From a0a432e11dc045b7b950234436d06510ebf02fcb Mon Sep 17 00:00:00 2001
From: Daan Schoone <d.schoone@presspage.com>
Date: Tue, 25 Mar 2025 14:48:24 +0100
Subject: [PATCH] feat(viewport): horizontal scroll with mouse wheel

Add support for the events of a horizontal mouse wheel and when holding
shift while using the regular mouse wheel now scrolls the screen left
and right.
---
 viewport/viewport.go | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/viewport/viewport.go b/viewport/viewport.go
index 4dc1c68..b9bccdf 100644
--- a/viewport/viewport.go
+++ b/viewport/viewport.go
@@ -466,16 +466,30 @@ func (m Model) updateAsModel(msg tea.Msg) (Model, tea.Cmd) {
 		}
 		switch msg.Button { //nolint:exhaustive
 		case tea.MouseButtonWheelUp:
-			lines := m.ScrollUp(m.MouseWheelDelta)
-			if m.HighPerformanceRendering {
-				cmd = ViewUp(m, lines)
+			if msg.Shift {
+				// Note that not every terminal emulator sends the shift event for mouse actions by default (looking at you Konsole)
+				m.ScrollLeft(m.horizontalStep)
+			} else {
+				lines := m.ScrollUp(m.MouseWheelDelta)
+				if m.HighPerformanceRendering {
+					cmd = ViewUp(m, lines)
+				}
 			}
 
 		case tea.MouseButtonWheelDown:
-			lines := m.ScrollDown(m.MouseWheelDelta)
-			if m.HighPerformanceRendering {
-				cmd = ViewDown(m, lines)
+			if msg.Shift {
+				m.ScrollRight(m.horizontalStep)
+			} else {
+				lines := m.ScrollDown(m.MouseWheelDelta)
+				if m.HighPerformanceRendering {
+					cmd = ViewDown(m, lines)
+				}
 			}
+		// Note that not every terminal emulator sends the horizontal wheel events by default (looking at you Konsole)
+		case tea.MouseButtonWheelLeft:
+			m.ScrollLeft(m.horizontalStep)
+		case tea.MouseButtonWheelRight:
+			m.ScrollRight(m.horizontalStep)
 		}
 	}