glfw/docs/rift.dox

/*!

@page rift_guide Using GLFW with LibOVR
 
@tableofcontents

This guide is intended to fill in the gaps between the
[Oculus PC SDK documentation](https://developer.oculus.com/documentation/) and
the rest of the GLFW documentation and is not a replacement for either.  It
requires you to use [native access](@ref native) and assumes a certain level of
proficiency with LibOVR, platform specific APIs and your chosen development
environment.

While GLFW has no explicit support for LibOVR, it is tested with and tries to
interoperate well with it.

@note Because of the speed of development of the Oculus SDK, this guide may
become outdated before the next release.  If this is a local copy of the
documentation, you may want to check the GLFW website for updates.  This
revision of the guide is written against version 0.4.4 of the SDK.


@section rift_include Including the LibOVR and GLFW header files

Both the OpenGL LibOVR header and the GLFW native header need macros telling
them what OS you are building for.  Because LibOVR only supports three major
desktop platforms, this can be solved with canonical predefined macros.

@code
#if defined(_WIN32)
 #define GLFW_EXPOSE_NATIVE_WIN32
 #define GLFW_EXPOSE_NATIVE_WGL
 #define OVR_OS_WIN32
#elif defined(__APPLE__)
 #define GLFW_EXPOSE_NATIVE_COCOA
 #define GLFW_EXPOSE_NATIVE_NSGL
 #define OVR_OS_MAC
#elif defined(__linux__)
 #define GLFW_EXPOSE_NATIVE_X11
 #define GLFW_EXPOSE_NATIVE_GLX
 #define OVR_OS_LINUX
#endif

#include <GLFW/glfw3.h>
#include <GLFW/glfw3native.h>

#include <OVR_CAPI_GL.h>
@endcode

Both the GLFW and LibOVR headers by default attempt to include the standard
OpenGL `GL/gl.h` header (`OpenGL/gl.h` on OS X).  If you wish to use a different
standard header or an [extension loading library](@ref context_glext_auto),
include that header before these.


@section rift_init Initializing LibOVR and GLFW

LibOVR needs to be initialized before GLFW.  This means calling at least
`ovr_Initialize`, `ovrHmd_Create` and `ovrHmd_ConfigureTracking` before @ref
glfwInit.  Similarly, LibOVR must be shut down after GLFW.  This means calling
`ovrHmd_Destroy` and `ovr_Shutdown` after @ref glfwTerminate.


@section rift_direct Direct HMD mode

Direct HMD mode is the recommended display mode for new applications, but the
Oculus Rift runtime currently (January 2015) only supports this mode on Windows.
In direct mode the HMD is not detectable as a GLFW monitor.


@subsection rift_direct_create Creating a window and context

If the HMD is in direct mode you can use either a full screen or a windowed mode
window, but full screen is only recommended if there is a monitor that supports
the resolution of the HMD.  Due to limitations in LibOVR, the size of the client
area of the window must equal the resolution of the HMD.

If the resolution of the HMD is much larger than the regular monitor, the window
may be resized by the window manager on creation.  One way to avoid this is to
make it undecorated with the [GLFW_DECORATED](@ref window_hints_wnd) window
hint.


@subsection rift_direct_attach Attaching the window to the HMD

Once you have created the window and context, you need to attach the native
handle of the GLFW window to the HMD.

@code
ovrHmd_AttachToWindow(hmd, glfwGetWin32Window(window), NULL, NULL);
@endcode


@section rift_extend Extend Desktop mode

Extend desktop mode is a legacy display mode, but is still (January 2015) the
only available mode on OS X and Linux, as well as on Windows machines that for
technical reasons do not yet support direct HMD mode.


@subsection rift_extend_detect Detecting a HMD with GLFW

If the HMD is in extend desktop mode you can deduce which GLFW monitor it
corresponds to and create a full screen window on that monitor.

On Windows, the native display device name of a GLFW monitor corresponds to the
display device name of the detected HMD as stored, in the `DisplayDeviceName`
member of `ovrHmdDesc`.

On OS X, the native display ID of a GLFW monitor corresponds to the display ID
of the detected HMD, as stored in the `DisplayId` member of `ovrHmdDesc`.

At the time of writing (January 2015), the Oculus SDK does not support detecting
which monitor corresponds to the HMD in any sane fashion, but as long as the HMD
is set up and rotated properly it can be found via the screen position and
resolution provided by LibOVR.  This method may instead find another monitor
that is mirroring the HMD, but this only matters if you intend to change its
video mode.

@code
int i, count;
GLFWmonitor** monitors = glfwGetMonitors(&count);

for (i = 0;  i < count;  i++)
{
#if defined(_WIN32)
    if (strcmp(glfwGetWin32Monitor(monitors[i]), hmd->DisplayDeviceName) == 0)
        return monitors[i];
#elif defined(__APPLE__)
    if (glfwGetCocoaMonitor(monitors[i]) == hmd->DisplayId)
        return monitors[i];
#elif defined(__linux__)
    int xpos, ypos;
    const GLFWvidmode* mode = glfwGetVideoMode(monitors[i]);
    glfwGetMonitorPos(monitors[i], &xpos, &ypos);

    if (hmd->WindowsPos.x == xpos &&
        hmd->WindowsPos.y == ypos &&
        hmd->Resolution.w == mode->width &&
        hmd->Resolution.h == mode->height)
    {
        return monitors[i];
    }
#endif
}
@endcode


@subsection rift_extend_create Creating a window and context

The window is created as a regular full screen window on the found monitor.  It
is usually a good idea to create a
[windowed full screen](@ref window_windowed_full_screen) window, as the HMD will
very likely already be set to the correct video mode.  However, in extend
desktop mode it behaves like a regular monitor and any supported video mode can
be requested.

If other monitors are mirroring the HMD and you request a different video mode,
all monitors in the mirroring set will get the new video mode.


@section rift_render Rendering to the HMD

@subsection rift_render_sdk SDK distortion rendering

If you wish to use SDK distortion rendering you will need some information from
GLFW to configure the renderer.  Below are the parts of the `ovrGLConfig` union
that need to be filled with from GLFW.  Note that there are other fields that
also need to be filled for `ovrHmd_ConfigureRendering` to succeed.

Before configuring SDK distortion rendering you should make your context
current.

@code
    int width, height;
    union ovrGLConfig config;

    glfwGetFramebufferSize(window, &width, &height);

    config.OGL.Header.BackBufferSize.w = width;
    config.OGL.Header.BackBufferSize.h = height;
#if defined(_WIN32)
    config.OGL.Window = glfwGetWin32Window(window);
#elif defined(__APPLE__)
#elif defined(__linux__)
    config.OGL.Disp = glfwGetX11Display();
#endif
@endcode

When using SDK distortion rendering you should not swap the buffers yourself, as
the HMD is updated by `ovrHmd_EndFrame`.


@subsection rift_render_custom Client distortion rendering

With client distortion rendering you are in full control of the contents of the
HMD and should render and swap the buffers normally.

*/