dynamic_rectangle.cpp

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/*
    RenderStack  Support library for OpenGL 3+
    Copyright (C) 2010  Timo Suoranta

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include "renderstack/dynamic_rectangle.hpp"
#include "renderstack/rs_gl.h"

namespace renderstack {

dynamic_rectangle::dynamic_rectangle()
{
    /*  Setup vertex format  */ 
    {
        vertex_attribute position(vertex_attribute_usage_position, GL_FLOAT, 0, 3);

        vertex_buffer()->vertex_format().append(position);
    }

    /*  Initialize buffers  */ 
    mesh::find_or_create_index_buffer(
        mesh_mode_edge_lines,
        GL_ELEMENT_ARRAY_BUFFER, 
        GL_STATIC_DRAW, 
        GL_UNSIGNED_INT, 
        GL_LINES
    );

    update(0.0f, 0.0f, 1.0f, 1.0f);
}

/*  TODO This is full update. You don't really need to redo index buffer  */ 
/*       if it has already been created.                                  */ 
void dynamic_rectangle::update(
    float x0, 
    float y0, 
    float x1, 
    float y1
)
{
    /*    2    3     0.. 3  corners     */ 
    /*                                  */ 
    /*                                  */ 
    /*    0    1                        */ 

    int vertex_index = 0;
    int index        = 0;

    buffer *vertex_buffer = mesh::vertex_buffer();
    buffer *index_buffer  = mesh::index_buffer(mesh_mode_edge_lines);

    vertex_buffer->begin_edit();
    index_buffer->begin_edit();

    /*  Vertices  */ 
    {
        vertex_buffer->set_index(index++); vertex_buffer->put_position(x0, y0, 0.0f);
        vertex_buffer->set_index(index++); vertex_buffer->put_position(x1, y0, 0.0f);
        vertex_buffer->set_index(index++); vertex_buffer->put_position(x0, y1, 0.0f);
        vertex_buffer->set_index(index++); vertex_buffer->put_position(x1, y1, 0.0f);
    }

    /*  Lines  */ 
    /*  Notice that you need to match end points for the lines  */ 
    /*  with start point of other line in order to get all      */ 
    /*  cornerpixels rasterized.                                */ 
    {
        index_buffer->set_index(vertex_index);
        index_buffer->line(0, 1);
        vertex_index += 2;
        index_buffer->set_index(vertex_index);
        index_buffer->line(1, 3);
        vertex_index += 2;
        index_buffer->set_index(vertex_index);
        index_buffer->line(3, 2);
        vertex_index += 2;
        index_buffer->set_index(vertex_index);
        index_buffer->line(2, 0);
        vertex_index += 2;
    }

    /*  Done  */ 
    vertex_buffer->end_edit(index);
    index_buffer->end_edit(vertex_index);
}

}