Java Tutorial/SWT/Layout Basics

A few terms that are used frequently when discussing layouts

1. Client area: the size of the composite"s bounds minus its trim.
2. Margins: the number of pixels placed on an edge of the layout.
3. Spacing: the number of pixels between the edges of children of a composite.
4. Preferred size: best-display size.

Laying Out Children of a Composite

public void layout(boolean changed)

Layouts

A layout can be used to control the position and size of children of a composite. Four standard layouts and one custom layout provided in SWT:

1. FillLayout
2. RowLayout
3. GridLayout
4. FormLayout
5. StackLayout

Layout term: bounds, client area

import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.RowLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
public class LayoutTerm {
  public static void main(String[] args) {
    Display display = new Display();
    Shell shell = new Shell(display);
    System.out.println("Bounds: " + shell.getBounds());
    System.out.println("Client area: " + shell.getClientArea());
    shell.setBackground(display.getSystemColor(SWT.COLOR_WHITE));
    RowLayout rowLayout = new RowLayout();
    shell.setLayout(rowLayout);
    Button button1 = new Button(shell, SWT.PUSH);
    button1.setText("button1");
    Button button2 = new Button(shell, SWT.PUSH);
    button2.setText("button2");
    Button button3 = new Button(shell, SWT.PUSH);
    button3.setText("button33333333333333333333333333333333333333");
    shell.pack();
    shell.open();
    System.out.println("button1: " + button1.getBounds());
    System.out.println("button2: " + button2.getBounds());
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch()) {
        display.sleep();
      }
    }
    display.dispose();
  }
}

Setting Layouts

public Layout getLayout()
    public void setLayout(Layout layout)

By default, a composite does not have any layout.

Using Layout Data Objects to control layout

import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Text;
public class LayoutDataControlLayout {
  public static void main(String[] args) {
    Display display = new Display();
    final Shell shell = new Shell(display);
    shell.setLayout(new GridLayout()); // Only with GridLayout you can use GridData
    Text text = new Text(shell, SWT.SINGLE|SWT.BORDER);
    text.setLayoutData(new GridData(GridData.GRAB_HORIZONTAL));
    
    shell.setSize(450, 100);
    shell.open();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch()) {
        display.sleep();
      }
    }
    display.dispose();
  }
}