From 2785f38eebd99e3df740c688b9df521f69fbdf89 Mon Sep 17 00:00:00 2001
From: Jason Lee <huacnlee@gmail.com>
Date: Sat, 29 Jun 2024 15:38:02 +0800
Subject: [PATCH] Add to blinking currsor support for Input.

---
 crates/ui/src/input.rs              | 50 ++++++++++++++++--
 crates/ui/src/input/blink_cursor.rs | 80 +++++++++++++++++++++++++++++
 2 files changed, 126 insertions(+), 4 deletions(-)
 create mode 100644 crates/ui/src/input/blink_cursor.rs

diff --git a/crates/ui/src/input.rs b/crates/ui/src/input.rs
index cb152510..cd268c9e 100644
--- a/crates/ui/src/input.rs
+++ b/crates/ui/src/input.rs
@@ -2,10 +2,13 @@ use std::ops::Range;
 
 use crate::event::InterativeElementExt as _;
 use crate::theme::ActiveTheme;
+use blink_cursor::BlinkCursor;
 use gpui::*;
 use prelude::FluentBuilder as _;
 use unicode_segmentation::*;
 
+mod blink_cursor;
+
 actions!(
     input,
     [
@@ -71,6 +74,7 @@ pub struct TextInput {
     focus_handle: FocusHandle,
     text: SharedString,
     placeholder: SharedString,
+    blink_cursor: Model<BlinkCursor>,
     selected_range: Range<usize>,
     selection_reversed: bool,
     marked_range: Option<Range<usize>>,
@@ -84,10 +88,13 @@ impl EventEmitter<TextEvent> for TextInput {}
 
 impl TextInput {
     pub fn new(cx: &mut ViewContext<Self>) -> Self {
-        Self {
-            focus_handle: cx.focus_handle(),
+        let focus_handle = cx.focus_handle();
+        let blink_cursor = cx.new_model(|cx| BlinkCursor::new(cx));
+        let input = Self {
+            focus_handle: focus_handle.clone(),
             text: "".into(),
             placeholder: "".into(),
+            blink_cursor,
             selected_range: 0..0,
             selection_reversed: false,
             marked_range: None,
@@ -95,7 +102,25 @@ impl TextInput {
             disabled: false,
             masked: false,
             appearance: true,
-        }
+        };
+
+        // Observe the blink cursor to repaint the view when it changes.
+        cx.observe(&input.blink_cursor, |_, _, cx| cx.notify())
+            .detach();
+        // Blink the cursor when the window is active, pause when it's not.
+        cx.observe_window_activation(|input, cx| {
+            if cx.is_window_active() {
+                input.blink_cursor.update(cx, |blink_cursor, cx| {
+                    blink_cursor.start(cx);
+                });
+            }
+        })
+        .detach();
+
+        cx.on_focus(&focus_handle, Self::on_focus).detach();
+        cx.on_blur(&focus_handle, Self::on_blur).detach();
+
+        input
     }
 
     /// Set the text of the input field.
@@ -288,6 +313,23 @@ impl TextInput {
             .find_map(|(idx, _)| (idx > offset).then_some(idx))
             .unwrap_or(self.text.len())
     }
+
+    /// Returns the true to let InputElement to render cursor, when Input is focused and current BlinkCursor is visible.
+    pub(crate) fn show_cursor(&self, cx: &WindowContext) -> bool {
+        self.focus_handle.is_focused(cx) && self.blink_cursor.read(cx).visible()
+    }
+
+    fn on_focus(&mut self, cx: &mut ViewContext<Self>) {
+        self.blink_cursor.update(cx, |blink_cursor, cx| {
+            blink_cursor.start(cx);
+        });
+    }
+
+    fn on_blur(&mut self, cx: &mut ViewContext<Self>) {
+        self.blink_cursor.update(cx, |blink_cursor, cx| {
+            blink_cursor.pause(cx);
+        });
+    }
 }
 
 impl ViewInputHandler for TextInput {
@@ -496,7 +538,7 @@ impl Element for TextElement {
             .unwrap();
 
         let cursor_pos = line.x_for_index(cursor);
-        let (selection, cursor) = if selected_range.is_empty() {
+        let (selection, cursor) = if selected_range.is_empty() && input.show_cursor(cx) {
             (
                 None,
                 Some(fill(
diff --git a/crates/ui/src/input/blink_cursor.rs b/crates/ui/src/input/blink_cursor.rs
new file mode 100644
index 00000000..0c9cd54f
--- /dev/null
+++ b/crates/ui/src/input/blink_cursor.rs
@@ -0,0 +1,80 @@
+use std::time::Duration;
+
+use gpui::{ModelContext, Timer};
+
+/// To manage the Input cursor blinking.
+///
+/// It will start blinking with a interval of 500ms.
+/// Every loop will notify the view to update the `visable`, and Input will observe this update to touch repaint.
+///
+/// The input painter will check if this in visible state, then it will draw the cursor.
+pub struct BlinkCursor {
+    interval: Duration,
+    blink_epoch: usize,
+    visible: bool,
+    paused: bool,
+    started: bool,
+}
+
+impl BlinkCursor {
+    pub fn new(_cx: &mut ModelContext<Self>) -> Self {
+        Self {
+            interval: Duration::from_millis(500),
+            visible: false,
+            paused: false,
+            started: false,
+            blink_epoch: 0,
+        }
+    }
+
+    /// Start the blinking
+    pub fn start(&mut self, cx: &mut ModelContext<Self>) {
+        if self.started {
+            return;
+        }
+
+        self.started = true;
+        self.paused = false;
+        self.blink(self.blink_epoch, cx);
+    }
+
+    fn next_epoch(&mut self) -> usize {
+        self.blink_epoch += 1;
+        self.blink_epoch
+    }
+
+    fn blink(&mut self, epoch: usize, cx: &mut ModelContext<Self>) {
+        if self.paused {
+            return;
+        }
+
+        if epoch != self.blink_epoch {
+            return;
+        }
+
+        self.visible = !self.visible;
+        cx.notify();
+
+        let epoch = self.next_epoch();
+
+        // Schedule the next blink
+        let interval = self.interval;
+        cx.spawn(|this, mut cx| async move {
+            Timer::after(interval).await;
+            if let Some(this) = this.upgrade() {
+                this.update(&mut cx, |this, cx| this.blink(epoch, cx)).ok();
+            }
+        })
+        .detach();
+    }
+
+    pub fn visible(&self) -> bool {
+        self.visible
+    }
+
+    pub fn pause(&mut self, cx: &mut ModelContext<Self>) {
+        self.paused = true;
+        self.started = false;
+        cx.notify();
+    }
+}