From 721d483cc33189150b28c8090aea97610e2e207b Mon Sep 17 00:00:00 2001
From: Daniel Imms <2193314+Tyriar@users.noreply.github.com>
Date: Thu, 11 Jul 2024 08:35:42 -0700
Subject: [PATCH] Implement zero scrollback+no mouse event wheel handling

---
 src/browser/CoreBrowserTerminal.ts | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/src/browser/CoreBrowserTerminal.ts b/src/browser/CoreBrowserTerminal.ts
index c6f12b52..2858e688 100644
--- a/src/browser/CoreBrowserTerminal.ts
+++ b/src/browser/CoreBrowserTerminal.ts
@@ -793,22 +793,21 @@ export class CoreBrowserTerminal extends CoreTerminal implements ITerminal {
 
       if (!this.buffer.hasScrollback) {
         // Convert wheel events into up/down events when the buffer does not have scrollback, this
-        // enables scrolling in apps hosted in the alt buffer such as vim or tmux.
-        // TODO: Impl
-        const amount = 0; // this.viewport!.getLinesScrolled(ev);
+        // enables scrolling in apps hosted in the alt buffer such as vim or tmux even when mouse
+        // events are not enabled.
+        // This used implementation used get the actual lines/partial lines scrolled from the
+        // viewport but since moving to the new viewport implementation has been simplified to
+        // simply send a single up or down sequence.
 
         // Do nothing if there's no vertical scroll
-        if (amount === 0) {
-          return;
+        const deltaY = (ev as WheelEvent).deltaY;
+        if (deltaY === 0) {
+          return false;
         }
 
         // Construct and send sequences
         const sequence = C0.ESC + (this.coreService.decPrivateModes.applicationCursorKeys ? 'O' : '[') + (ev.deltaY < 0 ? 'A' : 'B');
-        let data = '';
-        for (let i = 0; i < Math.abs(amount); i++) {
-          data += sequence;
-        }
-        this.coreService.triggerDataEvent(data, true);
+        this.coreService.triggerDataEvent(sequence, true);
         return this.cancel(ev, true);
       }