Backgrounds
The deck can show a moving picture or a wallpaper behind its cards. Pages slide over it and translucent cards, such as
the glass theme, show it through. Without a background setting nothing of this exists: no surface,
no frames, no cost.
"background": { "type": "shader", "name": "aurora", "speed": 0.5 }
"background": { "type": "image", "path": "D:/Pictures/wall.jpg" }| Key | For | Meaning |
|---|---|---|
type |
both | shader or image. |
name |
shader | A built-in name, or a folder in backgrounds/ next to the executable. |
speed |
shader | Multiplies time: 2 is twice as fast, 0 stops it. Default 1, from 0 to 10. |
scale |
shader | The resolution it is drawn at, as a fraction of the panel’s. Default 0.5, from 0.1 to 1. |
colors |
shader | One to four colours replacing the theme’s palette. |
path |
image | The picture. |
Any other key is a parameter of that shader. A background that is wrong is logged and the deck shows the theme’s background colour.
Built-in shaders
All four draw with the theme’s palette, so they follow the theme.
| Name | Looks like |
|---|---|
plasma |
slow warped fields of colour |
aurora |
three glowing curtains swaying along the longer side |
gradient |
a soft gradient whose bands drift |
julia |
a Julia set whose constant circles slowly (the heaviest) |
Cost
A moving shader is drawn on the GPU about 30 times a second, at scale times the panel’s size, stretched to fill it. At
the default half size that was about 3% of one CPU core and under 1% of the GPU on the panel UrDeck was made on. If a
shader is too heavy for your GPU, or a game beside the deck stutters, lower scale to 0.25. Frames stop while the deck
is hidden and while Windows has switched the display off. A background that does not move (a picture, speed 0) is drawn
once and costs nothing afterwards.
Your own
A background is a folder backgrounds/<name>/ next to the executable, holding a manifest.json and a shader written in
SkSL, the shading language of Skia. UrDeck ships a command line tool, urdeck-cli, that makes the folder
(shader init), checks it (shader validate) and renders a picture of it (shader render). The manifest has a schema, so
an editor can check it as you type:
{ "$schema": "https://urdeck.app/schemas/v1/shader-manifest.json" }Everything about writing one, the manifest reference and the checks the tool makes is in the backgrounds reference on GitHub.