JUCE/modules/juce_opengl/opengl/juce_OpenGLFrameBuffer.cpp

/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2020 - Raw Material Software Limited

   JUCE is an open source library subject to commercial or open-source
   licensing.

   By using JUCE, you agree to the terms of both the JUCE 6 End-User License
   Agreement and JUCE Privacy Policy (both effective as of the 16th June 2020).

   End User License Agreement: www.juce.com/juce-6-licence
   Privacy Policy: www.juce.com/juce-privacy-policy

   Or: You may also use this code under the terms of the GPL v3 (see
   www.gnu.org/licenses).

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

class OpenGLFrameBuffer::Pimpl
{
public:
    Pimpl (OpenGLContext& c, const int w, const int h,
           const bool wantsDepthBuffer, const bool wantsStencilBuffer)
        : context (c), width (w), height (h),
          textureID (0), frameBufferID (0), depthOrStencilBuffer (0),
          hasDepthBuffer (false), hasStencilBuffer (false)
    {
        // Framebuffer objects can only be created when the current thread has an active OpenGL
        // context. You'll need to create this object in one of the OpenGLContext's callbacks.
        jassert (OpenGLHelpers::isContextActive());

       #if JUCE_WINDOWS || JUCE_LINUX || JUCE_BSD
        if (context.extensions.glGenFramebuffers == nullptr)
            return;
       #endif

        context.extensions.glGenFramebuffers (1, &frameBufferID);
        bind();

        glGenTextures (1, &textureID);
        glBindTexture (GL_TEXTURE_2D, textureID);
        JUCE_CHECK_OPENGL_ERROR

        glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
        glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
        JUCE_CHECK_OPENGL_ERROR

        glTexImage2D (GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
        JUCE_CHECK_OPENGL_ERROR

        context.extensions.glFramebufferTexture2D (GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, textureID, 0);

        if (wantsDepthBuffer || wantsStencilBuffer)
        {
            context.extensions.glGenRenderbuffers (1, &depthOrStencilBuffer);
            context.extensions.glBindRenderbuffer (GL_RENDERBUFFER, depthOrStencilBuffer);
            jassert (context.extensions.glIsRenderbuffer (depthOrStencilBuffer));

            context.extensions.glRenderbufferStorage (GL_RENDERBUFFER,
                                      (wantsDepthBuffer && wantsStencilBuffer) ? (GLenum) GL_DEPTH24_STENCIL8
                                                                              #if JUCE_OPENGL_ES
                                                                               : (GLenum) GL_DEPTH_COMPONENT16,
                                                                              #else
                                                                               : (GLenum) GL_DEPTH_COMPONENT,
                                                                              #endif
                                      width, height);

            GLint params = 0;
            context.extensions.glGetRenderbufferParameteriv (GL_RENDERBUFFER, GL_RENDERBUFFER_DEPTH_SIZE, &params);
            context.extensions.glFramebufferRenderbuffer (GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthOrStencilBuffer);

            if (wantsStencilBuffer)
                context.extensions.glFramebufferRenderbuffer (GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, depthOrStencilBuffer);

            hasDepthBuffer = wantsDepthBuffer;
            hasStencilBuffer = wantsStencilBuffer;
        }

        unbind();
    }

    ~Pimpl()
    {
        if (OpenGLHelpers::isContextActive())
        {
            if (textureID != 0)
                glDeleteTextures (1, &textureID);

            if (depthOrStencilBuffer != 0)
                context.extensions.glDeleteRenderbuffers (1, &depthOrStencilBuffer);

            if (frameBufferID != 0)
                context.extensions.glDeleteFramebuffers (1, &frameBufferID);

            JUCE_CHECK_OPENGL_ERROR
        }
    }

    bool createdOk() const
    {
        return frameBufferID != 0 && textureID != 0;
    }

    void bind()
    {
        context.extensions.glBindFramebuffer (GL_FRAMEBUFFER, frameBufferID);
        JUCE_CHECK_OPENGL_ERROR
    }

    void unbind()
    {
        context.extensions.glBindFramebuffer (GL_FRAMEBUFFER, context.getFrameBufferID());
        JUCE_CHECK_OPENGL_ERROR
    }

    OpenGLContext& context;
    const int width, height;
    GLuint textureID, frameBufferID, depthOrStencilBuffer;
    bool hasDepthBuffer, hasStencilBuffer;

private:
    bool checkStatus() noexcept
    {
        const GLenum status = context.extensions.glCheckFramebufferStatus (GL_FRAMEBUFFER);

        return status == GL_NO_ERROR
            || status == GL_FRAMEBUFFER_COMPLETE;
    }

    JUCE_DECLARE_NON_COPYABLE (Pimpl)
};

//==============================================================================
class OpenGLFrameBuffer::SavedState
{
public:
    SavedState (OpenGLFrameBuffer& buffer, const int w, const int h)
        : width (w), height (h),
          data ((size_t) (w * h))
    {
        buffer.readPixels (data, Rectangle<int> (w, h));
    }

    bool restore (OpenGLContext& context, OpenGLFrameBuffer& buffer)
    {
        if (buffer.initialise (context, width, height))
        {
            buffer.writePixels (data, Rectangle<int> (width, height));
            return true;
        }

        return false;
    }

private:
    const int width, height;
    HeapBlock<PixelARGB> data;

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (SavedState)
};

//==============================================================================
OpenGLFrameBuffer::OpenGLFrameBuffer() {}
OpenGLFrameBuffer::~OpenGLFrameBuffer() {}

bool OpenGLFrameBuffer::initialise (OpenGLContext& context, int width, int height)
{
    jassert (context.isActive()); // The context must be active when creating a framebuffer!

    pimpl.reset();
    pimpl.reset (new Pimpl (context, width, height, false, false));

    if (! pimpl->createdOk())
        pimpl.reset();

    return pimpl != nullptr;
}

bool OpenGLFrameBuffer::initialise (OpenGLContext& context, const Image& image)
{
    if (! image.isARGB())
        return initialise (context, image.convertedToFormat (Image::ARGB));

    Image::BitmapData bitmap (image, Image::BitmapData::readOnly);

    return initialise (context, bitmap.width, bitmap.height)
            && writePixels ((const PixelARGB*) bitmap.data, image.getBounds());
}

bool OpenGLFrameBuffer::initialise (OpenGLFrameBuffer& other)
{
    auto* p = other.pimpl.get();

    if (p == nullptr)
    {
        pimpl.reset();
        return true;
    }

    const Rectangle<int> area (pimpl->width, pimpl->height);

    if (initialise (p->context, area.getWidth(), area.getHeight()))
    {
        pimpl->bind();

       #if ! JUCE_ANDROID
        glEnable (GL_TEXTURE_2D);
        clearGLError();
       #endif
        glBindTexture (GL_TEXTURE_2D, p->textureID);
        pimpl->context.copyTexture (area, area, area.getWidth(), area.getHeight(), false);
        glBindTexture (GL_TEXTURE_2D, 0);
        JUCE_CHECK_OPENGL_ERROR

        pimpl->unbind();
        return true;
    }

    return false;
}

void OpenGLFrameBuffer::release()
{
    pimpl.reset();
    savedState.reset();
}

void OpenGLFrameBuffer::saveAndRelease()
{
    if (pimpl != nullptr)
    {
        savedState.reset (new SavedState (*this, pimpl->width, pimpl->height));
        pimpl.reset();
    }
}

bool OpenGLFrameBuffer::reloadSavedCopy (OpenGLContext& context)
{
    if (savedState != nullptr)
    {
        std::unique_ptr<SavedState> state;
        std::swap (state, savedState);

        if (state->restore (context, *this))
            return true;

        std::swap (state, savedState);
    }

    return false;
}

int OpenGLFrameBuffer::getWidth() const noexcept            { return pimpl != nullptr ? pimpl->width : 0; }
int OpenGLFrameBuffer::getHeight() const noexcept           { return pimpl != nullptr ? pimpl->height : 0; }
GLuint OpenGLFrameBuffer::getTextureID() const noexcept     { return pimpl != nullptr ? pimpl->textureID : 0; }

bool OpenGLFrameBuffer::makeCurrentRenderingTarget()
{
    // trying to use a framebuffer after saving it with saveAndRelease()! Be sure to call
    // reloadSavedCopy() to put it back into GPU memory before using it..
    jassert (savedState == nullptr);

    if (pimpl == nullptr)
        return false;

    pimpl->bind();
    return true;
}

GLuint OpenGLFrameBuffer::getFrameBufferID() const noexcept
{
    return pimpl != nullptr ? pimpl->frameBufferID : 0;
}

GLuint OpenGLFrameBuffer::getCurrentFrameBufferTarget() noexcept
{
    GLint fb = {};
    glGetIntegerv (GL_FRAMEBUFFER_BINDING, &fb);
    return (GLuint) fb;
}

void OpenGLFrameBuffer::releaseAsRenderingTarget()
{
    if (pimpl != nullptr)
        pimpl->unbind();
}

void OpenGLFrameBuffer::clear (Colour colour)
{
    if (makeCurrentRenderingTarget())
    {
        OpenGLHelpers::clear (colour);
        releaseAsRenderingTarget();
    }
}

void OpenGLFrameBuffer::makeCurrentAndClear()
{
    if (makeCurrentRenderingTarget())
    {
        glClearColor (0, 0, 0, 0);
        glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
    }
}

bool OpenGLFrameBuffer::readPixels (PixelARGB* target, const Rectangle<int>& area)
{
    if (! makeCurrentRenderingTarget())
        return false;

    glPixelStorei (GL_PACK_ALIGNMENT, 4);
    glReadPixels (area.getX(), area.getY(), area.getWidth(), area.getHeight(),
                  JUCE_RGBA_FORMAT, GL_UNSIGNED_BYTE, target);

    pimpl->unbind();
    return true;
}

bool OpenGLFrameBuffer::writePixels (const PixelARGB* data, const Rectangle<int>& area)
{
    OpenGLTargetSaver ts (pimpl->context);

    if (! makeCurrentRenderingTarget())
        return false;

    glDisable (GL_DEPTH_TEST);
    glDisable (GL_BLEND);
    JUCE_CHECK_OPENGL_ERROR

    OpenGLTexture tex;
    tex.loadARGB (data, area.getWidth(), area.getHeight());

    glViewport (0, 0, pimpl->width, pimpl->height);
    pimpl->context.copyTexture (area, Rectangle<int> (area.getX(), area.getY(),
                                                      tex.getWidth(), tex.getHeight()),
                                pimpl->width, pimpl->height, true);

    JUCE_CHECK_OPENGL_ERROR
    return true;
}

} // namespace juce