Debian – How to extend the desktop to the 2nd monitor rather than just cloning it

debiandisplaydrivers

I have just installed Debian Wheezy for the first time and have had mixed success getting my system up and running. Currently my main issue is that I am unable to extend my desktop to my second screen.

I have an ATI radeon HD 7700 series graphics card connected to 2 displays. Running lspci results in this line, among others:

04:00.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI Cape Verde [Radeon HD 7700 Series]

Currently, both are cloned. I initially tried to follow the instructions for installing proprietary ATI drivers, which resulted in the 2nd display being detected but I was unable to extend the desktop rather than clone it (something about my virtual screen not being big enough).

I gathered that support might be better for the free version so I followed these instructions for removing said drivers, followed by these instructions to install the free ones.

As per the troubleshooting step in that page I ran this command:

dmesg | grep -E 'drm|radeon' | grep -iE 'firmware|microcode'

which produced this output:

[    4.925773] [drm] Loading VERDE Microcode  
[    4.990158] platform radeon_cp.0: firmware: agent loaded radeon/VERDE_pfp.bin into memory 
[    5.152647] platform radeon_cp.0: firmware: agent loaded radeon/VERDE_me.bin into memory 
[    5.236165] platform radeon_cp.0: firmware: agent loaded radeon/VERDE_ce.bin into memory [    5.260082] platform radeon_cp.0: firmware: agent loaded radeon/VERDE_rlc.bin into memory 
[    5.376566] platform radeon_cp.0: firmware: agent loaded radeon/VERDE_mc.bin into memory

That's different to the outputs on that page but then they don't really give anymore information so I just assumed everything had worked.

Anywho, now when I go to System Tools -> Preferences -> System Settings -> Display I just see a single display called Unknown, which clones across both of my monitors.

running xrandr -q produces this output:

xrandr: Failed to get size of gamma for output default Screen 0:
minimum 1680 x 1050, current 1680 x 1050, maximum 1680 x 1050 default
connected 1680×1050+0+0 0mm x 0mm 1680×1050 0.0*

FYI 1680×1050 is the native resolution of both monitors. I do not have a /etc/X11/xorg.conf file, and my /etc/X11/xorg.conf.d/ directory seems to be empty.

This is my first time running a linux system so I'm totally confused and would appreciate kind words and idiot-proof guidance.

Best Answer

I found this answer on AU in a Q&A titled: How can I set up dual monitor display with ATI driver?.

excerpt

Open a terminal and type:
  $ gksudo gedit /etc/X11/xorg.conf
In the sub-section "display" add this code or modify if already exist:
  virtual 2880 1024
Where 2880 and 1024 are the value returned by the error: required virtual size does not fit available size: requested=(2880, 1024), minimum=(320, 200), maximum=(1600, 1600).

Restart the computer.

Then you will be able to extend your desktop without issue.

In the OP's configuration he opted to use this:

virtual 3360 1050

Problem

It turns out there's already an open issue in the Chromium tracker about this annoying inconvenience. Existing options offered by Hangouts have major drawbacks:

Share Entire Screen: If you have multiple screens (I have three) and share "Entire Screen", other people in the hangout won't be able to see anything.
Share Application: If you only share a specific application, then:
- You will have to manually switch to other apps while streaming by going back to hangouts and switching Screen Share on/off.
- In some applications, extra windows (such as dialogs for preferences, menus, popups, etc.) won't be captured as part of the app you're sharing. And most of the times it's these dialogs you want to focus on.

Solution / workaround

A very good workaround is at Comment 18 of this same discussion, so all the credits should go to the comment's author.

I'll summarize the process here, which allows you to Share a Part/Area of your multi-monitor screen in Google Hangouts running in a Linux Machine.

Open VLC in "Screen Capture" mode and tell it which part of your X11 screen you want it to capture, using the appropriate Screen Module command-line parameters. You can either do this through GUI configuration OR using the command line:
```
vlc \
    --no-video-deco \
    --no-embedded-video \
    --screen-fps=20 \
    --screen-top=32 \
    --screen-left=0 \
    --screen-width=1920 \
    --screen-height=1000 \
    screen://
```
If VLC complains about not being able to open screen://, please make sure you have correct module installed. For me, on ubuntu 19.10, I had to install an additional package vlc-plugin-extra-access by invoking apt install vlc-plugin-access-extra.
Go back to Google Hangouts and share the newly opened VLC window, which now acts as your "portal" to the interesting part of your screen.

Important notes

Move the VLC window away from the part of the screen you are capturing to avoid inception effects.
Do NOT resize OR minimize the VLC window because it will affect the resolution of your screen share. If you want to get it out of your way while streaming to hangouts, just move it off-screen WITHOUT resizing it, or just pretend it's not there.
The mouse pointer is not captured by VLC in linux. The author of the workaround suggests a solution for this as well: ExtraMaus, a simple C programs which creates a "clone" of your mouse, but visible by VLC.

[TL;DR] Explaining the values I chose in the example

The screen:// parameter indicates we want to enable the Screen Capture module. You'll always use this parameter as is.
The flags --no-video-deco and --no-embedded-video hide the window menu and video control toolbar respectively. You don't want to share these through Hangouts, so I suggest you always include these parameters.
The --screen-fps=20 does not have to be 20. You can make it 30 or 10, since performance is primarily affected by how Chrome encodes the video stream.
The area of the screen you want to captured follows the standard convention [--screen-top, --screen-left, --screen-width, --screen-height]. Supposing I had two monitors, each 1920x1080, giving a total 3840x1080 "virtual" screen when placed one next to the other, I could give the following coordinates:
1. [ 0, 0, 1920, 1080] for my entire left screen
2. [ 0, 1920, 1920, 1080] for my entire right screen
3. [32, 0, 1920, 1000] for a part of my left screen which spans across its full width but trims 32 pixels from its top (where I usually have a window's title bar) and 1080-1000-32 = 48 pixels from its bottom (where I have my KDE taskbar).

Best Answer

Related Solutions

Shell – Sharing your desktop with Google Hangouts, dual monitor and GNOME Shell

Problem

Solution / workaround

Important notes

[TL;DR] Explaining the values I chose in the example

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