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path: root/src/libjin/render/canvas.cpp
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#include "../modules.h"
#if JIN_MODULES_RENDER

#include "../utils/macros.h"
#include "canvas.h" 
#include "window.h"

namespace jin
{
namespace render 
{

    shared Canvas* Canvas::createCanvas(int w, int h)
    {
        return new Canvas(w, h);
    }

    Canvas::Canvas(int w, int h) 
        : Drawable(w, h)
    {
        init();
    }

    Canvas::~Canvas()
    {
    }

    shared GLint Canvas::cur = -1; 

    bool Canvas::init()
    {
        setVertices(
            new float [DRAWABLE_V_SIZE] {
                0, 0,
                0, (float)height,
                (float)width, (float)height,
                (float)width, 0,
            },
            new float [DRAWABLE_V_SIZE] {
                0, 1,
                0, 0,
                1, 0,
                1, 1
            }
        );

        GLint current_fbo;
        glGetIntegerv(GL_DRAW_FRAMEBUFFER_BINDING, &current_fbo);

        // generate a new render buffer object 
        glGenFramebuffers(1, &fbo);
        glBindFramebuffer(GL_FRAMEBUFFER, fbo);

        // generate texture save target 
        glGenTextures(1, &texture);
        glBindTexture(GL_TEXTURE_2D, texture);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
        glBindTexture(GL_TEXTURE_2D, 0);
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0);

        GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
        
        // unbind framebuffer
        glBindFramebuffer(GL_FRAMEBUFFER, current_fbo);
        
        if (status != GL_FRAMEBUFFER_COMPLETE_EXT)
            return false;
        return true; 
    }

    bool Canvas::hasbind(GLint fbo)
    {
        return cur == fbo; 
    }

    /**
    * bind to canvas 
    */
    void Canvas::bind()
    {
        if (hasbind(fbo)) return;

        cur = fbo;

        glBindFramebuffer(GL_FRAMEBUFFER, fbo);

        glMatrixMode(GL_PROJECTION);
        glPushMatrix();
        glLoadIdentity();

        glViewport(0, 0, width, height);
        glOrtho(0, width, height, 0, -1, 1);

        // Switch back to modelview matrix
        glMatrixMode(GL_MODELVIEW);
        glPushMatrix();
        glLoadIdentity();
    }

    /**
    * bind to default screen render buffer. 
    */
    shared void Canvas::unbind()
    {
        if (hasbind(0)) return;
        
        cur = 0;

        glBindFramebuffer(GL_FRAMEBUFFER, 0);
        WindowSystem* wnd = WindowSystem::get();
        int ww = wnd->getW(),
            wh = wnd->getH();

        glViewport(0, 0, ww, wh);

        // load back to normal 
        glMatrixMode(GL_PROJECTION);
        glPushMatrix();
        glLoadIdentity();
        
        // set viewport matrix 
        glOrtho(0, ww, wh, 0, -1, 1);

        //  switch to model matrix  
        glMatrixMode(GL_MODELVIEW);
        glPushMatrix();
        glLoadIdentity();
    }

} // render
} // jin

#endif // JIN_MODULES_RENDER