From 97d2c8339e9a3e07c1c4eb8b76e2d7f816f1f56e Mon Sep 17 00:00:00 2001
From: Aram Drevekenin <aram@poor.dev>
Date: Thu, 17 Dec 2020 13:00:44 +0100
Subject: [PATCH] fix(compatibility): fix neovim scrolling (#107)

* fix(compatibility): fix neovim scrolling

* style(formatting): make rustfmt happy
---
 src/terminal_pane/scroll.rs        | 46 +++++++++++++-----------------
 src/terminal_pane/terminal_pane.rs | 16 +++++------
 2 files changed, 27 insertions(+), 35 deletions(-)

diff --git a/src/terminal_pane/scroll.rs b/src/terminal_pane/scroll.rs
index b6f66be9..886a58d3 100644
--- a/src/terminal_pane/scroll.rs
+++ b/src/terminal_pane/scroll.rs
@@ -312,8 +312,8 @@ pub struct Scroll {
     viewport_bottom_offset: Option<usize>,
     scroll_region: Option<(usize, usize)>, // start line, end line (if set, this is the area the will scroll)
     show_cursor: bool,
-    lines_outside_of_scroll_region: Option<Vec<CanonicalLine>>,
-    cursor_position_outside_of_scroll_region: Option<CursorPosition>,
+    alternative_buffer: Option<Vec<CanonicalLine>>,
+    alternative_cursor_position: Option<CursorPosition>,
 }
 
 impl Scroll {
@@ -329,8 +329,8 @@ impl Scroll {
             viewport_bottom_offset: None,
             scroll_region: None,
             show_cursor: true,
-            lines_outside_of_scroll_region: None,
-            cursor_position_outside_of_scroll_region: None,
+            alternative_buffer: None,
+            alternative_cursor_position: None,
         }
     }
     pub fn as_character_lines(&self) -> Vec<Vec<TerminalCharacter>> {
@@ -638,32 +638,26 @@ impl Scroll {
         let current_column = self.cursor_position.column_index;
         self.move_cursor_to(line, current_column);
     }
-    pub fn set_scroll_region(&mut self, top_line: usize, bottom_line: usize) {
-        if self.scroll_region.is_none() {
-            self.lines_outside_of_scroll_region = Some(self.canonical_lines.drain(..).collect());
-            self.cursor_position_outside_of_scroll_region = Some(self.cursor_position);
+    pub fn move_current_buffer_to_alternative_buffer(&mut self) {
+        self.alternative_buffer = Some(self.canonical_lines.drain(..).collect());
+        self.alternative_cursor_position = Some(self.cursor_position);
+        self.cursor_position.reset();
+    }
+    pub fn override_current_buffer_with_alternative_buffer(&mut self) {
+        if let Some(alternative_buffer) = self.alternative_buffer.as_mut() {
+            self.canonical_lines = alternative_buffer.drain(..).collect();
         }
+        if let Some(alternative_cursor_position) = self.alternative_cursor_position {
+            self.cursor_position = alternative_cursor_position;
+        }
+        self.alternative_buffer = None;
+        self.alternative_cursor_position = None;
+    }
+    pub fn set_scroll_region(&mut self, top_line: usize, bottom_line: usize) {
         self.scroll_region = Some((top_line, bottom_line));
     }
     pub fn clear_scroll_region(&mut self) {
-        if let Some(scroll_region) = self.scroll_region_absolute_indices() {
-            self.canonical_lines.drain(scroll_region.0..scroll_region.1);
-            self.cursor_position.reset();
-            self.scroll_region = None;
-        }
-        if let Some(lines_outside_of_scroll_region) = self.lines_outside_of_scroll_region.as_mut() {
-            self.canonical_lines = lines_outside_of_scroll_region.drain(..).collect();
-        }
-        if let Some(cursor_position_outside_of_scroll_region) =
-            self.cursor_position_outside_of_scroll_region
-        {
-            self.cursor_position = cursor_position_outside_of_scroll_region;
-        }
-        self.lines_outside_of_scroll_region = None;
-        self.cursor_position_outside_of_scroll_region = None;
-    }
-    pub fn set_scroll_region_to_screen_size(&mut self) {
-        self.scroll_region = Some((0, self.lines_in_view - 1)); // these are indices
+        self.scroll_region = None;
     }
     fn scroll_region_absolute_indices(&mut self) -> Option<(usize, usize)> {
         if self.scroll_region.is_none() {
diff --git a/src/terminal_pane/terminal_pane.rs b/src/terminal_pane/terminal_pane.rs
index 0901b8c9..ae0439a9 100644
--- a/src/terminal_pane/terminal_pane.rs
+++ b/src/terminal_pane/terminal_pane.rs
@@ -452,15 +452,6 @@ impl vte::Perform for TerminalPane {
                     (params[0] as usize - 1, params[1] as usize - 1)
                 }
             };
-            if params.len() >= 1 && params[0] == 0 {
-                // this is a hack
-                //
-                // the logic should *probably* be:
-                // if we get an instruction to move outside the scroll region
-                // (which is 1 indexed, so if we get 0 it's always(?) outside)
-                // we need to set it to screen size
-                self.scroll.set_scroll_region_to_screen_size();
-            }
             self.scroll.move_cursor_to(row, col);
         } else if c == 'A' {
             // move cursor up until edge of screen
@@ -481,6 +472,10 @@ impl vte::Perform for TerminalPane {
             };
             if first_intermediate_is_questionmark {
                 match params.get(0) {
+                    Some(&1049) => {
+                        self.scroll
+                            .override_current_buffer_with_alternative_buffer();
+                    }
                     Some(&25) => {
                         self.scroll.hide_cursor();
                         self.mark_for_rerender();
@@ -503,6 +498,9 @@ impl vte::Perform for TerminalPane {
                         self.scroll.show_cursor();
                         self.mark_for_rerender();
                     }
+                    Some(&1049) => {
+                        self.scroll.move_current_buffer_to_alternative_buffer();
+                    }
                     Some(&1) => {
                         self.cursor_key_mode = true;
                     }