| # User interface client |
| |
| Throughout this documentation, a "user interface client" refers to code that |
| creates a graphical user interface and responds to input events, such as mouse, |
| touch, and keyboard. |
| |
| ## A UI is composed with multiple APIs |
| |
| These UI functions are divided between a number of FIDL APIs to serve a |
| broad spectrum of [constituents](/docs/contribute/governance/api_council.md#values); |
| hence there is no single "UI API". Instead, a client implements its UI using |
| the APIs it needs. |
| |
|  |
| |
| Some examples include: |
| * [fuchsia.ui.composition.Flatland](/sdk/fidl/fuchsia.ui.composition/flatland.fidl) for views and graphics |
| * [fuchsia.ui.views.ViewRefFocused](/sdk/fidl/fuchsia.ui.views/view_ref_focused.fidl) |
| and [Focuser](/sdk/fidl/fuchsia.ui.views/focuser.fidl) for view focus management |
| * [fuchsia.ui.pointer](/sdk/fidl/fuchsia.ui.pointer) for mouse and touch |
| * [fuchsia.ui.input3.Keyboard](/sdk/fidl/fuchsia.ui.input3/keyboard.fidl) for keyboard |
| |
| ## A UI client has a View to place graphical content |
| |
| A UI client creates a [view](/docs/glossary#view) in the global view tree, and |
| within that view, presents graphical content to the user via a display. |
| |
| A view is the common unit of UI organization between UI clients on Fuchsia. For |
| example, a view can embed other views in a parent-child relationship, which |
| recursively creates the view tree. At the top, the root view attaches to the |
| display. |
| |
| ## A UI client receives input events and reacts appropriately |
| |
| The Fuchsia platform may send a UI client a sequence of input events initiated |
| by a user. Typically these input events are directed at the UI client's view. A |
| UI client is then responsible for reacting to input events that are directed to |
| its view; for example, it can update its graphical content based on a mouse |
| click event. |
