This is not completely straightforward, as the default behavior is not "random" as you say, but an attempt from the window manager to not get in the way of already-opened apps. Lots of users *expect* that.
Plus, in some contexts like tiling window managers remembering position is a concept that does not even make sense.
I will look into this later, but I think this is not up for applications decide individually.
The consensus on this is less clear than I thought. I expected to find official GNOME or X guidelines but there is nothing.
Opinions on Twitter were somewhat divided, but leaning towards application responsibility. A good point that was made is that the window manager cannot know positions of different documents of a same application. This does not apply to Polly, but shows that the window manager cannot be expected to cover all cases.
On the other hand, there certainly are applications that I personally do *not* expect to remember position, like terminals and file managers.
At the end of the day, until managers evolve this seems to be app-by-app analysis. I guess I'll implement this for Polly.
This is not completely straightforward, as the default behavior is not "random" as you say, but an attempt from the window manager to not get in the way of already-opened apps. Lots of users *expect* that.
Plus, in some contexts like tiling window managers remembering position is a concept that does not even make sense.
I will look into this later, but I think this is not up for applications decide individually.