From cc2f102141b75d4c5e93b39a3a1b3de2736c01fc Mon Sep 17 00:00:00 2001
From: Joscha <joscha@plugh.de>
Date: Sat, 21 May 2022 21:07:24 +0200
Subject: [PATCH] Position cursor via buffer

---
 examples/hello_world.rs |  1 +
 src/buffer.rs           | 39 +++++++++++++++++++++++++++++++--------
 src/terminal.rs         | 20 +++++++++++++++++++-
 3 files changed, 51 insertions(+), 9 deletions(-)

diff --git a/examples/hello_world.rs b/examples/hello_world.rs
index 0b4d6ca..44c10fa 100644
--- a/examples/hello_world.rs
+++ b/examples/hello_world.rs
@@ -24,6 +24,7 @@ fn main() -> io::Result<()> {
         "Press any key to exit",
         ContentStyle::default().on_dark_blue(),
     );
+    b.set_cursor(Some(Pos::new(16, 0)));
 
     // Show the buffer's contents on screen
     term.present()?;
diff --git a/src/buffer.rs b/src/buffer.rs
index 256e3ab..c666cda 100644
--- a/src/buffer.rs
+++ b/src/buffer.rs
@@ -51,6 +51,7 @@ impl Cell {
 pub struct Buffer {
     size: Size,
     data: Vec<Cell>,
+    cursor: Option<Pos>,
 }
 
 impl Buffer {
@@ -59,6 +60,7 @@ impl Buffer {
         Self {
             size: Size::ZERO,
             data: vec![],
+            cursor: None,
         }
     }
 
@@ -77,19 +79,32 @@ impl Buffer {
         self.size
     }
 
+    /// Resize the buffer and reset its contents.
+    ///
+    /// The buffer's contents are reset even if the buffer is already the
+    /// correct size.
     pub fn resize(&mut self, size: Size) {
-        let width: usize = size.width.into();
-        let height: usize = size.height.into();
-        let len = width * height;
+        if size == self.size() {
+            self.data.fill_with(Cell::empty);
+            self.cursor = None;
+        } else {
+            let width: usize = size.width.into();
+            let height: usize = size.height.into();
+            let len = width * height;
 
-        self.size = size;
-        self.data.clear();
-        self.data.resize_with(len, Cell::empty);
+            self.size = size;
+            self.data.clear();
+            self.data.resize_with(len, Cell::empty);
+            self.cursor = None;
+        }
     }
 
-    /// Reset all cells of the buffer to be empty and have no styling.
+    /// Reset the contents of the buffer.
+    ///
+    /// `buf.reset()` is equivalent to `buf.resize(buf.size())`.
     pub fn reset(&mut self) {
-        self.resize(self.size);
+        self.data.fill_with(Cell::empty);
+        self.cursor = None;
     }
 
     pub fn write(&mut self, mut pos: Pos, content: &str, style: ContentStyle) {
@@ -118,6 +133,14 @@ impl Buffer {
         }
     }
 
+    pub fn cursor(&self) -> Option<Pos> {
+        self.cursor
+    }
+
+    pub fn set_cursor(&mut self, pos: Option<Pos>) {
+        self.cursor = pos;
+    }
+
     pub fn cells(&self) -> Cells<'_> {
         Cells {
             buffer: self,
diff --git a/src/terminal.rs b/src/terminal.rs
index 482644b..7653855 100644
--- a/src/terminal.rs
+++ b/src/terminal.rs
@@ -1,7 +1,7 @@
 use std::io::Write;
 use std::{io, mem};
 
-use crossterm::cursor::MoveTo;
+use crossterm::cursor::{Hide, MoveTo, Show};
 use crossterm::style::{PrintStyledContent, StyledContent};
 use crossterm::terminal::{Clear, ClearType, EnterAlternateScreen, LeaveAlternateScreen};
 use crossterm::{ExecutableCommand, QueueableCommand};
@@ -65,9 +65,11 @@ impl Terminal {
         }
 
         self.draw_differences()?;
+        self.update_cursor()?;
         self.out.flush()?;
 
         mem::swap(&mut self.prev_buffer, &mut self.curr_buffer);
+        self.curr_buffer.reset();
 
         Ok(())
     }
@@ -80,7 +82,23 @@ impl Terminal {
                 .queue(MoveTo(x, y))?
                 .queue(PrintStyledContent(content))?;
         }
+        Ok(())
+    }
 
+    fn update_cursor(&mut self) -> io::Result<()> {
+        if let Some(pos) = self.curr_buffer.cursor() {
+            let size = self.curr_buffer.size();
+            let x_in_bounds = 0 <= pos.x && pos.x < size.width as i32;
+            let y_in_bounds = 0 <= pos.y && pos.y < size.height as i32;
+            if x_in_bounds && y_in_bounds {
+                self.out
+                    .queue(Show)?
+                    .queue(MoveTo(pos.x as u16, pos.y as u16))?;
+                return Ok(());
+            }
+        }
+
+        self.out.queue(Hide)?;
         Ok(())
     }
 }