Panning using xrandr

I had always been wondering, how can I reduce the size of my display to a smaller size, while keep the virtual size of my display to my current size, using a command.

“Wait, why would you need that?” You may ask. Well, that’s a secret trick that I’ve been playing for years —

When people playing videos, most people like to play in full screen mode, simply by switching to the full-screen playing mode from the video player. However, I never do that. Why?

Because I consider the method

1. a waste of my CPU power
2. a waste of the energy
3. yields less than optimal result, no matter how good the video player can stretch the video.

About the point 3, with nowadays screen size, using my 1920×1080 screen as an example, playing a 640×360 video would mean stretching the video 3 times both horizontally and vertically. In other words, the video player has to magically come up with 9 pixels from a single pixel of the video. No matter what magic it is, we can tell that it either produces bad result, or use an outrageous amount of CPU power. Is there any better solution? Yes, using my trick.

May people know that our monitor can render more than one resolution, but few would use anything less than the highest resolution. Playing low resolution videos is the perfect time to use lower monitor resolutions — the video player play the video as is, without any stretching, while you are viewing (almost) full screen. I call the first method the software solution and mine as hardware solution.

Now the problem is how to do it? Wouldn’t

xrandr -s <width>x<height>

do the trick? Well, yes it does. But the problem is that when I restore my display to its original size, all exiting window are shifted, jam-packing the upper left corner of the display, and even gnome menu icons are shifted two. That’s awful.

Quick answer:

To reduce to a smaller display size,

xrandr --output VGA-1 --mode 640x480 --panning 1920x1080

This will reduce the size of my display to a smaller size (640×480), while keep the virtual size of my display to my current size. To view the other virtual display area, just panning with the mouse.

To get a list of display size can be used, use xrandr. Here is output of mine:

$ xrandr
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 4096 x 4096
VGA-1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 477mm x 268mm panning 1920x1080+0+0
   1920x1080      60.0*+
   1280x1024      75.0     60.0
   1440x900       59.9
   1280x800       59.8
   1152x864       75.0
   1024x768       70.1     60.0
   800x600        60.3     56.2
   640x480        66.7     60.0
   720x400        70.1

It shows that the smaller sizes that I can use are, 1280×1024, 1440×900, 1280×800, …., 800×600, 720×400 and 640×480.

BTW, There is also an old X11 trick to change the screen resolution, Ctrl-Alt plus + or – from the number pad. That’s the trick that I’ve been playing for years. However, as you can tell, it’d be tiresome to do it now, because previously there’s about 3 modes that I can switch in between, and now it is tiresome to cycle through all the display mode above.

To restore,

xrandr -s 1920x1080

For details, read on.

documented on: 2011-02-02

---

Newsgroups: gmane.linux.debian.user
Date: Mon, 31 Jan 2011

> How to do panning using xrandr?
>
>  xrandr --panning <width>x<height>
>
> won't work -- I need to put --output <output> before --panning.

Sure.

> The problem is, I've searched everywhere, but every possible string I
> tried didn't work.

Don’t guess; ask your device: “xrandr -q” will tell you the name of detected devices.

Camaleón @gmail.com

---

Panning using xrandr_

> Don't guess; ask your device: "xrandr -q" will tell you the name of

Perfect, thanks a lot.

Now the question that I really want,

How can I reduce the size of my display to a smaller size, while keep the virtual size of my display to my current size, using panning to view all virtual display. I tried below, but it didn’t work as I expected . . .

---

Panning using xrandr_

On Tue, 01 Feb 2011 20:38:50 +0000, Camaleón wrote:

>> all virtual display. I tried below, but it didn't work as I expected:
>>
>>  xrandr -s 640x480 --output VGA-1 --panning 1920x1080
>
> Hum... if I understood correctly the xrandr man page, you should run
> something like:
>
> xrandr --output VGA-1 --mode 640x480 --fb 1920x1080 --panning 1920x1080

OMG! That’s perfect!

Thanks a thousand!!!

Just FTA, the –fb 1920×1080 is not really necessary. The relation between the “mode”, “panning” and “framebuffer” can be illustrated below,

┌──┳━━━━━━━━━━━━━━┳─────┬ ─ ─ ─ ─ ─ ┐
│  ┃     CRTC     ┃     │
│  ┃              ┃     │           │
│  ┃             X┃→    │
│  ┃              ┃     │           │  framebuffer
│  ┗━━━━━━━━━━━━━━┛     │
│                       │           │
│panning area           │
└───────────────────────┴ ─ ─ ─ ─ ─ ┘

If now –fb is specified, it default to the same size as panning:

┌──┳━━━━━━━━━━━━━━┳────────────┐
│  ┃     CRTC     ┃            │
│  ┃              ┃            │
│  ┃              ┃→           │
│  ┃           X←→┃            │
│  ┃       border_right        │
│  ┗━━━━━━━━━━━━━━┛            │
│                              │
│panning area                  │
└──────────────────────────────┘

Credit:

http://cgit.freedesktop.org/xorg/proto/randrproto/tree/randrproto.txt

Thanks again

xpt

documented on: 2011-02-02

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