With CSS Styling you can style your WebUI app any way you like. This flexibility does have a drawback though: it (obviously) requires CSS knowledge and you have to know quite some details about the DOM-tree that AIMMS is using for displaying WebUI apps, in order to target specific parts of the WebUI for styling. With theming we offer you a different way of styling your app. It requires less detailed knowledge than regular CSS styling, while still offering a way to make your apps look the way you want in most cases. Should you still require some additional tweaking after theming your app, you can just use the regular CSS styling side-by-side with it.

How To Use Theming

Setting up WebUI theming is quite straightforward. It requires just one .css file in the


subfolder of your AIMMS project. You can name this file as you like. It should contain a series of themable properties, which you can assign your own values. These properties are listed in logical groups in the base-theme-<AIMMS version>.css file, which you can use as a base for your work. It is located in a subfolder of the AIMMS installation folder:

C:\Users\<your name>\AppData\Local\AIMMS\IFA\Aimms\<your AIMMS version>\WebUIDev\www\resources\css

Each group and property is commented, to give you an idea for which part of the WebUI you can influence the appearance by changing its value.

On side-note: a pretty large section of that file is aimed at providing a Data Color palette for widgets that can show annotated data, like Charts. If you’re interested in exploring your options there, please read Data Coloring and Palettes too.

The values assigned in this base file are the values that are used by default in the WebUI AIMMS theme. Please note that in your .css file, you do not have to specify properties from the base file which you do not want to change. This will also make sure that you will benefit from the effect of potential future updates to the default values in the base file.

An Example

As an example of the usage of theming, suppose that you would like to change the background color of your WebUI app and the coloring of the buttons. In the default AIMMS theming, part of an app could look like this:


To accomplish the change, you should create a file (let’s call it yellow_theme.css) in the subfolder mentioned above. In the file, it requires just these lines:

:root {
/* Global app properties */
--color_bg_app-canvas: yellow;

/* Button properties */
--color_text_button_primary: #0768a9;
--color_bg_button_primary: #ffcc00;

to change the appearance of the app fragment into this:


As you see, it is a matter of selecting the right properties for your theming wishes and assigning them the right values to get the effect that you are after. For these values, you are not restricted to ‘simple’ values, like the color names/numbers above. It is perfectly possible to use, for example, the CSS-function linear-gradient(). This .css file:

:root {
/* Global app properties */
--color_bg_app-canvas: linear-gradient(
    to bottom right,
    #ffffff 0%,
    #0768a9 100%

/* Button properties */
--color_text_button_primary: #0768a9;
--color_bg_button_primary: #ffcc00;

will result in the following WebUI theme:


Obviously, using a function like linear-gradient(), it needs to make sense. That means that it can only be applied to background coloring options, but not to, say, text coloring options.

For borders, for example, by adding a specific border value like this:

--border_button_primary: 4px dotted blue;

the example above will change into the following:


Obviously it is a matter of taste whether you deem these last two examples beautiful, but it does illustrate that with changing just a handful of theming property settings, you can achieve far-reaching effects.

Value Inheritance

Since WebUI theming is based on CSS, it is also possible to use inheritance of property values using CSS’s var function. For example, if you want to color the background of the widget headers the same as the default text, you can write:

--color_bg_widget-header: var(--color_text_default);

Next to this kind of inheritance, it is also possible to ‘inherit’ from the standard AIMMS color palette. In the same folder as the base theme example file, in the global-custom-prop-constants.css file, these colors are listed for your reference. So, for example:

--color_bg_widget-header: var(--COLOR_AIMMS-YELLOW-DARK);

Would display the background of your widget headers in the standard AIMMS dark yellow color.

Moving From Custom CSS/Theming

Many clients have their apps styled using custom CSS. We advise you to move to the new AIMMS Theming, since it offers better maintainability and probably also backward compatibility in the future. The best way to migrate is to put aside all your existing custom CSS files by moving them somewhere outside your project folder, to keep as backup. From this ‘clean’ state, start theming your app as explained above. If, after that, you are not fully satisfied with the result, you can re-visit your previous custom CSS to see whether selected parts of it can be re-used to fill the gap.