Introducing multibuffers (#14668)

Co-Authored-By: Marshall <marshall@zed.dev>

Release Notes:

- Added a hint the first few times you open a multibuffer to explain
what is going on.

Co-authored-by: Marshall <marshall@zed.dev>

crates/welcome/src/multibuffer_hint.rs

@@ -0,0 +1,142 @@
+use std::collections::HashSet;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::OnceLock;
+
+use db::kvp::KEY_VALUE_STORE;
+use gpui::{AppContext, Empty, EntityId, EventEmitter};
+use ui::{prelude::*, ButtonLike, IconButtonShape, Tooltip};
+use workspace::item::ItemHandle;
+use workspace::{ToolbarItemEvent, ToolbarItemLocation, ToolbarItemView};
+
+pub struct MultibufferHint {
+    shown_on: HashSet<EntityId>,
+    active_item: Option<Box<dyn ItemHandle>>,
+}
+
+const NUMBER_OF_HINTS: usize = 10;
+
+const SHOWN_COUNT_KEY: &str = "MULTIBUFFER_HINT_SHOWN_COUNT";
+
+impl MultibufferHint {
+    pub fn new() -> Self {
+        Self {
+            shown_on: Default::default(),
+            active_item: None,
+        }
+    }
+}
+
+impl MultibufferHint {
+    fn counter() -> &'static AtomicUsize {
+        static SHOWN_COUNT: OnceLock<AtomicUsize> = OnceLock::new();
+        SHOWN_COUNT.get_or_init(|| {
+            let value: usize = KEY_VALUE_STORE
+                .read_kvp(SHOWN_COUNT_KEY)
+                .ok()
+                .flatten()
+                .and_then(|v| v.parse().ok())
+                .unwrap_or(0);
+
+            AtomicUsize::new(value)
+        })
+    }
+
+    fn shown_count() -> usize {
+        Self::counter().load(Ordering::Relaxed)
+    }
+
+    fn increment_count(cx: &mut AppContext) {
+        Self::set_count(Self::shown_count() + 1, cx)
+    }
+
+    pub(crate) fn set_count(count: usize, cx: &mut AppContext) {
+        Self::counter().store(count, Ordering::Relaxed);
+
+        db::write_and_log(cx, move || {
+            KEY_VALUE_STORE.write_kvp(SHOWN_COUNT_KEY.to_string(), format!("{}", count))
+        });
+    }
+
+    fn dismiss(&mut self, cx: &mut AppContext) {
+        Self::set_count(NUMBER_OF_HINTS, cx)
+    }
+}
+
+impl EventEmitter<ToolbarItemEvent> for MultibufferHint {}
+
+impl ToolbarItemView for MultibufferHint {
+    fn set_active_pane_item(
+        &mut self,
+        active_pane_item: Option<&dyn ItemHandle>,
+        cx: &mut ViewContext<Self>,
+    ) -> ToolbarItemLocation {
+        if Self::shown_count() > NUMBER_OF_HINTS {
+            return ToolbarItemLocation::Hidden;
+        }
+
+        let Some(active_pane_item) = active_pane_item else {
+            return ToolbarItemLocation::Hidden;
+        };
+
+        if active_pane_item.is_singleton(cx) {
+            return ToolbarItemLocation::Hidden;
+        }
+
+        if self.shown_on.insert(active_pane_item.item_id()) {
+            Self::increment_count(cx)
+        }
+
+        self.active_item = Some(active_pane_item.boxed_clone());
+        ToolbarItemLocation::Secondary
+    }
+}
+
+impl Render for MultibufferHint {
+    fn render(&mut self, cx: &mut ViewContext<Self>) -> impl IntoElement {
+        let Some(active_item) = self.active_item.as_ref() else {
+            return Empty.into_any_element();
+        };
+
+        if active_item.breadcrumbs(cx.theme(), cx).is_none() {
+            return Empty.into_any_element();
+        }
+
+        h_flex()
+            .px_2()
+            .justify_between()
+            .bg(cx.theme().status().info_background)
+            .rounded_md()
+            .child(
+                h_flex()
+                    .gap_2()
+                    .child(Label::new("You can edit results inline in multibuffers!"))
+                    .child(
+                        ButtonLike::new("open_docs")
+                            .style(ButtonStyle::Transparent)
+                            .child(
+                                h_flex()
+                                    .gap_1()
+                                    .child(Label::new("Read more…"))
+                                    .child(Icon::new(IconName::ArrowUpRight).size(IconSize::Small)),
+                            )
+                            .on_click(move |_event, cx| {
+                                cx.open_url("https://zed.dev/docs/multibuffers")
+                            }),
+                    ),
+            )
+            .child(
+                IconButton::new("dismiss", IconName::Close)
+                    .style(ButtonStyle::Transparent)
+                    .shape(IconButtonShape::Square)
+                    .icon_size(IconSize::Small)
+                    .on_click(cx.listener(|this, _event, cx| {
+                        this.dismiss(cx);
+                        cx.emit(ToolbarItemEvent::ChangeLocation(
+                            ToolbarItemLocation::Hidden,
+                        ))
+                    }))
+                    .tooltip(move |cx| Tooltip::text("Dismiss this hint", cx)),
+            )
+            .into_any_element()
+    }
+}

crates/welcome/src/welcome.rs

@@ -1,12 +1,13 @@
 mod base_keymap_picker;
 mod base_keymap_setting;
+mod multibuffer_hint;
 
 use client::{telemetry::Telemetry, TelemetrySettings};
 use db::kvp::KEY_VALUE_STORE;
 use gpui::{
-    svg, AnyElement, AppContext, EventEmitter, FocusHandle, FocusableView, InteractiveElement,
-    ParentElement, Render, Styled, Subscription, Task, View, ViewContext, VisualContext, WeakView,
-    WindowContext,
+    actions, svg, AnyElement, AppContext, EventEmitter, FocusHandle, FocusableView,
+    InteractiveElement, ParentElement, Render, Styled, Subscription, Task, View, ViewContext,
+    VisualContext, WeakView, WindowContext,
 };
 use settings::{Settings, SettingsStore};
 use std::sync::Arc;
@@ -19,6 +20,9 @@ use workspace::{
 };
 
 pub use base_keymap_setting::BaseKeymap;
+pub use multibuffer_hint::*;
+
+actions!(welcome, [ResetHints]);
 
 pub const FIRST_OPEN: &str = "first_open";
 
@@ -30,6 +34,8 @@ pub fn init(cx: &mut AppContext) {
             let welcome_page = WelcomePage::new(workspace, cx);
             workspace.add_item_to_active_pane(Box::new(welcome_page), None, cx)
         });
+        workspace
+            .register_action(|_workspace, _: &ResetHints, cx| MultibufferHint::set_count(0, cx));
     })
     .detach();