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/*
* Copyright (c) 2003 Sun Microsystems, Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* - Redistribution of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistribution in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* Neither the name of Sun Microsystems, Inc. or the names of
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* This software is provided "AS IS," without a warranty of any kind. ALL
* EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES,
* INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A
* PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN
* MIDROSYSTEMS, INC. ("SUN") AND ITS LICENSORS SHALL NOT BE LIABLE FOR
* ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
* DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL SUN OR
* ITS LICENSORS BE LIABLE FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR
* DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE
* DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY,
* ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE, EVEN IF
* SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
*
* You acknowledge that this software is not designed or intended for use
* in the design, construction, operation or maintenance of any nuclear
* facility.
*
* Sun gratefully acknowledges that this software was originally authored
* and developed by Kenneth Bradley Russell and Christopher John Kline.
*/
package net.java.games.jogl;
/** <P> The default implementation of the {@link
GLCapabilitiesChooser} interface, which provides consistent visual
selection behavior across platforms. The precise algorithm is
deliberately left loosely specified. Some properties are: </P>
<UL>
<LI> As long as there is at least one available non-null
GLCapabilities which matches the "stereo" option, will return a
valid index.
<LI> Attempts to match as closely as possible the given
GLCapabilities, but will select one with fewer capabilities (i.e.,
lower color depth) if necessary.
<LI> Prefers hardware-accelerated visuals to
non-hardware-accelerated.
<LI> If there is no exact match, prefers a more-capable visual to
a less-capable one.
<LI> If there is more than one exact match, chooses an arbitrary
one.
<LI> May select the opposite of a double- or single-buffered
visual (based on the user's request) in dire situations.
<LI> Color depth (including alpha) mismatches are weighted higher
than depth buffer mismatches, which are in turn weighted higher
than accumulation buffer (including alpha) and stencil buffer
depth mismatches.
</UL>
*/
public class DefaultGLCapabilitiesChooser implements GLCapabilitiesChooser {
private static final boolean DEBUG = false;
public int chooseCapabilities(GLCapabilities desired, GLCapabilities[] available) {
if (DEBUG) {
for (int i = 0; i < available.length; i++) {
System.err.println("Available " + i + ": " + available[i]);
}
}
// Create score array
int[] scores = new int[available.length];
int NO_SCORE = -9999999;
int DOUBLE_BUFFER_MISMATCH_PENALTY = 1000;
int STENCIL_MISMATCH_PENALTY = 500;
// Pseudo attempt to keep equal rank penalties scale-equivalent
// (e.g., stencil mismatch is 3 * accum because there are 3 accum
// components)
int COLOR_MISMATCH_PENALTY_SCALE = 36;
int DEPTH_MISMATCH_PENALTY_SCALE = 6;
int ACCUM_MISMATCH_PENALTY_SCALE = 1;
int STENCIL_MISMATCH_PENALTY_SCALE = 3;
for (int i = 0; i < scores.length; i++) {
scores[i] = NO_SCORE;
}
// Compute score for each
for (int i = 0; i < scores.length; i++) {
GLCapabilities cur = available[i];
if (cur == null) {
continue;
}
if (desired.getStereo() != cur.getStereo()) {
continue;
}
int score = 0;
// Compute difference in color depth
// (Note that this decides the direction of all other penalties)
score += (COLOR_MISMATCH_PENALTY_SCALE *
((cur.getRedBits() + cur.getGreenBits() + cur.getBlueBits() + cur.getAlphaBits()) -
(desired.getRedBits() + desired.getGreenBits() + desired.getBlueBits() + desired.getAlphaBits())));
// Compute difference in depth buffer depth
score += (DEPTH_MISMATCH_PENALTY_SCALE * sign(score) *
Math.abs(cur.getDepthBits() - desired.getDepthBits()));
// Compute difference in accumulation buffer depth
score += (ACCUM_MISMATCH_PENALTY_SCALE * sign(score) *
Math.abs((cur.getAccumRedBits() + cur.getAccumGreenBits() + cur.getAccumBlueBits() + cur.getAccumAlphaBits()) -
(desired.getAccumRedBits() + desired.getAccumGreenBits() + desired.getAccumBlueBits() + desired.getAccumAlphaBits())));
// Compute difference in stencil bits
score += STENCIL_MISMATCH_PENALTY_SCALE * sign(score) * (cur.getStencilBits() - desired.getStencilBits());
if (cur.getDoubleBuffered() != desired.getDoubleBuffered()) {
score += sign(score) * DOUBLE_BUFFER_MISMATCH_PENALTY;
}
if ((desired.getStencilBits() > 0) && (cur.getStencilBits() == 0)) {
score += sign(score) * STENCIL_MISMATCH_PENALTY;
}
scores[i] = score;
}
// Now prefer hardware-accelerated visuals by pushing scores of
// non-hardware-accelerated visuals out
boolean gotHW = false;
int maxAbsoluteHWScore = 0;
for (int i = 0; i < scores.length; i++) {
int score = scores[i];
if (score == NO_SCORE) {
continue;
}
GLCapabilities cur = available[i];
if (cur.getHardwareAccelerated()) {
int absScore = Math.abs(score);
if (!gotHW ||
(absScore > maxAbsoluteHWScore)) {
gotHW = true;
maxAbsoluteHWScore = absScore;
}
}
}
if (gotHW) {
for (int i = 0; i < scores.length; i++) {
int score = scores[i];
if (score == NO_SCORE) {
continue;
}
GLCapabilities cur = available[i];
if (!cur.getHardwareAccelerated()) {
if (score <= 0) {
score -= maxAbsoluteHWScore;
} else if (score > 0) {
score += maxAbsoluteHWScore;
}
scores[i] = score;
}
}
}
if (DEBUG) {
System.err.print("Scores: [");
for (int i = 0; i < available.length; i++) {
if (i > 0) {
System.err.print(",");
}
System.err.print(" " + scores[i]);
}
System.err.println(" ]");
}
// Ready to select. Choose score closest to 0.
int scoreClosestToZero = NO_SCORE;
int chosenIndex = -1;
for (int i = 0; i < scores.length; i++) {
int score = scores[i];
if (score == NO_SCORE) {
continue;
}
// Don't substitute a positive score for a smaller negative score
if ((scoreClosestToZero == NO_SCORE) ||
(Math.abs(score) < Math.abs(scoreClosestToZero) &&
((sign(scoreClosestToZero) < 0) || (sign(score) > 0)))) {
scoreClosestToZero = score;
chosenIndex = i;
}
}
if (chosenIndex < 0) {
throw new GLException("Unable to select one of the provided GLCapabilities");
}
if (DEBUG) {
System.err.println("Chosen index: " + chosenIndex);
System.err.println("Chosen capabilities:");
System.err.println(available[chosenIndex]);
}
return chosenIndex;
}
private static int sign(int score) {
if (score < 0) {
return -1;
}
return 1;
}
}
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