/**
 * Represents an OpenGL texture object. Contains convenience routines for enabling/disabling OpenGL
 * texture state, binding this texture, and computing texture coordinates for both the entire image
 * as well as a sub-image.
 *
 * <p><a name="nonpow2"><b>Non-power-of-two restrictions</b></a> <br>
 * When creating an OpenGL texture object, the Texture class will attempt to leverage the <a
 * href="http://www.opengl.org/registry/specs/ARB/texture_non_power_of_two.txt">GL_ARB_texture_non_power_of_two</a>
 * and <a
 * href="http://www.opengl.org/registry/specs/ARB/texture_rectangle.txt">GL_ARB_texture_rectangle</a>
 * extensions (in that order) whenever possible. If neither extension is available, the Texture
 * class will simply upload a non-pow2-sized image into a standard pow2-sized texture (without any
 * special scaling). Since the choice of extension (or whether one is used at all) depends on the
 * user's machine configuration, developers are recommended to use {@link #getImageTexCoords} and
 * {@link #getSubImageTexCoords}, as those methods will calculate the appropriate texture
 * coordinates for the situation.
 *
 * <p>One caveat in this approach is that certain texture wrap modes (e.g. <code>GL_REPEAT</code>)
 * are not legal when the GL_ARB_texture_rectangle extension is in use. Another issue to be aware of
 * is that in the default pow2 scenario, if the original image does not have pow2 dimensions, then
 * wrapping may not work as one might expect since the image does not extend to the edges of the
 * pow2 texture. If texture wrapping is important, it is recommended to use only pow2-sized images
 * with the Texture class.
 *
 * <p><a name="perftips"><b>Performance Tips</b></a> <br>
 * For best performance, try to avoid calling {@link #enable} / {@link #bind} / {@link #disable} any
 * more than necessary. For example, applications using many Texture objects in the same scene may
 * want to reduce the number of calls to both {@link #enable} and {@link #disable}. To do this it is
 * necessary to call {@link #getTarget} to make sure the OpenGL texture target is the same for all
 * of the Texture objects in use; non-power-of-two textures using the GL_ARB_texture_rectangle
 * extension use a different target than power-of-two textures using the GL_TEXTURE_2D target. Note
 * that when switching between textures it is necessary to call {@link #bind}, but when drawing many
 * triangles all using the same texture, for best performance only one call to {@link #bind} should
 * be made.
 *
 * <p><a name="premult"><b>Alpha premultiplication and blending</b></a> <br>
 * The mathematically correct way to perform blending in OpenGL (with the SrcOver "source over
 * destination" mode, or any other Porter-Duff rule) is to use "premultiplied color components",
 * which means the R/G/ B color components have already been multiplied by the alpha value. To make
 * things easier for developers, the Texture class will automatically convert non-premultiplied
 * image data into premultiplied data when storing it into an OpenGL texture. As a result, it is
 * important to use the correct blending function; for example, the SrcOver rule is expressed as:
 *
 * <pre>
 * gl.glBlendFunc(GL.GL_ONE, GL.GL_ONE_MINUS_SRC_ALPHA);
 * </pre>
 *
 * Also, when using a texture function like <code>GL_MODULATE</code> where the current color plays a
 * role, it is important to remember to make sure that the color is specified in a premultiplied
 * form, for example:
 *
 * <pre>
 * float a = ...;
 * float r = r * a;
 * float g = g * a;
 * float b = b * a;
 * gl.glColor4f(r, g, b, a);
 * </pre>
 *
 * For reference, here is a list of the Porter-Duff compositing rules and the associated OpenGL
 * blend functions (source and destination factors) to use in the face of premultiplied alpha:
 *
 * <p><CENTER>
 *
 * <TABLE WIDTH="75%">
 * <TR> <TD> Rule     <TD> Source                  <TD> Dest
 * <TR> <TD> Clear    <TD> GL_ZERO                 <TD> GL_ZERO
 * <TR> <TD> Src      <TD> GL_ONE                  <TD> GL_ZERO
 * <TR> <TD> SrcOver  <TD> GL_ONE                  <TD> GL_ONE_MINUS_SRC_ALPHA
 * <TR> <TD> DstOver  <TD> GL_ONE_MINUS_DST_ALPHA  <TD> GL_ONE
 * <TR> <TD> SrcIn    <TD> GL_DST_ALPHA            <TD> GL_ZERO
 * <TR> <TD> DstIn    <TD> GL_ZERO                 <TD> GL_SRC_ALPHA
 * <TR> <TD> SrcOut   <TD> GL_ONE_MINUS_DST_ALPHA  <TD> GL_ZERO
 * <TR> <TD> DstOut   <TD> GL_ZERO                 <TD> GL_ONE_MINUS_SRC_ALPHA
 * <TR> <TD> Dst      <TD> GL_ZERO                 <TD> GL_ONE
 * <TR> <TD> SrcAtop  <TD> GL_DST_ALPHA            <TD> GL_ONE_MINUS_SRC_ALPHA
 * <TR> <TD> DstAtop  <TD> GL_ONE_MINUS_DST_ALPHA  <TD> GL_SRC_ALPHA
 * <TR> <TD> AlphaXor <TD> GL_ONE_MINUS_DST_ALPHA  <TD> GL_ONE_MINUS_SRC_ALPHA
 * </TABLE>
 *
 * </CENTER>
 *
 * @author Chris Campbell
 * @author Kenneth Russell
 */
public class Texture {
  /** The GL target type. */
  private int target;
  /** The GL texture ID. */
  private int texID;
  /** The width of the texture. */
  private int texWidth;
  /** The height of the texture. */
  private int texHeight;
  /** The width of the image. */
  private int imgWidth;
  /** The height of the image. */
  private int imgHeight;
  /**
   * The original aspect ratio of the image, before any rescaling that might have occurred due to
   * using the GLU mipmap routines.
   */
  private float aspectRatio;
  /** Indicates whether the TextureData requires a vertical flip of the texture coords. */
  private boolean mustFlipVertically;
  /** Indicates whether we're using automatic mipmap generation support (GL_GENERATE_MIPMAP). */
  private boolean usingAutoMipmapGeneration;

  /** The texture coordinates corresponding to the entire image. */
  private TextureCoords coords;

  /** An estimate of the amount of texture memory this texture consumes. */
  private int estimatedMemorySize;

  private static final boolean DEBUG = Debug.debug("Texture");
  private static final boolean VERBOSE = Debug.verbose();

  // For testing alternate code paths on more capable hardware
  private static final boolean disableNPOT = Debug.isPropertyDefined("jogl.texture.nonpot");
  private static final boolean disableTexRect = Debug.isPropertyDefined("jogl.texture.notexrect");

  // For now make Texture constructor package-private to limit the
  // number of public APIs we commit to
  Texture(TextureData data) throws GLException {
    GL gl = GLU.getCurrentGL();
    texID = createTextureID(gl);

    updateImage(data);
  }

  // Constructor for use when creating e.g. cube maps, where there is
  // no initial texture data
  Texture(int target) throws GLException {
    GL gl = GLU.getCurrentGL();
    texID = createTextureID(gl);
    this.target = target;
  }

  /**
   * Enables this texture's target (e.g., GL_TEXTURE_2D) in the current GL context's state. This
   * method is a shorthand equivalent of the following OpenGL code:
   *
   * <pre>
   * gl.glEnable(texture.getTarget());
   * </pre>
   *
   * See the <a href="#perftips">performance tips</a> above for hints on how to maximize performance
   * when using many Texture objects.
   *
   * @throws GLException if no OpenGL context was current or if any OpenGL-related errors occurred
   */
  public void enable() throws GLException {
    GLU.getCurrentGL().glEnable(target);
  }

  /**
   * Disables this texture's target (e.g., GL_TEXTURE_2D) in the current GL context's state. This
   * method is a shorthand equivalent of the following OpenGL code:
   *
   * <pre>
   * gl.glDisable(texture.getTarget());
   * </pre>
   *
   * See the <a href="#perftips">performance tips</a> above for hints on how to maximize performance
   * when using many Texture objects.
   *
   * @throws GLException if no OpenGL context was current or if any OpenGL-related errors occurred
   */
  public void disable() throws GLException {
    GLU.getCurrentGL().glDisable(target);
  }

  /**
   * Binds this texture to the current GL context. This method is a shorthand equivalent of the
   * following OpenGL code:
   *
   * <pre>
   * gl.glBindTexture(texture.getTarget(), texture.getTextureObject());
   * </pre>
   *
   * See the <a href="#perftips">performance tips</a> above for hints on how to maximize performance
   * when using many Texture objects.
   *
   * @throws GLException if no OpenGL context was current or if any OpenGL-related errors occurred
   */
  public void bind() throws GLException {
    GLU.getCurrentGL().glBindTexture(target, texID);
  }

  /**
   * Disposes the native resources used by this texture object.
   *
   * @throws GLException if no OpenGL context was current or if any OpenGL-related errors occurred
   */
  public void dispose() throws GLException {
    GLU.getCurrentGL().glDeleteTextures(1, new int[] {texID}, 0);
    texID = 0;
  }

  /**
   * Returns the OpenGL "target" of this texture.
   *
   * @return the OpenGL target of this texture
   * @see javax.media.opengl.GL#GL_TEXTURE_2D
   * @see javax.media.opengl.GL#GL_TEXTURE_RECTANGLE_ARB
   */
  public int getTarget() {
    return target;
  }

  /**
   * Returns the width of the allocated OpenGL texture in pixels. Note that the texture width will
   * be greater than or equal to the width of the image contained within.
   *
   * @return the width of the texture
   */
  public int getWidth() {
    return texWidth;
  }

  /**
   * Returns the height of the allocated OpenGL texture in pixels. Note that the texture height will
   * be greater than or equal to the height of the image contained within.
   *
   * @return the height of the texture
   */
  public int getHeight() {
    return texHeight;
  }

  /**
   * Returns the width of the image contained within this texture. Note that for non-power-of-two
   * textures in particular this may not be equal to the result of {@link #getWidth}. It is
   * recommended that applications call {@link #getImageTexCoords} and {@link #getSubImageTexCoords}
   * rather than using this API directly.
   *
   * @return the width of the image
   */
  public int getImageWidth() {
    return imgWidth;
  }

  /**
   * Returns the height of the image contained within this texture. Note that for non-power-of-two
   * textures in particular this may not be equal to the result of {@link #getHeight}. It is
   * recommended that applications call {@link #getImageTexCoords} and {@link #getSubImageTexCoords}
   * rather than using this API directly.
   *
   * @return the height of the image
   */
  public int getImageHeight() {
    return imgHeight;
  }

  /**
   * Returns the original aspect ratio of the image, defined as (image width) / (image height),
   * before any scaling that might have occurred as a result of using the GLU mipmap routines.
   */
  public float getAspectRatio() {
    return aspectRatio;
  }

  /**
   * Returns the set of texture coordinates corresponding to the entire image. If the TextureData
   * indicated that the texture coordinates must be flipped vertically, the returned TextureCoords
   * will take that into account.
   *
   * @return the texture coordinates corresponding to the entire image
   */
  public TextureCoords getImageTexCoords() {
    return coords;
  }

  /**
   * Returns the set of texture coordinates corresponding to the specified sub-image. The (x1, y1)
   * and (x2, y2) points are specified in terms of pixels starting from the lower-left of the image.
   * (x1, y1) should specify the lower-left corner of the sub-image and (x2, y2) the upper-right
   * corner of the sub-image. If the TextureData indicated that the texture coordinates must be
   * flipped vertically, the returned TextureCoords will take that into account; this should not be
   * handled by the end user in the specification of the y1 and y2 coordinates.
   *
   * @return the texture coordinates corresponding to the specified sub-image
   */
  public TextureCoords getSubImageTexCoords(int x1, int y1, int x2, int y2) {
    if (target == GL.GL_TEXTURE_RECTANGLE_ARB) {
      if (mustFlipVertically) {
        return new TextureCoords(x1, texHeight - y1, x2, texHeight - y2);
      } else {
        return new TextureCoords(x1, y1, x2, y2);
      }
    } else {
      float tx1 = (float) x1 / (float) texWidth;
      float ty1 = (float) y1 / (float) texHeight;
      float tx2 = (float) x2 / (float) texWidth;
      float ty2 = (float) y2 / (float) texHeight;
      if (mustFlipVertically) {
        float yMax = (float) imgHeight / (float) texHeight;
        return new TextureCoords(tx1, yMax - ty1, tx2, yMax - ty2);
      } else {
        return new TextureCoords(tx1, ty1, tx2, ty2);
      }
    }
  }

  /**
   * Updates the entire content area of this texture using the data in the given image.
   *
   * @throws GLException if no OpenGL context was current or if any OpenGL-related errors occurred
   */
  public void updateImage(TextureData data) throws GLException {
    updateImage(data, 0);
  }

  /**
   * Indicates whether this texture's texture coordinates must be flipped vertically in order to
   * properly display the texture. This is handled automatically by {@link #getImageTexCoords
   * getImageTexCoords} and {@link #getSubImageTexCoords getSubImageTexCoords}, but applications may
   * generate or otherwise produce texture coordinates which must be corrected.
   */
  public boolean getMustFlipVertically() {
    return mustFlipVertically;
  }

  /**
   * Updates the content area of the specified target of this texture using the data in the given
   * image. In general this is intended for construction of cube maps.
   *
   * @throws GLException if no OpenGL context was current or if any OpenGL-related errors occurred
   */
  public void updateImage(TextureData data, int target) throws GLException {
    GL gl = GLU.getCurrentGL();

    imgWidth = data.getWidth();
    imgHeight = data.getHeight();
    aspectRatio = (float) imgWidth / (float) imgHeight;
    mustFlipVertically = data.getMustFlipVertically();

    int texTarget = 0;
    int texParamTarget = this.target;

    // See whether we have automatic mipmap generation support
    boolean haveAutoMipmapGeneration =
        (gl.isExtensionAvailable("GL_VERSION_1_4")
            || gl.isExtensionAvailable("GL_SGIS_generate_mipmap"));

    // Indicate to the TextureData what functionality is available
    data.setHaveEXTABGR(gl.isExtensionAvailable("GL_EXT_abgr"));
    data.setHaveGL12(gl.isExtensionAvailable("GL_VERSION_1_2"));

    // Note that automatic mipmap generation doesn't work for
    // GL_ARB_texture_rectangle
    if ((!isPowerOfTwo(imgWidth) || !isPowerOfTwo(imgHeight)) && !haveNPOT(gl)) {
      haveAutoMipmapGeneration = false;
    }

    boolean expandingCompressedTexture = false;
    if (data.getMipmap() && !haveAutoMipmapGeneration) {
      // GLU always scales the texture's dimensions to be powers of
      // two. It also doesn't really matter exactly what the texture
      // width and height are because the texture coords are always
      // between 0.0 and 1.0.
      imgWidth = nextPowerOfTwo(imgWidth);
      imgHeight = nextPowerOfTwo(imgHeight);
      texWidth = imgWidth;
      texHeight = imgHeight;
      texTarget = GL.GL_TEXTURE_2D;
    } else if ((isPowerOfTwo(imgWidth) && isPowerOfTwo(imgHeight)) || haveNPOT(gl)) {
      if (DEBUG) {
        if (isPowerOfTwo(imgWidth) && isPowerOfTwo(imgHeight)) {
          System.err.println("Power-of-two texture");
        } else {
          System.err.println("Using GL_ARB_texture_non_power_of_two");
        }
      }

      texWidth = imgWidth;
      texHeight = imgHeight;
      texTarget = GL.GL_TEXTURE_2D;
    } else if (haveTexRect(gl) && !data.isDataCompressed()) {
      // GL_ARB_texture_rectangle does not work for compressed textures
      if (DEBUG) {
        System.err.println("Using GL_ARB_texture_rectangle");
      }

      texWidth = imgWidth;
      texHeight = imgHeight;
      texTarget = GL.GL_TEXTURE_RECTANGLE_ARB;
    } else {
      // If we receive non-power-of-two compressed texture data and
      // don't have true hardware support for compressed textures, we
      // can fake this support by producing an empty "compressed"
      // texture image, using glCompressedTexImage2D with that to
      // allocate the texture, and glCompressedTexSubImage2D with the
      // incoming data.
      if (data.isDataCompressed()) {
        if (data.getMipmapData() != null) {

          // We don't currently support expanding of compressed,
          // mipmapped non-power-of-two textures to the nearest power
          // of two; the obvious port of the non-mipmapped code didn't
          // work
          throw new GLException(
              "Mipmapped non-power-of-two compressed textures only supported on OpenGL 2.0 hardware (GL_ARB_texture_non_power_of_two)");
        }

        expandingCompressedTexture = true;
      }

      if (DEBUG) {
        System.err.println("Expanding texture to power-of-two dimensions");
      }

      if (data.getBorder() != 0) {
        throw new RuntimeException(
            "Scaling up a non-power-of-two texture which has a border won't work");
      }
      texWidth = nextPowerOfTwo(imgWidth);
      texHeight = nextPowerOfTwo(imgHeight);
      texTarget = GL.GL_TEXTURE_2D;
    }

    texParamTarget = texTarget;
    setImageSize(imgWidth, imgHeight, texTarget);

    if (target != 0) {
      // Allow user to override auto detection and skip bind step (for
      // cubemap construction)
      texTarget = target;
      if (this.target == 0) {
        throw new GLException("Override of target failed; no target specified yet");
      }
      texParamTarget = this.target;
      gl.glBindTexture(texParamTarget, texID);
    } else {
      gl.glBindTexture(texTarget, texID);
    }

    if (data.getMipmap() && !haveAutoMipmapGeneration) {
      int[] align = new int[1];
      gl.glGetIntegerv(GL.GL_UNPACK_ALIGNMENT, align, 0); // save alignment
      gl.glPixelStorei(GL.GL_UNPACK_ALIGNMENT, data.getAlignment());

      if (data.isDataCompressed()) {
        throw new GLException("May not request mipmap generation for compressed textures");
      }

      try {
        GLU glu = new GLU();
        glu.gluBuild2DMipmaps(
            texTarget,
            data.getInternalFormat(),
            data.getWidth(),
            data.getHeight(),
            data.getPixelFormat(),
            data.getPixelType(),
            data.getBuffer());
      } finally {
        gl.glPixelStorei(GL.GL_UNPACK_ALIGNMENT, align[0]); // restore alignment
      }
    } else {
      checkCompressedTextureExtensions(data);
      Buffer[] mipmapData = data.getMipmapData();
      if (mipmapData != null) {
        int width = texWidth;
        int height = texHeight;
        for (int i = 0; i < mipmapData.length; i++) {
          if (data.isDataCompressed()) {
            // Need to use glCompressedTexImage2D directly to allocate and fill this image
            // Avoid spurious memory allocation when possible
            gl.glCompressedTexImage2D(
                texTarget,
                i,
                data.getInternalFormat(),
                width,
                height,
                data.getBorder(),
                mipmapData[i].remaining(),
                mipmapData[i]);
          } else {
            // Allocate texture image at this level
            gl.glTexImage2D(
                texTarget,
                i,
                data.getInternalFormat(),
                width,
                height,
                data.getBorder(),
                data.getPixelFormat(),
                data.getPixelType(),
                null);
            updateSubImageImpl(data, texTarget, i, 0, 0, 0, 0, data.getWidth(), data.getHeight());
          }

          width = Math.max(width / 2, 1);
          height = Math.max(height / 2, 1);
        }
      } else {
        if (data.isDataCompressed()) {
          if (!expandingCompressedTexture) {
            // Need to use glCompressedTexImage2D directly to allocate and fill this image
            // Avoid spurious memory allocation when possible
            gl.glCompressedTexImage2D(
                texTarget,
                0,
                data.getInternalFormat(),
                texWidth,
                texHeight,
                data.getBorder(),
                data.getBuffer().capacity(),
                data.getBuffer());
          } else {
            ByteBuffer buf =
                DDSImage.allocateBlankBuffer(texWidth, texHeight, data.getInternalFormat());
            gl.glCompressedTexImage2D(
                texTarget,
                0,
                data.getInternalFormat(),
                texWidth,
                texHeight,
                data.getBorder(),
                buf.capacity(),
                buf);
            updateSubImageImpl(data, texTarget, 0, 0, 0, 0, 0, data.getWidth(), data.getHeight());
          }
        } else {
          if (data.getMipmap() && haveAutoMipmapGeneration) {
            // For now, only use hardware mipmapping for uncompressed 2D
            // textures where the user hasn't explicitly specified
            // mipmap data; don't know about interactions between
            // GL_GENERATE_MIPMAP and glCompressedTexImage2D
            gl.glTexParameteri(texParamTarget, GL.GL_GENERATE_MIPMAP, GL.GL_TRUE);
            usingAutoMipmapGeneration = true;
          }

          gl.glTexImage2D(
              texTarget,
              0,
              data.getInternalFormat(),
              texWidth,
              texHeight,
              data.getBorder(),
              data.getPixelFormat(),
              data.getPixelType(),
              null);
          updateSubImageImpl(data, texTarget, 0, 0, 0, 0, 0, data.getWidth(), data.getHeight());
        }
      }
    }

    int minFilter = (data.getMipmap() ? GL.GL_LINEAR_MIPMAP_LINEAR : GL.GL_LINEAR);
    int magFilter = GL.GL_LINEAR;
    int wrapMode = (gl.isExtensionAvailable("GL_VERSION_1_2") ? GL.GL_CLAMP_TO_EDGE : GL.GL_CLAMP);

    // REMIND: figure out what to do for GL_TEXTURE_RECTANGLE_ARB
    if (texTarget != GL.GL_TEXTURE_RECTANGLE_ARB) {
      gl.glTexParameteri(texParamTarget, GL.GL_TEXTURE_MIN_FILTER, minFilter);
      gl.glTexParameteri(texParamTarget, GL.GL_TEXTURE_MAG_FILTER, magFilter);
      gl.glTexParameteri(texParamTarget, GL.GL_TEXTURE_WRAP_S, wrapMode);
      gl.glTexParameteri(texParamTarget, GL.GL_TEXTURE_WRAP_T, wrapMode);
      if (this.target == GL.GL_TEXTURE_CUBE_MAP) {
        gl.glTexParameteri(texParamTarget, GL.GL_TEXTURE_WRAP_R, wrapMode);
      }
    }

    // Don't overwrite target if we're loading e.g. faces of a cube
    // map
    if ((this.target == 0)
        || (this.target == GL.GL_TEXTURE_2D)
        || (this.target == GL.GL_TEXTURE_RECTANGLE_ARB)) {
      this.target = texTarget;
    }

    // This estimate will be wrong for cube maps
    estimatedMemorySize = data.getEstimatedMemorySize();
  }

  /**
   * Updates a subregion of the content area of this texture using the given data. If automatic
   * mipmap generation is in use (see {@link #isUsingAutoMipmapGeneration
   * isUsingAutoMipmapGeneration}), updates to the base (level 0) mipmap will cause the lower-level
   * mipmaps to be regenerated, and updates to other mipmap levels will be ignored. Otherwise, if
   * automatic mipmap generation is not in use, only updates the specified mipmap level and does not
   * re-generate mipmaps if they were originally produced or loaded.
   *
   * @param data the image data to be uploaded to this texture
   * @param mipmapLevel the mipmap level of the texture to set. If this is non-zero and the
   *     TextureData contains mipmap data, the appropriate mipmap level will be selected.
   * @param x the x offset (in pixels) relative to the lower-left corner of this texture
   * @param y the y offset (in pixels) relative to the lower-left corner of this texture
   * @throws GLException if no OpenGL context was current or if any OpenGL-related errors occurred
   */
  public void updateSubImage(TextureData data, int mipmapLevel, int x, int y) throws GLException {
    if (usingAutoMipmapGeneration && mipmapLevel != 0) {
      // When we're using mipmap generation via GL_GENERATE_MIPMAP, we
      // don't need to update other mipmap levels
      return;
    }
    bind();
    updateSubImageImpl(data, target, mipmapLevel, x, y, 0, 0, data.getWidth(), data.getHeight());
  }

  /**
   * Updates a subregion of the content area of this texture using the specified sub-region of the
   * given data. If automatic mipmap generation is in use (see {@link #isUsingAutoMipmapGeneration
   * isUsingAutoMipmapGeneration}), updates to the base (level 0) mipmap will cause the lower-level
   * mipmaps to be regenerated, and updates to other mipmap levels will be ignored. Otherwise, if
   * automatic mipmap generation is not in use, only updates the specified mipmap level and does not
   * re-generate mipmaps if they were originally produced or loaded. This method is only supported
   * for uncompressed TextureData sources.
   *
   * @param data the image data to be uploaded to this texture
   * @param mipmapLevel the mipmap level of the texture to set. If this is non-zero and the
   *     TextureData contains mipmap data, the appropriate mipmap level will be selected.
   * @param dstx the x offset (in pixels) relative to the lower-left corner of this texture where
   *     the update will be applied
   * @param dsty the y offset (in pixels) relative to the lower-left corner of this texture where
   *     the update will be applied
   * @param srcx the x offset (in pixels) relative to the lower-left corner of the supplied
   *     TextureData from which to fetch the update rectangle
   * @param srcy the y offset (in pixels) relative to the lower-left corner of the supplied
   *     TextureData from which to fetch the update rectangle
   * @param width the width (in pixels) of the rectangle to be updated
   * @param height the height (in pixels) of the rectangle to be updated
   * @throws GLException if no OpenGL context was current or if any OpenGL-related errors occurred
   */
  public void updateSubImage(
      TextureData data,
      int mipmapLevel,
      int dstx,
      int dsty,
      int srcx,
      int srcy,
      int width,
      int height)
      throws GLException {
    if (data.isDataCompressed()) {
      throw new GLException(
          "updateSubImage specifying a sub-rectangle is not supported for compressed TextureData");
    }
    if (usingAutoMipmapGeneration && mipmapLevel != 0) {
      // When we're using mipmap generation via GL_GENERATE_MIPMAP, we
      // don't need to update other mipmap levels
      return;
    }
    bind();
    updateSubImageImpl(data, target, mipmapLevel, dstx, dsty, srcx, srcy, width, height);
  }

  /**
   * Sets the OpenGL floating-point texture parameter for the texture's target. This gives control
   * over parameters such as GL_TEXTURE_MAX_ANISOTROPY_EXT. Causes this texture to be bound to the
   * current texture state.
   *
   * @throws GLException if no OpenGL context was current or if any OpenGL-related errors occurred
   */
  public void setTexParameterf(int parameterName, float value) {
    bind();
    GL gl = GLU.getCurrentGL();
    gl.glTexParameterf(target, parameterName, value);
  }

  /**
   * Sets the OpenGL multi-floating-point texture parameter for the texture's target. Causes this
   * texture to be bound to the current texture state.
   *
   * @throws GLException if no OpenGL context was current or if any OpenGL-related errors occurred
   */
  public void setTexParameterfv(int parameterName, FloatBuffer params) {
    bind();
    GL gl = GLU.getCurrentGL();
    gl.glTexParameterfv(target, parameterName, params);
  }

  /**
   * Sets the OpenGL multi-floating-point texture parameter for the texture's target. Causes this
   * texture to be bound to the current texture state.
   *
   * @throws GLException if no OpenGL context was current or if any OpenGL-related errors occurred
   */
  public void setTexParameterfv(int parameterName, float[] params, int params_offset) {
    bind();
    GL gl = GLU.getCurrentGL();
    gl.glTexParameterfv(target, parameterName, params, params_offset);
  }

  /**
   * Sets the OpenGL integer texture parameter for the texture's target. This gives control over
   * parameters such as GL_TEXTURE_WRAP_S and GL_TEXTURE_WRAP_T, which by default are set to
   * GL_CLAMP_TO_EDGE if OpenGL 1.2 is supported on the current platform and GL_CLAMP if not. Causes
   * this texture to be bound to the current texture state.
   *
   * @throws GLException if no OpenGL context was current or if any OpenGL-related errors occurred
   */
  public void setTexParameteri(int parameterName, int value) {
    bind();
    GL gl = GLU.getCurrentGL();
    gl.glTexParameteri(target, parameterName, value);
  }

  /**
   * Sets the OpenGL multi-integer texture parameter for the texture's target. Causes this texture
   * to be bound to the current texture state.
   *
   * @throws GLException if no OpenGL context was current or if any OpenGL-related errors occurred
   */
  public void setTexParameteriv(int parameterName, IntBuffer params) {
    bind();
    GL gl = GLU.getCurrentGL();
    gl.glTexParameteriv(target, parameterName, params);
  }

  /**
   * Sets the OpenGL multi-integer texture parameter for the texture's target. Causes this texture
   * to be bound to the current texture state.
   *
   * @throws GLException if no OpenGL context was current or if any OpenGL-related errors occurred
   */
  public void setTexParameteriv(int parameterName, int[] params, int params_offset) {
    bind();
    GL gl = GLU.getCurrentGL();
    gl.glTexParameteriv(target, parameterName, params, params_offset);
  }

  /**
   * Returns the underlying OpenGL texture object for this texture. Most applications will not need
   * to access this, since it is handled automatically by the bind() and dispose() APIs.
   */
  public int getTextureObject() {
    return texID;
  }

  /**
   * Returns an estimate of the amount of texture memory in bytes this Texture consumes. It should
   * only be treated as an estimate; most applications should not need to query this but instead let
   * the OpenGL implementation page textures in and out as necessary.
   */
  public int getEstimatedMemorySize() {
    return estimatedMemorySize;
  }

  /**
   * Indicates whether this Texture is using automatic mipmap generation (via the OpenGL texture
   * parameter GL_GENERATE_MIPMAP). This will automatically be used when mipmapping is requested via
   * the TextureData and either OpenGL 1.4 or the GL_SGIS_generate_mipmap extension is available. If
   * so, updates to the base image (mipmap level 0) will automatically propagate down to the lower
   * mipmap levels. Manual updates of the mipmap data at these lower levels will be ignored.
   */
  public boolean isUsingAutoMipmapGeneration() {
    return usingAutoMipmapGeneration;
  }

  // ----------------------------------------------------------------------
  // Internals only below this point
  //

  /**
   * Returns true if the given value is a power of two.
   *
   * @return true if the given value is a power of two, false otherwise
   */
  private static boolean isPowerOfTwo(int val) {
    return ((val & (val - 1)) == 0);
  }

  /**
   * Returns the nearest power of two that is larger than the given value. If the given value is
   * already a power of two, this method will simply return that value.
   *
   * @param val the value
   * @return the next power of two
   */
  private static int nextPowerOfTwo(int val) {
    int ret = 1;
    while (ret < val) {
      ret <<= 1;
    }
    return ret;
  }

  /** Updates the actual image dimensions; usually only called from <code>updateImage</code>. */
  private void setImageSize(int width, int height, int target) {
    imgWidth = width;
    imgHeight = height;
    if (target == GL.GL_TEXTURE_RECTANGLE_ARB) {
      if (mustFlipVertically) {
        coords = new TextureCoords(0, imgHeight, imgWidth, 0);
      } else {
        coords = new TextureCoords(0, 0, imgWidth, imgHeight);
      }
    } else {
      if (mustFlipVertically) {
        coords =
            new TextureCoords(
                0, (float) imgHeight / (float) texHeight, (float) imgWidth / (float) texWidth, 0);
      } else {
        coords =
            new TextureCoords(
                0, 0, (float) imgWidth / (float) texWidth, (float) imgHeight / (float) texHeight);
      }
    }
  }

  private void updateSubImageImpl(
      TextureData data,
      int newTarget,
      int mipmapLevel,
      int dstx,
      int dsty,
      int srcx,
      int srcy,
      int width,
      int height)
      throws GLException {
    GL gl = GLU.getCurrentGL();
    data.setHaveEXTABGR(gl.isExtensionAvailable("GL_EXT_abgr"));
    data.setHaveGL12(gl.isExtensionAvailable("GL_VERSION_1_2"));

    Buffer buffer = data.getBuffer();
    if (buffer == null && data.getMipmapData() == null) {
      // Assume user just wanted to get the Texture object allocated
      return;
    }

    int rowlen = data.getRowLength();
    int dataWidth = data.getWidth();
    int dataHeight = data.getHeight();
    if (data.getMipmapData() != null) {
      // Compute the width, height and row length at the specified mipmap level
      // Note we do not support specification of the row length for
      // mipmapped textures at this point
      for (int i = 0; i < mipmapLevel; i++) {
        width = Math.max(width / 2, 1);
        height = Math.max(height / 2, 1);

        dataWidth = Math.max(dataWidth / 2, 1);
        dataHeight = Math.max(dataHeight / 2, 1);
      }
      rowlen = 0;
      buffer = data.getMipmapData()[mipmapLevel];
    }

    // Clip incoming rectangles to what is available both on this
    // texture and in the incoming TextureData
    if (srcx < 0) {
      width += srcx;
      srcx = 0;
    }
    if (srcy < 0) {
      height += srcy;
      srcy = 0;
    }
    // NOTE: not sure whether the following two are the correct thing to do
    if (dstx < 0) {
      width += dstx;
      dstx = 0;
    }
    if (dsty < 0) {
      height += dsty;
      dsty = 0;
    }

    if (srcx + width > dataWidth) {
      width = dataWidth - srcx;
    }
    if (srcy + height > dataHeight) {
      height = dataHeight - srcy;
    }
    if (dstx + width > texWidth) {
      width = texWidth - dstx;
    }
    if (dsty + height > texHeight) {
      height = texHeight - dsty;
    }

    checkCompressedTextureExtensions(data);

    if (data.isDataCompressed()) {
      gl.glCompressedTexSubImage2D(
          newTarget,
          mipmapLevel,
          dstx,
          dsty,
          width,
          height,
          data.getInternalFormat(),
          buffer.remaining(),
          buffer);
    } else {
      int[] align = new int[1];
      int[] rowLength = new int[1];
      int[] skipRows = new int[1];
      int[] skipPixels = new int[1];
      gl.glGetIntegerv(GL.GL_UNPACK_ALIGNMENT, align, 0); // save alignment
      gl.glGetIntegerv(GL.GL_UNPACK_ROW_LENGTH, rowLength, 0); // save row length
      gl.glGetIntegerv(GL.GL_UNPACK_SKIP_ROWS, skipRows, 0); // save skipped rows
      gl.glGetIntegerv(GL.GL_UNPACK_SKIP_PIXELS, skipPixels, 0); // save skipped pixels
      gl.glPixelStorei(GL.GL_UNPACK_ALIGNMENT, data.getAlignment());
      if (DEBUG && VERBOSE) {
        System.out.println("Row length  = " + rowlen);
        System.out.println("skip pixels = " + srcx);
        System.out.println("skip rows   = " + srcy);
        System.out.println("dstx        = " + dstx);
        System.out.println("dsty        = " + dsty);
        System.out.println("width       = " + width);
        System.out.println("height      = " + height);
      }
      gl.glPixelStorei(GL.GL_UNPACK_ROW_LENGTH, rowlen);
      gl.glPixelStorei(GL.GL_UNPACK_SKIP_ROWS, srcy);
      gl.glPixelStorei(GL.GL_UNPACK_SKIP_PIXELS, srcx);

      gl.glTexSubImage2D(
          newTarget,
          mipmapLevel,
          dstx,
          dsty,
          width,
          height,
          data.getPixelFormat(),
          data.getPixelType(),
          buffer);
      gl.glPixelStorei(GL.GL_UNPACK_ALIGNMENT, align[0]); // restore alignment
      gl.glPixelStorei(GL.GL_UNPACK_ROW_LENGTH, rowLength[0]); // restore row length
      gl.glPixelStorei(GL.GL_UNPACK_SKIP_ROWS, skipRows[0]); // restore skipped rows
      gl.glPixelStorei(GL.GL_UNPACK_SKIP_PIXELS, skipPixels[0]); // restore skipped pixels
    }
  }

  private void checkCompressedTextureExtensions(TextureData data) {
    GL gl = GLU.getCurrentGL();
    if (data.isDataCompressed()) {
      switch (data.getInternalFormat()) {
        case GL.GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
        case GL.GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
        case GL.GL_COMPRESSED_RGBA_S3TC_DXT3_EXT:
        case GL.GL_COMPRESSED_RGBA_S3TC_DXT5_EXT:
          if (!gl.isExtensionAvailable("GL_EXT_texture_compression_s3tc")
              && !gl.isExtensionAvailable("GL_NV_texture_compression_vtc")) {
            throw new GLException("DXTn compressed textures not supported by this graphics card");
          }
          break;
        default:
          // FIXME: should test availability of more texture
          // compression extensions here
          break;
      }
    }
  }

  /**
   * Creates a new texture ID.
   *
   * @param gl the GL object associated with the current OpenGL context
   * @return a new texture ID
   */
  private static int createTextureID(GL gl) {
    int[] tmp = new int[1];
    gl.glGenTextures(1, tmp, 0);
    return tmp[0];
  }

  // Helper routines for disabling certain codepaths
  private static boolean haveNPOT(GL gl) {
    return (!disableNPOT && gl.isExtensionAvailable("GL_ARB_texture_non_power_of_two"));
  }

  private static boolean haveTexRect(GL gl) {
    return (!disableTexRect
        && TextureIO.isTexRectEnabled()
        && gl.isExtensionAvailable("GL_ARB_texture_rectangle"));
  }
}
public class WindowsOnscreenGLDrawable extends WindowsGLDrawable {
  public static final int LOCK_SURFACE_NOT_READY = 1;
  public static final int LOCK_SURFACE_CHANGED = 2;
  public static final int LOCK_SUCCESS = 3;

  protected Component component;

  // Variables for lockSurface/unlockSurface
  private JAWT_DrawingSurface ds;
  private JAWT_DrawingSurfaceInfo dsi;
  private JAWT_Win32DrawingSurfaceInfo win32dsi;

  // Indicates whether the component (if an onscreen context) has been
  // realized. Plausibly, before the component is realized the JAWT
  // should return an error or NULL object from some of its
  // operations; this appears to be the case on Win32 but is not true
  // at least with Sun's current X11 implementation (1.4.x), which
  // crashes with no other error reported if the DrawingSurfaceInfo is
  // fetched from a locked DrawingSurface during the validation as a
  // result of calling show() on the main thread. To work around this
  // we prevent any JAWT or OpenGL operations from being done until
  // addNotify() is called on the component.
  protected boolean realized;

  private static final boolean PROFILING = Debug.debug("WindowsOnscreenGLDrawable.profiling");
  private static final int PROFILING_TICKS = 200;
  private int profilingLockSurfaceTicks;
  private long profilingLockSurfaceTime;
  private int profilingUnlockSurfaceTicks;
  private long profilingUnlockSurfaceTime;
  private int profilingSwapBuffersTicks;
  private long profilingSwapBuffersTime;

  // Workaround for problems on Intel 82855 cards
  private int setPixelFormatFailCount;
  private static final int MAX_SET_PIXEL_FORMAT_FAIL_COUNT = 5;

  public WindowsOnscreenGLDrawable(
      Component component, GLCapabilities capabilities, GLCapabilitiesChooser chooser) {
    super(capabilities, chooser);
    this.component = component;
  }

  public GLContext createContext(GLContext shareWith) {
    return new WindowsOnscreenGLContext(this, shareWith);
  }

  public void setRealized(boolean realized) {
    this.realized = realized;
    if (!realized) {
      // Assume heavyweight widget was destroyed
      setChosenGLCapabilities(null);
      pixelFormatChosen = false;
    }
  }

  public void setSize(int width, int height) {
    component.setSize(width, height);
  }

  public int getWidth() {
    return component.getWidth();
  }

  public int getHeight() {
    return component.getHeight();
  }

  public void swapBuffers() throws GLException {
    boolean didLock = false;

    if (hdc == 0) {
      if (lockSurface() == LOCK_SURFACE_NOT_READY) {
        return;
      }
      didLock = true;
    }

    long startTime = 0;
    if (PROFILING) {
      startTime = System.currentTimeMillis();
    }

    if (!WGL.SwapBuffers(hdc) && (WGL.GetLastError() != 0)) {
      throw new GLException("Error swapping buffers");
    }

    if (PROFILING) {
      long endTime = System.currentTimeMillis();
      profilingSwapBuffersTime += (endTime - startTime);
      int ticks = PROFILING_TICKS;
      if (++profilingSwapBuffersTicks == ticks) {
        System.err.println(
            "SwapBuffers calls: "
                + profilingSwapBuffersTime
                + " ms / "
                + ticks
                + "  calls ("
                + ((float) profilingSwapBuffersTime / (float) ticks)
                + " ms/call)");
        profilingSwapBuffersTime = 0;
        profilingSwapBuffersTicks = 0;
      }
    }

    if (didLock) {
      unlockSurface();
    }
  }

  public int lockSurface() throws GLException {
    if (!realized) {
      return LOCK_SURFACE_NOT_READY;
    }
    if (hdc != 0) {
      throw new GLException("Surface already locked");
    }
    long startTime = 0;
    if (PROFILING) {
      startTime = System.currentTimeMillis();
    }
    ds = JAWT.getJAWT().GetDrawingSurface(component);
    if (ds == null) {
      // Widget not yet realized
      return LOCK_SURFACE_NOT_READY;
    }
    int res = ds.Lock();
    if ((res & JAWTFactory.JAWT_LOCK_ERROR) != 0) {
      throw new GLException("Unable to lock surface");
    }
    // See whether the surface changed and if so destroy the old
    // OpenGL context so it will be recreated (NOTE: removeNotify
    // should handle this case, but it may be possible that race
    // conditions can cause this code to be triggered -- should test
    // more)
    int ret = LOCK_SUCCESS;
    if ((res & JAWTFactory.JAWT_LOCK_SURFACE_CHANGED) != 0) {
      ret = LOCK_SURFACE_CHANGED;
    }
    dsi = ds.GetDrawingSurfaceInfo();
    if (dsi == null) {
      // Widget not yet realized
      ds.Unlock();
      JAWT.getJAWT().FreeDrawingSurface(ds);
      ds = null;
      return LOCK_SURFACE_NOT_READY;
    }
    win32dsi = (JAWT_Win32DrawingSurfaceInfo) dsi.platformInfo();
    hdc = win32dsi.hdc();
    if (hdc == 0) {
      // Widget not yet realized
      ds.FreeDrawingSurfaceInfo(dsi);
      ds.Unlock();
      JAWT.getJAWT().FreeDrawingSurface(ds);
      ds = null;
      dsi = null;
      win32dsi = null;
      return LOCK_SURFACE_NOT_READY;
    }
    if (!pixelFormatChosen) {
      try {
        choosePixelFormat(true);
        setPixelFormatFailCount = 0;
      } catch (RuntimeException e) {
        // Workaround for problems seen on Intel 82855 cards in particular
        // Make it look like the lockSurface() call didn't succeed
        unlockSurface();
        if (e instanceof GLException) {
          if (++setPixelFormatFailCount == MAX_SET_PIXEL_FORMAT_FAIL_COUNT) {
            setPixelFormatFailCount = 0;
            throw e;
          }
          return LOCK_SURFACE_NOT_READY;
        } else {
          // Probably a user error in the GLCapabilitiesChooser or similar.
          // Don't propagate non-GLExceptions out because calling code
          // expects to catch only that exception type
          throw new GLException(e);
        }
      }
    }
    if (PROFILING) {
      long endTime = System.currentTimeMillis();
      profilingLockSurfaceTime += (endTime - startTime);
      int ticks = PROFILING_TICKS;
      if (++profilingLockSurfaceTicks == ticks) {
        System.err.println(
            "LockSurface calls: "
                + profilingLockSurfaceTime
                + " ms / "
                + ticks
                + " calls ("
                + ((float) profilingLockSurfaceTime / (float) ticks)
                + " ms/call)");
        profilingLockSurfaceTime = 0;
        profilingLockSurfaceTicks = 0;
      }
    }
    return ret;
  }

  public void unlockSurface() {
    if (hdc == 0) {
      throw new GLException("Surface already unlocked");
    }
    long startTime = 0;
    if (PROFILING) {
      startTime = System.currentTimeMillis();
    }
    ds.FreeDrawingSurfaceInfo(dsi);
    ds.Unlock();
    JAWT.getJAWT().FreeDrawingSurface(ds);
    ds = null;
    dsi = null;
    win32dsi = null;
    hdc = 0;
    if (PROFILING) {
      long endTime = System.currentTimeMillis();
      profilingUnlockSurfaceTime += (endTime - startTime);
      int ticks = PROFILING_TICKS;
      if (++profilingUnlockSurfaceTicks == ticks) {
        System.err.println(
            "UnlockSurface calls: "
                + profilingUnlockSurfaceTime
                + " ms / "
                + ticks
                + " calls ("
                + ((float) profilingUnlockSurfaceTime / (float) ticks)
                + " ms/call)");
        profilingUnlockSurfaceTime = 0;
        profilingUnlockSurfaceTicks = 0;
      }
    }
  }
}
public class MacOSXAWTCGLGraphicsConfigurationFactory extends GraphicsConfigurationFactory {
  protected static final boolean DEBUG = com.sun.opengl.impl.Debug.debug("GraphicsConfiguration");

  public MacOSXAWTCGLGraphicsConfigurationFactory() {
    GraphicsConfigurationFactory.registerFactory(
        javax.media.nativewindow.awt.AWTGraphicsDevice.class, this);
  }

  public AbstractGraphicsConfiguration chooseGraphicsConfiguration(
      Capabilities capabilities, CapabilitiesChooser chooser, AbstractGraphicsScreen absScreen) {
    GraphicsDevice device = null;
    if (absScreen != null && !(absScreen instanceof AWTGraphicsScreen)) {
      throw new IllegalArgumentException(
          "This GraphicsConfigurationFactory accepts only AWTGraphicsScreen objects");
    }

    if (null == absScreen) {
      absScreen = AWTGraphicsScreen.createScreenDevice(-1);
    }
    AWTGraphicsScreen awtScreen = (AWTGraphicsScreen) absScreen;
    device = ((AWTGraphicsDevice) awtScreen.getDevice()).getGraphicsDevice();

    if (capabilities != null && !(capabilities instanceof GLCapabilities)) {
      throw new IllegalArgumentException(
          "This GraphicsConfigurationFactory accepts only GLCapabilities objects");
    }

    if (chooser != null && !(chooser instanceof GLCapabilitiesChooser)) {
      throw new IllegalArgumentException(
          "This GraphicsConfigurationFactory accepts only GLCapabilitiesChooser objects");
    }

    if (DEBUG) {
      System.err.println("MacOSXAWTCGLGraphicsConfigurationFactory: got " + absScreen);
    }

    long displayHandle = 0;

    MacOSXGraphicsDevice macDevice = new MacOSXGraphicsDevice();
    DefaultGraphicsScreen macScreen = new DefaultGraphicsScreen(macDevice, awtScreen.getIndex());
    if (DEBUG) {
      System.err.println("MacOSXAWTCGLGraphicsConfigurationFactory: made " + macScreen);
    }

    GraphicsConfiguration gc = device.getDefaultConfiguration();
    AWTGraphicsConfiguration.setupCapabilitiesRGBABits(capabilities, gc);
    if (DEBUG) {
      System.err.println("AWT Colormodel compatible: " + capabilities);
    }

    MacOSXCGLGraphicsConfiguration macConfig =
        (MacOSXCGLGraphicsConfiguration)
            GraphicsConfigurationFactory.getFactory(macDevice)
                .chooseGraphicsConfiguration(capabilities, chooser, macScreen);

    if (macConfig == null) {
      throw new GLException(
          "Unable to choose a GraphicsConfiguration: "
              + capabilities
              + ",\n\t"
              + chooser
              + "\n\t"
              + macScreen);
    }

    // FIXME: we have nothing to match .. so choose the default
    return new AWTGraphicsConfiguration(
        awtScreen,
        macConfig.getChosenCapabilities(),
        macConfig.getRequestedCapabilities(),
        gc,
        macConfig);
  }
}
/**
 * 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:
 *
 * <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.
 *   <LI>If a valid windowSystemRecommendedChoice parameter is supplied, chooses that instead of
 *       using the cross-platform code.
 * </UL>
 */
public class DefaultGLCapabilitiesChooser implements GLCapabilitiesChooser {
  private static final boolean DEBUG = Debug.debug("CapabilitiesChooser");

  public int chooseCapabilities(
      Capabilities desired, Capabilities[] available, int windowSystemRecommendedChoice) {
    GLCapabilities _desired = (GLCapabilities) desired;
    GLCapabilities[] _available = (GLCapabilities[]) available;

    if (DEBUG) {
      System.err.println("Desired: " + _desired);
      for (int i = 0; i < _available.length; i++) {
        System.err.println("Available " + i + ": " + _available[i]);
      }
      System.err.println("Window system's recommended choice: " + windowSystemRecommendedChoice);
    }

    if (windowSystemRecommendedChoice >= 0
        && windowSystemRecommendedChoice < _available.length
        && _available[windowSystemRecommendedChoice] != null) {
      if (DEBUG) {
        System.err.println(
            "Choosing window system's recommended choice of " + windowSystemRecommendedChoice);
        System.err.println(_available[windowSystemRecommendedChoice]);
      }
      return windowSystemRecommendedChoice;
    }

    // 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.isOnscreen() != cur.isOnscreen()) {
        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 NativeWindowException("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;
  }
}