dropdown_button: Add new component (#551)

## Regular
<img width="162" alt="image"
src="https://github.com/user-attachments/assets/4e597d0b-41d1-4b0e-9939-728cae71fe65"
/>

## Active
<img width="162" alt="image"
src="https://github.com/user-attachments/assets/0871ed6b-3188-44dd-93d4-5996f9213edc"
/>
<br />
<img width="162" alt="image"
src="https://github.com/user-attachments/assets/b05ccdc6-e405-47d0-97e7-470afadbbd38"
/>


## Break Change
Move `ButtonGroup` into the `button`.

crates/story/src/accordion_story.rs

@@ -3,8 +3,12 @@ use gpui::{
     VisualContext as _, WindowContext,
 };
 use ui::{
-    accordion::Accordion, button::Button, button_group::ButtonGroup, checkbox::Checkbox, h_flex,
+    accordion::Accordion,
-    switch::Switch, v_flex, IconName, Selectable, Sizable, Size,
+    button::{Button, ButtonGroup},
+    checkbox::Checkbox,
+    h_flex,
+    switch::Switch,
+    v_flex, IconName, Selectable, Sizable, Size,
 };
 
 pub struct AccordionStory {

crates/story/src/button_story.rs

@@ -1,11 +1,10 @@
 use gpui::{
-    px, ClickEvent, FocusableView, IntoElement, ParentElement as _, Render, Styled as _, View,
+    actions, px, ClickEvent, FocusableView, InteractiveElement, IntoElement, ParentElement as _,
-    ViewContext, VisualContext as _, WindowContext,
+    Render, Styled as _, View, ViewContext, VisualContext as _, WindowContext,
 };
 
 use ui::{
-    button::{Button, ButtonCustomVariant, ButtonVariants as _},
+    button::{Button, ButtonCustomVariant, ButtonGroup, ButtonVariants as _, DropdownButton},
-    button_group::ButtonGroup,
     checkbox::Checkbox,
     h_flex,
     prelude::FluentBuilder,
@@ -15,6 +14,8 @@ use ui::{
 
 use crate::section;
 
+actions!(button_story, [Disabled, Loading, Selected, Compact]);
+
 pub struct ButtonStory {
     focus_handle: gpui::FocusHandle,
     disabled: bool,
@@ -74,6 +75,10 @@ impl Render for ButtonStory {
         let toggle_multiple = self.toggle_multiple;
 
         v_flex()
+            .on_action(cx.listener(|this, _: &Disabled, _| this.disabled = !this.disabled))
+            .on_action(cx.listener(|this, _: &Loading, _| this.loading = !this.loading))
+            .on_action(cx.listener(|this, _: &Selected, _| this.selected = !this.selected))
+            .on_action(cx.listener(|this, _: &Compact, _| this.compact = !this.compact))
             .gap_6()
             .child(
                 h_flex()
@@ -546,6 +551,18 @@ impl Render for ButtonStory {
                             ),
                     ),
             )
+            .child(
+                section("Dropdown Button", cx).child(
+                    DropdownButton::new("dropdown-button")
+                        .button(Button::new("dropdown-button-button").label("Click Me"))
+                        .popup_menu(move |this, _| {
+                            this.menu("Disabled", Box::new(Disabled))
+                                .menu("Loading", Box::new(Loading))
+                                .menu("Selected", Box::new(Selected))
+                                .menu("Compact", Box::new(Compact))
+                        }),
+                ),
+            )
             .child(
                 section("Icon Button", cx)
                     .child(

crates/ui/src/button/dropdown_button.rs

@@ -0,0 +1,85 @@
+use gpui::{
+    prelude::FluentBuilder, Corner, Corners, Edges, ElementId, IntoElement, ParentElement,
+    RenderOnce, ViewContext, WindowContext,
+};
+
+use crate::{
+    h_flex,
+    popup_menu::{PopupMenu, PopupMenuExt},
+    IconName,
+};
+
+use super::Button;
+
+#[derive(IntoElement)]
+pub struct DropdownButton {
+    id: ElementId,
+    button: Option<Button>,
+    popup_menu: Option<Box<dyn Fn(PopupMenu, &mut ViewContext<PopupMenu>) -> PopupMenu + 'static>>,
+}
+
+impl DropdownButton {
+    pub fn new(id: impl Into<ElementId>) -> Self {
+        Self {
+            id: id.into(),
+            button: None,
+            popup_menu: None,
+        }
+    }
+
+    pub fn button(mut self, button: Button) -> Self {
+        self.button = Some(
+            button
+                .border_corners(Corners {
+                    top_left: true,
+                    top_right: false,
+                    bottom_left: true,
+                    bottom_right: false,
+                })
+                .border_edges(Edges {
+                    left: true,
+                    top: true,
+                    right: true,
+                    bottom: true,
+                }),
+        );
+        self
+    }
+
+    pub fn popup_menu(
+        mut self,
+        popup_menu: impl Fn(PopupMenu, &mut ViewContext<PopupMenu>) -> PopupMenu + 'static,
+    ) -> Self {
+        self.popup_menu = Some(Box::new(popup_menu));
+        self
+    }
+}
+
+impl RenderOnce for DropdownButton {
+    fn render(self, _: &mut WindowContext) -> impl IntoElement {
+        h_flex().when_some(self.button, |this, button| {
+            this.child(button)
+                .when_some(self.popup_menu, |this, popup_menu| {
+                    this.child(
+                        Button::new(self.id)
+                            .icon(IconName::ChevronDown)
+                            .border_edges(Edges {
+                                left: false,
+                                top: true,
+                                right: true,
+                                bottom: true,
+                            })
+                            .border_corners(Corners {
+                                top_left: false,
+                                top_right: true,
+                                bottom_left: false,
+                                bottom_right: true,
+                            })
+                            .popup_menu_with_anchor(Corner::TopRight, move |this, cx| {
+                                popup_menu(this, cx)
+                            }),
+                    )
+                })
+        })
+    }
+}

crates/ui/src/button/mod.rs

@@ -0,0 +1,7 @@
+mod button;
+mod button_group;
+mod dropdown_button;
+
+pub use button::*;
+pub use button_group::*;
+pub use dropdown_button::*;

crates/ui/src/lib.rs

@@ -14,7 +14,6 @@ pub mod animation;
 pub mod badge;
 pub mod breadcrumb;
 pub mod button;
-pub mod button_group;
 pub mod checkbox;
 pub mod clipboard;
 pub mod color_picker;