doc: random information about ANGLE and bundling dylibs on macOS.

I need to dedicate proper time to document all this, right now it's just
the most essential info.

doc/platforms-gl.dox

@@ -71,12 +71,14 @@ Various links gathered around the web:
     work around that issue by using half-float texture formats or doing the
     interpolation manually in a shader.
 
-@subsection platforms-gl-es-angle ANGLE
+@subsection platforms-gl-es-angle ANGLE OpenGL ES translation layer
 
 [ANGLE](https://github.com/google/angle) is a layer that translates OpenGL ES
-code to D3D, desktop GL or Vulkan, originally created for web browsers to
+code to D3D, desktop GL, Vulkan or Metal, originally created for web browsers
-provide better WebGL experience without relying on buggy OpenGL drivers on
+to provide better WebGL experience without relying on buggy OpenGL drivers on
-Windows.
+Windows or abandoned OpenGL drivers on Apple platforms. See
+@ref platforms-macos-gl-angle and @ref platforms-windows-gl-angle for further
+information.
 
 Related links:
 

doc/platforms-macos.dox

@@ -103,6 +103,40 @@ for information about all options.
 If you don't use CMake, these options can be set directly through Xcode UI, for
 example.
 
+@subsection platforms-macos-bundle-dylibs Bundling dylibs
+
+If your application relies on dylibs (such as `libGLESv2.dylib` /
+`libEGL.dylib` for @ref platforms-gl-es-angle "ANGLE"), there's a few extra
+steps compared to static libraries to get them working. First, these have to be
+put into the `Frameworks/` directory inside the bundle --- for example like
+below if you have them referenced with a CMake project. Additionally, the
+files may need to get signed when copied:
+
+@code{.cmake}
+set_source_files_properties(libGLESv2.dylib libEGL.dylib PROPERTIES
+    MACOSX_PACKAGE_LOCATION Frameworks
+    XCODE_FILE_ATTRIBUTES CodeSignOnCopy)
+@endcode
+
+Then, the `*.dylib` files need to have their install name changed to contan a
+RPATH entry, so the executable linking to them will know it has to look for
+them in the RPATH. For 3rd party `*.dylib` files it can be done with the
+following command, dynamic libraries built directly by CMake
+[should have this already set](https://cmake.org/cmake/help/latest/prop_tgt/MACOSX_RPATH.html).
+
+@code{.sh}
+install_name_tool -id "@rpath/libGLESv2.dylib" libGLESv2.dylib
+install_name_tool -id "@rpath/libEGL.dylib" libEGL.dylib
+@endcode
+
+Finally, the application executable needs to have the RPATH pointed to the
+framework location:
+
+@code{.sh}
+set_target_properties(my-application PROPERTIES
+    INSTALL_RPATH "@executable_path/../Frameworks")
+@endcode
+
 @section platforms-macos-hidpi HiDPI (Retina) support
 
 macOS and iOS is the only platform where HiDPI support of an app can't be
@@ -266,9 +300,13 @@ for MoltenVK.
 
 With Apple decision to focus on Metal, macOS OpenGL support is stuck on version
 4.1 (i.e., two versions before compute shaders are available). Moreover, OpenGL
-is deprecated since macOS 10.14.
+is deprecated since macOS 10.14. If you don't want to rely on the deprecated
+OpenGL driver, you have an option to use
+@ref platforms-macos-vulkan "Vulkan as shown above", go with ANGLE to translate
+OpenGL to Metal (details below), or go with Mesa Zink to translate OpenGL to
+Vulkan.
 
-These are known macOS-specific OpenGL issues:
+With the deprecated macOS drivers, these are the known issues:
 
 -   @ref GL::AbstractShaderProgram::validate() expects that the shader has a
     properly configured framebuffer bound along with proper @ref GL::Renderer
@@ -277,6 +315,14 @@ These are known macOS-specific OpenGL issues:
 -   `GL_TIMESTAMP` used by @ref GL::TimeQuery::timestamp() is not implemented
     on macOS and gives zero results.
 
+@subsection platforms-macos-gl-angle Using ANGLE to translate OpenGL to Metal
+
+@todoc cmake options to switch to GLES/EGL, mention getting the binaries from browser installs
+@todoc steps for building angle from scratch?
+@todoc reference this from the iOS guide
+
+See also @ref platforms-gl-es-angle for further information.
+
 */
 
 }

doc/platforms-windows.dox

@@ -170,6 +170,21 @@ console window lurking in the background. This can be fixed by creating your
 executable with @cmake add_executable(... WIN32 ...) @ce and linking to the
 @ref main "Corrade::Main" library. See its documentation for more information.
 
+@section platforms-windows-vulkan Vulkan on Windows
+
+@todoc document the horrendous process of installing the whole crazy SDK,
+    touching registry and whatnot
+
+@section platform-windows-gl OpenGL on Windows
+
+@subsection platforms-macos-gl-angle Using ANGLE to translate OpenGL to Direct3D
+
+@todoc cmake options to switch to GLES/EGL, mention getting the binaries from browser installs
+@todoc steps for building angle from scratch?
+@todoc reference this from the RT guide?
+
+See also @ref platforms-gl-es-angle for further information.
+
 @section platforms-windows-clang-cl Using Clang-CL
 
 As an alternative to MSVC it's possible to use [Clang-CL](https://clang.llvm.org/docs/UsersManual.html#clang-cl).