AbstractFramebuffer: Use correct target for GLES

OpenGL ES without GL_APPLE_framebuffer_multisample doesn't
support multiple draw or read bindings, so we need to use
GL_FRAMEBUFFER for that.

It seems as though the Magnum convention is to use use
FramebufferTarget::Draw for read-draw bindings, so Read and Draw
have been aliased to GL_FRAMEBUFFER in this case.

src/Magnum/AbstractFramebuffer.cpp

@@ -122,7 +122,7 @@ void AbstractFramebuffer::bindImplementationSingle(FramebufferTarget) {
 
     /* Binding the framebuffer finally creates it */
     _flags |= ObjectFlag::Created;
-    glBindFramebuffer(GL_FRAMEBUFFER, _id);
+    glBindFramebuffer(GLenum(FramebufferTarget::Draw), _id);
 }
 #endif
 
@@ -164,10 +164,10 @@ FramebufferTarget AbstractFramebuffer::bindImplementationSingle() {
 
         /* Binding the framebuffer finally creates it */
         _flags |= ObjectFlag::Created;
-        glBindFramebuffer(GL_FRAMEBUFFER, _id);
+        glBindFramebuffer(GLenum(FramebufferTarget::Draw), _id);
     }
 
-    return FramebufferTarget{};
+    return FramebufferTarget::Draw;
 }
 #endif
 
@@ -367,8 +367,8 @@ GLenum AbstractFramebuffer::checkStatusImplementationDefault(const FramebufferTa
 
 #ifdef MAGNUM_TARGET_GLES2
 GLenum AbstractFramebuffer::checkStatusImplementationSingle(FramebufferTarget) {
-    bindInternal(FramebufferTarget{});
-    return glCheckFramebufferStatus(GL_FRAMEBUFFER);
+    bindInternal(FramebufferTarget::Draw);
+    return glCheckFramebufferStatus(GLenum(FramebufferTarget::Draw));
 }
 #endif
 

src/Magnum/AbstractFramebuffer.h

@@ -117,19 +117,19 @@ enum class FramebufferTarget: GLenum {
     /** Frambebuffer reading target */
     #ifndef MAGNUM_TARGET_GLES2
     Read = GL_READ_FRAMEBUFFER,
-    #elif !defined(MAGNUM_TARGET_WEBGL)
+    #elif defined(CORRADE_TARGET_APPLE)
     Read = GL_READ_FRAMEBUFFER_APPLE,
     #else
-    Read,
+    Read = GL_FRAMEBUFFER,
     #endif
 
     /** Framebuffer drawing target */
     #ifndef MAGNUM_TARGET_GLES2
     Draw = GL_DRAW_FRAMEBUFFER,
-    #elif !defined(MAGNUM_TARGET_WEBGL)
+    #elif defined(CORRADE_TARGET_APPLE)
     Draw = GL_DRAW_FRAMEBUFFER_APPLE,
     #else
-    Draw,
+    Draw = GL_FRAMEBUFFER,
     #endif
 
     #ifdef MAGNUM_BUILD_DEPRECATED
@@ -140,10 +140,10 @@ enum class FramebufferTarget: GLenum {
     ReadDraw CORRADE_DEPRECATED_ENUM("use FramebufferTarget::Draw instead") =
         #ifndef MAGNUM_TARGET_GLES2
         GL_DRAW_FRAMEBUFFER
-        #elif !defined(MAGNUM_TARGET_WEBGL)
+        #elif defined(MAGNUM_TARGET_APPLE)
         GL_DRAW_FRAMEBUFFER_APPLE
         #else
-        1
+        GL_FRAMEBUFFER
         #endif
     #endif
 };