Theme · Platform: one platform for buttons and caps, icon themes, frosted panes

theme::Platform moves out of typography and shell's ControlsStyle folds
into it; the theme's platform starts as the system's. Window buttons Ely
draws, the title bar's layout and every key cap follow it, secondary
included, through typography::keys::keystroke; a title bar whose buttons
the OS draws follows the OS. primitives::IconTheme lays an owner's rules
by file name and extension over Ely's map, for every file icon.
shell::Vibrancy fills a pane with the palette's new glass, translucent
so a window opened Blurred shows its backdrop, solid under high contrast.
gpui 0.2.2 has no Mica; that line stays blocked.

src/primitives/files.rs

@@ -1,9 +1,68 @@
+use std::{collections::HashMap, sync::LazyLock};
+
+use gpui::{App, Global};
+
 use super::IconName;
 
-/// The icon a file's name suggests, by its extension.
-pub(crate) fn file_icon(name: &str) -> IconName {
-    let extension = name.rsplit_once('.').map(|(_, ext)| ext.to_lowercase());
-    match extension.as_deref() {
+/// Which icon a file shows: an owner's rules by name and by extension, laid over Ely's map. Without one, Ely's map alone.
+#[derive(Clone, Default)]
+pub struct IconTheme {
+    names: HashMap<String, IconName>,
+    extensions: HashMap<String, IconName>,
+}
+
+impl Global for IconTheme {}
+
+impl IconTheme {
+    /// A file of this exact name, in any case: `Cargo.toml`, `Dockerfile`.
+    pub fn name(mut self, name: &str, icon: IconName) -> Self {
+        self.names.insert(name.to_lowercase(), icon);
+        self
+    }
+
+    /// Files ending in this extension, given without its dot.
+    pub fn extension(mut self, extension: &str, icon: IconName) -> Self {
+        self.extensions.insert(extension.to_lowercase(), icon);
+        self
+    }
+
+    /// Serves every window from now on.
+    pub fn apply(self, cx: &mut App) {
+        log::info!(
+            "icon theme: {} names, {} extensions",
+            self.names.len(),
+            self.extensions.len()
+        );
+        cx.set_global(self);
+        cx.refresh_windows();
+    }
+
+    pub(crate) fn file(&self, name: &str) -> IconName {
+        let name = name.to_lowercase();
+        let extension = name.rsplit_once('.').map(|(_, extension)| extension);
+        self.names
+            .get(&name)
+            .or_else(|| extension.and_then(|extension| self.extensions.get(extension)))
+            .copied()
+            .unwrap_or_else(|| ely_icon(extension))
+    }
+}
+
+static ELY: LazyLock<IconTheme> = LazyLock::new(IconTheme::default);
+
+/// The owner's icon theme, or Ely's map alone.
+pub(crate) fn icon_theme(cx: &App) -> &IconTheme {
+    cx.try_global::<IconTheme>().unwrap_or(&ELY)
+}
+
+/// The icon a file's name suggests, under the owner's icon theme.
+pub(crate) fn file_icon(name: &str, cx: &App) -> IconName {
+    icon_theme(cx).file(name)
+}
+
+/// Ely's icon for a file by its extension, in lower case.
+fn ely_icon(extension: Option<&str>) -> IconName {
+    match extension {
         Some(
             "rs" | "ts" | "tsx" | "js" | "jsx" | "py" | "go" | "swift" | "c" | "h" | "cpp" | "java"
             | "kt" | "rb" | "php" | "css" | "html",
@@ -26,16 +85,32 @@ pub(crate) fn file_icon(name: &str) -> IconName {
 
 #[cfg(test)]
 mod tests {
-    use super::{IconName, file_icon};
+    use super::{IconName, IconTheme};
 
     #[test]
     fn a_name_picks_its_icon_by_its_last_extension() {
-        assert_eq!(file_icon("main.RS"), IconName::FileCode);
-        assert_eq!(file_icon("lift.PNG"), IconName::FileImage);
-        assert_eq!(file_icon("notes.md"), IconName::FileText);
-        assert_eq!(file_icon("backup.tar.gz"), IconName::FileArchive);
-        assert_eq!(file_icon(".env"), IconName::FileCog);
-        assert_eq!(file_icon("take.mov"), IconName::FileVideoCamera);
-        assert_eq!(file_icon("Makefile"), IconName::File);
+        assert_eq!(IconTheme::default().file("main.RS"), IconName::FileCode);
+        assert_eq!(IconTheme::default().file("lift.PNG"), IconName::FileImage);
+        assert_eq!(IconTheme::default().file("notes.md"), IconName::FileText);
+        assert_eq!(
+            IconTheme::default().file("backup.tar.gz"),
+            IconName::FileArchive
+        );
+        assert_eq!(IconTheme::default().file(".env"), IconName::FileCog);
+        assert_eq!(
+            IconTheme::default().file("take.mov"),
+            IconName::FileVideoCamera
+        );
+        assert_eq!(IconTheme::default().file("Makefile"), IconName::File);
+    }
+
+    #[test]
+    fn an_owners_rules_come_before_elys_map() {
+        let theme = IconTheme::default()
+            .name("Cargo.toml", IconName::Package)
+            .extension("RS", IconName::Braces);
+        assert_eq!(theme.file("cargo.TOML"), IconName::Package);
+        assert_eq!(theme.file("main.rs"), IconName::Braces);
+        assert_eq!(theme.file("deploy.toml"), IconName::FileCog);
     }
 }

src/primitives/mod.rs

@@ -18,7 +18,8 @@ mod tests;
 pub use backdrop::{Backdrop, Place};
 pub use disclosure::Disclosure;
 pub use divider::Divider;
-pub(crate) use files::file_icon;
+pub use files::IconTheme;
+pub(crate) use files::{file_icon, icon_theme};
 pub use focus::{FocusNext, FocusPrev, FocusRing, FocusScope};
 pub(crate) use focus::{Takeover, give_back, hand_back, hold_focus, tab_stop, take_focus};
 pub use ghost::DragGhost;