Annoying display bug! Please help me, I'm about to give up :) (5 Viewers)

[Vasilich]

@Owlsroost
it should have smth to do with DPI scaling, as that strange resolution (above in logs) 1536x864 is actually 1920x1080 downscaled to exactly 20% (or you can get 1920 from 1536 by enlarging the latter to 25%). What function do we use to detect display resolution? maybe it is not DPI-aware? or its behaviour was changed in recent windows version?

 

[mbuzina]

@Vasilich @Owlsroost : I do guess this issue is based on the DPI settings as well. Here is a Guide to making Applications DPI aware for Win 8.1 : http://go.microsoft.com/fwlink/p/?LinkID=307061

Right now we need to state that Win 8.1 is not properly supported due to this issue.

 

[Owlsroost]

What function do we use to detect display resolution?

No idea - I've never looked at the code. I know what dshowhelper uses, which is why I aksed for the evr logs earlier (so I could check if that is reporting the correct monitor size).

I agree that the new DPI scaling changes in 8.1 are likely to be the problem here - reading some of the MS document, it looks like 8.1 is trying to get 'clever' about handling DPI scaling....

 

[mbuzina]

I think I found a temporary workaround (it is not nice as you need to "disable" all the DPI features).

1. Go To Control Panel, Appearance & Personalization, Display
2. Enable "Let me choose one scaling level for all my displays"
3. Choose Radio Button "Smaller (100%)"
4. Log Off/Log On

Now MP should stay as big as it is. Unfortunately you will not get any scaling for your system anymore (so please Devs, make this App Multi-Monitor-DPI aware (which should not be too hard as MP by itself just always needs 100%)).

 

[mbuzina]

So, as this seems to be a real issue, how about logging it as a bug?

 

[Owlsroost]

go ahead....but remember to say how to reproduce it and add the workaround as a comment.

 

[Sebastiii]

I have try to quickly debug and set DPI to larger (Windows tell me that i'm @ 1920x1080) but MP and C# code tell :
{Bounds = {X=1280,Y=0,Width=1280,Height=720} WorkingArea = {X=1280,Y=0,Width=1280,Height=720} Primary = false DeviceName = "\\\\.\\DISPLAY2"}
-> 1280x720.

I think this is the issue (if i understand correctly) if we can find a way to MP get screen correct resolution and not the DPI one, i think it will be good

 

[mbuzina]

Yes, that is the issue (It should not be tooo hard).

The word document linked above shows the steps (Page 18)

· SetProcessDpiAwareness (or DPI manifest entry) sets the process to a specified DPI awareness level, which then determines how Windows scales the UI. This supersedes SetProcessDPIAware. Note: you can also set the DPI awareness level in the application manifest.
· GetProcessDpiAwareness returns the DPI awareness level. This supersedes IsProcessDPIAware.
· GetDpiForMonitor returns the DPI for a monitor.
· The WM_DPICHANGED window notification is sent to per-monitor DPI-aware applications when a window’s position changes such that most of its area intersects a monitor with a DPI that is different from the DPI before the position change. To create an application that resizes and re-renders itself when a user moves it to a different display, you use this notification.
· Note: the WM_DPICHANGED notification is not sent when the user changes the desktop scaling value in Control Panel.

So we should call SetProcessDpiAwareness(_Process_DPI_Awareness.Process_Per_Monitor_DPI_Aware) (http://msdn.microsoft.com/library/windows/desktop/dn302122.aspx) early before any Resolution checking is done and probably that should be it (we might listen to the message as well, but I guess since it has no impact on MP rendering...).

 

[Owlsroost]

Seb - you need to read the MS documentation that mbuzina linked to above - and this http://msdn.microsoft.com/en-us/library/windows/desktop/dd464646(v=vs.85).aspx and http://msdn.microsoft.com/en-us/library/windows/desktop/ee308410(v=vs.85).aspx (which may be the simplest way of saying 'don't mess with me' to the OS if I'm understanding it correctly. It's also the solution MS recomends - it suggests the 'DPI awareness' method calls are not the best way normally).

I think we need to play by the MS 'rules' here, otherwise we'll be in trouble with this issue again at some point....

 

[Sebastiii]

Good news
It seems that i have something to try It detect the right Monitor value.

I have add the change for MP and Configuration, now we need to someone to reproduce the issue (Because right now i can't with or without the patch).
I can provide bin against master