When you connect two (or more) monitors to your computer, you can drag an application window from one to another monitor. Now, what if your second monitor is your smartphone, or tablet and you are able to drag window to it and interact with your fingers? Sound cool, isn’t it?

iDisplay is one such app that allows you to turn your mobile device into a second monitor. It was launched a year back for iPhone/iPod Touch/iPad. A new Android version was made available last month and it now works on a Android smartphone and tablet.

There are two parts to make this app work. You have to install the desktop client (available for Mac and Windows) and the mobile app (supports blackberry, Windows Mobile and several Symbian models too).

Download the iDisplay desktop client for Android.

Install it in your system. Once it has finished installing and configuring your display settings, you should see the icon lying at the system tray. Hover your mouse over it and you should see the IP address and port detail. Record this down.

Next, install the iDisplay app from the market (The app costs $4.99. You can also download a free trial version from the ShapeServices site).

Run the iDisplay app. Make sure that your computer and your mobile device are connected to the same WIFI network. On the first run, it will scan the local network for the iDisplay desktop client. If found, it will auto connect to it. If not, you will have to enter the IP address and port manually.

Once you are connected, you will be able to use it as a second monitor.

Practical use for iDisplay

While this app is cool, the only practical usage I can think of is to make your desktop application touchable. By moving your application to the mobile device, you can interact with the application with your fingers (zooming, paning, tap to activate features). But even then, the performance is often slow and undesirable.

If you are using a netbook (with 10.1 inches monitor), using the iPad or Android table as a second monitor is also a great way to double the screen size of your computer. This can be really convenient, especially when you are on the move.

One thing to note is that the Android app force close several times while I am testing it for this article.

You will want to get this only if you own a tablet. Using it on a smartphone with small screen doesn’t fulfill any needs at all.

iDisplay for Android

Many laptop owners often connect their machines to external displays, whether monitors, televisions, or projectors. For display chips that support XrandR, the setup is usually rather simple. For users with Nvidia chips, it is still easy but not quick. To switch to an external display, you either have to configure it in the xorg.conf file to automatically recognize it or use nvidia-settings and click through a series of options each time you want to use it.

With Disper, a free on-the-fly display switching utility, you can quickly and easily switch to an external display, clone your screens, extend a display, and choose from any of the supported resolutions. Disper is a command line utility, but after a few initial command entries, you can easily bind it to a shortcut key or run it from a single command by using a basic script.

Installation

The Disper website lists binary package archives for Ubuntu, ArchLinux, and OpenSUSE. Follow your distribution’s normal installation procedures to install. For all other distributions, Disper uses python and is easy to install from source. To install:

1. Download the latest version

2. Open a terminal window

3.. Extract the contents of the archive:

tar zxvf disper_0.2.3.tar.gz

4. Go to the src/ directory:

cd trunk/src

5. Type:

make install

Alternative, you can run the program without installing, directly from the src directory:

./cli.py

Initial Setup

Disper should recognize your VGA, DVI, or HDMI connection right away. The first thing to do with Disper is to identify your displays. Enter the following command:

disper –list

The output will look like this:

display DFP-0: HannStar Display Corp HSD121PHW1

resolutions: …960×540, 832×624, 1024×768, 1366×768

display DFP-1: SONY TV

resolutions: …1400×1050, 1600×1024, 1680×1050, 1280×720, 1920×1080

Note: I truncated the lower resolutions, but the full list will show all of them.

Usage

If you just want to clone your display, you can enter one command:

disper -c

Unfortunately, if your device has an odd maximum resolution like my netbook (1366×768), this will result in both screens switching to something like 1024×768. That may be fine for projectors, but if you want to play movies, TV shows, or games on your television, for example, you will want to use custom settings.

For example, if I wanted to display only on my television in 720p resolution, I would enter:

disper -S -r 1280×720

The uppercase “S” refers to the external display. To switch back to the default netbook display, I would enter:

disper -s

This will automatically detect the default resolution and return to it. (Notice the lowercase “s”).

At any time, you can have Disper display the current settings with:

disper -p

The output will look like:

backend: nvidia

associated displays: DFP-0

metamode: DFP-0: 1366×768 @1366×768 +0+0

scaling: aspect-scaled

Extending the displays takes advantage of Nvidia’s Twinview, all with a single command. For example, if I wanted two screens, with my TV screen above my laptop, I would type:

disper -e -r 1366×768,1920×1080 -t top

This would give me a normal laptop screen plus a 1080p full resolution TV screen.

Simplifying

While typing in disper commands may be simple for some, others may not see it as having much of an advantage over using nvidia-settings or a graphical frontend for XrandR. To truly make it simple, you need to create a script and/or menu shortcuts.

For switching to the Sony TV, as in the example above, the script could be as simple as:

#!/bin/sh

disper -S -r 1280×720

Make sure to make your script executable with:

chmod a+x script-name

You could also come up with something more complex that will automatically detect displays and switch back and forth. You could then bind the command to a shortcut using your desktop environment (For example, in KDE, use kmenuedit, where you can assign a keyboard shortcut to a command). You can also create a script for each setting and then easily switch to the one you need from the run command dialog (Alt+F2).

For more information about Disper and links to custom scripts to make switching displays easier, visit the project’s website.

Dual monitor setup in Linux has never been easier. While methods such as the xinerama extension sometimes drive people insane, using RandR (Resize and Rotate) is quick and painless. This will allow you to use both monitors as one big screen instead of two identical ones (cloning). Follow these simple steps to get started.

Note: This HOWTO assumes that you are using the opensource drivers for your video card (ATI or Intel). Nvidia and AMD proprietary drivers come with their dual screen components.

1. Setup your xorg.conf configuration file:

Edit it as root:

gksudo gedit /etc/X11/xorg.conf

(in GNOME) or

kdesudo kate /etc/X11/xorg.conf

(in KDE)

2. Create a subsection under the “Screen” section with the following.

SubSection "Display"
Depth 24
Modes "1440x900" "1440x900" #the resolutions of your monitors
Virtual 2880 800
EndSubSection

Xrandr will function without these xorg.conf lines, but it will limit the size of your desktop.

For my computer, I am using two monitors with 1440×900 resolution. If you have a different resolution, put those resolutions under “modes” and then combine the width of both for “virtual”. In other words, if you have a 1280×800 monitor, it would be “Virtual 2560 800″.

3. Save your changes, exit and restart X.

4. Now, you can setup your dual screens however you like. First find out some information about the screens. Open a terminal emulator and type:

xrandr -q

It should tell you the name of each screen and its current resolution. On my computer, my screens are “DVI-0″ and “DVI-1″.

5. To make one large desktop including both screens, run this command:

xrandr --auto --output DVI-0 --mode 1440x900 --right-of DVI-1

DVI-0 is on the right, and DVI-1 is on the left.

6. Create a script called “startxrandr” to run this command whenever you want.

#!/bin/sh
xrandr --auto --output DVI-0 --mode 1440x900 --right-of DVI-1

7. Make sure to make the script executable

chmod a+x startxrandr

That is all it takes. You can play around with it and see all of xrandr’s commands by running “xrandr -help”.

Notes:

There are also a few GUI applications that allow you to control xrandr.  Check with your Linux distribution.

You can set xrandr to run when your display manager or desktop environment starts. See the its documentation for startup applications.

KDE and GNOME will automatically configure two screens correctly so that maximizing a window will only fill one of the screens. Some desktop environments do not yet have support for this. You will have to test the one you use. You should have no problems with Compiz.

You can have two monitors with different resolutions, which is useful if you are using a laptop connected to a larger monitor.

In KDE, each screen will automatically be a different activity, and you can apply different widgets on each.

Some applications, especially those that rely on SDL (like many Linux games), may not honor your xrandr settings. If you are lucky, it will just clone the game on both screens. For applications like Boxee, you will need to set the environment variable before starting it:

export SDL_VIDEO_FULLSCREEN_HEAD=1