FindOpenGL: support finding GLES2 and GLES3

This also makes the EGL component not GLVND-specific, so documentation
and tests are updated accordingly.

3 files changed, 142 insertions, 21 deletions

diff --git a/Tests/FindOpenGL/Test/CMakeLists.txt b/Tests/FindOpenGL/Test/CMakeLists.txt
index 9004a98..7c805c0 100644
--- a/Tests/FindOpenGL/Test/CMakeLists.txt
+++ b/Tests/FindOpenGL/Test/CMakeLists.txt
@@ -44,28 +44,115 @@ else()
   add_test(NAME test_comp_glx_novnd COMMAND test_comp_glx_novnd)
 endif()
 
-# EGL is only available on Linux+GLVND at present.
-if(OpenGL_TEST_VND)
-  find_package(OpenGL COMPONENTS OpenGL EGL)
-  if(OpenGL_EGL_FOUND)
-    add_executable(test_comp_egl main.c)
-    target_link_libraries(test_comp_egl PRIVATE OpenGL::OpenGL OpenGL::EGL)
-    add_test(NAME test_comp_egl COMMAND test_comp_egl)
-    # EGL-only code should not link to GLX.
-    execute_process(COMMAND ldd test_comp_egl
-                    OUTPUT_VARIABLE LDD_OUT
-                    ERROR_VARIABLE LDD_ERR)
-    if("${LDD_OUT}" MATCHES "GLX")
-      message(FATAL_ERROR "EGL-only code links to GLX!")
-    endif()
+find_package(OpenGL COMPONENTS OpenGL EGL)
+if(OpenGL_EGL_FOUND)
+  add_executable(test_comp_egl main.c)
+  target_link_libraries(test_comp_egl PRIVATE OpenGL::OpenGL OpenGL::EGL)
+  add_test(NAME test_comp_egl COMMAND test_comp_egl)
+  # EGL-only code should not link to GLX.
+  get_target_property(iface_libs OpenGL::EGL INTERFACE_LINK_LIBRARIES)
+  if(iface_libs MATCHES "GLX")
+    message(FATAL_ERROR "EGL-only code links to GLX!")
+  endif()
+endif()
+
+# all three COMPONENTS together.
+find_package(OpenGL COMPONENTS OpenGL EGL GLX)
+if(OpenGL_EGL_FOUND AND OpenGL_GLX_FOUND)
+  add_executable(test_comp_both main.c)
+  target_link_libraries(test_comp_both PRIVATE OpenGL::OpenGL OpenGL::EGL
+                        OpenGL::GLX)
+  add_test(NAME test_comp_both COMMAND test_comp_both)
+endif()
+
+find_package(OpenGL COMPONENTS GLES2)
+if(OpenGL_GLES2_FOUND)
+  add_executable(test_comp_gles2 main_gles2.c)
+  target_link_libraries(test_comp_gles2 PRIVATE OpenGL::GLES2)
+  add_test(NAME test_comp_gles2 COMMAND test_comp_gles2)
+  # GLES2-only code should not link to OpenGL
+  get_target_property(iface_libs test_comp_gles2 LINK_LIBRARIES)
+  if(iface_libs MATCHES "OpenGL::OpenGL")
+    message(FATAL_ERROR "GLES2-only code links to OpenGL!")
   endif()
+endif()
+
+# GLES2 and EGL together.
+find_package(OpenGL COMPONENTS GLES2 EGL)
+if(OpenGL_GLES2_FOUND AND OpenGL_EGL_FOUND)
+  add_executable(test_comp_gles2_egl main_gles2.c)
+  target_link_libraries(test_comp_gles2_egl PRIVATE OpenGL::GLES2
+                        OpenGL::EGL)
+  add_test(NAME test_comp_gles2_egl COMMAND test_comp_gles2_egl)
+  # GLES2-EGL-only code should not link to OpenGL or GLX
+  get_target_property(iface_libs test_comp_gles2_egl LINK_LIBRARIES)
+  if(iface_libs MATCHES "OpenGL::OpenGL")
+    message(FATAL_ERROR "GLES2-only code links to OpenGL!")
+  endif()
+  if(iface_libs MATCHES "GLX")
+    message(FATAL_ERROR "GLES2-EGL-only code links to GLX!")
+  endif()
+endif()
 
-  # all three COMPONENTS together.
-  find_package(OpenGL COMPONENTS OpenGL EGL GLX)
-  if(OpenGL_EGL_FOUND AND OpenGL_GLX_FOUND)
-    add_executable(test_comp_both main.c)
-    target_link_libraries(test_comp_both PRIVATE OpenGL::OpenGL OpenGL::EGL
-                          OpenGL::GLX)
-    add_test(NAME test_comp_both COMMAND test_comp_both)
+# GLES2 and GLX together.
+find_package(OpenGL COMPONENTS GLES2 GLX)
+if(OpenGL_GLES2_FOUND AND OpenGL_GLX_FOUND)
+  add_executable(test_comp_gles2_glx main_gles2.c)
+  target_link_libraries(test_comp_gles2_glx PRIVATE OpenGL::GLES2
+                        OpenGL::GLX)
+  add_test(NAME test_comp_gles2_glx COMMAND test_comp_gles2_glx)
+  # GLES2-GLX-only code should not link to OpenGL or EGL
+  get_target_property(iface_libs test_comp_gles2_glx LINK_LIBRARIES)
+  if(iface_libs MATCHES "OpenGL::OpenGL")
+    message(FATAL_ERROR "GLES2-only code links to OpenGL!")
+  endif()
+  if(iface_libs MATCHES "EGL")
+    message(FATAL_ERROR "GLES2-GLX-only code links to EGL!")
+  endif()
+endif()
+
+find_package(OpenGL COMPONENTS GLES3)
+if(OpenGL_GLES3_FOUND)
+  add_executable(test_comp_gles3 main_gles3.c)
+  target_link_libraries(test_comp_gles3 PRIVATE OpenGL::GLES3)
+  add_test(NAME test_comp_gles3 COMMAND test_comp_gles3)
+  # GLES3-only code should not link to OpenGL.
+  get_target_property(iface_libs test_comp_gles3 LINK_LIBRARIES)
+  if(iface_libs MATCHES "OpenGL::OpenGL")
+    message(FATAL_ERROR "GLES3-only code links to OpenGL!")
+  endif()
+endif()
+
+# GLES3 and EGL together.
+find_package(OpenGL COMPONENTS GLES3 EGL)
+if(OpenGL_GLES3_FOUND AND OpenGL_EGL_FOUND)
+  add_executable(test_comp_gles3_egl main_gles3.c)
+  target_link_libraries(test_comp_gles3_egl PRIVATE OpenGL::GLES3
+                        OpenGL::EGL)
+  add_test(NAME test_comp_gles3_egl COMMAND test_comp_gles3_egl)
+  # GLES3-EGL-only code should not link to OpenGL or GLX
+  get_target_property(iface_libs test_comp_gles3_egl LINK_LIBRARIES)
+  if(iface_libs MATCHES "OpenGL::OpenGL")
+    message(FATAL_ERROR "GLES3-only code links to OpenGL!")
+  endif()
+  if(iface_libs MATCHES "GLX")
+    message(FATAL_ERROR "GLES3-EGL-only code links to GLX!")
+  endif()
+endif()
+
+# GLES3 and GLX together.
+find_package(OpenGL COMPONENTS GLES3 GLX)
+if(OpenGL_GLES3_FOUND AND OpenGL_GLX_FOUND)
+  add_executable(test_comp_gles3_glx main_gles3.c)
+  target_link_libraries(test_comp_gles3_glx PRIVATE OpenGL::GLES3
+                        OpenGL::GLX)
+  add_test(NAME test_comp_gles3_glx COMMAND test_comp_gles3_glx)
+  # GLESr-GLX-only code should not link to OpenGL or EGL
+  get_target_property(iface_libs test_comp_gles3_glx LINK_LIBRARIES)
+  if(iface_libs MATCHES "OpenGL::OpenGL")
+    message(FATAL_ERROR "GLES3-only code links to OpenGL!")
+  endif()
+  if(iface_libs MATCHES "EGL")
+    message(FATAL_ERROR "GLES3-GLX-only code links to EGL!")
   endif()
 endif()
diff --git a/Tests/FindOpenGL/Test/main_gles2.c b/Tests/FindOpenGL/Test/main_gles2.c
new file mode 100644
index 0000000..52f5936
--- /dev/null
+++ b/Tests/FindOpenGL/Test/main_gles2.c
@@ -0,0 +1,17 @@
+#ifdef _WIN32
+#  error "GLES2 cannot be tested on WIN32 platforms."
+#endif
+#ifdef __APPLE__
+#  error "GLES2 cannot be tested on macOS platform."
+#else
+#  include <GLES2/gl2.h>
+#endif
+
+#include <stdio.h>
+
+int main()
+{
+  /* Reference a GL symbol without requiring a context at runtime.  */
+  printf("&glGetString = %p\n", &glGetString);
+  return 0;
+}
diff --git a/Tests/FindOpenGL/Test/main_gles3.c b/Tests/FindOpenGL/Test/main_gles3.c
new file mode 100644
index 0000000..875f73c
--- /dev/null
+++ b/Tests/FindOpenGL/Test/main_gles3.c
@@ -0,0 +1,17 @@
+#ifdef _WIN32
+#  error "GLES3 cannot be tested on WIN32 platforms."
+#endif
+#ifdef __APPLE__
+#  error "GLES3 cannot be tested on macOS platform."
+#else
+#  include <GLES3/gl3.h>
+#endif
+
+#include <stdio.h>
+
+int main()
+{
+  /* Reference a GL symbol without requiring a context at runtime.  */
+  printf("&glGetString = %p\n", &glGetString);
+  return 0;
+}