From 2f7fd0c53d6d64043530ccb6d208217a6ed5718c Mon Sep 17 00:00:00 2001
From: rhysd <lin90162@yahoo.co.jp>
Date: Sat, 23 Jul 2022 19:20:20 +0900
Subject: [PATCH 1/3] implement `TextArea::scroll` and `CursorMove::InViewport`

---
 src/cursor.rs   | 13 ++++++++++
 src/textarea.rs | 13 +++++++---
 src/widget.rs   | 65 +++++++++++++++++++++++++++++++++++++------------
 3 files changed, 72 insertions(+), 19 deletions(-)

diff --git a/src/cursor.rs b/src/cursor.rs
index 260a949..d031b64 100644
--- a/src/cursor.rs
+++ b/src/cursor.rs
@@ -1,3 +1,4 @@
+use crate::widget::Viewport;
 use crate::word::{find_word_start_backward, find_word_start_forward};
 #[cfg(feature = "arbitrary")]
 use arbitrary::Arbitrary;
@@ -187,6 +188,7 @@ pub enum CursorMove {
     /// assert_eq!(textarea.cursor(), (2, 4));
     /// ```
     Jump(u16, u16),
+    InViewport,
 }
 
 impl CursorMove {
@@ -194,6 +196,7 @@ impl CursorMove {
         &self,
         (row, col): (usize, usize),
         lines: &[String],
+        viewport: &Viewport,
     ) -> Option<(usize, usize)> {
         use CursorMove::*;
 
@@ -271,6 +274,16 @@ impl CursorMove {
                 let col = fit_col(*col as usize, &lines[row]);
                 Some((row, col))
             }
+            InViewport => {
+                let (row_top, col_top, row_bottom, col_bottom) = viewport.position();
+
+                let row = row.clamp(row_top as usize, row_bottom as usize);
+                let row = cmp::min(row, lines.len() - 1);
+                let col = col.clamp(col_top as usize, col_bottom as usize);
+                let col = fit_col(col, &lines[row]);
+
+                Some((row, col))
+            }
         }
     }
 }
diff --git a/src/textarea.rs b/src/textarea.rs
index 91a3801..b14aff2 100644
--- a/src/textarea.rs
+++ b/src/textarea.rs
@@ -5,7 +5,7 @@ use crate::input::{Input, Key};
 #[cfg(feature = "search")]
 use crate::search::Search;
 use crate::util::spaces;
-use crate::widget::{Renderer, ScrollTop};
+use crate::widget::{Renderer, Viewport};
 use crate::word::{find_word_end_forward, find_word_start_backward};
 use tui::style::{Modifier, Style};
 use tui::text::Spans;
@@ -42,7 +42,7 @@ pub struct TextArea<'a> {
     history: History,
     cursor_line_style: Style,
     line_number_style: Option<Style>,
-    pub(crate) scroll_top: ScrollTop,
+    pub(crate) viewport: Viewport,
     cursor_style: Style,
     yank: String,
     #[cfg(feature = "search")]
@@ -138,7 +138,7 @@ impl<'a> TextArea<'a> {
             history: History::new(50),
             cursor_line_style: Style::default().add_modifier(Modifier::UNDERLINED),
             line_number_style: None,
-            scroll_top: ScrollTop::default(),
+            viewport: Viewport::default(),
             cursor_style: Style::default().add_modifier(Modifier::REVERSED),
             yank: String::new(),
             #[cfg(feature = "search")]
@@ -868,7 +868,7 @@ impl<'a> TextArea<'a> {
     /// assert_eq!(textarea.cursor(), (1, 1));
     /// ```
     pub fn move_cursor(&mut self, m: CursorMove) {
-        if let Some(cursor) = m.next_cursor(self.cursor, &self.lines) {
+        if let Some(cursor) = m.next_cursor(self.cursor, &self.lines, &self.viewport) {
             self.cursor = cursor;
         }
     }
@@ -1462,4 +1462,9 @@ impl<'a> TextArea<'a> {
     pub fn set_search_style(&mut self, style: Style) {
         self.search.style = style;
     }
+
+    pub fn scroll(&mut self, delta_row: i16, delta_col: i16) {
+        self.viewport.scroll(delta_row, delta_col);
+        self.move_cursor(CursorMove::InViewport);
+    }
 }
diff --git a/src/widget.rs b/src/widget.rs
index 4e21cf6..23e2348 100644
--- a/src/widget.rs
+++ b/src/widget.rs
@@ -1,13 +1,13 @@
 use crate::textarea::TextArea;
 use crate::util::num_digits;
 use std::cmp;
-use std::sync::atomic::{AtomicU32, Ordering};
+use std::sync::atomic::{AtomicU64, Ordering};
 use tui::buffer::Buffer;
 use tui::layout::Rect;
 use tui::text::Text;
 use tui::widgets::{Paragraph, Widget};
 
-// &mut 'a (u16, u16) is not available since TextAreaWidget instance totally takes over the ownership of TextArea
+// &mut 'a (u16, u16, u16, u16) is not available since Renderer instance totally takes over the ownership of TextArea
 // instance. In the case, the TextArea instance cannot be accessed from any other objects since it is mutablly
 // borrowed.
 //
@@ -16,25 +16,60 @@ use tui::widgets::{Paragraph, Widget};
 // manage states of textarea instances separately.
 // https://docs.rs/tui/latest/tui/terminal/struct.Frame.html#method.render_stateful_widget
 #[derive(Default)]
-pub struct ScrollTop(AtomicU32);
+pub struct Viewport(AtomicU64);
 
-impl Clone for ScrollTop {
+impl Clone for Viewport {
     fn clone(&self) -> Self {
         let u = self.0.load(Ordering::Relaxed);
-        ScrollTop(AtomicU32::new(u))
+        Viewport(AtomicU64::new(u))
     }
 }
 
-impl ScrollTop {
-    fn load(&self) -> (u16, u16) {
+impl Viewport {
+    pub fn scroll_top(&self) -> (u16, u16) {
         let u = self.0.load(Ordering::Relaxed);
         ((u >> 16) as u16, u as u16)
     }
 
-    fn store(&self, row: u16, col: u16) {
-        let u = ((row as u32) << 16) | col as u32;
+    pub fn position(&self) -> (u16, u16, u16, u16) {
+        let u = self.0.load(Ordering::Relaxed);
+        let width = (u >> 48) as u16;
+        let height = (u >> 32) as u16;
+        let row_top = (u >> 16) as u16;
+        let col_top = u as u16;
+
+        let row_bottom = row_top.saturating_add(height).saturating_sub(1);
+        let col_bottom = col_top.saturating_add(width).saturating_sub(1);
+
+        (
+            row_top,
+            col_top,
+            cmp::max(row_top, row_bottom),
+            cmp::max(col_top, col_bottom),
+        )
+    }
+
+    fn store(&self, row: u16, col: u16, width: u16, height: u16) {
+        // Pack four u16 values into one u64 value
+        let u =
+            ((width as u64) << 48) | ((height as u64) << 32) | ((row as u64) << 16) | col as u64;
         self.0.store(u, Ordering::Relaxed);
     }
+
+    pub fn scroll(&mut self, delta_row: i16, delta_col: i16) {
+        fn apply_scroll(pos: u16, delta: i16) -> u16 {
+            if delta >= 0 {
+                pos.saturating_add(delta as u16)
+            } else {
+                pos.saturating_sub(-delta as u16)
+            }
+        }
+
+        let u = self.0.get_mut();
+        let row = apply_scroll((*u >> 16) as u16, delta_row);
+        let col = apply_scroll(*u as u16, delta_col);
+        *u = (*u & 0xffff_ffff_0000_0000) | ((row as u64) << 16) | (col as u64);
+    }
 }
 
 pub struct Renderer<'a>(&'a TextArea<'a>);
@@ -59,7 +94,7 @@ impl<'a> Renderer<'a> {
 
 impl<'a> Widget for Renderer<'a> {
     fn render(self, area: Rect, buf: &mut Buffer) {
-        let inner_area = if let Some(b) = self.0.block() {
+        let Rect { width, height, .. } = if let Some(b) = self.0.block() {
             b.inner(area)
         } else {
             area
@@ -76,11 +111,11 @@ impl<'a> Widget for Renderer<'a> {
         }
 
         let cursor = self.0.cursor();
-        let (top_row, top_col) = self.0.scroll_top.load();
-        let top_row = next_scroll_top(top_row, cursor.0 as u16, inner_area.height);
-        let top_col = next_scroll_top(top_col, cursor.1 as u16, inner_area.width);
+        let (top_row, top_col) = self.0.viewport.scroll_top();
+        let top_row = next_scroll_top(top_row, cursor.0 as u16, height);
+        let top_col = next_scroll_top(top_col, cursor.1 as u16, width);
 
-        let text = self.text(top_row as usize, inner_area.height as usize);
+        let text = self.text(top_row as usize, height as usize);
         let mut inner = Paragraph::new(text).style(self.0.style());
         if let Some(b) = self.0.block() {
             inner = inner.block(b.clone());
@@ -90,7 +125,7 @@ impl<'a> Widget for Renderer<'a> {
         }
 
         // Store scroll top position for rendering on the next tick
-        self.0.scroll_top.store(top_row, top_col);
+        self.0.viewport.store(top_row, top_col, width, height);
 
         inner.render(area, buf);
     }

From b54fe5c01d42cc0ba1f546c5c7233264d79d39ae Mon Sep 17 00:00:00 2001
From: rhysd <lin90162@yahoo.co.jp>
Date: Sat, 23 Jul 2022 20:09:26 +0900
Subject: [PATCH 2/3] implement vertial mouse scroll with both crossterm and
 termion supports

---
 examples/termion.rs | 22 +++++++++-------
 src/input.rs        | 64 ++++++++++++++++++++++++++++++++++++---------
 src/textarea.rs     | 14 ++++++++++
 3 files changed, 78 insertions(+), 22 deletions(-)

diff --git a/examples/termion.rs b/examples/termion.rs
index 9a1ebea..3d7e2b4 100644
--- a/examples/termion.rs
+++ b/examples/termion.rs
@@ -3,17 +3,17 @@ use std::io;
 use std::sync::mpsc;
 use std::thread;
 use std::time::Duration;
-use termion::event::Key;
+use termion::event::Event as TermEvent;
 use termion::input::{MouseTerminal, TermRead};
 use termion::raw::IntoRawMode;
 use termion::screen::AlternateScreen;
 use tui::backend::TermionBackend;
 use tui::widgets::{Block, Borders};
 use tui::Terminal;
-use tui_textarea::TextArea;
+use tui_textarea::{Input, Key, TextArea};
 
 enum Event {
-    Key(Key),
+    Term(TermEvent),
     Tick,
 }
 
@@ -25,12 +25,12 @@ fn main() -> Result<(), Box<dyn Error>> {
     let mut term = Terminal::new(backend)?;
 
     let events = {
-        let keys = io::stdin().keys();
+        let events = io::stdin().events();
         let (tx, rx) = mpsc::channel();
         let keys_tx = tx.clone();
         thread::spawn(move || {
-            for key in keys.flatten() {
-                keys_tx.send(Event::Key(key)).unwrap();
+            for event in events.flatten() {
+                keys_tx.send(Event::Term(event)).unwrap();
             }
         });
         thread::spawn(move || loop {
@@ -49,10 +49,12 @@ fn main() -> Result<(), Box<dyn Error>> {
 
     loop {
         match events.recv()? {
-            Event::Key(Key::Esc) => break,
-            Event::Key(key) => {
-                textarea.input(key);
-            }
+            Event::Term(event) => match event.into() {
+                Input { key: Key::Esc, .. } => break,
+                input => {
+                    textarea.input(input);
+                }
+            },
             Event::Tick => {}
         }
         term.draw(|f| {
diff --git a/src/input.rs b/src/input.rs
index 60b9c7b..5eccc21 100644
--- a/src/input.rs
+++ b/src/input.rs
@@ -1,9 +1,12 @@
 #[cfg(feature = "arbitrary")]
 use arbitrary::Arbitrary;
 #[cfg(feature = "crossterm")]
-use crossterm::event::{Event as CrosstermEvent, KeyCode, KeyEvent, KeyModifiers};
+use crossterm::event::{
+    Event as CrosstermEvent, KeyCode, KeyEvent, KeyModifiers, MouseEvent as CrosstermMouseEvent,
+    MouseEventKind as CrosstermMouseEventKind,
+};
 #[cfg(feature = "termion")]
-use termion::event::{Event as TerimonEvent, Key as TermionKey};
+use termion::event::{Event as TermionEvent, Key as TermionKey, MouseEvent as TermionMouseEvent};
 
 /// Backend-agnostic key input kind.
 #[non_exhaustive]
@@ -27,6 +30,10 @@ pub enum Key {
     PageUp,
     PageDown,
     Esc,
+    /// Virtual key to scroll down by mouse
+    MouseScrollDown,
+    /// Virtual key to scroll up by mouse
+    MouseScrollUp,
     /// An invalid key input (this key is always ignored by [`TextArea`](crate::TextArea)).
     Null,
 }
@@ -90,10 +97,10 @@ impl Default for Input {
 impl From<CrosstermEvent> for Input {
     /// Convert [`crossterm::event::Event`] to [`Input`].
     fn from(event: CrosstermEvent) -> Self {
-        if let CrosstermEvent::Key(key) = event {
-            Self::from(key)
-        } else {
-            Self::default()
+        match event {
+            CrosstermEvent::Key(key) => Self::from(key),
+            CrosstermEvent::Mouse(mouse) => Self::from(mouse),
+            _ => Self::default(),
         }
     }
 }
@@ -126,14 +133,29 @@ impl From<KeyEvent> for Input {
     }
 }
 
+#[cfg(feature = "crossterm")]
+impl From<CrosstermMouseEvent> for Input {
+    /// Convert [`crossterm::event::MouseEvent`] to [`Input`].
+    fn from(mouse: CrosstermMouseEvent) -> Self {
+        let key = match mouse.kind {
+            CrosstermMouseEventKind::ScrollDown => Key::MouseScrollDown,
+            CrosstermMouseEventKind::ScrollUp => Key::MouseScrollUp,
+            _ => return Self::default(),
+        };
+        let ctrl = mouse.modifiers.contains(KeyModifiers::CONTROL);
+        let alt = mouse.modifiers.contains(KeyModifiers::ALT);
+        Self { key, ctrl, alt }
+    }
+}
+
 #[cfg(feature = "termion")]
-impl From<TerimonEvent> for Input {
+impl From<TermionEvent> for Input {
     /// Convert [`termion::event::Event`] to [`Input`].
-    fn from(event: TerimonEvent) -> Self {
-        if let TerimonEvent::Key(key) = event {
-            Self::from(key)
-        } else {
-            Self::default()
+    fn from(event: TermionEvent) -> Self {
+        match event {
+            TermionEvent::Key(key) => Self::from(key),
+            TermionEvent::Mouse(mouse) => Self::from(mouse),
+            _ => Self::default(),
         }
     }
 }
@@ -176,3 +198,21 @@ impl From<TermionKey> for Input {
         Input { key, ctrl, alt }
     }
 }
+
+#[cfg(feature = "termion")]
+impl From<TermionMouseEvent> for Input {
+    /// Convert [`termion::event::MouseEvent`] to [`Input`].
+    fn from(mouse: TermionMouseEvent) -> Self {
+        use termion::event::MouseButton;
+        let key = match mouse {
+            TermionMouseEvent::Press(MouseButton::WheelUp, ..) => Key::MouseScrollUp,
+            TermionMouseEvent::Press(MouseButton::WheelDown, ..) => Key::MouseScrollDown,
+            _ => return Self::default(),
+        };
+        Self {
+            key,
+            ctrl: false,
+            alt: false,
+        }
+    }
+}
diff --git a/src/textarea.rs b/src/textarea.rs
index b14aff2..f8f682c 100644
--- a/src/textarea.rs
+++ b/src/textarea.rs
@@ -441,6 +441,20 @@ impl<'a> TextArea<'a> {
                 ctrl: true,
                 alt: false,
             } => self.paste(),
+            Input {
+                key: Key::MouseScrollDown,
+                ..
+            } => {
+                self.scroll(1, 0);
+                false
+            }
+            Input {
+                key: Key::MouseScrollUp,
+                ..
+            } => {
+                self.scroll(-1, 0);
+                false
+            }
             _ => false,
         };
 

From 63ae3503d4d71f1ddaa53ca93c03d3c29996778c Mon Sep 17 00:00:00 2001
From: rhysd <lin90162@yahoo.co.jp>
Date: Sun, 24 Jul 2022 08:41:05 +0900
Subject: [PATCH 3/3] add document and doc tests for `TextArea::scroll` and
 `CursorMove::InViewport`

---
 README.md       |  5 +++++
 src/cursor.rs   | 31 ++++++++++++++++++++++++++++
 src/textarea.rs | 54 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 90 insertions(+)

diff --git a/README.md b/README.md
index 357fd1a..2a722dd 100644
--- a/README.md
+++ b/README.md
@@ -15,6 +15,7 @@ text editor can be easily put as part of your TUI application.
 - Line number
 - Cursor line highlight
 - Search with regular expressions
+- Mouse scrolling
 - Yank support. Paste text deleted with `C-k`, `C-j`, ...
 - Backend agnostic. [crossterm][], [termion][], and your own backend are all supported
 - Multiple textarea widgets in the same screen
@@ -410,9 +411,11 @@ notify how to move the cursor.
 | `textarea.move_cursor(CursorMove::Top)`              | Move cursor to top of lines                  |
 | `textarea.move_cursor(CursorMove::Bottom)`           | Move cursor to bottom of lines               |
 | `textarea.move_cursor(CursorMove::Jump(row, col))`   | Move cursor to (row, col) position           |
+| `textarea.move_cursor(CursorMove::InViewport)`       | Move cursor to stay in the viewport          |
 | `textarea.set_search_pattern(pattern)`               | Set a pattern for text search                |
 | `textarea.search_forward(match_cursor)`              | Move cursor to next match of text search     |
 | `textarea.search_back(match_cursor)`                 | Move cursor to previous match of text search |
+| `textarea.scroll(rows, cols)`                        | Scroll the viewport                          |
 
 To define your own key mappings, simply call the above methods in your code instead of `TextArea::input()` method. The
 following example defines modal key mappings like Vim.
@@ -465,6 +468,8 @@ loop {
             Input { key: Key::Esc, .. } => textarea.set_search_pattern("").unwrap(),
             Input { key: Key::Char('n'), .. } => textarea.search_forward(),
             Input { key: Key::Char('N'), .. } => textarea.search_back(),
+            Input { key: Key::Char('e'), ctrl: true .. } => textarea.scroll(1, 0),
+            Input { key: Key::Char('y'), ctrl: true .. } => textarea.scroll(-1, 0),
             _ => {},
         },
         Mode::Insert => match read()?.into() {
diff --git a/src/cursor.rs b/src/cursor.rs
index d031b64..6c52530 100644
--- a/src/cursor.rs
+++ b/src/cursor.rs
@@ -188,6 +188,37 @@ pub enum CursorMove {
     /// assert_eq!(textarea.cursor(), (2, 4));
     /// ```
     Jump(u16, u16),
+    /// Move cursor to keep it within the viewport. For example, when a viewport displays line 8 to line 16:
+    ///
+    /// - cursor at line 4 is moved to line 8
+    /// - cursor at line 20 is moved to line 16
+    /// - cursor at line 12 is not moved
+    ///
+    /// This is useful when you moved a cursor but you don't want to move the viewport.
+    /// ```
+    /// # use tui::buffer::Buffer;
+    /// # use tui::layout::Rect;
+    /// # use tui::widgets::Widget;
+    /// use tui_textarea::{TextArea, CursorMove};
+    ///
+    /// // Let's say terminal height is 8.
+    ///
+    /// // Create textarea with 20 lines "0", "1", "2", "3", ...
+    /// // The viewport is displaying from line 1 to line 8.
+    /// let mut textarea: TextArea = (0..20).into_iter().map(|i| i.to_string()).collect();
+    /// # // Call `render` at least once to populate terminal size
+    /// # let r = Rect { x: 0, y: 0, width: 24, height: 8 };
+    /// # let mut b = Buffer::empty(r.clone());
+    /// # textarea.widget().render(r, &mut b);
+    ///
+    /// // Move cursor to the end of lines (line 20). It is outside the viewport (line 1 to line 8)
+    /// textarea.move_cursor(CursorMove::Bottom);
+    /// assert_eq!(textarea.cursor(), (19, 0));
+    ///
+    /// // Cursor is moved to line 8 to enter the viewport
+    /// textarea.move_cursor(CursorMove::InViewport);
+    /// assert_eq!(textarea.cursor(), (7, 0));
+    /// ```
     InViewport,
 }
 
diff --git a/src/textarea.rs b/src/textarea.rs
index f8f682c..0152301 100644
--- a/src/textarea.rs
+++ b/src/textarea.rs
@@ -519,6 +519,20 @@ impl<'a> TextArea<'a> {
                 self.insert_newline();
                 true
             }
+            Input {
+                key: Key::MouseScrollDown,
+                ..
+            } => {
+                self.scroll(1, 0);
+                false
+            }
+            Input {
+                key: Key::MouseScrollUp,
+                ..
+            } => {
+                self.scroll(-1, 0);
+                false
+            }
             _ => false,
         }
     }
@@ -1460,6 +1474,7 @@ impl<'a> TextArea<'a> {
     }
 
     /// Set the text style at matches of text search. The default style is colored with blue in background.
+    ///
     /// ```
     /// use tui::style::{Style, Color};
     /// use tui_textarea::TextArea;
@@ -1477,6 +1492,45 @@ impl<'a> TextArea<'a> {
         self.search.style = style;
     }
 
+    /// Scroll the textarea by `delta_row` rows (vertically) and `delta_col` columns (horizontally). Positive scroll
+    /// amount means scrolling down or right. And negative scroll amount means scrolling up or left. The cursor will not
+    /// move until it goes out the viewport. When the cursor position is outside the viewport after scroll, the cursor
+    /// position will be adjusted to stay in the viewport using the same logic as [`CursorMove::InViewport`].
+    ///
+    /// ```
+    /// # use tui::buffer::Buffer;
+    /// # use tui::layout::Rect;
+    /// # use tui::widgets::Widget;
+    /// use tui_textarea::TextArea;
+    ///
+    /// // Let's say terminal height is 8.
+    ///
+    /// // Create textarea with 20 lines "0", "1", "2", "3", ...
+    /// let mut textarea: TextArea = (0..20).into_iter().map(|i| i.to_string()).collect();
+    /// # // Call `render` at least once to populate terminal size
+    /// # let r = Rect { x: 0, y: 0, width: 24, height: 8 };
+    /// # let mut b = Buffer::empty(r.clone());
+    /// # textarea.widget().render(r, &mut b);
+    ///
+    /// // Scroll down by 15 lines. Since terminal height is 8, cursor will go out
+    /// // the viewport.
+    /// textarea.scroll(15, 0);
+    /// // So the cursor position was updated to stay in the viewport after the scrolling.
+    /// assert_eq!(textarea.cursor(), (15, 0));
+    ///
+    /// // Scroll up by 5 lines. Since the scroll amount is smaller than the terminal
+    /// // height, cursor position will not be updated.
+    /// textarea.scroll(-5, 0);
+    /// assert_eq!(textarea.cursor(), (15, 0));
+    ///
+    /// // Scroll up by 5 lines again. The terminal height is 8. So a cursor reaches to
+    /// // the top of viewport after scrolling up by 7 lines. Since we have already
+    /// // scrolled up by 5 lines, scrolling up by 5 lines again makes the cursor overrun
+    /// // the viewport by 5 - 2 = 3 lines. To keep the cursor stay in the viewport, the
+    /// // cursor position will be adjusted from line 15 to line 12.
+    /// textarea.scroll(-5, 0);
+    /// assert_eq!(textarea.cursor(), (12, 0));
+    /// ```
     pub fn scroll(&mut self, delta_row: i16, delta_col: i16) {
         self.viewport.scroll(delta_row, delta_col);
         self.move_cursor(CursorMove::InViewport);