I have just started using TeamViewer and each time I log on through TeamViewer it moves my dock from my center (main) monitor to my left monitor (2 of 3). I have the dock locked so I don't have a clue what to try next. There is no problem relocating the dock back to my center monitor but the next time I remotely log on it moves again.
any thoughts are appreciated

Does this happen on the remote session or on the computer you're using to connect remotely?

Also, the dock displays the monitors in left to right, top to bottom order. The primary is also marked as such. Next time it happens, check in the Dock Properties panel to see if the monitor order has changed or there is a new primary monitor.

The dock changes from the primary monitor (#3 center) to the left monitor (#2). Dock properties > position shows the change for the dock position but still shows monitor 3 as the primary. The drop down numbers the monitors 1-2-3 from the top with 3 always showing as primary.

The problem occurs when I'm using my iPad client to access the data on to my windows 10 desktop (where Winstep is installed). The dock changes monitors as soon as I log on to access the desktop and both the iPad and desktop display show the change.

If it makes any difference, Windows display settings show my monitors numbered 2-3-1 from left to right

Hope this helps

No, monitor numbering is arbitrary. The Winstep application just lists them in a logical way (top to bottom, left to right). The Primary Monitor is always the one with (0,0) as the top left coordinates.



So, the number of monitors and their disposition (as shown in Dock Properties) does not change at all... The only thing that happens is the dock switching to a different monitor, right?

Hmmm... Only a guess, but the iPad logging into your desktop might, for some reason, trigger a re-enumeration of the available monitors, which also makes the dock re-check where it is on the screen. Or perhaps temporarily changes screen resolution/coordinates (too fast for you to see but enough to trigger the re-enumeration).

Still doesn't explain the dock moving to the other monitor, but this can happen because the dock uses its x,y top corner coordinates to determine in which monitor it currently is (i.e.; which monitor is closest to the dock's current position) and then 'inserts' itself into that monitor. This mechanism is what allows physically unplugging a monitor and still have the dock automatically moving to one of the remaining available monitors instead of staying off-screen.

If the dock's x,y coordinates are suddenly inside monitor #2 instead of monitor #3 for whatever reason, then the dock automatically moves to monitor #2. If a micro-second later monitor #3 becomes available again, the dock will remain at monitor #2, which is now its 'new home'.

Something like that is happening. But why?

How large is your dock? Does it extend from one edge of the screen to the other? Perhaps a screenshot would help.

As you can see the dock is pretty much full width. I can remove some items if necessary to see if that makes any difference. Would two different size monitors make any difference? My primary monitor is a 19" 1600x1200 resolution (4:3 format) my left and right are 20" 1680x1050 (16:9) format.

The only other thing I can see is when I am logged on through TeamViewer my primary monitor display on my desktop appears larger as if I have zoomed in from 125% to -say- 150%. The other two monitors stay the same with no change.

BTW, your first paragraph is a correct statement

I think this might be the problem right there. Windows 10 added individual DPI scaling per monitor. This means you can have 100 DPIs in one monitor, 150 in another, and so on.

All fine and dandy, but the rest of the world is only just now beginning to add high DPI support to their applications. Now Microsoft wants you to add high-DPI support per-monitor too.

I don't even know how that works... I mean, what if you have half of one window in one monitor at 100 DPI and the other half in another monitor at 150 DPI?

Currently Winstep applications have full support for high DPI, but not for high DPI *per monitor*.

So, more than likely no correctable problem due to Winstep and just something I must deal with when using TeamViewer?

*If* it's indeed a *per-monitor* DPI issue caused by TeamViewer + Windows 10, I don't see it being corrected any time soon. Microsoft's implementation is, as usual, a huge mess. Just read this random example for a taste.

However, it is just an hypothesis - could just as easily be some kind of a bug in the application itself (although I doubt it, given your description).

Anyway, even if it is a per monitor DPI issue, have you tried already playing with the TeamViewer settings for the host screen resolution/DPI (I don't use TM, so I don't know what settings it has)?