PARIS — As Wang Xinyu stood at the net under the relentless heat on Court 7, things were about to get even hotter.Serving at deuce, and trailing to Germany’s Tamara Korpatsch 5-2 in the first set of their second-round match at the French Open, the Chinese No. 32 seed saw a forehand called out by a line judge. After the call, Korpatsch had walked forward to where it landed, before moving a little to her right and pointing to a mark.Per Roland Garros custom, chair umpire Aurelie Tourte descended from her chair to check. Roland Garros is the only Grand Slam not to use electronic line calling, with line judges, the chair umpire, and the players using the traces left by their shots to see whether or not the ball is in or out.After consulting the mark, Tourte ruled that Wang’s forehand was out.Wang was not happy. After asking the umpire — who told her she would get a code violation — she went over to Korpatsch’s side of the net to see for herself. The crowd booed as Wang gestured to her team, who sat right above the baseline where the ball landed.Once Wang got there, the two players argued over which ball mark should be considered. That argument lingered toward the end of the match, when Korpatsch refused to shake hands with Wang after three sets full of incident, including a code violation for Korpatsch for celebrating too early.