Support OpenGL ES 3.0 building on Web

For some reason, the equivalent requested context (WebGL 2.0) is not provided, despite being properly requested.

src/platforms/rcore_web.c

@@ -45,7 +45,9 @@
 *
 **********************************************************************************************/
 
-#include "GLFW/glfw3.h"                 // GLFW3: Windows, OpenGL context and Input management
+#define GLFW_INCLUDE_NONE       // Disable the standard OpenGL header inclusion on GLFW3
+                                // NOTE: Already provided by rlgl implementation (on glad.h)
+#include "GLFW/glfw3.h"         // GLFW3: Windows, OpenGL context and Input management
 
 #include <emscripten/emscripten.h>      // Emscripten functionality for C
 #include <emscripten/html5.h>           // Emscripten HTML5 library
@@ -759,6 +761,7 @@ int InitPlatform(void)
     }
     else if (rlGetVersion() == RL_OPENGL_ES_30) // Request OpenGL ES 3.0 context
     {
+        // TODO: It seems WebGL 2.0 context is not set despite being requested
         glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
         glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
         glfwWindowHint(GLFW_CLIENT_API, GLFW_OPENGL_ES_API);

src/rlgl.h

@@ -799,10 +799,14 @@ RLAPI void rlLoadDrawQuad(void);     // Load and draw a quad
     #define GLAD_FREE RL_FREE
 
     #define GLAD_GL_IMPLEMENTATION
-    #include "external/glad.h"      // GLAD extensions loading library, includes OpenGL headers
+    #include "external/glad.h"          // GLAD extensions loading library, includes OpenGL headers
 #endif
 
-#if defined(GRAPHICS_API_OPENGL_ES2)
+#if defined(GRAPHICS_API_OPENGL_ES3)
+    #include <GLES3/gl3.h>              // OpenGL ES 3.0 library
+    #define GL_GLEXT_PROTOTYPES
+    #include <GLES2/gl2ext.h>           // OpenGL ES 2.0 extensions library
+#elif defined(GRAPHICS_API_OPENGL_ES2)
     // NOTE: OpenGL ES 2.0 can be enabled on PLATFORM_DESKTOP,
     // in that case, functions are loaded from a custom glad for OpenGL ES 2.0
     #if defined(PLATFORM_DESKTOP) || defined(PLATFORM_DESKTOP_SDL)
@@ -823,9 +827,6 @@ RLAPI void rlLoadDrawQuad(void);     // Load and draw a quad
     typedef void (GL_APIENTRYP PFNGLVERTEXATTRIBDIVISOREXTPROC) (GLuint index, GLuint divisor);
     #endif
 #endif
-#if defined(GRAPHICS_API_OPENGL_ES3)
-    #include <GLES3/gl3.h>
-#endif
 
 #include <stdlib.h>                     // Required for: malloc(), free()
 #include <string.h>                     // Required for: strcmp(), strlen() [Used in rlglInit(), on extensions loading]
@@ -902,8 +903,10 @@ RLAPI void rlLoadDrawQuad(void);     // Load and draw a quad
 
 #if defined(GRAPHICS_API_OPENGL_ES2)
     #define glClearDepth                 glClearDepthf
-    #define GL_READ_FRAMEBUFFER         GL_FRAMEBUFFER
-    #define GL_DRAW_FRAMEBUFFER         GL_FRAMEBUFFER
+    #if !defined(GRAPHICS_API_OPENGL_ES3)
+        #define GL_READ_FRAMEBUFFER         GL_FRAMEBUFFER
+        #define GL_DRAW_FRAMEBUFFER         GL_FRAMEBUFFER
+    #endif
 #endif
 
 // Default shader vertex attribute names to set location points