Crate icon 

Turns out finding icons correctly on linux is kind of hard.

This crate, icon, implements the XDG icon theme specification fully, while (hopefully) giving maximum coverage in usecases without sacrificing speed or compliance.

Quick start

// Find all icon themes using the standard locations.
let icons = icon::Icons::new();

// Find an icon named "firefox" with size 128x128 in theme "Adwaita"
let firefox: Option<icon::IconFile> = icons.find_icon("firefox", 128, 1, "Adwaita");

println!("Firefox icon is at {:?}", firefox.unwrap().path())

See Icons.

Feature flags

By default, no features are enabled.

• log: Enable logging, which introduces a dependency on the log crate.
• cache: Enables the caching versions of Icons and Theme (IconsCache and ThemeCache), which introduces a dependency on qp-trie.

Icon matching

Matching a desired size and scale for an icon to the actual file for that size and scale isn’t as simple as you’d hope for it to be.

Concretely, icon themes organize icons into subdirectories that have a number of properties that specify how the icons in them are allowed to be used:

• Directories can contain scalable graphics (SVGs), and specify a minimum and maximum pixel size at which those graphics may be used. For example, an icon theme may have simplified SVGs for displaying small icons, and more complex SVGs for when the icons are larger.
• In case an odd size is requested, for example 30x30px (a size not present in most icon themes), applications are expected to find the next best match for that size. To accommodate that, icon directories specify the base size of its icons and a threshold wherein applications can choose to up- or downscale icons when an exact match to exist. For example, hicolor’s 32x32 directory specifies a threshold value of 2, meaning icons from 30x30px to 34x34px may be displayed using the 32x32px images.

icon (this crate)’s job is to make finding the correct icon for a given query as simple as possible.

High level design

Finding icons is a multi-stage procedure, and depending on your use case, you might want to stop doing work at any one of them. This crate is laid out to allow you to do exactly that, befitting those who need to find just one icon in one theme but also those who need a reliable cache of many icons for many themes.

In general, the steps are as follows:

1. Finding standalone icons and themes:

   Icons are found either in icon themes or ‘standalone’ (outside a theme) in XDG base directories. While a number of directories should always be scanned for icons, the user or application is allowed to search additional directories as it sees fit.

   IconSearch handles this part, and is also the main entrypoint for icon.

2. Parsing and resolving icon themes:

   Each icon theme lives in a directory in the root of one or more of the “search directories”. The name of its directory is called the theme’s internal name, and in it lies the theme’s definition, index.theme.

   Icon themes also can declare other icon themes from which they inherit. For that reason, we also need to do the additional work of figuring out the inheritance tree of each theme, removing (transitive) duplicates from the inheritance tree, etc.

3. Finding icons:

   Once a full picture of icons and theme ‘graphs’ is obtained, we can start looking up icons.

Alternative crates

• linicon also implements icon finding, but:

  • it does not scan “standalone” icons correctly, such as those usually found in /usr/share/pixmaps.
  • it adopts a one-shot approach, repeating all parsing and file-finding work for each icon.
  • it does not provide support for caching.
  • it does not perform spec-compliant icon matching. (no support for “closest” icon matching, among other problems)

• icon-loader also implements icon finding, but:

  • like linicon, it does not scan “standalone” icons correctly.
  • it does not perform spec-compliant icon matching. (does not match icons in directory size ranges correctly)
  • it only supports a rust-native icon cache, which you cannot opt out of.
  • it provides only icon loading—you cannot use it to obtain information about Icon Themes.

Modules

states

Marker types used for the IconSearch builder.

Structs

DirectoryIndex

The “formal description” of a subdirectory in an Icon Theme, as specified by the Icon Theme specification.

IconFile

The path to an icon along with its detected file type.

IconLocations

Locations icons may be found at.

IconSearch

Icons and icon themes are looked for in a set of directories.

Icons

Main struct to locate icon files.

IconsCachecache

Caching version of Icons.

Theme

An icon theme.

ThemeCachecache

Caching version of Theme.

ThemeIndex

The “formal description” of a theme as specified by the Icon Theme specification.

ThemeInfo

Information about an icon theme.

Enums

DirectoryType

The type of image scaling used for an icon theme subdirectory.

FileType

Supported image file formats for icons.

ThemeParseError

An error occurred during theme index parsing.