//
// Copyright 2016 Pixar
//
// Licensed under the Apache License, Version 2.0 (the "Apache License")
// with the following modification; you may not use this file except in
// compliance with the Apache License and the following modification to it:
// Section 6. Trademarks. is deleted and replaced with:
//
// 6. Trademarks. This License does not grant permission to use the trade
//    names, trademarks, service marks, or product names of the Licensor
//    and its affiliates, except as required to comply with Section 4(c) of
//    the License and to reproduce the content of the NOTICE file.
//
// You may obtain a copy of the Apache License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the Apache License with the above modification is
// distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the Apache License for the specific
// language governing permissions and limitations under the Apache License.
//
#include "pxr/imaging/garch/glPlatformDebugContext.h"

#include "pxr/imaging/garch/gl.h"
#include "pxr/base/tf/diagnostic.h"
#include "pxr/base/tf/getenv.h"
#include "pxr/base/arch/defines.h"

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/* static */
bool
GarchGLPlatformDebugContext::IsEnabledDebugOutput()
{
    static bool isEnabledDebugOutput =
        TfGetenvBool("GLF_ENABLE_DEBUG_OUTPUT", false);
    return isEnabledDebugOutput;
}

/* static */
bool
GarchGLPlatformDebugContext::IsEnabledCoreProfile()
{
    static bool isEnabledCoreProfile =
        TfGetenvBool("GLF_ENABLE_CORE_PROFILE", false);
    return isEnabledCoreProfile;
}

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////////////////////////////////////////////////////////////
#if defined(ARCH_OS_LINUX)

#include <GL/glx.h>
#include <GL/glxtokens.h>
#include <X11/Xlib.h>

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class GarchGLPlatformDebugContextPrivate {
public:
    GarchGLPlatformDebugContextPrivate(
        int majorVersion, int minorVersion,
        bool coreProfile, bool directRendering);
    ~GarchGLPlatformDebugContextPrivate();

    void MakeCurrent();

    Display *_dpy;
    GLXContext _ctx;
};

GarchGLPlatformDebugContextPrivate::GarchGLPlatformDebugContextPrivate(
        int majorVersion, int minorVersion,
        bool coreProfile, bool directRendering)
    : _dpy(NULL)
    , _ctx(NULL)
{
    Display *shareDisplay = glXGetCurrentDisplay();
    GLXContext shareContext = glXGetCurrentContext();

    int fbConfigId = 0;
    glXQueryContext(shareDisplay, shareContext, GLX_FBCONFIG_ID, &fbConfigId);
    int screen = 0;
    glXQueryContext(shareDisplay, shareContext, GLX_SCREEN, &screen);

    int configSpec[] = {
        GLX_FBCONFIG_ID, fbConfigId,
        None, 
    };
    GLXFBConfig *configs = NULL;
    int configCount = 0;
    configs = glXChooseFBConfig(shareDisplay, screen, configSpec, &configCount);
    if (!TF_VERIFY(configCount > 0)) {
        return;
    }

    const int profile =
        coreProfile
            ? GLX_CONTEXT_CORE_PROFILE_BIT_ARB
            : GLX_CONTEXT_COMPATIBILITY_PROFILE_BIT_ARB;

    int attribs[] = {
        GLX_CONTEXT_MAJOR_VERSION_ARB, majorVersion,
        GLX_CONTEXT_MINOR_VERSION_ARB, minorVersion,
        GLX_CONTEXT_PROFILE_MASK_ARB, profile,
        GLX_CONTEXT_FLAGS_ARB, GLX_CONTEXT_DEBUG_BIT_ARB,
        0,
    };

    // Extension entry points must be resolved at run-time.
    PFNGLXCREATECONTEXTATTRIBSARBPROC createContextAttribs =
        (PFNGLXCREATECONTEXTATTRIBSARBPROC)
            glXGetProcAddressARB((const GLubyte*)"glXCreateContextAttribsARB");

    // Create a GL context with the requested capabilities.
    if (createContextAttribs) {
        _ctx = (*createContextAttribs)(shareDisplay, configs[0],
                                       shareContext, directRendering,
                                       attribs);
    } else {
        TF_WARN("Unable to create GL debug context.");
        XVisualInfo *vis = glXGetVisualFromFBConfig(shareDisplay, configs[0]);
        _ctx = glXCreateContext(shareDisplay, vis,
                                shareContext, directRendering);
    }
    if (!TF_VERIFY(_ctx)) {
        return;
    }

    _dpy = shareDisplay;
}

GarchGLPlatformDebugContextPrivate::~GarchGLPlatformDebugContextPrivate()
{
    if (_dpy && _ctx) {
        glXDestroyContext(_dpy, _ctx);
    }
}

void
GarchGLPlatformDebugContextPrivate::MakeCurrent()
{
    glXMakeCurrent(glXGetCurrentDisplay(), glXGetCurrentDrawable(), _ctx);
}

void *GarchSelectCoreProfileMacVisual()
{
    return nullptr;
}

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#endif // ARCH_OS_LINUX

////////////////////////////////////////////////////////////

#if defined(ARCH_OS_DARWIN)

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// XXX: implement debug context
class GarchGLPlatformDebugContextPrivate {
public:
    GarchGLPlatformDebugContextPrivate(
        int majorVersion, int minorVersion,
        bool coreProfile, bool directRendering) {}
    ~GarchGLPlatformDebugContextPrivate() {}

  void MakeCurrent() {}
};

void *GarchSelectCoreProfileMacVisual();  // extern obj-c

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#endif // ARCH_OS_DARWIN


////////////////////////////////////////////////////////////

#if defined(ARCH_OS_WINDOWS)

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// XXX: implement debug context
class GarchGLPlatformDebugContextPrivate {
public:
    GarchGLPlatformDebugContextPrivate(
        int majorVersion, int minorVersion,
        bool coreProfile, bool directRendering) {}
    ~GarchGLPlatformDebugContextPrivate() {}

  void MakeCurrent() {}
};

void *GarchSelectCoreProfileMacVisual()
{
    return nullptr;
}

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#endif // ARCH_OS_WINDOWS

////////////////////////////////////////////////////////////

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GarchGLPlatformDebugContext::GarchGLPlatformDebugContext(int majorVersion,
                                                       int minorVersion,
                                                       bool coreProfile,
                                                       bool directRendering)
    : _coreProfile(coreProfile)

{
    if (!GarchGLPlatformDebugContext::IsEnabledDebugOutput()) {
        return;
    }
    _private.reset(new GarchGLPlatformDebugContextPrivate(majorVersion,
                                                         minorVersion,
                                                         coreProfile,
                                                         directRendering));
}

GarchGLPlatformDebugContext::~GarchGLPlatformDebugContext()
{
    // nothing
}

/* virtual */
void
GarchGLPlatformDebugContext::makeCurrent()
{
    // note: if not enabled, returns without making context current.
    if (!GarchGLPlatformDebugContext::IsEnabledDebugOutput()) {
        return;
    }

    if (!TF_VERIFY(_private)) {
        return;
    }

    _private->MakeCurrent();
}

void*
GarchGLPlatformDebugContext::chooseMacVisual()
{
    if (_coreProfile ||
        GarchGLPlatformDebugContext::IsEnabledCoreProfile()) {
        return GarchSelectCoreProfileMacVisual();
    } else {
        return nullptr;
    }
    return nullptr;
}

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