#' @export
#' @keywords internal
#' @rdname tmap_internal
tmapGridLines = function(shpTM, dt, gp, bbx, facet_row, facet_col, facet_page, id, pane, group, o, ...) {
	
	rc_text = frc(facet_row, facet_col)
	
	res = select_sf(shpTM, dt[!is.na(dt$lwd), ])
	shp = res$shp
	dt = res$dt
	
	gp = impute_gp(gp, dt)
	gp = rescale_gp(gp, o$scale_down)
	
	gp = gp_to_gpar(gp, sel = "col", o = o, type = "lines")
	grb = sf::st_as_grob(shp, gp = gp, name = paste0("lines_", id))
	
	gts = get("gts", .TMAP_GRID)
	gt = gts[[facet_page]]
	
	gt_name = paste0("gt_facet_", rc_text)
	
	gt = grid::addGrob(gt, grb, gPath = grid::gPath(gt_name))
	
	gts[[facet_page]] = gt
	
	assign("gts", gts, envir = .TMAP_GRID)
	NULL	
}
