GL: improve extension docs.

doc/opengl-support.dox

@@ -23,6 +23,8 @@
     DEALINGS IN THE SOFTWARE.
 */
 
+namespace Magnum {
+
 /** @page opengl-support Support state
 @brief List of (un)supported OpenGL features and extensions.
 
@@ -37,6 +39,11 @@ The extension implementation is considered complete if all its defined types,
 functions and enum values are exposed through the API, except for features
 listed below in @ref opengl-unsupported-features.
 
+All extensions from the below lists are available in the @ref GL::Extensions
+namespace and it's possible to check for their availability using
+@ref GL::Context::isExtensionSupported(). See its documentation for more
+information.
+
 @subsection opengl-support-21 OpenGL 2.1
 
 The core subset of OpenGL 2.1 should be fully implemented, except for the
@@ -334,6 +341,8 @@ supported. ESSL 3.10 is supported.
 Features that have their equivalents implemented in desktop version are
 supported. ESSL 3.20 is supported.
 
+@m_class{m-fullwidth}
+
 Extension                                   | Status
 ------------------------------------------- | ------
 @gl_extension{EXT,color_buffer_half_float}  | |
@@ -362,6 +371,9 @@ Extension                                   | Status
 
 @subsection opengl-support-es30-extensions OpenGL ES 2.0 extensions to match ES 3.0 functionality
 
+Unless said otherwise, these are not exposed in the @ref GL::Extensions
+namespace on @ref MAGNUM_TARGET_GLES2 "OpenGL ES 3.0 builds".
+
 @m_class{m-fullwidth}
 
 Extension                                   | Status
@@ -472,6 +484,9 @@ supported.
 
 @subsection opengl-support-webgl20-extensions WebGL 1.0 extensions to match WebGL 2.0 functionality
 
+Unless said otherwise, these are not available in the @ref GL::Extensions
+namespace on @ref MAGNUM_TARGET_GLES2 "WebGL 2.0 builds".
+
 @m_class{m-fullwidth}
 
 Extension                                   | Status
@@ -585,3 +600,5 @@ See also @ref opengl-unsupported and @ref deprecated.
 See also @ref opengl-deprecated.
 
 */
+
+}

src/Magnum/GL/Context.h

@@ -565,8 +565,9 @@ class MAGNUM_GL_EXPORT Context {
         /**
          * @brief Whether given extension is supported
          *
-         * Extensions usable with this function are listed in @ref Extensions
-         * namespace in header @ref Extensions.h. Example usage:
+         * Extensions usable with this function are listed in the
+         * @ref Extensions namespace in the @ref Extensions.h header and in the
+         * @ref opengl-support "OpenGL support tables". Example usage:
          *
          * @snippet MagnumGL.cpp Context-isExtensionSupported
          *

src/Magnum/GL/Extensions.h

@@ -46,10 +46,12 @@ namespace Magnum { namespace GL {
 
 Each extension is a @cpp struct @ce named hierarchically by prefix, vendor and
 extension name taken from list at @ref opengl-support, for example
-`GL::Extensions::ARB::texture_storage`. Note that desktop extensions are
-available only on desktop build, OpenGL ES 2.0 extensions which are part of ES
-3.0 are available only on @ref MAGNUM_TARGET_GLES2 "OpenGL ES 2.0 build",
-vendor OpenGL ES extensions are available only on
+`GL::Extensions::ARB::texture_storage`. Note that, unless said otherwise,
+desktop extensions are available only on desktop build, OpenGL ES 2.0
+extensions which are part of ES 3.0 are available only on
+@ref MAGNUM_TARGET_GLES2 "OpenGL ES 2.0 builds", WebGL 1.0 extensions which are
+part of WebGL 2.0 are available only on @ref MAGNUM_TARGET_GLES2 "WebGL 1.0"
+builds, OpenGL ES extensions are available only on
 @ref MAGNUM_TARGET_GLES "OpenGL ES builds" and WebGL extensions are available
 only on @ref MAGNUM_TARGET_WEBGL "WebGL builds".
 
@@ -254,7 +256,6 @@ namespace AMD {
     _extension(171,NV,conditional_render,               GL210, GL300) // #346
     /* NV_draw_texture not supported */                               // #430
 }
-/* IMPORTANT: if this line is > 329 (73 + size), don't forget to update array size in Context.h */
 #elif defined(MAGNUM_TARGET_WEBGL)
 namespace ANGLE {
     #ifdef MAGNUM_TARGET_GLES2