Today I had to dismantle my screens and keyboard so that a blinds
fitter could stand on my desk to replace vertical blind slats.

After I reconnected but before rebooting my 21.1 system, I connected a
previous 20.3 drive to try and find a file. It was working fine.

After I powered down switched to the 21.1 system althoughn the screens appeared as I last saw them but the mouse cursor refused to travel from the right-hand (primary) screen to the left screen. To do that i had to push it off the right of the right-hand screen whereupon it appears on the left of the left hand screen.

Nothing I do in the Display settings will correct it.

Before someone tells me to Google it, I did but every useful sounding page just gave me 404!

I used to be able to handle such things by editing xorg.conf but we don't have those any more it seems.

On 6/8/2023 4:33 PM, pinnerite wrote:
> Today I had to dismantle my screens and keyboard so that a blinds
> fitter could stand on my desk to replace vertical blind slats.
>
> After I reconnected but before rebooting my 21.1 system, I connected a
> previous 20.3 drive to try and find a file. It was working fine.
>
> After I powered down switched to the 21.1 system althoughn the screens appeared as I last saw them but the mouse cursor refused to travel from the right-hand (primary) screen to the left screen. To do that i had to push it off the right of the right-hand screen whereupon it appears on the left of the left hand screen.
>
> Nothing I do in the Display settings will correct it.
>
> Before someone tells me to Google it, I did but every useful sounding page just gave me 404!
>
> I used to be able to handle such things by editing xorg.conf but we don't have those any more it seems.
>

The Linux Mint forums are offline until Friday (404).
The maintenance messages is at the top level.
Pages within the DB return 404, implying that the
forum server consults a separate DB server for the pages.

I've noticed that the distros seem to have the ability
to "remember missing monitors". This implies state information.

But, this can also be bad, because if you plug the monitors
into the wrong ports, depending on the implementation, the
left and right monitors could have their roles switched. Either
the monitors are remembered by port numbers (DP #1 and DP #2),
or they could be tracked by EDID serial number (monitor samsung 12345
and monitor samsung 24680).

And with the 404's right now from the forum, I don't
know if I'm going to track this down either. As to which
subsystem stores the info. It's not like the old days,
where pointing you at xorg.conf would answer all questions :-)

And really, we don't want to repair this manually as such.
It would be better to discover how the automation was
intended to do this, so we don't break something in a worse way.
for example, xorg.conf is "automatically generated" these
days, for the most part. And that has implications as to
what bits are always automatically generated, and what
bits are held in gconf, xrandr, or whatever.

It's never going to do the right thing, on dual monitors, the first time.

It remembers settings from one section to the next.

Now, what happens when you move the monitors to different ports.
Did they handle that properly, or not ? Good good question.

Paul

On Fri, 9 Jun 2023 00:27:27 -0400
Paul <nospam@needed.invalid> wrote:

> On 6/8/2023 4:33 PM, pinnerite wrote:
> > Today I had to dismantle my screens and keyboard so that a blinds
> > fitter could stand on my desk to replace vertical blind slats.
> >
> > After I reconnected but before rebooting my 21.1 system, I connected a
> > previous 20.3 drive to try and find a file. It was working fine.
> >
> > After I powered down switched to the 21.1 system althoughn the screens appeared as I last saw them but the mouse cursor refused to travel from the right-hand (primary) screen to the left screen. To do that i had to push it off the right of the right-hand screen whereupon it appears on the left of the left hand screen.
> >
> > Nothing I do in the Display settings will correct it.
> >
> > Before someone tells me to Google it, I did but every useful sounding page just gave me 404!
> >
> > I used to be able to handle such things by editing xorg.conf but we don't have those any more it seems.
> >
>
> The Linux Mint forums are offline until Friday (404).
> The maintenance messages is at the top level.
> Pages within the DB return 404, implying that the
> forum server consults a separate DB server for the pages.
>
> I've noticed that the distros seem to have the ability
> to "remember missing monitors". This implies state information.
>
> But, this can also be bad, because if you plug the monitors
> into the wrong ports, depending on the implementation, the
> left and right monitors could have their roles switched. Either
> the monitors are remembered by port numbers (DP #1 and DP #2),
> or they could be tracked by EDID serial number (monitor samsung 12345
> and monitor samsung 24680).
>
> And with the 404's right now from the forum, I don't
> know if I'm going to track this down either. As to which
> subsystem stores the info. It's not like the old days,
> where pointing you at xorg.conf would answer all questions :-)
>
> And really, we don't want to repair this manually as such.
> It would be better to discover how the automation was
> intended to do this, so we don't break something in a worse way.
> for example, xorg.conf is "automatically generated" these
> days, for the most part. And that has implications as to
> what bits are always automatically generated, and what
> bits are held in gconf, xrandr, or whatever.
>
> It's never going to do the right thing, on dual monitors, the first time.
>
> It remembers settings from one section to the next.
>
> Now, what happens when you move the monitors to different ports.
> Did they handle that properly, or not ? Good good question.
>
> Paul
>

The two brand new identical monitors are driven by two brand old
identical graphics cards, rather than the on-board graphics.

When, while doubting my sanity,I switched them over hoping to expect a
change, I was disappointed.

Alan

On 6/9/2023 2:56 AM, pinnerite wrote:

> The two brand new identical monitors are driven by two brand old
> identical graphics cards, rather than the on-board graphics.
>
> When, while doubting my sanity,I switched them over hoping to expect a
> change, I was disappointed.
>
> Alan

I may have related my experience with this once before.

I had two FX5200, an AGP one and a PCI one. I was watching
the desktop on two monitors, when all of the sudden, out of
the blue, the screens blinked, and the left and right monitors
swapped roles. And the numbering of the graphics
cards had changed. So Card #1 is Card #2 and Card #2 is Card #1.
And the side effect of this, was the monitor positions swapped.

Weird stuff can happen, when hardware bits are identical.
In that case, the drivers do not distinguish between
AGP and PCI, just that the model type (and associated driver)
are both for FX5200.

*******

Since the forum is down, I only have the teaser sentences
in Google to work with. For example, I see:

Open the file manager and make hidden files visible.
Now go into the folder .config inside of your home.
Rename the file monitors.xml ...

Presumably, the person is renaming that file to monitors.xml.bak
so that a new monitors.xml can be generated.

OK, I'm running LinuxMint 21,2 Vera and Cinnamon 5.6.8

I just plugged in my fake monitor (a VGA connector, three 75 ohm
termination resistors, a DP to VGA adapter) into the video card.
The Display panel shows two monitors. I made a slight shift in
the fake 1024x768 monitor, so it aligns with the baseline. The fake
monitor runs 1024x768, since the EDID chip is missing and there is
no declaration about resolution whatsoever.

This created ~/.config/cinnamon-monitors.xml

So not only does it create a monitors file, it also labels the
DE as part of the name, in case you run/login to more than one DE.

You can see, for my one "real" monitor, it does keep a serial number.

<monitors version="2">
<configuration>
<logicalmonitor>
<x>0</x>
<y>0</y>
<scale>1</scale>
<primary>yes</primary>
<monitor>
<monitorspec>
<connector>HDMI-0</connector>
<vendor>NEC</vendor>
<product>NEC LCD1765</product>
<serial>37115679QA</serial> <=== serial number of my "real" monitor
</monitorspec>
<mode>
<width>1280</width>
<height>1024</height>
<rate>60.019741058349609</rate>
</mode>
</monitor>
</logicalmonitor>
<logicalmonitor>
<x>1280</x> <=== fake monitor is to the right
<y>256</y> <=== positive Y, seems to be downwards direction
<scale>1</scale>
<monitor>
<monitorspec>
<connector>DP-2</connector>
<vendor>RTK</vendor>
<product>0x1d1a</product>
<serial>0x01010101</serial>
</monitorspec>
<mode>
<width>1024</width>
<height>768</height>
<rate>60.003841400146484</rate>
</mode>
</monitor>
</logicalmonitor>
</configuration>
</monitors>

The real monitor is on an HDMI adapter. The fake monitor is on a DP adapter.
The video card has only one HDMI port, but there are several DP ports (1,2,3).

[Picture] Screenshot showing monitor setup

https://i.postimg.cc/SQ2X4s7J/dual-monitor-w-pointer.jpg

Now, is that the only file that matters ???

Paul

On Fri, 9 Jun 2023 04:15:07 -0400
Paul <nospam@needed.invalid> wrote:

> On 6/9/2023 2:56 AM, pinnerite wrote:
>
> > The two brand new identical monitors are driven by two brand old
> > identical graphics cards, rather than the on-board graphics.
> >
> > When, while doubting my sanity,I switched them over hoping to expect a
> > change, I was disappointed.
> >
> > Alan
>
> I may have related my experience with this once before.
>
> I had two FX5200, an AGP one and a PCI one. I was watching
> the desktop on two monitors, when all of the sudden, out of
> the blue, the screens blinked, and the left and right monitors
> swapped roles. And the numbering of the graphics
> cards had changed. So Card #1 is Card #2 and Card #2 is Card #1.
> And the side effect of this, was the monitor positions swapped.
>
> Weird stuff can happen, when hardware bits are identical.
> In that case, the drivers do not distinguish between
> AGP and PCI, just that the model type (and associated driver)
> are both for FX5200.
>
> *******
>
> Since the forum is down, I only have the teaser sentences
> in Google to work with. For example, I see:
>
> Open the file manager and make hidden files visible.
> Now go into the folder .config inside of your home.
> Rename the file monitors.xml ...
>
> Presumably, the person is renaming that file to monitors.xml.bak
> so that a new monitors.xml can be generated.
>
> OK, I'm running LinuxMint 21,2 Vera and Cinnamon 5.6.8
>
> I just plugged in my fake monitor (a VGA connector, three 75 ohm
> termination resistors, a DP to VGA adapter) into the video card.
> The Display panel shows two monitors. I made a slight shift in
> the fake 1024x768 monitor, so it aligns with the baseline. The fake
> monitor runs 1024x768, since the EDID chip is missing and there is
> no declaration about resolution whatsoever.
>
> This created ~/.config/cinnamon-monitors.xml
>
> So not only does it create a monitors file, it also labels the
> DE as part of the name, in case you run/login to more than one DE.
>
> You can see, for my one "real" monitor, it does keep a serial number.
>
> <monitors version="2">
> <configuration>
> <logicalmonitor>
> <x>0</x>
> <y>0</y>
> <scale>1</scale>
> <primary>yes</primary>
> <monitor>
> <monitorspec>
> <connector>HDMI-0</connector>
> <vendor>NEC</vendor>
> <product>NEC LCD1765</product>
> <serial>37115679QA</serial> <=== serial number of my "real" monitor
> </monitorspec>
> <mode>
> <width>1280</width>
> <height>1024</height>
> <rate>60.019741058349609</rate>
> </mode>
> </monitor>
> </logicalmonitor>
> <logicalmonitor>
> <x>1280</x> <=== fake monitor is to the right
> <y>256</y> <=== positive Y, seems to be downwards direction
> <scale>1</scale>
> <monitor>
> <monitorspec>
> <connector>DP-2</connector>
> <vendor>RTK</vendor>
> <product>0x1d1a</product>
> <serial>0x01010101</serial>
> </monitorspec>
> <mode>
> <width>1024</width>
> <height>768</height>
> <rate>60.003841400146484</rate>
> </mode>
> </monitor>
> </logicalmonitor>
> </configuration>
> </monitors>
>
> The real monitor is on an HDMI adapter. The fake monitor is on a DP adapter.
> The video card has only one HDMI port, but there are several DP ports (1,2,3).
>
> [Picture] Screenshot showing monitor setup
>
> https://i.postimg.cc/SQ2X4s7J/dual-monitor-w-pointer.jpg
>
> Now, is that the only file that matters ???
>
> Paul

I don't have .config/cinnamon-monitors.xml just
a .config/cinnamon-monitors.xml~

That contains details of monitors that have been relegated to the
recycling bin!

Alan

On 6/9/2023 10:52 AM, pinnerite wrote:
> On Fri, 9 Jun 2023 04:15:07 -0400
> Paul <nospam@needed.invalid> wrote:
>
>> On 6/9/2023 2:56 AM, pinnerite wrote:
>>
>>> The two brand new identical monitors are driven by two brand old
>>> identical graphics cards, rather than the on-board graphics.
>>>
>>> When, while doubting my sanity,I switched them over hoping to expect a
>>> change, I was disappointed.
>>>
>>> Alan
>>
>> I may have related my experience with this once before.
>>
>> I had two FX5200, an AGP one and a PCI one. I was watching
>> the desktop on two monitors, when all of the sudden, out of
>> the blue, the screens blinked, and the left and right monitors
>> swapped roles. And the numbering of the graphics
>> cards had changed. So Card #1 is Card #2 and Card #2 is Card #1.
>> And the side effect of this, was the monitor positions swapped.
>>
>> Weird stuff can happen, when hardware bits are identical.
>> In that case, the drivers do not distinguish between
>> AGP and PCI, just that the model type (and associated driver)
>> are both for FX5200.
>>
>> *******
>>
>> Since the forum is down, I only have the teaser sentences
>> in Google to work with. For example, I see:
>>
>> Open the file manager and make hidden files visible.
>> Now go into the folder .config inside of your home.
>> Rename the file monitors.xml ...
>>
>> Presumably, the person is renaming that file to monitors.xml.bak
>> so that a new monitors.xml can be generated.
>>
>> OK, I'm running LinuxMint 21,2 Vera and Cinnamon 5.6.8
>>
>> I just plugged in my fake monitor (a VGA connector, three 75 ohm
>> termination resistors, a DP to VGA adapter) into the video card.
>> The Display panel shows two monitors. I made a slight shift in
>> the fake 1024x768 monitor, so it aligns with the baseline. The fake
>> monitor runs 1024x768, since the EDID chip is missing and there is
>> no declaration about resolution whatsoever.
>>
>> This created ~/.config/cinnamon-monitors.xml
>>
>> So not only does it create a monitors file, it also labels the
>> DE as part of the name, in case you run/login to more than one DE.
>>
>> You can see, for my one "real" monitor, it does keep a serial number.
>>
>> <monitors version="2">
>> <configuration>
>> <logicalmonitor>
>> <x>0</x>
>> <y>0</y>
>> <scale>1</scale>
>> <primary>yes</primary>
>> <monitor>
>> <monitorspec>
>> <connector>HDMI-0</connector>
>> <vendor>NEC</vendor>
>> <product>NEC LCD1765</product>
>> <serial>37115679QA</serial> <=== serial number of my "real" monitor
>> </monitorspec>
>> <mode>
>> <width>1280</width>
>> <height>1024</height>
>> <rate>60.019741058349609</rate>
>> </mode>
>> </monitor>
>> </logicalmonitor>
>> <logicalmonitor>
>> <x>1280</x> <=== fake monitor is to the right
>> <y>256</y> <=== positive Y, seems to be downwards direction
>> <scale>1</scale>
>> <monitor>
>> <monitorspec>
>> <connector>DP-2</connector>
>> <vendor>RTK</vendor>
>> <product>0x1d1a</product>
>> <serial>0x01010101</serial>
>> </monitorspec>
>> <mode>
>> <width>1024</width>
>> <height>768</height>
>> <rate>60.003841400146484</rate>
>> </mode>
>> </monitor>
>> </logicalmonitor>
>> </configuration>
>> </monitors>
>>
>> The real monitor is on an HDMI adapter. The fake monitor is on a DP adapter.
>> The video card has only one HDMI port, but there are several DP ports (1,2,3).
>>
>> [Picture] Screenshot showing monitor setup
>>
>> https://i.postimg.cc/SQ2X4s7J/dual-monitor-w-pointer.jpg
>>
>> Now, is that the only file that matters ???
>>
>> Paul
>
> I don't have .config/cinnamon-monitors.xml just
> a .config/cinnamon-monitors.xml~
>
> That contains details of monitors that have been relegated to the
> recycling bin!
>
> Alan
>

Is it a permissions problem ?

Try renaming cinnamon-monitors.xml~ to cinnamon-monitors.xml.bak,
so that any editing procedure has room to work. Also, look
to see if there is any sort of lock file that might be stopping
the edit process.

Paul

On Fri, 9 Jun 2023 13:04:05 -0400
Paul <nospam@needed.invalid> wrote:

> On 6/9/2023 10:52 AM, pinnerite wrote:
> > On Fri, 9 Jun 2023 04:15:07 -0400
> > Paul <nospam@needed.invalid> wrote:
> >
> >> On 6/9/2023 2:56 AM, pinnerite wrote:
> >>
> >>> The two brand new identical monitors are driven by two brand old
> >>> identical graphics cards, rather than the on-board graphics.
> >>>
> >>> When, while doubting my sanity,I switched them over hoping to expect a
> >>> change, I was disappointed.
> >>>
> >>> Alan
> >>
> >> I may have related my experience with this once before.
> >>
> >> I had two FX5200, an AGP one and a PCI one. I was watching
> >> the desktop on two monitors, when all of the sudden, out of
> >> the blue, the screens blinked, and the left and right monitors
> >> swapped roles. And the numbering of the graphics
> >> cards had changed. So Card #1 is Card #2 and Card #2 is Card #1.
> >> And the side effect of this, was the monitor positions swapped.
> >>
> >> Weird stuff can happen, when hardware bits are identical.
> >> In that case, the drivers do not distinguish between
> >> AGP and PCI, just that the model type (and associated driver)
> >> are both for FX5200.
> >>
> >> *******
> >>
> >> Since the forum is down, I only have the teaser sentences
> >> in Google to work with. For example, I see:
> >>
> >> Open the file manager and make hidden files visible.
> >> Now go into the folder .config inside of your home.
> >> Rename the file monitors.xml ...
> >>
> >> Presumably, the person is renaming that file to monitors.xml.bak
> >> so that a new monitors.xml can be generated.
> >>
> >> OK, I'm running LinuxMint 21,2 Vera and Cinnamon 5.6.8
> >>
> >> I just plugged in my fake monitor (a VGA connector, three 75 ohm
> >> termination resistors, a DP to VGA adapter) into the video card.
> >> The Display panel shows two monitors. I made a slight shift in
> >> the fake 1024x768 monitor, so it aligns with the baseline. The fake
> >> monitor runs 1024x768, since the EDID chip is missing and there is
> >> no declaration about resolution whatsoever.
> >>
> >> This created ~/.config/cinnamon-monitors.xml
> >>
> >> So not only does it create a monitors file, it also labels the
> >> DE as part of the name, in case you run/login to more than one DE.
> >>
> >> You can see, for my one "real" monitor, it does keep a serial number.
> >>
> >> <monitors version="2">
> >> <configuration>
> >> <logicalmonitor>
> >> <x>0</x>
> >> <y>0</y>
> >> <scale>1</scale>
> >> <primary>yes</primary>
> >> <monitor>
> >> <monitorspec>
> >> <connector>HDMI-0</connector>
> >> <vendor>NEC</vendor>
> >> <product>NEC LCD1765</product>
> >> <serial>37115679QA</serial> <=== serial number of my "real" monitor
> >> </monitorspec>
> >> <mode>
> >> <width>1280</width>
> >> <height>1024</height>
> >> <rate>60.019741058349609</rate>
> >> </mode>
> >> </monitor>
> >> </logicalmonitor>
> >> <logicalmonitor>
> >> <x>1280</x> <=== fake monitor is to the right
> >> <y>256</y> <=== positive Y, seems to be downwards direction
> >> <scale>1</scale>
> >> <monitor>
> >> <monitorspec>
> >> <connector>DP-2</connector>
> >> <vendor>RTK</vendor>
> >> <product>0x1d1a</product>
> >> <serial>0x01010101</serial>
> >> </monitorspec>
> >> <mode>
> >> <width>1024</width>
> >> <height>768</height>
> >> <rate>60.003841400146484</rate>
> >> </mode>
> >> </monitor>
> >> </logicalmonitor>
> >> </configuration>
> >> </monitors>
> >>
> >> The real monitor is on an HDMI adapter. The fake monitor is on a DP adapter.
> >> The video card has only one HDMI port, but there are several DP ports (1,2,3).
> >>
> >> [Picture] Screenshot showing monitor setup
> >>
> >> https://i.postimg.cc/SQ2X4s7J/dual-monitor-w-pointer.jpg
> >>
> >> Now, is that the only file that matters ???
> >>
> >> Paul
> >
> > I don't have .config/cinnamon-monitors.xml just
> > a .config/cinnamon-monitors.xml~
> >
> > That contains details of monitors that have been relegated to the
> > recycling bin!
> >
> > Alan
> >
>
> Is it a permissions problem ?
>
> Try renaming cinnamon-monitors.xml~ to cinnamon-monitors.xml.bak,
> so that any editing procedure has room to work. Also, look
> to see if there is any sort of lock file that might be stopping
> the edit process.
>
> Paul
>

Yesterday, a search wouldn't show up cinnamon-monitors.xml.
Today I found both cinnamon-monitors.xml and cinnamon-monitors.xml~.

The contents of both do not seem to convey anything helpful.

Here is the former:

<monitors version="2">
<configuration>
<logicalmonitor>
<x>0</x>
<y>0</y>
<scale>1</scale>
<primary>yes</primary>
<monitor>
<monitorspec>
<connector>HDMI-0</connector>
<vendor>HPN</vendor>
<product>HP M22f FHD</product>
<serial>3CM2370SP4 </serial>
</monitorspec>
<mode>
<width>1920</width>
<height>1080</height>
<rate>60</rate>
</mode>
</monitor>
</logicalmonitor>
<logicalmonitor>
<x>1920</x>
<y>0</y>
<scale>1</scale>
<monitor>
<monitorspec>
<connector>HDMI-1-1</connector>
<vendor>HPN</vendor>
<product>HP M22f FHD</product>
<serial>3CM2370SPG </serial>
</monitorspec>
<mode>
<width>1920</width>
<height>1080</height>
<rate>60</rate>
</mode>
</monitor>
</logicalmonitor>
</configuration>
</monitors>

Alan

--
Linux Mint 21.1 kernel version 5.15.0-73-generic Cinnamon 5.6.8

On 6/10/2023 3:06 PM, pinnerite wrote:

> Yesterday, a search wouldn't show up cinnamon-monitors.xml.
> Today I found both cinnamon-monitors.xml and cinnamon-monitors.xml~.
>
> The contents of both do not seem to convey anything helpful.
>
> Here is the former:
>
> <monitors version="2">
> <configuration>
> <logicalmonitor>
> <x>0</x>
> <y>0</y>
> <scale>1</scale>
> <primary>yes</primary>
> <monitor>
> <monitorspec>
> <connector>HDMI-0</connector>
> <vendor>HPN</vendor>
> <product>HP M22f FHD</product>
> <serial>3CM2370SP4 </serial>
> </monitorspec>
> <mode>
> <width>1920</width>
> <height>1080</height>
> <rate>60</rate>
> </mode>
> </monitor>
> </logicalmonitor>
> <logicalmonitor>
> <x>1920</x>
> <y>0</y>
> <scale>1</scale>
> <monitor>
> <monitorspec>
> <connector>HDMI-1-1</connector>
> <vendor>HPN</vendor>
> <product>HP M22f FHD</product>
> <serial>3CM2370SPG </serial>
> </monitorspec>
> <mode>
> <width>1920</width>
> <height>1080</height>
> <rate>60</rate>
> </mode>
> </monitor>
> </logicalmonitor>
> </configuration>
> </monitors>
>

It's definitely a rock and a hard place. Check and see if the
xrandr plugin has been disabled, or some executable is missing.

https://gist.github.com/JonasAlfredsson/9d14aba3486aab72a8c9c11deb00da9f

"I guess it is worth to point out that these issues arise when
utilizing the proprietary Nvidia official graphics drivers and
is not a problem with the open source Nouveau drivers.
But those drivers has their own issues"

Well, not really, because xorg.conf is really toast. You can't
expect to cart that around now. Maybe a couple distro releases
ago, xorg.conf was still working (because I was still using it).

I think these could be running off different video cards.
Can you run both monitors off one video card, for testing purposes ?
Maybe it would take a DVI-D to HDMI adapter ?

<connector>HDMI-0</connector>
<connector>HDMI-1-1</connector>

Paul

>On Thu, 8 Jun 2023 21:33:29 +0100, pinnerite <pinnerite@gmail.com> wrote:

>Today I had to dismantle my screens and keyboard so that a blinds
>fitter could stand on my desk to replace vertical blind slats.

A nun was taking a bath when she heard a knock on the door.
"Who is it?" she said.
"It's the blind man" a voice replied.
"OK I guess you can come in" she said.
So the guy comes in, looks at her, and says:
"Hey, nice tits. Where do want the blinds."

On Sat, 10 Jun 2023 22:24:43 -0400
Paul <nospam@needed.invalid> wrote:

> On 6/10/2023 3:06 PM, pinnerite wrote:
>
> > Yesterday, a search wouldn't show up cinnamon-monitors.xml.
> > Today I found both cinnamon-monitors.xml and cinnamon-monitors.xml~.
> >
> > The contents of both do not seem to convey anything helpful.
> >
> > Here is the former:
> >
> > <monitors version="2">
> > <configuration>
> > <logicalmonitor>
> > <x>0</x>
> > <y>0</y>
> > <scale>1</scale>
> > <primary>yes</primary>
> > <monitor>
> > <monitorspec>
> > <connector>HDMI-0</connector>
> > <vendor>HPN</vendor>
> > <product>HP M22f FHD</product>
> > <serial>3CM2370SP4 </serial>
> > </monitorspec>
> > <mode>
> > <width>1920</width>
> > <height>1080</height>
> > <rate>60</rate>
> > </mode>
> > </monitor>
> > </logicalmonitor>
> > <logicalmonitor>
> > <x>1920</x>
> > <y>0</y>
> > <scale>1</scale>
> > <monitor>
> > <monitorspec>
> > <connector>HDMI-1-1</connector>
> > <vendor>HPN</vendor>
> > <product>HP M22f FHD</product>
> > <serial>3CM2370SPG </serial>
> > </monitorspec>
> > <mode>
> > <width>1920</width>
> > <height>1080</height>
> > <rate>60</rate>
> > </mode>
> > </monitor>
> > </logicalmonitor>
> > </configuration>
> > </monitors>
> >
>
> It's definitely a rock and a hard place. Check and see if the
> xrandr plugin has been disabled, or some executable is missing.
>
> https://gist.github.com/JonasAlfredsson/9d14aba3486aab72a8c9c11deb00da9f
>
> "I guess it is worth to point out that these issues arise when
> utilizing the proprietary Nvidia official graphics drivers and
> is not a problem with the open source Nouveau drivers.
> But those drivers has their own issues"
>
> Well, not really, because xorg.conf is really toast. You can't
> expect to cart that around now. Maybe a couple distro releases
> ago, xorg.conf was still working (because I was still using it).
>
> I think these could be running off different video cards.
> Can you run both monitors off one video card, for testing purposes ?
> Maybe it would take a DVI-D to HDMI adapter ?
>
> <connector>HDMI-0</connector>
> <connector>HDMI-1-1</connector>
>
> Paul
>
>

The link that you provided looked quite exciting. However I have ATi
(AMD) chips and therefore drivers. But it did encourage me to
experiment.

First I switched the displays (in the settings) and made the left-hand
one the primary (counter-intuitive for me).

That caused the mouse to travel the correct way between the screens.

BUT, it also caused the desktop icons and the task bar (bottom panel)
to apear on the left screen.

Now this is in Cinnamon.

I right-clicked on the desktop and selected Customise.
At the foot in blue is Desktop settings.

At Desktop Layout I (eventually) selected "Show desktop icons on primary monitor only.
The only desktop icons selected beneath that are "Computer", "Rubbsish bin" an "Network".
However when it reset all my desktop icons and the panel were on the right-hand screen as desired and all was well in the Pinnerite household.

Thank you everyone for your help and advice.

Regards, Alan

--
Linux Mint 21.1 kernel version 5.15.0-73-generic Cinnamon 5.6.8