Finding Screen Size and units

[Thomas Sjöholm]

Hi!

I want to do some cool math, but need the size of the screen in order to do it. I can’t find a way to access the screen size in any way. I think that it should be possible as the Eye Tracker needs to know that in order to do the math to find where on the screen I am looking…

How do I access screen size?
Is it possible to find height and width separately?
What unit is the screen size given in?
Is the unit received from “EyePositionDataEventParams” on the Left/Right-Eye-X/Y/Z millimeters?

BTW, documentation á la
http://docs.oracle.com/javase/7/docs/api/
http://slick.ninjacave.com/javadoc/
http://lwjgl.org/javadoc/
http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/
https://docs.unity3d.com/Documentation/ScriptReference/
is very much requested 🙂

[Robert [Tobii]]

Hi Thomas,

I recall that you are working with Unity. In that case you can use Screen.currentResolution to get the screen size in pixels.
http://docs.unity3d.com/Documentation/ScriptReference/Screen-currentResolution.html

The EyePositionData is indeed in millimeters, with the origin in the center of the screen, Z axis facing outwards.

Thank you for your feedback regarding API docs. We have thought about using Doxygen or some other tool to auto-generate the docs from the C API header files, but have not prioritized it yet. Add it as a Feature Request and we’ll see how many others who want it urgently.

[Thomas Sjöholm]

It is correct that I currently work in Unity. What I actually want is the real world size of the screen. It should be accessible as the ET needs it in order to know where the screen is.

[Thomas Sjöholm]

It appears that I only need the (real world) width of the screen (preferably in millimeters) for my current purpose. Is it possible to access in any way?

[Robert [Tobii]]

Hi Thomas,

I was not sure this value was exposed through the API, but there is a way (although a bit cumbersome)

1) In the EyeXHost class, add a connection changed listener (to make sure you are connected). In there, call GetSettingsAsync method on the Interaction Context:

            _context.ConnectionStateChanged += (sender, e) => 
            {
                if (e.State == ConnectionState.Connected)
                {
                    _context.GetSettingsAsync(SettingsPaths.EyeTracking, OnDisplaySizeSettingEvent);
                }
            };

2) Use this code to extract the width and height in millimeters

    private void OnDisplaySizeSettingEvent(SettingsBag settings)
    {
        Size2 displaySize;       
        PropertyBag data = (PropertyBag)settings.Data;
        
        InteractionProperty eyetrackingProperty;
        data.TryGetProperty(SettingsPaths.EyeTracking, out eyetrackingProperty);
        
        InteractionProperty displaySizeProperty;
        ((PropertyBag)eyetrackingProperty.Value).TryGetProperty(SettingsPaths.DisplaySize, out displaySizeProperty);
        
        displaySize = (Size2)displaySizeProperty.GetValueAs(typeof(Size2));
        
        print("Display size: " + displaySize.Width + " x " + displaySize.Height + " mm");
    }

Not the easiest way as I said, but it works for me

[Thomas Sjöholm]

Forgot to say thanks! Just what I wanted 🙂

[Robert [Tobii]]

Update: If you are using the latest Unity SDK package (version 0.14 or later), you only need these lines in OnDisplaySizeSettingEvent

    private void OnDisplaySizeSettingEvent(SettingsBag settings)
    {
        Size2 displaySize;       
        settings.TryGetSettingValue(out displaySize, SettingsPaths.EyeTracking, SettingsPaths.DisplaySize);

        print("Display size: " + displaySize.Width + " x " + displaySize.Height + " mm");
    }

[Jason Walker]

@Robert [Tobii]

Are these examples still valid for the latest sdk ( tobii 4C) ideally i would like to know pixel size of calibrated display that the 4c is working with ….

Cheers
Jay

[Grant [Tobii]]

Hi @jaymonkey, the samples should still work fine with the latest SDK.. did you have some issues running the samples yourself?

[Jason Walker]

I have all the samples included in the SDK building and running fine (both x86 & x64) i’ve got my middle ware running great but im currently getting screen resolution via two keys from a .ini file … these two keys are the x and y dimensions (in pixels) of the screen that the 4C is being used with … was just wondering if there is a function in the SDK that will do this … the examples in this thread return the dimensions in mm ??? so is there similar for pixels … ??

if so any chance you could post a quick example ??

Cheers
Jay

[Grant [Tobii]]

Hi Jason, it seems like Unity exposes Screen size in their own API

Screen.width
public static int width;

As specified in their online documentation, did you manage to find this already?
Thanks for the update.

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