Why use layouts?

1.5: Why use layouts?

MATLAB ships with a GUI design tool called GUIDE. This doesn't use layouts, but forces users to manually position each element. This approach is a much faster way to build simple user-interfaces, so why would you want to use layouts?

The over-riding reason for using layouts or layout managers is to gain control of the resizing behaviour of the interface without having to write a complex "ResizeFcn". If you simply position user-interface elements directly (either using GUIDE or programmatically), you have two choices about what happens when the window resizes:

For example:

1. The user-interface components scale with the window (normalised units)
We didn't really want the buttons to grow but everything resizes in proportion.

f = figure( 'Position', 200*ones(1,4) );
axes( 'Parent', f, ...
    'Units', 'Normalized', ...
    'OuterPosition', [0.02 0.2 0.96 0.8] );
uicontrol( 'Parent', f, ...
    'Units', 'Normalized', ...
    'Position', [0.02 0.02 0.46 0.16], ...
    'String', 'Button 1' );
uicontrol( 'Parent', f, ...
    'Units', 'Normalized', ...
    'Position', [0.52 0.02 0.46 0.16], ...
    'String', 'Button 2' );

2. The user-interface components stay fixed and the window resize creates empty space (pixel units)
Although the buttons don't now grow, neither does the axes, which looks very odd.

f = figure( 'Position', 200*ones(1,4) );
axes( 'Parent', f, ...
    'Units', 'Pixels', ...
    'OuterPosition', [10 35 190 175] );
uicontrol( 'Parent', f, ...
    'Units', 'Pixels', ...
    'Position', [5 5 90 25], ...
    'String', 'Button 1' );
uicontrol( 'Parent', f, ...
    'Units', 'Pixels', ...
    'Position', [105 5 90 25], ...
    'String', 'Button 2' );

Neither of these alternatives is particularly useful for a serious user-interface. Typically there are user-interface components that should be fixed size: icons, buttons, selectors etc; and others that should resize with the window: graphs, images, prose text etc. To achieve this one needs to be able to specify which interface components should be fixed size and which variable. Over the last two decades, layouts have been shown to be the method of choice for achieving this.

For example:

Using layouts, some user-interface components scale with the window, others stay fixed

f = figure( 'Position', 200*ones(1,4) );
vbox = uiextras.VBox( 'Parent', f );
axes( 'Parent', vbox );
hbox = uiextras.HButtonBox( 'Parent', vbox, 'Padding', 5 );
uicontrol( 'Parent', hbox, ...
    'String', 'Button 1' );
uicontrol( 'Parent', hbox, ...
    'String', 'Button 2' );
set( vbox, 'Sizes', [-1 35] )