGL2=1")
     endif()

modules/FindOpenGLES3.cmake

@@ -82,6 +82,10 @@ if(NOT TARGET OpenGLES3::OpenGLES3)
     # Emscripten needs a special flag to use WebGL 2. CMake 3.13 allows to set
     # this via INTERFACE_LINK_OPTIONS, for older versions we modify the global
     # CMAKE_EXE_LINKER_FLAGS inside FindMagnum.cmake.
+    # TODO since 1.39.19 it's possible to use `-sUSE_WEBGL2=1`, which can be
+    #   then passed via target_link_libraries() etc. without requiring CMake
+    #   3.13: https://github.com/emscripten-core/emscripten/blob/main/ChangeLog.md#13919-07072020
+    #   -- change to that once we drop support for older Emscripten versions
     if(CORRADE_TARGET_EMSCRIPTEN AND NOT CMAKE_VERSION VERSION_LESS 3.13)
         # I could probably use target_link_options() here, but let's be
         # consistent with the rest

src/CMakeLists.txt

@@ -40,6 +40,10 @@ endif()
 # `-s USE_WEBGL2=1` linker option is propagated from FindOpenGLES3.cmake
 # already. If not (and the GL library is used), we need to modify the global
 # CMAKE_EXE_LINKER_FLAGS.
+# TODO since 1.39.19 it's possible to use `-sUSE_WEBGL2=1`, which can be then
+#   passed via target_link_libraries() etc. without requiring CMake 3.13
+#   https://github.com/emscripten-core/emscripten/blob/main/ChangeLog.md#13919-07072020
+#   -- change to that once we drop support for older Emscripten versions
 if(CORRADE_TARGET_EMSCRIPTEN AND CMAKE_VERSION VERSION_LESS 3.13 AND WITH_GL AND NOT TARGET_GLES2)
     set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -s USE_WEBGL2=1")
 endif()