DebugTools: fix a build system corner case.

doc/changelog.dox

@@ -138,6 +138,9 @@ See also:
     [mosra/magnum#297](https://github.com/mosra/magnum/pull/297))
 -   Imroved initial Emscripten setup on Windows to be more frictionless (see
     [mosra/toolchains#4](https://github.com/mosra/toolchains/pull/4))
+-   @ref DebugTools no longer unconditionally requires the @ref Trade library
+    in case @ref Corrade::TestSuite is found. The @ref DebugTools::CompareImage
+    documentation was updated to mention the optionality.
 
 @subsection changelog-latest-bugfixes Bug fixes
 

src/Magnum/DebugTools/CMakeLists.txt

@@ -110,7 +110,7 @@ endif()
 
 # Build the TestSuite-related functionality only if it is present
 find_package(Corrade COMPONENTS TestSuite)
-if(Corrade_TestSuite_FOUND)
+if(Corrade_TestSuite_FOUND AND WITH_TRADE)
     list(APPEND MagnumDebugTools_GracefulAssert_SRCS
         CompareImage.cpp)
 
@@ -148,7 +148,7 @@ elseif(BUILD_STATIC_PIC)
     set_target_properties(MagnumDebugTools PROPERTIES POSITION_INDEPENDENT_CODE ON)
 endif()
 target_link_libraries(MagnumDebugTools PUBLIC Magnum)
-if(Corrade_TestSuite_FOUND)
+if(Corrade_TestSuite_FOUND AND WITH_TRADE)
     target_link_libraries(MagnumDebugTools PUBLIC
         Corrade::TestSuite
         MagnumTrade)
@@ -189,7 +189,7 @@ if(BUILD_TESTS)
         set_target_properties(MagnumDebugToolsTestLib PROPERTIES POSITION_INDEPENDENT_CODE ON)
     endif()
     target_link_libraries(MagnumDebugToolsTestLib PUBLIC Magnum)
-    if(Corrade_TestSuite_FOUND)
+    if(Corrade_TestSuite_FOUND AND WITH_TRADE)
         target_link_libraries(MagnumDebugToolsTestLib PUBLIC
             Corrade::TestSuite
             MagnumTrade)

src/Magnum/DebugTools/CompareImage.h

@@ -142,7 +142,12 @@ namespace Magnum { namespace DebugTools {
 /**
 @brief Image comparator
 
-To be used with @ref Corrade::TestSuite. Basic use is really simple:
+To be used with @ref Corrade::TestSuite.
+
+@note This class is available only if Magnum is compiled with `WITH_TRADE`
+    enabled (done by default). See @ref building-features for more information.
+
+Basic use is really simple:
 
 @snippet debugtools-compareimage.cpp 0
 

src/Magnum/DebugTools/Test/CMakeLists.txt

@@ -23,7 +23,7 @@
 #   DEALINGS IN THE SOFTWARE.
 #
 
-if(Corrade_TestSuite_FOUND)
+if(WITH_TRADE)
     # Otherwise CMake complains that Corrade::PluginManager is not found, wtf
     find_package(Corrade REQUIRED PluginManager)