Extending MATLAB uicontrol - oop

Question

I'd like to customize some of the MATLAB uicontrols (such as the drop-down box) to give them more user-friendly functionality.
My question is: Is it possible to extend/inherit the uicontrol? If so, how do you do it? If not, is there a workaround?
I have tried this basic code just to get it setup, but I receive the following error:
The specified super-class 'uicontrol' contains a parse error or cannot be found on
MATLAB's search path, possibly shadowed by another file with the same name.
classdef ComboBox < uicontrol
methods(Access = public)
function obj = ComboBox()
set(obj, 'Style', 'popup');
end
end
end
The error occurs when I try to add it to a figure:
cmb = ComboBox();
set(cmb, 'Parent', obj.ui_figure);
Edit: After thinking about it, I think this would be a decent workaround, however, I'd still like to know how to extend uicontrol if it's possible.
classdef ComboBox < uicontrol
properties(Access = public)
Control;
end
methods(Access = public)
function obj = ComboBox(parent, items)
obj.Control = uicontrol();
set(obj.Control, 'Style', 'popup');
set(obj.Control, 'Parent', parent);
set(obj.Control, 'String', items);
end
end
end

Answer 1

There is no documented way (as of R2013a) to write subclasses to MATLAB Handle Graphics
classes. In fact, because of the way MATLAB stores the hg objects, we can't even get
the class of an hg object easily. For example:
>> fig = figure();
>> class(f)
ans =
double
>> isa(f, 'figure')
ans =
0
>> ishghandle(f)
ans =
1
One solution to this is to write a class which subclasses either handle, or
hgsetget, and keeps a handle to a uicontrol object as a private property.
For example:
classdef ComboBox < hgsetget
properties (Access = private)
Control
end
properties
% extend the functionality of your new uicontrol with additional
% properties
newProp1
newProp2
end
properties (Dependent = true)
% make any properties of uicontrol for which you want to still
% allow access as dependent properties. define set and get methods
% for these properties below
fontSize
foregroundColor
backgroundColor
items
end
methods
function obj = ComboBox(parent, items)
obj.Control = uicontrol(parent, 'Style', 'popup', ...
'String', items);
% make sure to delete this object if you delete the uicontrol
set(obj.Control, 'DeleteFcn', {#(source, eventData)delete(obj)})
end
% Define set and get methods for your new properties. These methods
% will set the actual properties, and then modify the uicontrol in
% some way
function prop = get.newProp1(obj)
prop = obj.newProp1;
end
function set.newProp1(obj, newVal)
obj.newProp1 = newVal;
% do something else
end
function prop = get.newProp2(obj)
prop = obj.newProp2;
end
function set.newProp2(obj, newVal)
obj.newProp2 = newVal;
% do something else
end
% Define set and get methods for any uicontrol properties you wish
% to retain. These methods will simply redirect calls to the
% uicontrol object.
function size = get.fontSize(obj)
size = get(obj.Control, 'FontSize');
end
function set.fontSize(obj, newSize)
set(obj.Control, 'FontSize', newSize);
end
function color = get.backgroundColor(obj)
color = get(obj.Control, 'BackgroundColor');
end
function set.backgroundColor(obj, newColor)
set(obj.Control, 'BackgroundColor', newColor);
end
function color = get.foregroundColor(obj)
color = get(obj.Control, 'ForegroundColor');
end
function set.foregroundColor(obj, newColor)
set(obj.Control, 'ForegroundColor', newColor);
end
% You can even rename some uicontrol properties to fit your
% purpose.
function items = get.items(obj)
items = get(obj.Control, 'String');
end
function set.items(obj, newItems)
set(obj.Control, 'String', newItems);
end
end
end
You can then use the ComboBox as you would any other uicontrol handle:
obj = ComboBox(figure, 'hello|goodbye');
set(obj, 'items', 'newItem1|newItem2');
There are undocumented ways of extending handle graphics classes,
but I'm not familiar with them. Check out this reference:
http://undocumentedmatlab.com/blog/introduction-to-udd/