compile imgui with opengl es 3 on linux

Author: Shivansps

CMakeLists.txt

@@ -146,9 +146,13 @@ endif()
 
 if(FSO_BUILD_WITH_OPENGL_ES)
 	add_definitions(-DUSE_OPENGL_ES)
+	IF(FSO_BUILD_WITH_OPENXR)
+		MESSAGE(WARNING "FSO_BUILD_WITH_OPENXR is ON. But not supported on OpenGL ES for now - setting to OFF.")
+		SET(FSO_BUILD_WITH_OPENXR OFF CACHE BOOL "" FORCE)
+	endif()
 endif()
 
-IF(NOT APPLE)
+IF(NOT APPLE AND NOT ANDROID AND NOT FSO_BUILD_WITH_OPENGL_ES)
 	SET(OPENXR_BUILD_DEFAULT ON)
 ELSE()
 	SET(OPENXR_BUILD_DEFAULT OFF)

freespace2/SDLGraphicsOperations.cpp

@@ -283,7 +283,11 @@ std::unique_ptr<os::OpenGLContext> SDLGraphicsOperations::createOpenGLContext(os
 
 
 	ImGui_ImplSDL2_InitForOpenGL(viewport->toSDLWindow(), ctx);
+	#ifndef USE_OPENGL_ES
 	ImGui_ImplOpenGL3_Init();
+	#else
+	ImGui_ImplOpenGL3_Init("#version 300 es");
+	#endif
 
 	return std::unique_ptr<os::OpenGLContext>(new SDLOpenGLContext(ctx));
 }

lib/imgui/CMakeLists.txt

@@ -39,8 +39,10 @@ TARGET_LINK_LIBRARIES(imgui PUBLIC sdl2)
 target_link_libraries(imgui PUBLIC compiler)
 
 if(FSO_BUILD_WITH_OPENGL_ES)
-    # IMGUI needs to link against OpenGL ES 3
-    if(ANDROID)
+    # IMGUI needs to link against OpenGL ES 3, the NDK already has it
+    # For Linux this adds a dependency: libgles2-mesa-dev
+    if(ANDROID OR MAKE_SYSTEM_NAME MATCHES "Linux")
+    	add_definitions(-DIMGUI_IMPL_OPENGL_ES3)
     	find_library(GLESv3_LIB GLESv3)
     	target_link_libraries(imgui PRIVATE ${GLESv3_LIB})
     endif()

lib/opengl/gl/CMakeLists.txt

@@ -55,7 +55,11 @@ elseif(CMAKE_SYSTEM_NAME MATCHES "Linux")
 			"glad_glx/src/glad_glx.c")
 	target_include_directories(glad_glx SYSTEM PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}/glad_glx/include")
 	set_target_properties(glad_glx PROPERTIES FOLDER "3rdparty")
-	target_link_libraries(glad_glx PUBLIC glad)
+	if(NOT FSO_BUILD_WITH_OPENGL_ES)
+		target_link_libraries(glad_glx PUBLIC glad)
+	else()
+		target_link_libraries(glad_glx PUBLIC glad_gles)
+	endif()
 	suppress_warnings(glad_glx)
 
 	# On Linux we need GLX in addition to OpenGL, so attach GLX to OGL if we're here