From 7439e35258fd47d079bebcdb09454e3b667c2a7b Mon Sep 17 00:00:00 2001
From: Joshua Ashton <joshua@froggi.es>
Date: Sat, 11 May 2024 07:25:35 +0100
Subject: [PATCH] InputEmulation: Implement scroll_discrete support

Fixes scrolling in Steam Input
---
 src/InputEmulation.cpp | 19 ++++++++++++++++++-
 src/InputEmulation.h   |  2 ++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/InputEmulation.cpp b/src/InputEmulation.cpp
index a6daae8309..58d0cee07d 100644
--- a/src/InputEmulation.cpp
+++ b/src/InputEmulation.cpp
@@ -167,6 +167,13 @@ namespace gamescope
                 }
                 break;
 
+                case EIS_EVENT_SCROLL_DISCRETE:
+                {
+                    m_flScrollAccum[0] += eis_event_scroll_get_discrete_dx( pEisEvent ) / 120.0;
+                    m_flScrollAccum[1] += eis_event_scroll_get_discrete_dy( pEisEvent ) / 120.0;
+                }
+                break;
+
                 case EIS_EVENT_KEYBOARD_KEY:
                 {
                     wlserver_lock();
@@ -186,7 +193,17 @@ namespace gamescope
 
                 case EIS_EVENT_FRAME:
                 {
-                    // Not used currently, maybe we want to accum scroll?
+                    double flScrollX = m_flScrollAccum[0];
+                    double flScrollY = m_flScrollAccum[1];
+                    m_flScrollAccum[0] = 0.0;
+                    m_flScrollAccum[1] = 0.0;
+
+                    if ( flScrollX == 0.0 && flScrollY == 0.0 )
+                        return;
+
+                    wlserver_lock();
+                    wlserver_mousewheel( flScrollX, flScrollY, ++s_uSequence );
+                    wlserver_unlock();
                 }
                 break;
 
diff --git a/src/InputEmulation.h b/src/InputEmulation.h
index 9dde5d6f5d..1084f9ddf3 100644
--- a/src/InputEmulation.h
+++ b/src/InputEmulation.h
@@ -19,5 +19,7 @@ namespace gamescope
     private:
         eis *m_pEis = nullptr;
         int m_nFd = -1;
+
+        double m_flScrollAccum[2]{};
     };
 }