Question

I am subclassing the Canvas in SWT, and calling pack() inside of the constructor,
the Canvas’ size is computed as 64×64.

There is no Style or layout inside of my class.

• How is the size computed at this here?
• How can I change the size of my class? this.setSize() doesn’t work.

    public MyClass(Composite parent, int style) {
        super(parent, SWT.NONE);
        this.setBackground(getDisplay().getSystemColor(SWT.COLOR_YELLOW));

        this.computeSize(1000, 1000, true);
        this.pack();

        Point s = this.getSize();
        System.out.println(s.x); //prints 64
    }

Answer 1

You don’t give yourself the size : it is given by the layout of the component using your MyClass.

So your canvas should be ready to handle any size.