From 2a7b368441fbb3b742845dbd84f9c77162556d14 Mon Sep 17 00:00:00 2001
From: Alexandre Bury <alexandre.bury@gmail.com>
Date: Mon, 10 Jun 2024 09:37:47 -0400
Subject: [PATCH] Make backend persistence opt-in

---
 cursive-core/src/backend.rs        | 8 ++++++++
 cursive/src/backends/crossterm.rs  | 4 ++++
 cursive/src/backends/curses/n.rs   | 4 ++++
 cursive/src/backends/curses/pan.rs | 4 ++++
 cursive/src/backends/termion.rs    | 4 ++++
 5 files changed, 24 insertions(+)

diff --git a/cursive-core/src/backend.rs b/cursive-core/src/backend.rs
index 99e67e80..c0bcd849 100644
--- a/cursive-core/src/backend.rs
+++ b/cursive-core/src/backend.rs
@@ -81,6 +81,14 @@ pub trait Backend {
     /// Any call to `print_at` from now on should use the given effect.
     fn set_effect(&self, effect: theme::Effect);
 
+    /// Returns `true` if the backend has persistent output.
+    ///
+    /// If true, this means that output stays there between calls to
+    /// `refresh()`, so only delta needs to be sent.
+    fn is_persistent(&self) -> bool {
+        false
+    }
+
     /// Disables the given effect.
     fn unset_effect(&self, effect: theme::Effect);
 
diff --git a/cursive/src/backends/crossterm.rs b/cursive/src/backends/crossterm.rs
index 5e0234e8..51ecc7ef 100644
--- a/cursive/src/backends/crossterm.rs
+++ b/cursive/src/backends/crossterm.rs
@@ -327,6 +327,10 @@ impl Drop for Backend {
 }
 
 impl backend::Backend for Backend {
+    fn is_persistent(&self) -> bool {
+        true
+    }
+
     fn poll_event(&mut self) -> Option<Event> {
         match poll(Duration::from_millis(1)) {
             Ok(true) => match read() {
diff --git a/cursive/src/backends/curses/n.rs b/cursive/src/backends/curses/n.rs
index 14497d4b..17750b79 100644
--- a/cursive/src/backends/curses/n.rs
+++ b/cursive/src/backends/curses/n.rs
@@ -322,6 +322,10 @@ impl backend::Backend for Backend {
         "ncurses"
     }
 
+    fn is_persistent(&self) -> bool {
+        true
+    }
+
     fn set_title(&mut self, title: String) {
         write_to_tty(format!("\x1B]0;{title}\x07").as_bytes()).unwrap();
     }
diff --git a/cursive/src/backends/curses/pan.rs b/cursive/src/backends/curses/pan.rs
index 1fd3fb26..cedaa9ad 100644
--- a/cursive/src/backends/curses/pan.rs
+++ b/cursive/src/backends/curses/pan.rs
@@ -377,6 +377,10 @@ impl backend::Backend for Backend {
         "pancurses"
     }
 
+    fn is_persistent(&self) -> bool {
+        true
+    }
+
     fn set_title(&mut self, title: String) {
         print!("\x1B]0;{title}\x07");
         stdout().flush().expect("could not flush stdout");
diff --git a/cursive/src/backends/termion.rs b/cursive/src/backends/termion.rs
index 3d613a6c..b2d80e4d 100644
--- a/cursive/src/backends/termion.rs
+++ b/cursive/src/backends/termion.rs
@@ -267,6 +267,10 @@ impl backend::Backend for Backend {
         "termion"
     }
 
+    fn is_persistent(&self) -> bool {
+        true
+    }
+
     fn set_title(&mut self, title: String) {
         write!(self.terminal.get_mut(), "\x1B]0;{title}\x07").unwrap();
     }