CMake: Compile in OSMesa on Linux, if found.

cmake/CMakeLists.txt

 # Boilerplate.
 cmake_minimum_required (VERSION 3.1)   # First version with CMAKE_CXX_STANDARD.
 project (skimake)
 set (CMAKE_CXX_STANDARD 11)
 
 # Default to Release mode.  We're mainly targeting Skia users, not Skia developers.
 if (NOT CMAKE_BUILD_TYPE)
     set (CMAKE_BUILD_TYPE Release)
 endif ()
 
@@ skipping 82 matching lines @@
 # Make our ports choices.
 remove_srcs(
     ../src/*moz*   # We're probably not Mozilla.
     ../src/gpu/GrContextFactory.cpp                  # For internal testing only.
     ../src/gpu/gl/GrGLCreateNativeInterface_none.cpp
     ../src/gpu/gl/GrGLDefaultInterface_none.cpp
     ../src/gpu/gl/SkCreatePlatformGLContext*.cpp     # For internal testing only.
     ../src/gpu/gl/command_buffer/*
     ../src/gpu/gl/egl/*
     ../src/gpu/gl/iOS/*
-    ../src/gpu/gl/mesa/*
     ../src/opts/SkBitmapProcState_opts_none.cpp
     ../src/opts/SkBlitMask_opts_none.cpp
     ../src/opts/SkBlitRow_opts_none.cpp
     ../src/ports/SkFontMgr_empty_factory.cpp
     ../src/ports/SkGlobalInitialization_chromium.cpp
     ../src/ports/SkImageDecoder_empty.cpp
     ../src/ports/SkImageGenerator_none.cpp
     ../src/ports/SkTLS_none.cpp)
 
 remove_srcs(../src/codec/*)  # TODO: Requires Chromium's libjpeg-turbo, and incompatible giflib.
 
 # Certain files must be compiled with support for SSSE3 or SSE4.1 intrinsics.
 file (GLOB_RECURSE ssse3_srcs ../src/*ssse3*.cpp ../src/*SSSE3*.cpp)
 file (GLOB_RECURSE sse41_srcs ../src/*sse4*.cpp ../src/*SSE4*.cpp)
 set_source_files_properties(${ssse3_srcs} PROPERTIES COMPILE_FLAGS -mssse3)
 set_source_files_properties(${sse41_srcs} PROPERTIES COMPILE_FLAGS -msse4.1)
 
 # Detect our optional dependencies.
 # If we can't find them, don't build the parts of Skia that use them.
 find_package (Lua)
 find_package (ZLIB)
 # No find_package for libwebp as far as I can tell, so simulate it here.
 find_path (WEBP_INCLUDE_DIRS "webp/decode.h")
 find_library (WEBP_LIBRARIES webp)
+find_path (OSMESA_INCLUDE_DIRS "GL/osmesa.h")
+find_library(OSMESA_LIBRARIES "OSMesa")
 
 if (UNIX AND NOT APPLE)
     find_package (Freetype)
     # Same deal for fontconfig.
     find_path (FONTCONFIG_INCLUDE_DIRS "fontconfig/fontconfig.h")
     find_library (FONTCONFIG_LIBRARIES fontconfig)
     find_package (GIF)
     find_package (JPEG)
     find_package (PNG)
 endif()
@@ skipping 51 matching lines @@
 if (FONTCONFIG_INCLUDE_DIRS AND FONTCONFIG_LIBRARIES)
     list (APPEND private_includes ${FONTCONFIG_INCLUDE_DIRS})
     list (APPEND libs             ${FONTCONFIG_LIBRARIES})
 endif()
 
 if (APPLE)
     find_library(APPLICATION_SERVICES_FRAMEWORK ApplicationServices REQUIRED)
     list (APPEND libs ${APPLICATION_SERVICES_FRAMEWORK})
 endif()
 
+if (OSMESA_LIBRARIES AND OSMESA_INCLUDE_DIRS)
+    list (APPEND libs             ${OSMESA_LIBRARIES})
+    list (APPEND private_includes ${OSMESA_INCLUDE_DIRS})
+    list (APPEND public_defines   "-DSK_MESA=1")
+    message("-- Found OSMesa: " ${OSMESA_LIBRARIES})
+else()
+    remove_srcs(../src/gpu/gl/mesa/*)
+    message("-- Could NOT find OSMesa")
+endif()
+
 find_package(OpenGL REQUIRED)
 list (APPEND libs  ${OPENGL_LIBRARIES})
 
 # This is our main output, libskia.so.
 # We mostly build an .so here because it helps test we've linked everything,
 # not so much that we think Skia is a good candidate to ship as a shared library.
 add_library (skia SHARED ${srcs})
 
+list (APPEND private_defines "-DSKIA_DLL")
+
 target_compile_definitions(skia
-    PUBLIC
-    PRIVATE -DSKIA_DLL)
+    PUBLIC  ${public_defines}
+    PRIVATE ${private_defines})
 
 target_include_directories(skia
     PUBLIC  ${public_includes}
     PRIVATE ${private_includes})
 
 target_link_libraries(skia
     PUBLIC
     PRIVATE ${libs})
 
 
 set_target_properties(skia PROPERTIES
     COMPILE_FLAGS "-fno-exceptions -fno-rtti -Wno-deprecated-declarations"
     CXX_VISIBILITY_PRESET hidden
     VISIBILITY_INLINES_HIDDEN true)
 
 # Experimental C API install:
 file(GLOB cheaders "../include/c/*.h")
 install(FILES ${cheaders} DESTINATION include)
 install(TARGETS skia DESTINATION lib)
 
 # Now build a simple example app that uses Skia via libskia.so.
 add_executable(example example.cpp)
 target_link_libraries(example skia ${OPENGL_LIBRARIES})