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crates/strato-ui-renderer/src/windowing/winit/linux/cursor_theme.rs

StratoSDK / crates / strato-ui-renderer / src / windowing / winit / linux / cursor_theme.rs

1	use std::{env, path::PathBuf};
2	use tini::Ini;
3
4	static CURSOR_DIR_NAME: &'static &str = &"cursors";
5	static CURSOR_INDEX_FILE_NAME: &'static &str = &"index.theme";
6	static THEME_FILE_CURSOR_SECTION: &'static &str = &"Icon Theme";
7	static THEME_FILE_INHERITS_KEY: &'static &str = &"Inherits";
8
9	static ENV_DATA_DIRS: &'static &str = &"XDG_DATA_DIRS";
10	static ENV_CURSOR_THEME: &'static &str = &"XCURSOR_THEME";
11
12	static DEFAULT_THEME: &'static &str = &"default";
13	static KNOWN_THEMES: &[&str] = &["Yaru", "Adwaita"];
14
15	pub fn ensure_cursor_theme() {
16	// If the XCURSOR_THEME value is explicitly set,
17	// then we do not want to modify the user's environment
18	if env::var(ENV_CURSOR_THEME).is_ok() {
19	return;
20	}
21
22	let crawler = CursorThemeCrawler::new();
23
24	if let Some(theme) = crawler.determine_cursor_theme() {
25	// winit and it's dependencies will automatically check for
26	// the default theme, so we do not need to mess with the
27	// env var here.
28	if theme != *DEFAULT_THEME {
29	env::set_var(ENV_CURSOR_THEME, theme);
30	}
31	}
32	}
33
34	struct CursorThemeCrawler {
35	/// Directories to search when looking for a cursor theme.
36	/// Directories are searched in vec order from first to last.
37	/// However, because themes can reference other themes, it is
38	/// possible for search results to traverse multiple directories.
39	/// For example, a default theme can be found in directories[1]
40	/// that inherits from a theme in directories[3], which itself
41	/// inherits from a theme in directories[0]
42	directories: Vec<PathBuf>,
43	}
44
45	fn non_empty_var(name: &str) -> Option<String> {
46	env::var(name).ok().filter(\|val\| !val.is_empty())
47	}
48
49	impl CursorThemeCrawler {
50	pub fn new() -> Self {
51	// Per https://specifications.freedesktop.org/icon-theme-spec/icon-theme-spec-latest.html#directory_layout,
52	// we search:
53	// - $HOME/.icons (for backwards compatibility)
54	// - $XDG_DATA_HOME/icons (technically this should be part of XDG_DATA_DIRS, but we add it in here)
55	// - Defaults to $HOME/.local/share
56	// - $XDG_DATA_DIRS/icons
57	// - Defaults to /usr/local/share/:/usr/share/
58	// - /usr/share/pixmaps
59	let mut directories = vec![];
60
61	let xdg_data_dirs = non_empty_var(ENV_DATA_DIRS)
62	.or_else(\|\| Some("/usr/local/share/:/usr/share/".to_string()));
63
64	if let Some(home) = dirs::home_dir() {
65	directories.push(home.join(".icons"));
66	}
67	if let Some(xdg_data_home) = dirs::data_dir() {
68	directories.push(xdg_data_home.join("icons"));
69	}
70	if let Some(xdg_data_dirs) = xdg_data_dirs {
71	for dir in xdg_data_dirs.split(':') {
72	if !dir.is_empty() {
73	directories.push(PathBuf::from(dir).join("icons"));
74	}
75	}
76	}
77	directories.push(PathBuf::from("/usr/share/pixmaps"));
78	Self { directories }
79	}
80
81	/// First checks to see if there is a default cursor theme set.
82	/// If there is no default set, we check a list of known themes.
83	/// The first theme to be confirmed exist is returned, else None
84	/// is returned.
85	fn determine_cursor_theme(&self) -> Option<String> {
86	if self.check_cursor_theme(DEFAULT_THEME) {
87	return Some(DEFAULT_THEME.to_string());
88	}
89
90	for theme in KNOWN_THEMES {
91	if self.check_cursor_theme(theme) {
92	return Some((*theme).to_string());
93	}
94	}
95	None
96	}
97
98	/// Returns true if an icon theme exists and has a `cursors/`
99	/// folder, indicating that the cursors for that theme are installed.
100	/// Per the specification, an icon theme can exist along multiple
101	/// directories. As long as at least one of those directories
102	/// contains the `cursors/` subdir, we consider it valid
103	fn check_cursor_theme_installed(&self, theme: &str) -> bool {
104	for dir in &self.directories {
105	if dir.join(theme).join(CURSOR_DIR_NAME).exists() {
106	return true;
107	}
108	}
109	false
110	}
111
112	/// Checks that a given icon theme is a valid cursor theme.
113	///
114	/// When we check a cursor theme, we verify that either:
115	/// a. The icon theme has a cursors/ folder
116	/// b. The icon theme inherits from an existing cursor theme.
117	///
118	/// This can cause us to traverse multiple themes as part of our validation.
119	/// we do this verification to handle cases like the `adwaita-icon-theme`
120	/// deb packages, which sets Adwaita to the default icon theme without
121	/// installing a cursor theme.
122	fn check_cursor_theme(&self, root_theme: &str) -> bool {
123	let mut visited = std::collections::HashSet::from([root_theme.to_string()]);
124	let mut pending = std::collections::VecDeque::from([root_theme.to_string()]);
125
126	while let Some(theme) = pending.pop_front() {
127	if self.check_cursor_theme_installed(&theme) {
128	return true;
129	}
130
131	// Per the spec, the first index.theme found when traversing
132	// the directories is used
133	let inherited_themes = &self
134	.directories
135	.iter()
136	.filter_map(\|index_dir\| {
137	let index_path = index_dir.join(&theme).join(CURSOR_INDEX_FILE_NAME);
138	if let Ok(theme_file) = Ini::from_file(&index_path) {
139	theme_file.get_vec_with_sep::<String>(
140	THEME_FILE_CURSOR_SECTION,
141	THEME_FILE_INHERITS_KEY,
142	",",
143	)
144	} else {
145	None
146	}
147	})
148	.next();
149
150	if let Some(inherited_themes) = inherited_themes {
151	for new_theme in inherited_themes {
152	if !visited.contains(new_theme) {
153	visited.insert(new_theme.clone());
154	pending.push_back(new_theme.clone());
155	}
156	}
157	}
158	}
159
160	false
161	}
162	}
163
164	#[cfg(test)]
165	#[path = "cursor_theme_tests.rs"]
166	mod tests;
167

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