ui: Add support for rendering Icons from external files (#23195)

This PR adds support for rendering `Icon`s from external files.
Previously this could only be used with icons embedded in the binary.

To achieve this we currently need to use the `img` element until the
`svg` element supports:

1. Loading SVGs from external files
2. Rendering polychrome SVGs

Release Notes:

- N/A

crates/ui/src/components/icon.rs

@@ -3,8 +3,11 @@
 mod decorated_icon;
 mod icon_decoration;
 
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+
 pub use decorated_icon::*;
-use gpui::{svg, AnimationElement, Hsla, IntoElement, Rems, Transformation};
+use gpui::{img, svg, AnimationElement, Hsla, IntoElement, Rems, Transformation};
 pub use icon_decoration::*;
 use serde::{Deserialize, Serialize};
 use strum::{EnumIter, EnumString, IntoStaticStr};
@@ -324,9 +327,34 @@ impl From<IconName> for Icon {
     }
 }
 
+/// The source of an icon.
+enum IconSource {
+    /// An SVG embedded in the Zed binary.
+    Svg(SharedString),
+    /// An image file located at the specified path.
+    ///
+    /// Currently our SVG renderer is missing support for the following features:
+    /// 1. Loading SVGs from external files.
+    /// 2. Rendering polychrome SVGs.
+    ///
+    /// In order to support icon themes, we render the icons as images instead.
+    Image(Arc<Path>),
+}
+
+impl IconSource {
+    fn from_path(path: impl Into<SharedString>) -> Self {
+        let path = path.into();
+        if path.starts_with("icons/file_icons") {
+            Self::Svg(path)
+        } else {
+            Self::Image(Arc::from(PathBuf::from(path.as_ref())))
+        }
+    }
+}
+
 #[derive(IntoElement)]
 pub struct Icon {
-    path: SharedString,
+    source: IconSource,
     color: Color,
     size: Rems,
     transformation: Transformation,
@@ -335,7 +363,7 @@ pub struct Icon {
 impl Icon {
     pub fn new(icon: IconName) -> Self {
         Self {
-            path: icon.path().into(),
+            source: IconSource::Svg(icon.path().into()),
             color: Color::default(),
             size: IconSize::default().rems(),
             transformation: Transformation::default(),
@@ -344,7 +372,7 @@ impl Icon {
 
     pub fn from_path(path: impl Into<SharedString>) -> Self {
         Self {
-            path: path.into(),
+            source: IconSource::from_path(path),
             color: Color::default(),
             size: IconSize::default().rems(),
             transformation: Transformation::default(),
@@ -377,12 +405,20 @@ impl Icon {
 
 impl RenderOnce for Icon {
     fn render(self, cx: &mut WindowContext) -> impl IntoElement {
-        svg()
+        match self.source {
+            IconSource::Svg(path) => svg()
                 .with_transformation(self.transformation)
                 .size(self.size)
                 .flex_none()
-            .path(self.path)
+                .path(path)
                 .text_color(self.color.color(cx))
+                .into_any_element(),
+            IconSource::Image(path) => img(path)
+                .size(self.size)
+                .flex_none()
+                .text_color(self.color.color(cx))
+                .into_any_element(),
+        }
     }
 }