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The Dasher.java Java example source code
/*
* Copyright (c) 2007, 2011, 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
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package sun.java2d.pisces;
import sun.awt.geom.PathConsumer2D;
/**
* The <code>Dasher class takes a series of linear commands
* (<code>moveTo, lineTo, close and
* <code>end) and breaks them into smaller segments according to a
* dash pattern array and a starting dash phase.
*
* <p> Issues: in J2Se, a zero length dash segment as drawn as a very
* short dash, whereas Pisces does not draw anything. The PostScript
* semantics are unclear.
*
*/
final class Dasher implements sun.awt.geom.PathConsumer2D {
private final PathConsumer2D out;
private final float[] dash;
private final float startPhase;
private final boolean startDashOn;
private final int startIdx;
private boolean starting;
private boolean needsMoveTo;
private int idx;
private boolean dashOn;
private float phase;
private float sx, sy;
private float x0, y0;
// temporary storage for the current curve
private float[] curCurvepts;
/**
* Constructs a <code>Dasher.
*
* @param out an output <code>PathConsumer2D.
* @param dash an array of <code>floats containing the dash pattern
* @param phase a <code>float containing the dash phase
*/
public Dasher(PathConsumer2D out, float[] dash, float phase) {
if (phase < 0) {
throw new IllegalArgumentException("phase < 0 !");
}
this.out = out;
// Normalize so 0 <= phase < dash[0]
int idx = 0;
dashOn = true;
float d;
while (phase >= (d = dash[idx])) {
phase -= d;
idx = (idx + 1) % dash.length;
dashOn = !dashOn;
}
this.dash = dash;
this.startPhase = this.phase = phase;
this.startDashOn = dashOn;
this.startIdx = idx;
this.starting = true;
// we need curCurvepts to be able to contain 2 curves because when
// dashing curves, we need to subdivide it
curCurvepts = new float[8 * 2];
}
public void moveTo(float x0, float y0) {
if (firstSegidx > 0) {
out.moveTo(sx, sy);
emitFirstSegments();
}
needsMoveTo = true;
this.idx = startIdx;
this.dashOn = this.startDashOn;
this.phase = this.startPhase;
this.sx = this.x0 = x0;
this.sy = this.y0 = y0;
this.starting = true;
}
private void emitSeg(float[] buf, int off, int type) {
switch (type) {
case 8:
out.curveTo(buf[off+0], buf[off+1],
buf[off+2], buf[off+3],
buf[off+4], buf[off+5]);
break;
case 6:
out.quadTo(buf[off+0], buf[off+1],
buf[off+2], buf[off+3]);
break;
case 4:
out.lineTo(buf[off], buf[off+1]);
}
}
private void emitFirstSegments() {
for (int i = 0; i < firstSegidx; ) {
emitSeg(firstSegmentsBuffer, i+1, (int)firstSegmentsBuffer[i]);
i += (((int)firstSegmentsBuffer[i]) - 1);
}
firstSegidx = 0;
}
// We don't emit the first dash right away. If we did, caps would be
// drawn on it, but we need joins to be drawn if there's a closePath()
// So, we store the path elements that make up the first dash in the
// buffer below.
private float[] firstSegmentsBuffer = new float[7];
private int firstSegidx = 0;
// precondition: pts must be in relative coordinates (relative to x0,y0)
// fullCurve is true iff the curve in pts has not been split.
private void goTo(float[] pts, int off, final int type) {
float x = pts[off + type - 4];
float y = pts[off + type - 3];
if (dashOn) {
if (starting) {
firstSegmentsBuffer = Helpers.widenArray(firstSegmentsBuffer,
firstSegidx, type - 2);
firstSegmentsBuffer[firstSegidx++] = type;
System.arraycopy(pts, off, firstSegmentsBuffer, firstSegidx, type - 2);
firstSegidx += type - 2;
} else {
if (needsMoveTo) {
out.moveTo(x0, y0);
needsMoveTo = false;
}
emitSeg(pts, off, type);
}
} else {
starting = false;
needsMoveTo = true;
}
this.x0 = x;
this.y0 = y;
}
public void lineTo(float x1, float y1) {
float dx = x1 - x0;
float dy = y1 - y0;
float len = (float) Math.sqrt(dx*dx + dy*dy);
if (len == 0) {
return;
}
// The scaling factors needed to get the dx and dy of the
// transformed dash segments.
float cx = dx / len;
float cy = dy / len;
while (true) {
float leftInThisDashSegment = dash[idx] - phase;
if (len <= leftInThisDashSegment) {
curCurvepts[0] = x1;
curCurvepts[1] = y1;
goTo(curCurvepts, 0, 4);
// Advance phase within current dash segment
phase += len;
if (len == leftInThisDashSegment) {
phase = 0f;
idx = (idx + 1) % dash.length;
dashOn = !dashOn;
}
return;
}
float dashdx = dash[idx] * cx;
float dashdy = dash[idx] * cy;
if (phase == 0) {
curCurvepts[0] = x0 + dashdx;
curCurvepts[1] = y0 + dashdy;
} else {
float p = leftInThisDashSegment / dash[idx];
curCurvepts[0] = x0 + p * dashdx;
curCurvepts[1] = y0 + p * dashdy;
}
goTo(curCurvepts, 0, 4);
len -= leftInThisDashSegment;
// Advance to next dash segment
idx = (idx + 1) % dash.length;
dashOn = !dashOn;
phase = 0;
}
}
private LengthIterator li = null;
// preconditions: curCurvepts must be an array of length at least 2 * type,
// that contains the curve we want to dash in the first type elements
private void somethingTo(int type) {
if (pointCurve(curCurvepts, type)) {
return;
}
if (li == null) {
li = new LengthIterator(4, 0.01f);
}
li.initializeIterationOnCurve(curCurvepts, type);
int curCurveoff = 0; // initially the current curve is at curCurvepts[0...type]
float lastSplitT = 0;
float t = 0;
float leftInThisDashSegment = dash[idx] - phase;
while ((t = li.next(leftInThisDashSegment)) < 1) {
if (t != 0) {
Helpers.subdivideAt((t - lastSplitT) / (1 - lastSplitT),
curCurvepts, curCurveoff,
curCurvepts, 0,
curCurvepts, type, type);
lastSplitT = t;
goTo(curCurvepts, 2, type);
curCurveoff = type;
}
// Advance to next dash segment
idx = (idx + 1) % dash.length;
dashOn = !dashOn;
phase = 0;
leftInThisDashSegment = dash[idx];
}
goTo(curCurvepts, curCurveoff+2, type);
phase += li.lastSegLen();
if (phase >= dash[idx]) {
phase = 0f;
idx = (idx + 1) % dash.length;
dashOn = !dashOn;
}
}
private static boolean pointCurve(float[] curve, int type) {
for (int i = 2; i < type; i++) {
if (curve[i] != curve[i-2]) {
return false;
}
}
return true;
}
// Objects of this class are used to iterate through curves. They return
// t values where the left side of the curve has a specified length.
// It does this by subdividing the input curve until a certain error
// condition has been met. A recursive subdivision procedure would
// return as many as 1<
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