Restructure ui into just elements and components (#3023)

This PR restructures the `ui` crate into just `elements` and
`components`.

This was already done on the `gpui2-ui` branch, just getting it onto
`main`.

Release Notes:

- N/A

---------

Co-authored-by: Nate Butler <nate@zed.dev>

crates/ui/src/components/palette.rs

@@ -0,0 +1,124 @@
+use std::marker::PhantomData;
+
+use crate::prelude::OrderMethod;
+use crate::theme::theme;
+use crate::{label, palette_item, LabelColor, PaletteItem};
+use gpui2::elements::div::ScrollState;
+use gpui2::style::{StyleHelpers, Styleable};
+use gpui2::{elements::div, IntoElement};
+use gpui2::{Element, ParentElement, ViewContext};
+
+#[derive(Element)]
+pub struct Palette<V: 'static> {
+    view_type: PhantomData<V>,
+    scroll_state: ScrollState,
+    input_placeholder: &'static str,
+    empty_string: &'static str,
+    items: Vec<PaletteItem>,
+    default_order: OrderMethod,
+}
+
+pub fn palette<V: 'static>(scroll_state: ScrollState) -> Palette<V> {
+    Palette {
+        view_type: PhantomData,
+        scroll_state,
+        input_placeholder: "Find something...",
+        empty_string: "No items found.",
+        items: vec![],
+        default_order: OrderMethod::default(),
+    }
+}
+
+impl<V: 'static> Palette<V> {
+    pub fn items(mut self, mut items: Vec<PaletteItem>) -> Self {
+        items.sort_by_key(|item| item.label);
+        self.items = items;
+        self
+    }
+
+    pub fn placeholder(mut self, input_placeholder: &'static str) -> Self {
+        self.input_placeholder = input_placeholder;
+        self
+    }
+
+    pub fn empty_string(mut self, empty_string: &'static str) -> Self {
+        self.empty_string = empty_string;
+        self
+    }
+
+    // TODO: Hook up sort order
+    pub fn default_order(mut self, default_order: OrderMethod) -> Self {
+        self.default_order = default_order;
+        self
+    }
+
+    fn render(&mut self, _: &mut V, cx: &mut ViewContext<V>) -> impl IntoElement<V> {
+        let theme = theme(cx);
+
+        div()
+            .w_96()
+            .rounded_lg()
+            .fill(theme.lowest.base.default.background)
+            .border()
+            .border_color(theme.lowest.base.default.border)
+            .flex()
+            .flex_col()
+            .child(
+                div()
+                    .flex()
+                    .flex_col()
+                    .gap_px()
+                    .child(
+                        div().py_0p5().px_1().flex().flex_col().child(
+                            div().px_2().py_0p5().child(
+                                label(self.input_placeholder).color(LabelColor::Placeholder),
+                            ),
+                        ),
+                    )
+                    .child(div().h_px().w_full().fill(theme.lowest.base.default.border))
+                    .child(
+                        div()
+                            .py_0p5()
+                            .px_1()
+                            .flex()
+                            .flex_col()
+                            .grow()
+                            .max_h_96()
+                            .overflow_y_scroll(self.scroll_state.clone())
+                            .children(
+                                vec![if self.items.is_empty() {
+                                    Some(
+                                        div()
+                                            .flex()
+                                            .flex_row()
+                                            .justify_between()
+                                            .px_2()
+                                            .py_1()
+                                            .child(
+                                                label(self.empty_string).color(LabelColor::Muted),
+                                            ),
+                                    )
+                                } else {
+                                    None
+                                }]
+                                .into_iter()
+                                .flatten(),
+                            )
+                            .children(self.items.iter().map(|item| {
+                                div()
+                                    .flex()
+                                    .flex_row()
+                                    .justify_between()
+                                    .px_2()
+                                    .py_0p5()
+                                    .rounded_lg()
+                                    .hover()
+                                    .fill(theme.lowest.base.hovered.background)
+                                    .active()
+                                    .fill(theme.lowest.base.pressed.background)
+                                    .child(palette_item(item.label, item.keybinding))
+                            })),
+                    ),
+            )
+    }
+}