A still from a concept video from Samsung showing how a foldable smartphone might look. Samsung One of the longest-running rumors in the mobile industry is Samsung's foldable smartphone.

Samsung is believed to have been developing a smartphone with a screen that can fold and bend — but so far, it has never seen the light of day.

However, according to a report from the Korean news site ETNews, it might finally be unveiled later this year.

A prototype of the device will be launched and given to partners to test and to assess demand from consumers, according to the report. But don't expect a commercial release in 2017 — only "thousands" of the devices will be made at first, with mass production and a proper launch expected for 2018, the report said.

This backs up an earlier report from The Korea Herald, which suggested the device would be unveiled in the third quarter and said Samsung hoped to "roll out more than 100,000 units."

A foldable smartphone, in theory, makes a lot of sense. It lets a user double the size of the screen without taking up more space in their pocket — or shrink the size of the device when it's not being used. It would also provide Samsung with a major selling point to use in its ongoing war with Apple for control of the premium smartphone market.

ETNews reports that Samsung showed an early prototype of the device to some "major mobile network providers" at Mobile World Congress, a big industry conference in Barcelona, earlier this year.

The project is alternately known as "Project Valley" and "Galaxy X," according to PC Advisor.

A Samsung representative did not immediately respond to a request for comment. But don't expect the company to shed much light on the matter. Samsung, like most tech companies, tends not to comment on rumors and speculation about unannounced products.

However, a patent application from the electronics company that came to light in November shows how the foldable smartphone might look. The device in the application has a fold in the middle of the screen, letting the user close it like a retro clamshell phone.

Unfolded, it looks like a more traditional smartphone — albeit longer than most phones on the market today.

A word of caution: Just because a tech company patents something doesn't necessarily mean it will make its way into a finished product. If Samsung does launch a folding smartphone this year, it may end up looking different.

But at the very least, the images give insight into how Samsung is approaching the problem and how its engineers envision a folding smartphone might look.

Samsung has been talking publicly about the potential of foldable screens and displays since at least 2013. Now they might soon be a reality.

(Above: Part of a 2013 video from Samsung showing off a concept foldable smartphone.)