chore: move some components to custom ui crate (#10)

Reviewed-on: https://git.reya.su/reya/signed/pulls/10

crates/signed_ui/src/user_avatar.rs

@@ -0,0 +1,48 @@
+use gpui::prelude::*;
+use gpui::{App, SharedString, StyleRefinement, Window};
+use gpui_component::avatar::Avatar;
+use gpui_component::{ActiveTheme, Sizable, StyledExt};
+
+/// A user avatar: the gpui-component [`Avatar`] sized small and rounded with
+/// the theme radius, showing the user's picture or a name-initials fallback.
+#[derive(IntoElement)]
+pub struct UserAvatar {
+    name: SharedString,
+    picture: Option<SharedString>,
+    style: StyleRefinement,
+}
+
+impl UserAvatar {
+    /// Create an avatar for `name`; the name seeds the initials fallback
+    /// shown when no picture is set.
+    pub fn new(name: impl Into<SharedString>) -> Self {
+        Self {
+            name: name.into(),
+            picture: None,
+            style: StyleRefinement::default(),
+        }
+    }
+
+    /// The user's picture URL, if known.
+    pub fn picture(mut self, picture: Option<impl Into<SharedString>>) -> Self {
+        self.picture = picture.map(Into::into);
+        self
+    }
+}
+
+impl Styled for UserAvatar {
+    fn style(&mut self) -> &mut StyleRefinement {
+        &mut self.style
+    }
+}
+
+impl RenderOnce for UserAvatar {
+    fn render(self, _window: &mut Window, cx: &mut App) -> impl IntoElement {
+        Avatar::new()
+            .name(self.name)
+            .when_some(self.picture, |this, url| this.src(url))
+            .rounded(cx.theme().radius)
+            .refine_style(&self.style)
+            .small()
+    }
+}