From 929fa5474d5838d4c58dca8b0e576f5add49156b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bla=C5=BE=20Hrastnik?= <blaz@mxxn.io>
Date: Sat, 19 Sep 2020 11:56:56 +0900
Subject: [PATCH] Simple cursor scrolling.

---
 helix-term/src/editor.rs | 38 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/helix-term/src/editor.rs b/helix-term/src/editor.rs
index e1288e07..397ce8df 100644
--- a/helix-term/src/editor.rs
+++ b/helix-term/src/editor.rs
@@ -277,7 +277,17 @@ impl Editor {
             // Handle key events
             let mut event = reader.next().await;
             match event {
-                // TODO: handle resize events
+                Some(Ok(Event::Resize(width, height))) => {
+                    self.size = (width, height);
+                    let area = Rect::new(0, 0, width, height);
+                    self.surface = Surface::empty(area);
+                    self.cache = Surface::empty(area);
+
+                    // TODO: simplistic ensure cursor in view for now
+                    self.ensure_cursor_in_view();
+
+                    self.render();
+                }
                 Some(Ok(Event::Key(KeyEvent {
                     code: KeyCode::Char('q'),
                     ..
@@ -310,6 +320,9 @@ impl Editor {
                                     } => helix_core::commands::insert_char(state, '\n'),
                                     _ => (), // skip
                                 }
+                                // TODO: simplistic ensure cursor in view for now
+                                self.ensure_cursor_in_view();
+
                                 self.render();
                             }
                             Mode::Normal => {
@@ -318,6 +331,9 @@ impl Editor {
                                     // TODO: handle count other than 1
                                     command(state, 1);
 
+                                    // TODO: simplistic ensure cursor in view for now
+                                    self.ensure_cursor_in_view();
+
                                     self.render();
                                 }
                             }
@@ -333,6 +349,26 @@ impl Editor {
         }
     }
 
+    fn ensure_cursor_in_view(&mut self) {
+        if let Some(state) = &mut self.state {
+            let cursor = state.selection().cursor();
+            let line = state.doc().char_to_line(cursor) as u16;
+            let document_end = self.first_line + self.size.1.saturating_sub(1) - 1;
+
+            let padding = 5u16;
+
+            // TODO: side scroll
+
+            if line > document_end.saturating_sub(padding) {
+                // scroll down
+                self.first_line += line - (document_end.saturating_sub(padding));
+            } else if line < self.first_line + padding {
+                // scroll up
+                self.first_line = line.saturating_sub(padding);
+            }
+        }
+    }
+
     pub async fn run(&mut self) -> Result<(), Error> {
         enable_raw_mode()?;