GL2Transformhelper.java

/*
 * Copyright 2015 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.geom.AffineTransform;

import com.jogamp.opengl.GL;
import com.jogamp.opengl.GL2;
import com.jogamp.opengl.fixedfunc.GLMatrixFunc;

import org.jogamp.glg2d.GLGraphics2D;
import org.jogamp.glg2d.impl.AbstractMatrixHelper;

public class GL2Transformhelper extends AbstractMatrixHelper {
  protected GL2 gl;

  private float[] matrixBuf = new float[16];

  @Override
  public void setG2D(GLGraphics2D g2d) {
    super.setG2D(g2d);
    gl = g2d.getGLContext().getGL().getGL2();

    setupGLView();
    flushTransformToOpenGL();
  }

  protected void setupGLView() {
    int[] viewportDimensions = new int[4];
    gl.glGetIntegerv(GL.GL_VIEWPORT, viewportDimensions, 0);
    int width = viewportDimensions[2];
    int height = viewportDimensions[3];

    // setup projection
    gl.glMatrixMode(GLMatrixFunc.GL_PROJECTION);
    gl.glLoadIdentity();
    gl.glOrtho(0, width, 0, height, -1, 1);

    // the MODELVIEW matrix will get adjusted later

    gl.glMatrixMode(GL.GL_TEXTURE);
    gl.glLoadIdentity();
  }

  /**
   * Sends the {@code AffineTransform} that's on top of the stack to the video
   * card.
   */
  protected void flushTransformToOpenGL() {
    float[] matrix = getGLMatrix(stack.peek());

    gl.glMatrixMode(GLMatrixFunc.GL_MODELVIEW);
    gl.glLoadMatrixf(matrix, 0);
  }

  /**
   * Gets the GL matrix for the {@code AffineTransform} with the change of
   * coordinates inlined. Since Java2D uses the upper-left as 0,0 and OpenGL
   * uses the lower-left as 0,0, we have to pre-multiply the matrix before
   * loading it onto the video card.
   */
  protected float[] getGLMatrix(AffineTransform transform) {
    matrixBuf[0] = (float) transform.getScaleX();
    matrixBuf[1] = -(float) transform.getShearY();
    matrixBuf[4] = (float) transform.getShearX();
    matrixBuf[5] = -(float) transform.getScaleY();
    matrixBuf[10] = 1;
    matrixBuf[12] = (float) transform.getTranslateX();
    matrixBuf[13] = g2d.getCanvasHeight() - (float) transform.getTranslateY();
    matrixBuf[15] = 1;

    return matrixBuf;
  }
}