Atmosphere/troposphere/daybreak/nanovg/include/nanovg/nanovg_gl_utils.h

//
// Copyright (c) 2009-2013 Mikko Mononen memon@inside.org
//
// This software is provided 'as-is', without any express or implied
// warranty.  In no event will the authors be held liable for any damages
// arising from the use of this software.
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
// 1. The origin of this software must not be misrepresented; you must not
//    claim that you wrote the original software. If you use this software
//    in a product, an acknowledgment in the product documentation would be
//    appreciated but is not required.
// 2. Altered source versions must be plainly marked as such, and must not be
//    misrepresented as being the original software.
// 3. This notice may not be removed or altered from any source distribution.
//
#ifndef NANOVG_GL_UTILS_H
#define NANOVG_GL_UTILS_H

#ifdef USE_OPENGL

struct NVGLUframebuffer {
    NVGcontext* ctx;
    GLuint fbo;
    GLuint rbo;
    GLuint texture;
    int image;
};
typedef struct NVGLUframebuffer NVGLUframebuffer;

// Helper function to create GL frame buffer to render to.
void nvgluBindFramebuffer(NVGLUframebuffer* fb);
NVGLUframebuffer* nvgluCreateFramebuffer(NVGcontext* ctx, int w, int h, int imageFlags);
void nvgluDeleteFramebuffer(NVGLUframebuffer* fb);

#endif // NANOVG_GL_UTILS_H

#ifdef NANOVG_GL_IMPLEMENTATION

#if defined(NANOVG_GL3) || defined(NANOVG_GLES2) || defined(NANOVG_GLES3)
// FBO is core in OpenGL 3>.
#	define NANOVG_FBO_VALID 1
#elif defined(NANOVG_GL2)
// On OS X including glext defines FBO on GL2 too.
#	ifdef __APPLE__
#		include <OpenGL/glext.h>
#		define NANOVG_FBO_VALID 1
#	endif
#endif

static GLint defaultFBO = -1;

NVGLUframebuffer* nvgluCreateFramebuffer(NVGcontext* ctx, int w, int h, int imageFlags)
{
#ifdef NANOVG_FBO_VALID
    GLint defaultFBO;
    GLint defaultRBO;
    NVGLUframebuffer* fb = NULL;

    glGetIntegerv(GL_FRAMEBUFFER_BINDING, &defaultFBO);
    glGetIntegerv(GL_RENDERBUFFER_BINDING, &defaultRBO);

    fb = (NVGLUframebuffer*)malloc(sizeof(NVGLUframebuffer));
    if (fb == NULL) goto error;
    memset(fb, 0, sizeof(NVGLUframebuffer));

    fb->image = nvgCreateImageRGBA(ctx, w, h, imageFlags | NVG_IMAGE_FLIPY | NVG_IMAGE_PREMULTIPLIED, NULL);

#if defined NANOVG_GL2
    fb->texture = nvglImageHandleGL2(ctx, fb->image);
#elif defined NANOVG_GL3
    fb->texture = nvglImageHandleGL3(ctx, fb->image);
#elif defined NANOVG_GLES2
    fb->texture = nvglImageHandleGLES2(ctx, fb->image);
#elif defined NANOVG_GLES3
    fb->texture = nvglImageHandleGLES3(ctx, fb->image);
#endif

    fb->ctx = ctx;

    // frame buffer object
    glGenFramebuffers(1, &fb->fbo);
    glBindFramebuffer(GL_FRAMEBUFFER, fb->fbo);

    // render buffer object
    glGenRenderbuffers(1, &fb->rbo);
    glBindRenderbuffer(GL_RENDERBUFFER, fb->rbo);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_STENCIL_INDEX8, w, h);

    // combine all
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, fb->texture, 0);
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, fb->rbo);

    if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
#ifdef GL_DEPTH24_STENCIL8
        // If GL_STENCIL_INDEX8 is not supported, try GL_DEPTH24_STENCIL8 as a fallback.
        // Some graphics cards require a depth buffer along with a stencil.
        glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, w, h);
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, fb->texture, 0);
        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, fb->rbo);

        if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
#endif // GL_DEPTH24_STENCIL8
            goto error;
    }

    glBindFramebuffer(GL_FRAMEBUFFER, defaultFBO);
    glBindRenderbuffer(GL_RENDERBUFFER, defaultRBO);
    return fb;
error:
    glBindFramebuffer(GL_FRAMEBUFFER, defaultFBO);
    glBindRenderbuffer(GL_RENDERBUFFER, defaultRBO);
    nvgluDeleteFramebuffer(fb);
    return NULL;
#else
    NVG_NOTUSED(ctx);
    NVG_NOTUSED(w);
    NVG_NOTUSED(h);
    NVG_NOTUSED(imageFlags);
    return NULL;
#endif
}

void nvgluBindFramebuffer(NVGLUframebuffer* fb)
{
#ifdef NANOVG_FBO_VALID
    if (defaultFBO == -1) glGetIntegerv(GL_FRAMEBUFFER_BINDING, &defaultFBO);
    glBindFramebuffer(GL_FRAMEBUFFER, fb != NULL ? fb->fbo : defaultFBO);
#else
    NVG_NOTUSED(fb);
#endif
}

void nvgluDeleteFramebuffer(NVGLUframebuffer* fb)
{
#ifdef NANOVG_FBO_VALID
    if (fb == NULL) return;
    if (fb->fbo != 0)
        glDeleteFramebuffers(1, &fb->fbo);
    if (fb->rbo != 0)
        glDeleteRenderbuffers(1, &fb->rbo);
    if (fb->image >= 0)
        nvgDeleteImage(fb->ctx, fb->image);
    fb->ctx = NULL;
    fb->fbo = 0;
    fb->rbo = 0;
    fb->texture = 0;
    fb->image = -1;
    free(fb);
#else
    NVG_NOTUSED(fb);
#endif
}

#endif

#endif // NANOVG_GL_IMPLEMENTATION