How to customize App Designer figures in more ways than officially documented?

Question

A recently published article in UndocumentedMatlab, mentions that App Designer figures are actually web pages using the Dojo Toolkit. This means we could theoretica

Answer 1

In order to succeed in this task, we need several things:

• Find where the HTML/CSS are located (so we can manipulate them).
• Find which element of the DOM we want to edit.
• Find what is the change we need to make.
• Find a way to manipulate the element using MATLAB.

---

Working step by step:

1. Find where the figure's HTML/CSS are stored/located

win = struct(struct(struct(app).UIFigure).Controller).Container.CEF;
URL = win.URL; % Needed only for testing in browser

2. Find which element of the DOM we need to edit

data_tag = char(struct(app.ListBox).Controller.ProxyView.PeerNode.getId);

Validation using a browser:

3. Find what is the change we need to make

Since we want to manipulate text alignment, we google some relevant keywords and find the CSS text-align property. Then we try it manually to see if it really works:

4. Find a way to manipulate the element using MATLAB

Using dojo.style and dojo.query:

win.executeJS(['dojo.style(dojo.query("[data-tag^=''' data_tag ''']")[0],"textAlign","center")']);

---

Complete code for this answer:

classdef domDemo < matlab.apps.AppBase

    % Properties that correspond to app components
    properties (Access = public)
        UIFigure     matlab.ui.Figure          % UI Figure
        LabelListBox matlab.ui.control.Label   % List Box
        ListBox      matlab.ui.control.ListBox % Item 1, Item 2, Item 3, It...
    end

    methods (Access = private)

        % Code that executes after component creation
        function startupFcn(app)
          % Customizations (aka "MAGIC GOES HERE"):
          drawnow; rez = [];
          warning off MATLAB:HandleGraphics:ObsoletedProperty:JavaFrame
          warning off MATLAB:structOnObject            
          while ~strcmp(rez,'"center"')
            try                
              % 1. Get a handle to the webwindow:
              win = struct(struct(struct(app).UIFigure).Controller).Container.CEF;
              % 2. Find which element of the DOM we want to edit (as before):
              data_tag = char(struct(app.ListBox).Controller.ProxyView.PeerNode.getId);    
              % 3. Manipulate the DOM via a JS command
              rez = win.executeJS(['dojo.style(dojo.query("[data-tag^=''' ...
                data_tag ''']")[0],"textAlign","center")']);
            catch
              pause(1); % Give the figure (webpage) some more time to load
            end
          end
        end
    end

    % App initialization and construction
    methods (Access = private)

        % Create UIFigure and components
        function createComponents(app)

            % Create UIFigure
            app.UIFigure = uifigure;
            app.UIFigure.Position = [100 100 260 147];
            app.UIFigure.Name = 'UI Figure';
            setAutoResize(app, app.UIFigure, true)

            % Create LabelListBox
            app.LabelListBox = uilabel(app.UIFigure);
            app.LabelListBox.HorizontalAlignment = 'right';
            app.LabelListBox.Position = [50 93 44 15];
            app.LabelListBox.Text = 'List Box';

            % Create ListBox
            app.ListBox = uilistbox(app.UIFigure);
            app.ListBox.Position = [109 36 100 74];

        end
    end

    methods (Access = public)

        % Construct app
        function app = domDemo()

            % Create and configure components
            createComponents(app)

            % Register the app with App Designer
            registerApp(app, app.UIFigure)

            % Execute the startup function
            runStartupFcn(app, @startupFcn)

            if nargout == 0
                clear app
            end
        end

        % Code that executes before app deletion
        function delete(app)

            % Delete UIFigure when app is deleted
            delete(app.UIFigure)
        end
    end
end