refactors & viewport fix

CMakeLists.txt

@@ -1,27 +1,20 @@
-cmake_minimum_required(VERSION 3.1 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.8 FATAL_ERROR)
 project(padlab C)
-set(CMAKE_C_STANDARD 99)
 set(TARGET padlab)
 
+set(CMAKE_C_STANDARD 99)
+
 find_package(SDL2 REQUIRED)
 find_package(OpenGL)
 
 set(SOURCES
 	maths.h
-	draw.h
+	draw.h  $<IF:$<BOOL:${OPENGL_FOUND}>,draw_opengl.c,draw.c>
 	stick.c stick.h
 	analogue.c)
 
-if (OPENGL_FOUND)
-	list(APPEND SOURCES draw_opengl.c)
-else()
-	list(APPEND SOURCES draw.c)
-endif()
-
 add_executable(${TARGET} ${SOURCES})
-target_link_libraries(${TARGET} SDL2::SDL2 m)
-if (OPENGL_FOUND)
-	target_link_libraries(${TARGET} OpenGL::GL)
-endif()
+target_link_libraries(${TARGET}
+	SDL2::SDL2 $<$<BOOL:${OPENGL_FOUND}>:OpenGL::GL> m)
 target_compile_options(${TARGET} PRIVATE
 	-Wall -Wextra -pedantic -Wno-unused-parameter)