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This is a backport of OpenJFX 8 to run on Java 7.
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/*
 * Copyright (c) 2009, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */

package com.sun.prism.es2;

import com.sun.prism.impl.VertexBuffer;

class ES2VertexBuffer extends VertexBuffer {
    private GLContext glCtx;

    ES2VertexBuffer(int maxQuads) {
        super(maxQuads);
    }

    /**
     * Enables vertex attributes and arrays for the given GL instance.  This
     * state is per-GLContext and currently does not change for the life of
     * the ES2VertexBuffer, so it is best to call this just once after the
     * creation of each GLContext (i.e., for each ES2ContextState).  This
     * is made possible by using the same attribute-name-to-index-value
     * binding for all ES2Shaders, meaning that positionAttr always maps to 0,
     * colorAttr always maps to 1, and so on.  That way we can set up the
     * vertex attribute pointers just once, and they will be automatically
     * bound as needed each time glUseProgram() is called.
     */

    protected static final int BYTES_PER_FLOAT = 4;

    void disableVertexAttributes(GLContext glCtx) {
        this.glCtx = glCtx;

        glCtx.disableVertexAttributes();
    }

    void enableVertexAttributes(GLContext glCtx) {
        this.glCtx = glCtx;

        glCtx.enableVertexAttributes();
    }

    @Override
    protected void drawQuads(int numVertices) {
        glCtx.drawIndexedQuads(coordArray, colorArray, numVertices);
    }

    @Override
    protected void drawTriangles(int numTriangles, float fData[], byte cData[]) {
        glCtx.drawTriangleList(numTriangles, fData, cData);
    }

    // protected void flush(int numVertices) { glCtx.drawTriangleArrays(0, numVertices); }

    public static short [] getQuadIndices16bit(int numQuads) {
        short data[] = new short[numQuads * 6];

        for (int i = 0; i != numQuads; ++i) {
            int vtx = i * 4;
            int idx = i * 6;
            data[idx+0] = (short) (vtx+0);
            data[idx+1] = (short) (vtx+1);
            data[idx+2] = (short) (vtx+2);

            data[idx+3] = (short) (vtx+2);
            data[idx+4] = (short) (vtx+1);
            data[idx+5] = (short) (vtx+3);
        }

        return data;
    }

    public int genQuadsIndexBuffer(int numQuads) {
        if (numQuads * 6 > 0x10000)
            throw new IllegalArgumentException("vertex indices overflow");

        return glCtx.createIndexBuffer16(getQuadIndices16bit(numQuads));
    }

}