How can I tell which is the primary monitor in the monitors array?

[mgabor3141]

[BoboTiG]

There is no proper way. My guess would be that the first monitor retrieved is the primary one, but I may be wrong.

[halldorfannar]

Is this for Windows? Because I would like to propose this enhancement:

Expose primary monitor flag on Windows

Summary

Currently, there's no clean way to identify which monitor is the Windows primary monitor. Users must infer it by checking for coordinates (left=0, top=0), which works but isn't explicit.

Proposal

Expose the MONITORINFOF_PRIMARY flag from the Windows API by:

1. Calling GetMonitorInfo in the EnumDisplayMonitors callback
2. Checking mi.dwFlags & MONITORINFOF_PRIMARY
3. Either:
   • Add an "is_primary": bool field to each monitor dict, or
   • Provide a primary_monitor property on the MSS class

Current Workaround

def get_primary_monitor(sct):
    """Find the primary monitor (the one at origin 0,0)."""
    for monitor in sct.monitors[1:]:  # Skip monitors[0] which is "all"
        if monitor["left"] == 0 and monitor["top"] == 0:
            return monitor
    return sct.monitors[1]  # Fallback

Platform

Windows only (other platforms may have similar concepts but different APIs).

[BoboTiG]

Lets start with Windows then. Adding a "is_primary": bool field to each monitor dict seems good to me.

[BoboTiG]

And, we could provide the property as well, it will lower the work for all downstream projects.

[halldorfannar]

Yes, doing both sounds good. Please assign this issue to me.

[halldorfannar]

I will probably do something like this for the property:

@property
def primary_monitor(self) -> Monitor:
    """Return the primary monitor."""
    for monitor in self._monitors[1:]:
        if monitor.get("is_primary"):
            return monitor
    return self._monitors[1]  # Fallback to first

That way it will work even for Linux without "is_primary" field (we will eventually add it though). I could also have it return an exception with NotImplemented, if preferred.

[BoboTiG]

I would vote for a default value on other OS rather than raising an exception. You POC seems good!

[halldorfannar]

@jholveck and I discussed this task this morning and one thing that we would like your verdict on is the following:

So far the monitor object has just been a dict. This makes a lot of sense because it has contained homogenous data (screen coordinates). With the addition of is_primary boolean that changes. We also discussed that eventually it would be nice to include device names in the monitor data as well (makes identification easier). At that point we would have screen coordinates, boolean and string in the dict. This naturally smells like a class object at that point. We can make __get_item__ accessor so that dict like access would still work. That way the change would be backwards compatible. Or do you prefer that we keep it as a dict?

What do you think?

[BoboTiG]

I like the idea of a class object with __get_item__!