/********************************************************************************/ /**
 \file      OVR_CAPI_GL.h
 \brief     OpenGL-specific structures used by the CAPI interface.
 \copyright Copyright (c) Facebook Technologies, LLC and its affiliates. All rights reserved.
 ************************************************************************************/

#ifndef OVR_CAPI_GL_h
#define OVR_CAPI_GL_h

#include "OVR_CAPI.h"

#if !defined(OVR_EXPORTING_CAPI)

/// Creates a TextureSwapChain suitable for use with OpenGL.
///
/// \param[in]  session Specifies an ovrSession previously returned by ovr_Create.
/// \param[in]  desc Specifies the requested texture properties.
///             See notes for more info about texture format.
/// \param[out] out_TextureSwapChain Returns the created ovrTextureSwapChain,
///             which will be valid upon a successful return value, else it will be NULL.
///             This texture swap chain must be eventually destroyed via
//              ovr_DestroyTextureSwapChain before destroying the session with ovr_Destroy.
///
/// \return Returns an ovrResult indicating success or failure. In the case of failure, use
///         ovr_GetLastErrorInfo to get more information.
///
/// \note The \a format provided should be thought of as the format the distortion compositor will
///       use when reading the contents of the texture. To that end, it is highly recommended
///       that the application requests texture swap chain formats that are in sRGB-space
///       (e.g. OVR_FORMAT_R8G8B8A8_UNORM_SRGB) as the distortion compositor does sRGB-correct
///       rendering. Furthermore, the app should then make sure "glEnable(GL_FRAMEBUFFER_SRGB);"
///       is called before rendering into these textures. Even though it is not recommended,
///       if the application would like to treat the texture as a linear format and do
///       linear-to-gamma conversion in GLSL, then the application can avoid
///       calling "glEnable(GL_FRAMEBUFFER_SRGB);", but should still pass in an sRGB variant for
///       the \a format. Failure to do so will cause the distortion compositor to apply incorrect
///       gamma conversions leading to gamma-curve artifacts.
///
/// \see ovr_GetTextureSwapChainLength
/// \see ovr_GetTextureSwapChainCurrentIndex
/// \see ovr_GetTextureSwapChainDesc
/// \see ovr_GetTextureSwapChainBufferGL
/// \see ovr_DestroyTextureSwapChain
///
OVR_PUBLIC_FUNCTION(ovrResult)
ovr_CreateTextureSwapChainGL(
    ovrSession session,
    const ovrTextureSwapChainDesc* desc,
    ovrTextureSwapChain* out_TextureSwapChain);

/// Get a specific buffer within the chain as a GL texture name
///
/// \param[in]  session Specifies an ovrSession previously returned by ovr_Create.
/// \param[in]  chain Specifies an ovrTextureSwapChain previously returned
///             by ovr_CreateTextureSwapChainGL
/// \param[in]  index Specifies the index within the chain to retrieve.
///             Must be between 0 and length (see ovr_GetTextureSwapChainLength)
///             or may pass -1 to get the buffer at the CurrentIndex location.
///             (Saving a call to GetTextureSwapChainCurrentIndex)
/// \param[out] out_TexId Returns the GL texture object name associated with
///             the specific index requested
///
/// \return Returns an ovrResult indicating success or failure.
///         In the case of failure, use ovr_GetLastErrorInfo to get more information.
///
OVR_PUBLIC_FUNCTION(ovrResult)
ovr_GetTextureSwapChainBufferGL(
    ovrSession session,
    ovrTextureSwapChain chain,
    int index,
    unsigned int* out_TexId);

/// Creates a Mirror Texture which is auto-refreshed to mirror Rift contents produced by this
/// application.
///
/// A second call to ovr_CreateMirrorTextureWithOptionsGL for a given ovrSession before destroying
/// the first one is not supported and will result in an error return.
///
/// \param[in]  session Specifies an ovrSession previously returned by ovr_Create.
/// \param[in]  desc Specifies the requested mirror texture description.
/// \param[out] out_MirrorTexture Specifies the created ovrMirrorTexture, which will be
///             valid upon a successful return value, else it will be NULL.
///             This texture must be eventually destroyed via ovr_DestroyMirrorTexture before
///             destroying the session with ovr_Destroy.
///
/// \return Returns an ovrResult indicating success or failure. In the case of failure, use
///         ovr_GetLastErrorInfo to get more information.
///
/// \note The \a format provided should be thought of as the format the distortion compositor will
///       use when writing into the mirror texture. It is highly recommended that mirror textures
//        are requested as sRGB formats because the distortion compositor does sRGB-correct
///       rendering. If the application requests a non-sRGB format (e.g. R8G8B8A8_UNORM) as the
///       mirror texture, then the application might have to apply a manual linear-to-gamma
///       conversion when reading from the mirror texture. Failure to do so can result in
//        incorrect gamma conversions leading to gamma-curve artifacts and color banding.
///
/// \see ovr_GetMirrorTextureBufferGL
/// \see ovr_DestroyMirrorTexture
///
OVR_PUBLIC_FUNCTION(ovrResult)
ovr_CreateMirrorTextureWithOptionsGL(
    ovrSession session,
    const ovrMirrorTextureDesc* desc,
    ovrMirrorTexture* out_MirrorTexture);

/// Deprecated. Use ovr_CreateMirrorTextureWithOptionsGL instead
///
/// Same as ovr_CreateMirrorTextureWithOptionsGL except doesn't use ovrMirrorOptions flags as part
/// of ovrMirrorTextureDesc's MirrorOptions field, and defaults to ovrMirrorOption_PostDistortion
///
/// \see ovrMirrorOptions, ovr_CreateMirrorTextureWithOptionsGL
///
OVR_PUBLIC_FUNCTION(ovrResult)
ovr_CreateMirrorTextureGL(
    ovrSession session,
    const ovrMirrorTextureDesc* desc,
    ovrMirrorTexture* out_MirrorTexture);

/// Get a the underlying buffer as a GL texture name
///
/// \param[in]  session Specifies an ovrSession previously returned by ovr_Create.
/// \param[in]  mirrorTexture Specifies an ovrMirrorTexture previously returned
//              by ovr_CreateMirrorTextureWithOptionsGL
/// \param[out] out_TexId Specifies the GL texture object name associated with the mirror texture
///
/// \return Returns an ovrResult indicating success or failure. In the case of failure, use
///         ovr_GetLastErrorInfo to get more information.
///
OVR_PUBLIC_FUNCTION(ovrResult)
ovr_GetMirrorTextureBufferGL(
    ovrSession session,
    ovrMirrorTexture mirrorTexture,
    unsigned int* out_TexId);

#endif // !defined(OVR_EXPORTING_CAPI)

#endif // OVR_CAPI_GL_h