Mikko Rantanen, Roope Hintz, Matt Duchene and Mikael Granlund each had a goal and an assist, and Wyatt Johnston scored in his third straight game for the Stars (47-21-4), who have won four straight and are 5-0-2 in their past seven.
Dallas moved within four points of the Winnipeg Jets for first in the Central Division and Western Conference.
"Winning's fun no matter what it looks like," DeSmith said. "Right now, we're winning games and just trying to better ourselves every night and try to ramp it up before playoffs because that's when the games become really hard and really tiring and really physical. We just have to get our game in a good place before that."
Nazem Kadri scored twice to extend his goal-scoring streak to five games (seven goals), and Dustin Wolf made 14 saves for the Flames (34-26-11), who had a four-game winning streak end.
"It's one of those games where we felt we certainly deserved it," Kadri said. "Unfortunate to come out with the loss, but you've got to tip your cap. Their goaltender made some incredible saves. I don't think you can get discouraged with that one."
Calgary is six points behind the St. Louis Blues, who won 3-2 against the Nashville Predators on Thursday, for the second wild card into the Stanley Cup Playoffs from the West with three games in hand.
"I think we win that game most nights," Flames forward Blake Coleman said. "I don't think anybody is disappointed with our effort tonight. I thought everybody showed up and left it on the ice and sometimes it just doesn't go your way."
Dallas scored twice in 1:16 in the second period to jump out to a 3-1 lead.
Johnston made it 2-1 at 12:55 when he lifted his own rebound over a sprawled Wolf after driving wide around Daniil Miromanov, and Granlund pushed it to 3-1 at 14:11 when he one-timed a centering pass from Mason Marchment at the top of the crease.
"We have so many skilled guys and guys who can make plays and guys who can score, so that makes us really dangerous even if we don't generate as much as we want to," Johnston said. "At the same time, you don't want to have to rely on only a few number of chances offensively. You want to be generating a lot more."