From ef3b9cc521d131246d439d2e425175d88272d2c2 Mon Sep 17 00:00:00 2001
From: Pavel Strakhov <ri@idzaaus.org>
Date: Sun, 31 Mar 2024 21:53:32 +0100
Subject: [PATCH] Hide cursor based on selection, preedit, or config

---
 src/edit/editor.rs  | 22 ++++++++++++++++++++--
 src/edit/mod.rs     | 24 ++++++++++++++++++++++++
 src/edit/syntect.rs |  4 ++++
 src/edit/vi.rs      |  4 ++++
 4 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/src/edit/editor.rs b/src/edit/editor.rs
index 1231002cec..b2c4026871 100644
--- a/src/edit/editor.rs
+++ b/src/edit/editor.rs
@@ -25,6 +25,11 @@ pub struct Editor<'buffer> {
     cursor_moved: bool,
     auto_indent: bool,
     change: Option<Change>,
+    // A preedit was specified with non-empty text but with empty cursor,
+    // indicating that the cursor should be hidden
+    has_preedit_without_cursor: bool,
+    // Set with `set_cursor_hidden`
+    cursor_hidden_by_setting: bool,
 }
 
 fn cursor_glyph_opt(cursor: &Cursor, run: &LayoutRun) -> Option<(usize, f32)> {
@@ -104,6 +109,8 @@ impl<'buffer> Editor<'buffer> {
             cursor_moved: false,
             auto_indent: false,
             change: None,
+            has_preedit_without_cursor: false,
+            cursor_hidden_by_setting: false,
         }
     }
 
@@ -191,8 +198,14 @@ impl<'buffer> Editor<'buffer> {
                 }
 
                 // Draw cursor
-                if let Some((x, y)) = cursor_position(&self.cursor, &run) {
-                    f(x, y, 1, line_height as u32, cursor_color);
+                let cursor_hidden = self.cursor_hidden_by_setting
+                    || self.has_preedit_without_cursor
+                    || self.has_selection();
+
+                if !cursor_hidden {
+                    if let Some((x, y)) = cursor_position(&self.cursor, &run) {
+                        f(x, y, 1, line_height as u32, cursor_color);
+                    }
                 }
 
                 for glyph in run.glyphs.iter() {
@@ -255,6 +268,11 @@ impl<'buffer> Edit<'buffer> for Editor<'buffer> {
         }
     }
 
+    fn set_cursor_hidden(&mut self, hidden: bool) {
+        self.cursor_hidden_by_setting = hidden;
+        self.set_redraw(true);
+    }
+
     fn selection(&self) -> Selection {
         self.selection
     }
diff --git a/src/edit/mod.rs b/src/edit/mod.rs
index d9d4fd11db..5385022773 100644
--- a/src/edit/mod.rs
+++ b/src/edit/mod.rs
@@ -203,9 +203,33 @@ pub trait Edit<'buffer> {
     /// Get the current cursor
     fn cursor(&self) -> Cursor;
 
+    /// Hide or show the cursor
+    ///
+    /// This should be used to hide the cursor, for example,
+    /// when the editor is unfocused, when the text is not editable,
+    /// or to implement cursor blinking.
+    ///
+    /// Note that even after `set_cursor_hidden(false)`, the editor may
+    /// choose to hide the cursor based on internal state, for example,
+    /// when there is a selection or when there is a preedit without a cursor.
+    fn set_cursor_hidden(&mut self, hidden: bool);
+
     /// Set the current cursor
     fn set_cursor(&mut self, cursor: Cursor);
 
+    /// Returns true if some text is selected
+    fn has_selection(&self) -> bool {
+        match self.selection() {
+            Selection::None => false,
+            Selection::Normal(selection) => {
+                let cursor = self.cursor();
+                selection.line != cursor.line || selection.index != cursor.index
+            }
+            Selection::Line(selection) => selection.line != self.cursor().line,
+            Selection::Word(_) => true,
+        }
+    }
+
     /// Get the current selection position
     fn selection(&self) -> Selection;
 
diff --git a/src/edit/syntect.rs b/src/edit/syntect.rs
index d6ef2d8871..75b1e23dd3 100644
--- a/src/edit/syntect.rs
+++ b/src/edit/syntect.rs
@@ -256,6 +256,10 @@ impl<'syntax_system, 'buffer> Edit<'buffer> for SyntaxEditor<'syntax_system, 'bu
         self.editor.selection()
     }
 
+    fn set_cursor_hidden(&mut self, hidden: bool) {
+        self.editor.set_cursor_hidden(hidden);
+    }
+
     fn set_selection(&mut self, selection: Selection) {
         self.editor.set_selection(selection);
     }
diff --git a/src/edit/vi.rs b/src/edit/vi.rs
index 08dfd480fb..e697f4f6ec 100644
--- a/src/edit/vi.rs
+++ b/src/edit/vi.rs
@@ -1165,6 +1165,10 @@ impl<'syntax_system, 'buffer> Edit<'buffer> for ViEditor<'syntax_system, 'buffer
     fn cursor_position(&self) -> Option<(i32, i32)> {
         self.editor.cursor_position()
     }
+
+    fn set_cursor_hidden(&mut self, hidden: bool) {
+        self.editor.set_cursor_hidden(hidden);
+    }
 }
 
 impl<'font_system, 'syntax_system, 'buffer>