WaylandBackend: wire up wl_touch implementation

The Wayland backend had wl_touch declared but never hooked up, so touch
input was silently dropped when running nested.

Tested with variations of `gamescope -e -- steam -steamdeck -steamos3
-steampal -gamepadui` on KDE Wayland, Gnome, and Cosmic.

Closes: #1606

Author: matte-schwartz

src/Backends/WaylandBackend.cpp

@@ -556,6 +556,7 @@ namespace gamescope
         uint32_t m_uAxisSource = WL_POINTER_AXIS_SOURCE_WHEEL;
 
 		wl_surface *m_pCurrentCursorSurface = nullptr;
+		wl_surface *m_pCurrentTouchSurface = nullptr;
 
         std::optional<wl_fixed_t> m_ofPendingCursorX;
         std::optional<wl_fixed_t> m_ofPendingCursorY;
@@ -592,6 +593,15 @@ namespace gamescope
 
 	    void Wayland_RelativePointer_RelativeMotion( zwp_relative_pointer_v1 *pRelativePointer, uint32_t uTimeHi, uint32_t uTimeLo, wl_fixed_t fDx, wl_fixed_t fDy, wl_fixed_t fDxUnaccel, wl_fixed_t fDyUnaccel );
         static const zwp_relative_pointer_v1_listener s_RelativePointerListener;
+
+        void Wayland_Touch_Down( wl_touch *pTouch, uint32_t uSerial, uint32_t uTime, wl_surface *pSurface, int32_t nId, wl_fixed_t fX, wl_fixed_t fY );
+        void Wayland_Touch_Up( wl_touch *pTouch, uint32_t uSerial, uint32_t uTime, int32_t nId );
+        void Wayland_Touch_Motion( wl_touch *pTouch, uint32_t uTime, int32_t nId, wl_fixed_t fX, wl_fixed_t fY );
+        void Wayland_Touch_Frame( wl_touch *pTouch );
+        void Wayland_Touch_Cancel( wl_touch *pTouch );
+        void Wayland_Touch_Shape( wl_touch *pTouch, int32_t nId, wl_fixed_t fMajor, wl_fixed_t fMinor );
+        void Wayland_Touch_Orientation( wl_touch *pTouch, int32_t nId, wl_fixed_t fOrientation );
+        static const wl_touch_listener s_TouchListener;
     };
     const wl_registry_listener CWaylandInputThread::s_RegistryListener =
     {
@@ -629,6 +639,16 @@ namespace gamescope
     {
         .relative_motion = WAYLAND_USERDATA_TO_THIS( CWaylandInputThread, Wayland_RelativePointer_RelativeMotion ),
     };
+    const wl_touch_listener CWaylandInputThread::s_TouchListener =
+    {
+        .down        = WAYLAND_USERDATA_TO_THIS( CWaylandInputThread, Wayland_Touch_Down ),
+        .up          = WAYLAND_USERDATA_TO_THIS( CWaylandInputThread, Wayland_Touch_Up ),
+        .motion      = WAYLAND_USERDATA_TO_THIS( CWaylandInputThread, Wayland_Touch_Motion ),
+        .frame       = WAYLAND_USERDATA_TO_THIS( CWaylandInputThread, Wayland_Touch_Frame ),
+        .cancel      = WAYLAND_USERDATA_TO_THIS( CWaylandInputThread, Wayland_Touch_Cancel ),
+        .shape       = WAYLAND_USERDATA_TO_THIS( CWaylandInputThread, Wayland_Touch_Shape ),
+        .orientation = WAYLAND_USERDATA_TO_THIS( CWaylandInputThread, Wayland_Touch_Orientation ),
+    };
 
     class CWaylandBackend : public CBaseBackend
     {
@@ -3024,6 +3044,20 @@ namespace gamescope
                 wl_keyboard_add_listener( m_pKeyboard, &s_KeyboardListener, this );
             }
         }
+
+        if ( !!( uCapabilities & WL_SEAT_CAPABILITY_TOUCH ) != !!m_pTouch )
+        {
+            if ( m_pTouch )
+            {
+                wl_touch_release( m_pTouch );
+                m_pTouch = nullptr;
+            }
+            else
+            {
+                m_pTouch = wl_seat_get_touch( m_pSeat );
+                wl_touch_add_listener( m_pTouch, &s_TouchListener, this );
+            }
+        }
     }
 
     void CWaylandInputThread::Wayland_Seat_Name( wl_seat *pSeat, const char *pName )
@@ -3250,6 +3284,78 @@ namespace gamescope
         wlserver_unlock();
     }
 
+    // Touch
+
+    void CWaylandInputThread::Wayland_Touch_Down( wl_touch *pTouch, uint32_t uSerial, uint32_t uTime, wl_surface *pSurface, int32_t nId, wl_fixed_t fX, wl_fixed_t fY )
+    {
+        if ( !IsGamescopeToplevel( pSurface ) )
+            return;
+
+        m_pCurrentTouchSurface = pSurface;
+
+        CWaylandPlane *pPlane = (CWaylandPlane *)wl_surface_get_user_data( m_pCurrentTouchSurface );
+        if ( !pPlane )
+            return;
+
+        auto oState = pPlane->GetCurrentState();
+        if ( !oState )
+            return;
+
+        uint32_t uScale = oState->uFractionalScale;
+        double flX = ( wl_fixed_to_double( fX ) * uScale / 120.0 + oState->nDestX ) / g_nOutputWidth;
+        double flY = ( wl_fixed_to_double( fY ) * uScale / 120.0 + oState->nDestY ) / g_nOutputHeight;
+
+        wlserver_lock();
+        wlserver_touchdown( flX, flY, nId, ++m_uFakeTimestamp );
+        wlserver_unlock();
+    }
+    void CWaylandInputThread::Wayland_Touch_Up( wl_touch *pTouch, uint32_t uSerial, uint32_t uTime, int32_t nId )
+    {
+        wlserver_lock();
+        wlserver_touchup( nId, ++m_uFakeTimestamp );
+        wlserver_unlock();
+    }
+    void CWaylandInputThread::Wayland_Touch_Motion( wl_touch *pTouch, uint32_t uTime, int32_t nId, wl_fixed_t fX, wl_fixed_t fY )
+    {
+        if ( !m_pCurrentTouchSurface )
+            return;
+
+        CWaylandPlane *pPlane = (CWaylandPlane *)wl_surface_get_user_data( m_pCurrentTouchSurface );
+        if ( !pPlane )
+            return;
+
+        auto oState = pPlane->GetCurrentState();
+        if ( !oState )
+            return;
+
+        uint32_t uScale = oState->uFractionalScale;
+        double flX = ( wl_fixed_to_double( fX ) * uScale / 120.0 + oState->nDestX ) / g_nOutputWidth;
+        double flY = ( wl_fixed_to_double( fY ) * uScale / 120.0 + oState->nDestY ) / g_nOutputHeight;
+
+        wlserver_lock();
+        wlserver_touchmotion( flX, flY, nId, ++m_uFakeTimestamp );
+        wlserver_unlock();
+    }
+    void CWaylandInputThread::Wayland_Touch_Frame( wl_touch *pTouch )
+    {
+    }
+    void CWaylandInputThread::Wayland_Touch_Cancel( wl_touch *pTouch )
+    {
+        wlserver_lock();
+        std::set<uint32_t> touchIds = wlserver.touch_down_ids;
+        for ( uint32_t nId : touchIds )
+            wlserver_touchup( nId, ++m_uFakeTimestamp );
+        wlserver_unlock();
+
+        m_pCurrentTouchSurface = nullptr;
+    }
+    void CWaylandInputThread::Wayland_Touch_Shape( wl_touch *pTouch, int32_t nId, wl_fixed_t fMajor, wl_fixed_t fMinor )
+    {
+    }
+    void CWaylandInputThread::Wayland_Touch_Orientation( wl_touch *pTouch, int32_t nId, wl_fixed_t fOrientation )
+    {
+    }
+
     /////////////////////////
     // Backend Instantiator
     /////////////////////////