ui2: Reorganize components (#3228)

This PR reorganizes the components in the `ui2` crate.

The distinction between "elements" and "components" is now gone, with
all of the reusable components living under `components/`.

The components that we built while prototyping but will eventually live
in other crates currently reside in the `to_extract/` module.

Release Notes:

- N/A

crates/ui2/src/components/label.rs

@@ -0,0 +1,216 @@
+use gpui2::{relative, rems, Hsla, WindowContext};
+use smallvec::SmallVec;
+
+use crate::prelude::*;
+#[derive(Default, PartialEq, Copy, Clone)]
+pub enum LabelColor {
+    #[default]
+    Default,
+    Muted,
+    Created,
+    Modified,
+    Deleted,
+    Disabled,
+    Hidden,
+    Placeholder,
+    Accent,
+}
+
+impl LabelColor {
+    pub fn hsla(&self, cx: &WindowContext) -> Hsla {
+        match self {
+            Self::Default => cx.theme().colors().text,
+            Self::Muted => cx.theme().colors().text_muted,
+            Self::Created => cx.theme().status().created,
+            Self::Modified => cx.theme().status().modified,
+            Self::Deleted => cx.theme().status().deleted,
+            Self::Disabled => cx.theme().colors().text_disabled,
+            Self::Hidden => cx.theme().status().hidden,
+            Self::Placeholder => cx.theme().colors().text_placeholder,
+            Self::Accent => cx.theme().colors().text_accent,
+        }
+    }
+}
+
+#[derive(Default, PartialEq, Copy, Clone)]
+pub enum LineHeightStyle {
+    #[default]
+    TextLabel,
+    /// Sets the line height to 1
+    UILabel,
+}
+
+#[derive(Component)]
+pub struct Label {
+    label: SharedString,
+    line_height_style: LineHeightStyle,
+    color: LabelColor,
+    strikethrough: bool,
+}
+
+impl Label {
+    pub fn new(label: impl Into<SharedString>) -> Self {
+        Self {
+            label: label.into(),
+            line_height_style: LineHeightStyle::default(),
+            color: LabelColor::Default,
+            strikethrough: false,
+        }
+    }
+
+    pub fn color(mut self, color: LabelColor) -> Self {
+        self.color = color;
+        self
+    }
+
+    pub fn line_height_style(mut self, line_height_style: LineHeightStyle) -> Self {
+        self.line_height_style = line_height_style;
+        self
+    }
+
+    pub fn set_strikethrough(mut self, strikethrough: bool) -> Self {
+        self.strikethrough = strikethrough;
+        self
+    }
+
+    fn render<V: 'static>(self, _view: &mut V, cx: &mut ViewContext<V>) -> impl Component<V> {
+        div()
+            .when(self.strikethrough, |this| {
+                this.relative().child(
+                    div()
+                        .absolute()
+                        .top_1_2()
+                        .w_full()
+                        .h_px()
+                        .bg(LabelColor::Hidden.hsla(cx)),
+                )
+            })
+            .text_size(rems(1.))
+            .when(self.line_height_style == LineHeightStyle::UILabel, |this| {
+                this.line_height(relative(1.))
+            })
+            .text_color(self.color.hsla(cx))
+            .child(self.label.clone())
+    }
+}
+
+#[derive(Component)]
+pub struct HighlightedLabel {
+    label: SharedString,
+    color: LabelColor,
+    highlight_indices: Vec<usize>,
+    strikethrough: bool,
+}
+
+impl HighlightedLabel {
+    pub fn new(label: impl Into<SharedString>, highlight_indices: Vec<usize>) -> Self {
+        Self {
+            label: label.into(),
+            color: LabelColor::Default,
+            highlight_indices,
+            strikethrough: false,
+        }
+    }
+
+    pub fn color(mut self, color: LabelColor) -> Self {
+        self.color = color;
+        self
+    }
+
+    pub fn set_strikethrough(mut self, strikethrough: bool) -> Self {
+        self.strikethrough = strikethrough;
+        self
+    }
+
+    fn render<V: 'static>(self, _view: &mut V, cx: &mut ViewContext<V>) -> impl Component<V> {
+        let highlight_color = cx.theme().colors().text_accent;
+
+        let mut highlight_indices = self.highlight_indices.iter().copied().peekable();
+
+        let mut runs: SmallVec<[Run; 8]> = SmallVec::new();
+
+        for (char_ix, char) in self.label.char_indices() {
+            let mut color = self.color.hsla(cx);
+
+            if let Some(highlight_ix) = highlight_indices.peek() {
+                if char_ix == *highlight_ix {
+                    color = highlight_color;
+
+                    highlight_indices.next();
+                }
+            }
+
+            let last_run = runs.last_mut();
+
+            let start_new_run = if let Some(last_run) = last_run {
+                if color == last_run.color {
+                    last_run.text.push(char);
+                    false
+                } else {
+                    true
+                }
+            } else {
+                true
+            };
+
+            if start_new_run {
+                runs.push(Run {
+                    text: char.to_string(),
+                    color,
+                });
+            }
+        }
+
+        div()
+            .flex()
+            .when(self.strikethrough, |this| {
+                this.relative().child(
+                    div()
+                        .absolute()
+                        .top_px()
+                        .my_auto()
+                        .w_full()
+                        .h_px()
+                        .bg(LabelColor::Hidden.hsla(cx)),
+                )
+            })
+            .children(
+                runs.into_iter()
+                    .map(|run| div().text_color(run.color).child(run.text)),
+            )
+    }
+}
+
+/// A run of text that receives the same style.
+struct Run {
+    pub text: String,
+    pub color: Hsla,
+}
+
+#[cfg(feature = "stories")]
+pub use stories::*;
+
+#[cfg(feature = "stories")]
+mod stories {
+    use super::*;
+    use crate::Story;
+    use gpui2::{Div, Render};
+
+    pub struct LabelStory;
+
+    impl Render for LabelStory {
+        type Element = Div<Self>;
+
+        fn render(&mut self, cx: &mut ViewContext<Self>) -> Self::Element {
+            Story::container(cx)
+                .child(Story::title_for::<_, Label>(cx))
+                .child(Story::label(cx, "Default"))
+                .child(Label::new("Hello, world!"))
+                .child(Story::label(cx, "Highlighted"))
+                .child(HighlightedLabel::new(
+                    "Hello, world!",
+                    vec![0, 1, 2, 7, 8, 12],
+                ))
+        }
+    }
+}