mirror of
https://gitlab.freedesktop.org/wlroots/wlroots.git
synced 2024-11-28 18:12:30 +00:00
87 lines
3.5 KiB
Markdown
87 lines
3.5 KiB
Markdown
# Architecture
|
|
|
|
This document describes the high-level design of wlroots. wlroots is modular:
|
|
each module can be used mostly independently from the rest of wlroots. For
|
|
instance, some wlroots-based compositors only use its backends, some only use
|
|
its protocol implementations.
|
|
|
|
## Backends
|
|
|
|
Backends are responsible for exposing input devices and output devices.
|
|
wlroots provides DRM and libinput backends to directly drive physical
|
|
devices, Wayland and X11 backends to run nested inside another compositor,
|
|
and a headless backend. A special "multi" backend is used to combine together
|
|
multiple backends, for instance DRM and libinput. Compositors can also
|
|
implement their own custom backends if they have special needs.
|
|
|
|
Input devices such as pointers, keyboards, touch screens, tablets, switches
|
|
are supported. They emit input events (e.g. a keyboard key is pressed) which
|
|
compositors can handle and forward to Wayland clients.
|
|
|
|
Output devices are tasked with presenting buffers to the user. They also
|
|
provide feedback, for instance presentation timestamps. Some backends support
|
|
more advanced functionality, such as displaying multiple buffers (e.g. for the
|
|
cursor image) or basic 2D transformations (e.g. rotation, clipping, scaling).
|
|
|
|
## Renderers
|
|
|
|
Renderers provide utilities to import buffers submitted by Wayland clients,
|
|
and a basic 2D drawing API suitable for simple compositors. wlroots provides
|
|
renderer implementations based on OpenGL ES 2, Vulkan and Pixman. Just like
|
|
backends, compositors can implement their own renderers, or use the graphics
|
|
APIs directly.
|
|
|
|
To draw an image onto a buffer, compositors will first need to create a
|
|
texture, representing a source of pixels the renderer can sample from. This can
|
|
be done either by uploading pixels from CPU memory, or by importing already
|
|
existing GPU memory via DMA-BUFs. Compositors can then create a render pass
|
|
and submit drawing operations. Once they are done drawing, compositors can
|
|
submit the rendered buffer to an output.
|
|
|
|
## Protocol implementations
|
|
|
|
A number of Wayland interface implementations are provided.
|
|
|
|
### Plumbing protocols
|
|
|
|
wlroots ships unopinionated implementations of core plumbing interfaces, for
|
|
instance:
|
|
|
|
- `wl_compositor` and `wl_surface`
|
|
- `wl_seat` and all input-related interfaces
|
|
- Buffer factories such as `wl_shm` and linux-dmabuf
|
|
- Additional protocols such as viewporter and presentation-time
|
|
|
|
### Shells
|
|
|
|
Shells give a meaning to surfaces. There are many kinds of surfaces:
|
|
application windows, tooltips, right-click menus, desktop panels, wallpapers,
|
|
lock screens, on-screen keyboards, and so on. Each of these use-cases is
|
|
fulfilled with a shell. wlroots supports xdg-shell for regular windows and
|
|
popups, Xwayland for interoperability with X11 applications, layer-shell for
|
|
desktop UI elements, and more.
|
|
|
|
### Other protocols
|
|
|
|
Many other protocol implementations are included, for instance:
|
|
|
|
- xdg-activation for raising application windows
|
|
- idle-inhibit for preventing the screen from blanking when the user is
|
|
watching a video
|
|
- ext-idle-notify for notifying when the user is idle
|
|
|
|
## Helpers
|
|
|
|
wlroots provides additional helpers which can make it easier for compositors to
|
|
tie everything together:
|
|
|
|
- `wlr_output_layout` organises output devices in the physical space
|
|
- `wlr_cursor` stores the current position and image of the cursor
|
|
- `wlr_scene` provides a declarative way to display surfaces
|
|
|
|
## tinywl
|
|
|
|
tinywl is a minimal wlroots compositor. It implements basic stacking window
|
|
management and only supports xdg-shell. It's extensively commented and is a
|
|
good learning resource for developers new to wlroots.
|