Users may want to increase the font size on the app screens for better readability. Except for the captions and text on images, users should be able to resize the text up to 200% without loss of content or functionality and without the use of assistive technologies.
Both Android and IOS provides means for the users to increase the font-size through the accessibility features in the settings. Upon the use of such features, content authors should make sure that the content or functionality is not lost on the screen. It’s also required to ensure that no attributes or controls in the code should restrict font resizing.
How to allow font resize
There may be different ways of allowing the content to be resized or to avoid font resize. Here is one of those ways.
<?xml version=”1.0″ encoding=”utf-8″?><TextView
To support the auto font size on the apps, content authors should use scaled fonts. Scaled fonts can either be created from system fonts or for custom fonts.
To provide a dynamic size to a system font while using the interface builder, select the text style from the font drop down, then mark the Dynamic Type option Automatically adjust font.
Content authors can also do this from the source code by using preferred font method. Assign this UI font method to the user interface elements such as labels, text fields and text views. Next, set the adjustsFontForContentSizeCategory property on the text control to true. This tells the text control that it should adjust the text size based on the Dynamic Type setting provided by user.
label.font = UIFont.preferredFont(forTextStyle: .body)
label.adjustsFontForContentSizeCategory = true
The above two processes will only allow the font resize for the system fonts, They do not have control on the custom fonts. Look at the information from Apple IOS guidance for additional information on dynamic font style for custom font.
WCAG Success criteria
1.4.4 Resize text (Level AA)