From 801f0a041ff4c52b80d06eb9e6a08e636cfc70be Mon Sep 17 00:00:00 2001
From: bruvzg <7645683+bruvzg@users.noreply.github.com>
Date: Tue, 13 Oct 2020 18:58:55 +0300
Subject: [PATCH] [macOS] Suppress momentum scrolling after key press or
 modifier change to prevent unexpected change of action.

---
 platform/osx/display_server_osx.mm | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/platform/osx/display_server_osx.mm b/platform/osx/display_server_osx.mm
index cd5b71890c75..1ad7117b3912 100644
--- a/platform/osx/display_server_osx.mm
+++ b/platform/osx/display_server_osx.mm
@@ -63,6 +63,8 @@
 
 #define DS_OSX ((DisplayServerOSX *)(DisplayServerOSX::get_singleton()))
 
+static bool ignore_momentum_scroll = false;
+
 static void _get_key_modifier_state(unsigned int p_osx_state, Ref<InputEventWithModifiers> r_state) {
 	r_state->set_shift((p_osx_state & NSEventModifierFlagShift));
 	r_state->set_control((p_osx_state & NSEventModifierFlagControl));
@@ -1304,6 +1306,8 @@ - (void)keyDown:(NSEvent *)event {
 	ERR_FAIL_COND(!DS_OSX->windows.has(window_id));
 	DisplayServerOSX::WindowData &wd = DS_OSX->windows[window_id];
 
+	ignore_momentum_scroll = true;
+
 	// Ignore all input if IME input is in progress
 	if (!imeInputEventInProgress) {
 		NSString *characters = [event characters];
@@ -1348,6 +1352,8 @@ - (void)keyDown:(NSEvent *)event {
 }
 
 - (void)flagsChanged:(NSEvent *)event {
+	ignore_momentum_scroll = true;
+
 	// Ignore all input if IME input is in progress
 	if (!imeInputEventInProgress) {
 		DisplayServerOSX::KeyEvent ke;
@@ -1507,6 +1513,14 @@ - (void)scrollWheel:(NSEvent *)event {
 		deltaY *= 0.03;
 	}
 
+	if ([event momentumPhase] != NSEventPhaseNone) {
+		if (ignore_momentum_scroll) {
+			return;
+		}
+	} else {
+		ignore_momentum_scroll = false;
+	}
+
 	if ([event phase] != NSEventPhaseNone || [event momentumPhase] != NSEventPhaseNone) {
 		sendPanEvent(window_id, deltaX, deltaY, [event modifierFlags]);
 	} else {