Huawei explains how the palm rejection on the Mate 30 Pro works

The Horizon Display on the Huawei Mate 30 Pro is curved at an 88° angle and covers up a significant portion of the sides of the phone. This obviously brings worries about unwanted touches as you hold the phone, however Huawei VP Li Xiaolong explains that this will not be a problem.

The screen is divided into three areas – the flat surface on the front and two smaller areas on the side. Touches from the side areas are ignored, so the touchscreen will function like a typical flat panel most of the time.

The curved sides of the Horizon Display enable virtual media and game controls

There are some cases when the touch functionality of the side areas is enabled, e.g. for the volume buttons, shoulder buttons for games or a shutter key for the camera. For example, to activate the volume controls, you need to double tap the side. Product Manager Bruce Lee believes that people will get used to this quickly and will find it convenient.

Here’s a video showing the side controls in action:

However, cases for the Mate 30 Pro will need to leave the side of the phone exposed to allow you access to the volume controls. You can see it in these two cases, for example:

The cases for the Huawei Mate 30 Pro leave the side of the screen exposed

Source (in Chinese)