From cb2fc22c5a57a686029e8f0b8efc0238ed541413 Mon Sep 17 00:00:00 2001
From: Joscha <joscha@plugh.de>
Date: Sun, 31 Jul 2022 23:09:39 +0200
Subject: [PATCH] Scroll with ctrl+e and ctrl+d

---
 src/ui/chat/tree.rs        | 11 +++++++----
 src/ui/chat/tree/cursor.rs | 17 +++++++++++++++++
 src/ui/chat/tree/layout.rs |  5 ++++-
 3 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/src/ui/chat/tree.rs b/src/ui/chat/tree.rs
index aed3381..52c34cf 100644
--- a/src/ui/chat/tree.rs
+++ b/src/ui/chat/tree.rs
@@ -34,6 +34,10 @@ struct InnerTreeViewState<M: Msg, S: MsgStore<M>> {
     /// to a different message such that it remains visible.
     make_cursor_visible: bool,
 
+    /// Scroll the view on the next render. Positive values scroll up and
+    /// negative values scroll down.
+    scroll: i32,
+
     editor: EditorState,
 }
 
@@ -45,6 +49,7 @@ impl<M: Msg, S: MsgStore<M>> InnerTreeViewState<M, S> {
             last_cursor_line: 0,
             cursor: Cursor::Bottom,
             make_cursor_visible: false,
+            scroll: 0,
             editor: EditorState::new(),
         }
     }
@@ -56,11 +61,9 @@ impl<M: Msg, S: MsgStore<M>> InnerTreeViewState<M, S> {
             KeyCode::Char('g') | KeyCode::Home => self.move_cursor_to_top().await,
             KeyCode::Char('G') | KeyCode::End => self.move_cursor_to_bottom().await,
             KeyCode::Char('y') if event.modifiers == KeyModifiers::CONTROL => {
-                self.last_cursor_line += 1;
-            }
-            KeyCode::Char('e') if event.modifiers == KeyModifiers::CONTROL => {
-                self.last_cursor_line -= 1;
+                self.scroll_up(1).await
             }
+            KeyCode::Char('e') if event.modifiers == KeyModifiers::CONTROL => self.scroll_down(1),
             _ => return false,
         }
         true
diff --git a/src/ui/chat/tree/cursor.rs b/src/ui/chat/tree/cursor.rs
index 1b9b7f0..25c5aff 100644
--- a/src/ui/chat/tree/cursor.rs
+++ b/src/ui/chat/tree/cursor.rs
@@ -223,6 +223,23 @@ impl<M: Msg, S: MsgStore<M>> InnerTreeViewState<M, S> {
         // Not really necessary; only here for consistency with other methods
         self.make_cursor_visible = true;
     }
+
+    pub async fn scroll_up(&mut self, amount: i32) {
+        self.scroll += amount;
+
+        if let Cursor::Bottom = self.cursor {
+            // Move cursor to bottommost message, if it exists
+            if let Some(mut id) = self.store.last_tree_id().await {
+                let tree = self.store.tree(&id).await;
+                while Self::find_last_child(&tree, &mut id) {}
+                self.cursor = Cursor::Msg(id);
+            }
+        }
+    }
+
+    pub fn scroll_down(&mut self, amount: i32) {
+        self.scroll -= amount;
+    }
 }
 
 /*
diff --git a/src/ui/chat/tree/layout.rs b/src/ui/chat/tree/layout.rs
index e716985..ce35c57 100644
--- a/src/ui/chat/tree/layout.rs
+++ b/src/ui/chat/tree/layout.rs
@@ -285,7 +285,8 @@ impl<M: Msg, S: MsgStore<M>> InnerTreeViewState<M, S> {
         // The basic idea is this:
         //
         // First, layout a full screen of blocks around self.last_cursor, using
-        // self.last_cursor_line for offset positioning.
+        // self.last_cursor_line for offset positioning. At this point, any
+        // outstanding scrolling is performed as well.
         //
         // Then, check if self.cursor is somewhere in these blocks. If it is, we
         // now know the position of our own cursor. If it is not, it has jumped
@@ -305,6 +306,7 @@ impl<M: Msg, S: MsgStore<M>> InnerTreeViewState<M, S> {
         let mut blocks = self
             .layout_initial_seed(frame, &last_cursor_path, &cursor_path)
             .await;
+        blocks.blocks_mut().offset(self.scroll);
         self.fill_screen_and_clamp_scrolling(frame, &mut blocks)
             .await;
 
@@ -329,6 +331,7 @@ impl<M: Msg, S: MsgStore<M>> InnerTreeViewState<M, S> {
         self.last_cursor = self.cursor.clone();
         self.last_cursor_line = self.cursor_line(&blocks);
         self.make_cursor_visible = false;
+        self.scroll = 0;
 
         blocks
     }