org.jogamp.glg2d.impl.gl2.FastLineVisitor.java Source code

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Here is the source code for org.jogamp.glg2d.impl.gl2.FastLineVisitor.java

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/*
 * Copyright 2013 Brandon Borkholder
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.jogamp.glg2d.impl.gl2;

import java.awt.BasicStroke;
import java.nio.FloatBuffer;
import org.lwjgl.BufferUtils;

import org.lwjgl.opengl.GL11;
import org.lwjgl.opengl.GLContext;

import org.jogamp.glg2d.VertexBuffer;
import org.jogamp.glg2d.impl.SimplePathVisitor;

/**
 * Draws a line using the native GL implementation of a line. This is only
 * appropriate if the width of the line is less than a certain number of pixels
 * (not coordinate units) so that the user cannot see that the join and
 * endpoints are different. See {@link #isValid(BasicStroke)} for a set of
 * useful criteria.
 */
public class FastLineVisitor extends SimplePathVisitor {
    protected FloatBuffer testMatrix = BufferUtils.createFloatBuffer(16);

    protected VertexBuffer buffer = VertexBuffer.getSharedBuffer();

    protected GLContext context;

    protected BasicStroke stroke;

    protected float glLineWidth;

    @Override
    public void setGLContext(GLContext ctx) {
        context = ctx;
    }

    @Override
    public void setStroke(BasicStroke stroke) {
        GL11.glLineWidth(glLineWidth);
        GL11.glPointSize(glLineWidth);

        /*
         * Not perfect copy of the BasicStroke implementation, but it does get
         * decently close. The pattern is pretty much the same. I think it's pretty
         * much impossible to do with out a fragment shader and only the fixed
         * function pipeline.
         */
        float[] dash = stroke.getDashArray();
        if (dash != null) {
            float totalLength = 0;
            for (float f : dash) {
                totalLength += f;
            }

            float lengthSoFar = 0;
            int prevIndex = 0;
            int mask = 0;
            for (int i = 0; i < dash.length; i++) {
                lengthSoFar += dash[i];

                int nextIndex = (int) (lengthSoFar / totalLength * 16);
                for (int j = prevIndex; j < nextIndex; j++) {
                    mask |= (~i & 1) << j;
                }

                prevIndex = nextIndex;
            }

            /*
             * XXX Should actually use the stroke phase, but not sure how yet.
             */

            GL11.glEnable(GL11.GL_LINE_STIPPLE);
            int factor = (int) totalLength;
            GL11.glLineStipple(factor >> 4, (short) mask);
        } else {
            GL11.glDisable(GL11.GL_LINE_STIPPLE);
        }

        this.stroke = stroke;
    }

    /**
     * Returns {@code true} if this class can reasonably render the line. This
     * takes into account whether or not the transform will blow the line width
     * out of scale and it obvious that we aren't drawing correct corners and line
     * endings.
     * 
     * <p>
     * Note: This must be called before {@link #setStroke(BasicStroke)}. If this
     * returns {@code false} then this renderer should not be used.
     * </p>
     */
    public boolean isValid(BasicStroke stroke) {
        // if the dash length is odd, I don't know how to handle that yet
        float[] dash = stroke.getDashArray();
        if (dash != null && (dash.length & 1) == 1) {
            return false;
        }

        GL11.glGetFloat(GL11.GL_MODELVIEW_MATRIX, testMatrix);

        float scaleX = Math.abs(testMatrix.get(0));
        float scaleY = Math.abs(testMatrix.get(5));

        // scales are different, we can't get a good line width
        if (Math.abs(scaleX - scaleY) > 1e-6) {
            return false;
        }

        float strokeWidth = stroke.getLineWidth();

        // gl line width is in pixels, convert to pixel width
        glLineWidth = strokeWidth * scaleX;

        // we'll only try if it's a thin line
        return glLineWidth <= 2;
    }

    @Override
    public void moveTo(float[] vertex) {
        drawLine(false);
        buffer.addVertex(vertex, 0, 1);
    }

    @Override
    public void lineTo(float[] vertex) {
        buffer.addVertex(vertex, 0, 1);
    }

    @Override
    public void closeLine() {
        drawLine(true);
    }

    protected void drawLine(boolean close) {
        FloatBuffer buf = buffer.getBuffer();
        int p = buf.position();
        buffer.drawBuffer(close ? GL11.GL_LINE_LOOP : GL11.GL_LINE_STRIP);

        /*
         * We'll ignore butt endcaps, but we'll pretend like we're drawing round,
         * bevel or miter corners as well as round or square corners by just putting
         * a point there. Since our line should be very thin, pixel-wise, it
         * shouldn't be noticeable.
         */
        if (stroke.getDashArray() == null) {
            buf.position(p);
            buffer.drawBuffer(GL11.GL_POINTS);
        }
    }

    @Override
    public void beginPoly(int windingRule) {
        buffer.clear();

        /*
         * pen hangs down and to the right. See java.awt.Graphics
         */
        GL11.glMatrixMode(GL11.GL_MODELVIEW);
        GL11.glPushMatrix();
        GL11.glTranslatef(0.5f, 0.5f, 0);

        GL11.glPushAttrib(GL11.GL_LINE_BIT | GL11.GL_POINT_BIT);
    }

    @Override
    public void endPoly() {
        drawLine(false);
        GL11.glDisable(GL11.GL_LINE_STIPPLE);
        GL11.glPopMatrix();

        GL11.glPopAttrib();
    }
}