cmake: add qnx support

Co-authored-by: elahav <elahav@users.noreply.github.com>

cmake/sdlchecks.cmake

@@ -911,6 +911,22 @@ macro(CheckOpenGLES)
   endif()
 endmacro()
 
+# Requires:
+# - EGL
+macro(CheckQNXScreen)
+  if(QNX AND HAVE_OPENGL_EGL)
+    check_c_source_compiles("
+        #include <screen/screen.h>
+        int main (int argc, char** argv) { return 0; }" HAVE_QNX_SCREEN)
+    if(HAVE_QNX_SCREEN)
+      set(SDL_VIDEO_DRIVER_QNX 1)
+      file(GLOB QNX_VIDEO_SOURCES ${SDL2_SOURCE_DIR}/src/video/qnx/*.c)
+      list(APPEND SOURCE_FILES ${QNX_VIDEO_SOURCES})
+      list(APPEND EXTRA_LIBS screen EGL)
+    endif()
+  endif()
+endmacro()
+
 # Requires:
 # - nada
 # Optional:
@@ -961,6 +977,8 @@ macro(CheckPTHREAD)
     elseif(EMSCRIPTEN)
       set(PTHREAD_CFLAGS "-D_REENTRANT -pthread")
       set(PTHREAD_LDFLAGS "-pthread")
+    elseif(QNX)
+      # pthread support is baked in
     else()
       set(PTHREAD_CFLAGS "-D_REENTRANT")
       set(PTHREAD_LDFLAGS "-lpthread")

cmake/sdlplatform.cmake

@@ -28,6 +28,8 @@ macro(SDL_DetectCMakePlatform)
       set(SDL_CMAKE_PLATFORM AIX)
     elseif(CMAKE_SYSTEM_NAME MATCHES "Minix.*")
       set(SDL_CMAKE_PLATFORM MINIX)
+    elseif(CMAKE_SYSTEM_NAME MATCHES "QNX")
+      set(SDL_CMAKE_PLATFORM QNX)
     endif()
   elseif(APPLE)
     if(CMAKE_SYSTEM_NAME MATCHES ".*Darwin.*")