From 13244de5c2af4a0f0a880c53eee89a6e464c5406 Mon Sep 17 00:00:00 2001
From: Manuel Alfayate Corchete <redwindwanderer@gmail.com>
Date: Tue, 22 Dec 2020 17:17:30 +0100
Subject: [PATCH] [Buildsystem] Only build KMSDRM support if EGL+OpenGL is
 detected by CMake.

---
 CMakeLists.txt        |  2 ++
 cmake/sdlchecks.cmake | 21 ++++++++++++++++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index b9b9eb620..59ca6bec9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1180,6 +1180,8 @@ elseif(UNIX AND NOT APPLE AND NOT ANDROID AND NOT RISCOS)
     CheckOpenGLESX11()
     CheckWayland()
     CheckVivante()
+    # Need to check EGL before checking KMSDRM because KMSDRM depends on it.
+    CheckEGLKMSDRM()
     CheckKMSDRM()
   endif()
 
diff --git a/cmake/sdlchecks.cmake b/cmake/sdlchecks.cmake
index a9434c85a..56f0a6a01 100644
--- a/cmake/sdlchecks.cmake
+++ b/cmake/sdlchecks.cmake
@@ -757,6 +757,25 @@ macro(CheckOpenGLX11)
   endif()
 endmacro()
 
+# Requires:
+# - PkgCheckModules
+macro(CheckEGLKMSDRM)
+  if (HAVE_VIDEO_OPENGLES OR HAVE_VIDEO_OPENGL)
+    pkg_check_modules(EGL egl)
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} ${EGL_CFLAGS}")
+    check_c_source_compiles("
+	#define EGL_API_FB
+	#define MESA_EGL_NO_X11_HEADERS
+	#define EGL_NO_X11
+	#include <EGL/egl.h>
+	#include <EGL/eglext.h>
+	int main (int argc, char** argv) {}" HAVE_VIDEO_OPENGL_EGL)
+    if(HAVE_VIDEO_OPENGL_EGL)
+	set(SDL_VIDEO_OPENGL_EGL 1)
+    endif()
+  endif()
+endmacro()
+
 # Requires:
 # - PkgCheckModules
 macro(CheckOpenGLESX11)
@@ -1152,7 +1171,7 @@ endmacro(CheckRPI)
 macro(CheckKMSDRM)
   if(VIDEO_KMSDRM)
     pkg_check_modules(KMSDRM libdrm gbm egl)
-    if(KMSDRM_FOUND)
+    if(KMSDRM_FOUND AND HAVE_VIDEO_OPENGL_EGL)
       link_directories(
         ${KMSDRM_LIBRARY_DIRS}
       )