Not exiting copy-mode if there's a selection

[mgrant0]

If you set-option -g mouse on and scroll up with the mouse-wheel in copy-mode. You drag a selection with the mouse, but it's longer than what's visible so you scroll down. When the window reaches the bottom, copy-mode exits and the selection goes away.

Is there some way, for example, a key binding that I could bind WheelDownPane to something which would not exit copy-mode if #{selection_present} is true?

Here's the stock binding for WheelDownPane:

bind -Tcopy-mode WheelDownPane { select-pane; send -N5 -X scroll-down }

Looking at window_copy_cmd_scroll_down(), it tests data->scroll_exit to determine if it should exit copy-mode. I am not sure how this could get set when scrolling up with the mouse wheel.