From 8c6298d9ba3c7aa6aeac7594ab78c6da81df4984 Mon Sep 17 00:00:00 2001
From: Steve Pronovost <spronovo@microsoft.com>
Date: Mon, 10 May 2021 11:41:00 -0700
Subject: [PATCH] Fix scroll rotation to work both with standard and precision
 wheels

Fix wheel increments such that we send a movement update to our
Wayland clients every 12 wheel increments for smmooth scrolling
on high precision wheels or pads, but only bump the discrete wheel
tick every 120 wheel increments so it aligns properly with standard
wheel which always do +120/-120 increment at every wheel notch.
---
 libweston/backend-rdp/rdp.c | 32 ++++++++++++++++++++++++--------
 libweston/backend-rdp/rdp.h |  4 ++--
 2 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/libweston/backend-rdp/rdp.c b/libweston/backend-rdp/rdp.c
index 4029021ca..099125390 100644
--- a/libweston/backend-rdp/rdp.c
+++ b/libweston/backend-rdp/rdp.c
@@ -1467,6 +1467,7 @@ static FREERDP_CB_RET_TYPE
 xf_mouseEvent(rdpInput *input, UINT16 flags, UINT16 x, UINT16 y)
 {
 	RdpPeerContext *peerContext = (RdpPeerContext *)input->context;
+	struct rdp_backend *b = peerContext->rdpBackend;
 	uint32_t button = 0;
 	bool need_frame = false;
 	struct timespec time;
@@ -1510,7 +1511,7 @@ xf_mouseEvent(rdpInput *input, UINT16 flags, UINT16 x, UINT16 y)
 		int ivalue;
 		double value;
 
-		/* DEFAULT_AXIS_STEP_DISTANCE is stolen from compositor-x11.c
+		/*
 		 * The RDP specs says the lower bits of flags contains the "the number of rotation
 		 * units the mouse wheel was rotated".
 		 *
@@ -1520,22 +1521,37 @@ xf_mouseEvent(rdpInput *input, UINT16 flags, UINT16 x, UINT16 y)
 			ivalue = (int)((char)(flags & 0xff));
 		else
 			ivalue = (flags & 0xff);
-		peerContext->accumWheelRotation += ivalue;
-		if (abs(peerContext->accumWheelRotation) >= 12) {
-			/* multiply -1 is due to directional swap to match Windows direction of scroll. */
-			value = (double)(peerContext->accumWheelRotation / 12) * -1;
+
+		/* Flip the scroll direction as the RDP direction is inverse of X/Wayland */
+		ivalue *= -1;
+
+		/*
+		 * Accumulate the wheel increments.
+		 *
+		 * Every 12 wheel increments, we will send an update to our Wayland
+		 * clients with an updated value for the wheel for smooth scrolling.
+		 *
+		 * Every 120 wheel increments, we tick one discrete wheel click.
+		 */
+		peerContext->accumWheelRotationPrecise += ivalue;
+		peerContext->accumWheelRotationDiscrete += ivalue;
+		if (abs(peerContext->accumWheelRotationPrecise) >= 12) {
+			value = (double)(peerContext->accumWheelRotationPrecise / 12);
 
 			weston_event.axis = WL_POINTER_AXIS_VERTICAL_SCROLL;
-			weston_event.value = DEFAULT_AXIS_STEP_DISTANCE * value;
-			weston_event.discrete = (int)value;
+			weston_event.value = value;
+			weston_event.discrete = peerContext->accumWheelRotationDiscrete / 120;
 			weston_event.has_discrete = true;
 
+			rdp_debug_verbose(b, "wheel: value:%f discrete:%d\n", weston_event.value, weston_event.discrete);
+
 			weston_compositor_get_time(&time);
 
 			notify_axis(peerContext->item.seat, &time, &weston_event);
 			need_frame = true;
 
-			peerContext->accumWheelRotation %= 12;
+			peerContext->accumWheelRotationPrecise %= 12;
+			peerContext->accumWheelRotationDiscrete %= 120;
 		}
 	}
 
diff --git a/libweston/backend-rdp/rdp.h b/libweston/backend-rdp/rdp.h
index 8763d9588..d798e580d 100644
--- a/libweston/backend-rdp/rdp.h
+++ b/libweston/backend-rdp/rdp.h
@@ -110,7 +110,6 @@
 #include "shared/timespec-util.h"
 
 #define MAX_FREERDP_FDS 32
-#define DEFAULT_AXIS_STEP_DISTANCE 10
 #define RDP_MODE_FREQ 60 * 1000
 #define RDP_MAX_MONITOR 16 // RDP max monitors.
 
@@ -273,7 +272,8 @@ struct rdp_peer_context {
 
 	bool button_state[5];
 	char key_state[0xff/8]; // one bit per key.
-	int accumWheelRotation;
+	int accumWheelRotationPrecise;
+	int accumWheelRotationDiscrete;
 
 	// RAIL support
 	HANDLE vcm;