RowLayouter.java

/*
 * Copyright (c) 2011, the Dart project authors.
 * 
 * Licensed under the Eclipse Public License v1.0 (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.eclipse.org/legal/epl-v10.html
 * 
 * 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 com.google.dart.tools.ui.internal.util;

import org.eclipse.core.runtime.Assert;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.widgets.Control;

/**
 * Helper class to layout a number of children if the composite uses a <code>GridLayout</code>. If
 * the numbers of widgets to be layouted into one row is smaller than the number of columns defined
 * for the grid layout the helper class assigns a corresponing value to the <code>
 * GridData.horizontalSpan</code> field. Additionally a row layouter manages a default
 * <code>GridData</code> object for each column. If set this grid data is used for the widget if it
 * doesn't manage its own grid data object. Call one of the <code>perform</code> methods to assign
 * the correct grid data objects to a set of widgets according to the number of columns passed to
 * the layouter's constructor.
 */
public class RowLayouter {

  public int spanHorizontalAlignment = -1;
  public int spanGrabExcessHorizontalSpace = -1;
  public int spanHorizontalSpan = -1;
  public int spanHorizontalIndent = -1;
  public int spanWidthHint = -1;

  public int spanVerticalAlignment = -1;
  public int spanGrabExcessVerticalSpace = -1;
  public int spanVerticalSpan = -1;
  public int spanHeightHint = -1;

  private int fNumColumns;
  private boolean fOrder;
  private Control fLastControl;
  private GridData[] fDefaultGridDatas = new GridData[4];

  public RowLayouter(int numColumns) {
    this(numColumns, false);
  }

  public RowLayouter(int numColumns, boolean order) {
    fNumColumns = numColumns;
    fOrder = order;
  }

  public GridData getGridData(int index) {
    if (index > fDefaultGridDatas.length) {
      return null;
    }

    return cloneGridData(fDefaultGridDatas[index]);
  }

  public int numColumns() {
    return fNumColumns;
  }

  public void perform(Control c1) {
    perform(new Control[] {c1}, 0);
  }

  public void perform(Control c1, Control c2, Control c3, int span) {
    perform(new Control[] {c1, c2, c3}, span);
  }

  public void perform(Control c1, Control c2, int span) {
    perform(new Control[] {c1, c2}, span);
  }

  public void perform(Control[] controls, int spanColumn) {
    int numColumns = numColumns();
    Assert.isTrue(controls.length <= numColumns);
    order(controls);
    int gridIndex = 0;
    for (int i = 0; i < controls.length; i++) {
      Control control = controls[i];
      GridData gd = (GridData) control.getLayoutData();
      if (gd == null) {
        gd = getGridData(gridIndex);
      }

      if (i == spanColumn) {
        int span = numColumns - (controls.length - 1);
        gridIndex += span;
        if (gd == null) {
          gd = new GridData();
        }
        applyDelta(gd);
        gd.horizontalSpan = span;
      } else {
        gridIndex++;
      }
      control.setLayoutData(gd);
    }
  }

  public void setDefaultGridData(GridData gd, int index) {
    if (index >= fDefaultGridDatas.length) {
      GridData[] newDatas = new GridData[index + 4];
      System.arraycopy(fDefaultGridDatas, 0, newDatas, 0, fDefaultGridDatas.length);
      fDefaultGridDatas = newDatas;
    }
    fDefaultGridDatas[index] = gd;
  }

  public void setDefaultSpan() {
    spanHorizontalAlignment = GridData.FILL;
    spanGrabExcessHorizontalSpace = 1;
  }

  protected GridData cloneGridData(GridData gd) {
    if (gd == null) {
      return null;
    }

    GridData result = new GridData();
    result.horizontalAlignment = gd.horizontalAlignment;
    result.grabExcessHorizontalSpace = gd.grabExcessHorizontalSpace;
    result.horizontalSpan = gd.horizontalSpan;
    result.horizontalIndent = gd.horizontalIndent;
    result.widthHint = gd.widthHint;

    result.verticalAlignment = gd.verticalAlignment;
    result.grabExcessVerticalSpace = gd.grabExcessVerticalSpace;
    result.verticalSpan = gd.verticalSpan;
    result.heightHint = gd.heightHint;
    return result;
  }

  protected void order(Control[] controls) {
    if (!fOrder) {
      return;
    }

    for (int i = 0; i < controls.length; i++) {
      Control control = controls[i];
      control.moveBelow(fLastControl);
      fLastControl = control;
    }
  }

  private void applyDelta(GridData gd) {
    if (spanHorizontalAlignment != -1) {
      gd.horizontalAlignment = spanHorizontalAlignment;
    }

    if (spanGrabExcessHorizontalSpace != -1) {
      if (spanGrabExcessHorizontalSpace == 0) {
        gd.grabExcessHorizontalSpace = false;
      } else {
        gd.grabExcessHorizontalSpace = true;
      }
    }

    if (spanHorizontalSpan != -1) {
      gd.horizontalSpan = spanHorizontalSpan;
    }

    if (spanHorizontalIndent != -1) {
      gd.horizontalIndent = spanHorizontalIndent;
    }

    if (spanWidthHint != -1) {
      gd.widthHint = spanWidthHint;
    }

    if (spanVerticalAlignment != -1) {
      gd.verticalAlignment = spanVerticalAlignment;
    }

    if (spanGrabExcessVerticalSpace != -1) {
      if (spanGrabExcessVerticalSpace == 0) {
        gd.grabExcessVerticalSpace = false;
      } else {
        gd.grabExcessVerticalSpace = true;
      }
    }

    if (spanVerticalSpan != -1) {
      gd.verticalSpan = spanVerticalSpan;
    }

    if (spanHeightHint != -1) {
      gd.heightHint = spanHeightHint;
    }
  }
}