Merge pull request #100444 from Sauermann/fix-view-panner-mouse-warp

Fix `ViewPanner` panning-mouse-warp

scene/main/viewport.cpp

@@ -1377,6 +1377,40 @@ void Viewport::warp_mouse(const Vector2 &p_position) {
 	Input::get_singleton()->warp_mouse(gpos);
 }
 
+Point2 Viewport::wrap_mouse_in_rect(const Vector2 &p_relative, const Rect2 &p_rect) {
+	// Move the mouse cursor from its current position to a location bounded by `p_rect`
+	// in accordance with a heuristic that takes the traveled distance `p_relative` of the mouse
+	// into account.
+
+	// All parameters are in viewport coordinates.
+	// p_relative denotes the distance to the previous mouse position.
+	// p_rect denotes the area, in which the mouse should be confined in.
+
+	// The relative distance reported for the next event after a warp is in the boundaries of the
+	// size of the rect on that axis, but it may be greater, in which case there's no problem as
+	// fmod() will warp it, but if the pointer has moved in the opposite direction between the
+	// pointer relocation and the subsequent event, the reported relative distance will be less
+	// than the size of the rect and thus fmod() will be disabled for handling the situation.
+	// And due to this mouse warping mechanism being stateless, we need to apply some heuristics
+	// to detect the warp: if the relative distance is greater than the half of the size of the
+	// relevant rect (checked per each axis), it will be considered as the consequence of a former
+	// pointer warp.
+
+	const Point2 rel_sign(p_relative.x >= 0.0f ? 1 : -1, p_relative.y >= 0.0 ? 1 : -1);
+	const Size2 warp_margin = p_rect.size * 0.5f;
+	const Point2 rel_warped(
+			Math::fmod(p_relative.x + rel_sign.x * warp_margin.x, p_rect.size.x) - rel_sign.x * warp_margin.x,
+			Math::fmod(p_relative.y + rel_sign.y * warp_margin.y, p_rect.size.y) - rel_sign.y * warp_margin.y);
+
+	const Point2 pos_local = get_mouse_position() - p_rect.position;
+	const Point2 pos_warped(Math::fposmod(pos_local.x, p_rect.size.x), Math::fposmod(pos_local.y, p_rect.size.y));
+	if (pos_warped != pos_local) {
+		warp_mouse(pos_warped + p_rect.position);
+	}
+
+	return rel_warped;
+}
+
 void Viewport::_gui_sort_roots() {
 	if (!gui.roots_order_dirty) {
 		return;