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Developing an Application



Cascading Style Sheets (CSS)

Cascading Style Sheets (CSS) is a language for describing how content is presented. Its purpose is help separating content (HTML) from presentation. OutSystems uses the Silk framework (except for the themes based on London theme) and each theme has its own CSS. You can either add new styles or modify the existing ones by copying them from the base theme.

These elements have their own CSS which you can edit:

  • Themes
  • Web Screens and Emails
  • Web Blocks
  • Widgets (complex widgets have more than one style)

Editing and applying CSS

CSS is edited in Style Sheet Editor. You can open it by double-clicking Style Classes property in Properties Pane when you edit an element that can have CSS. Enter the classes of the widget into Style Classes and they will be applied to the selected element. The styles classes are entered like this:

  • In web applications, without quotes and separated by a space (bold red)
  • In mobile, with quotes and separated by a space ("bold red")

You can also open Style Sheet Editor by clicking the CSS button in the Main Editor toolbar. Select the tab with the application name and define or edit the style to make it available to the whole application. Alternatively, select the tab with the name of the currently selected screen or block to narrow the scope of the style to that screen or block.

CSS specificity

Not all styles have the same priority. Use the order Service Studio imports the style sheets to calculate how browsers will apply your styles. Note that inline styles can be used as well.

  1. System style sheet for Container widgets in the Grid
  2. Web Blocks style sheet
  3. Theme style sheet, which also includes a base theme (if specified)
  4. Web Screens or Emails style sheet
  5. Theme extra style sheet, with the Grid settings defined in the Theme properties

Inline CSS

If you must use the inline CSS you can create it by adding style in the Extended Properties and then entering the CSS rules (for example, "background-color: green;")

ID attribute and classes

You can specify id and classes of the HTML element in the Properties Pane. Enter your classes without quotes and separated by a space.

  • The Name field corresponds to the id attribute of the element.
  • The Style Classes field correspond to class attribute of the element.

OutSystems Grid

OutSystems uses a high-level grid system. If you specify the number of columns in the Theme grid settings, the width of elements can be expressed in columns. In some properties (for example, Margin Top), Service Studio converts auto to Auto. The Auto indicates the values are calculated automatically.

Importing CSS

Use the @import CSS at-rule in Style Sheet Editor to import style rules from other locations.

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