C# and Ubuntu - How do I get size of primary screen?

Question

I'm trying to determine the size of my primary screen so I can capture its image. My setup is a laptop that has a 1600x900 display, and an external monitor that's 1920x1080. The code that gets the size runs fine on Windows, but gives the wrong result on Ubuntu (using MonoDevelop).

    Rectangle capture_rect = System.Windows.Forms.Screen.PrimaryScreen.Bounds;
    Console.WriteLine("width={0} height={1}", capture_rect.Height, capture_rect.Width);

The result on Ubuntu is "width=3520 height=1080". If I disconnect the external monitor, I get the correct result, which is "width=1600 height=900". Any idea why I get the wrong value on Ubuntu with multiple displays?

Answer 1

Instead of using .NET to get the screen dimensions, I used Linux "xrandr". Here's my code:

public Rectangle GetDisplaySize()
{
    // Use xrandr to get size of screen located at offset (0,0).
    System.Diagnostics.Process p = new System.Diagnostics.Process();
    p.StartInfo.UseShellExecute = false;
    p.StartInfo.RedirectStandardOutput = true;
    p.StartInfo.FileName = "xrandr";
    p.Start();
    string output = p.StandardOutput.ReadToEnd();
    p.WaitForExit();
    var match = System.Text.RegularExpressions.Regex.Match(output, @"(\d+)x(\d+)\+0\+0");
    var w = match.Groups[1].Value;
    var h = match.Groups[2].Value;
    Rectangle r = new Rectangle();
    r.Width = int.Parse(w);
    r.Height = int.Parse(h);
    Console.WriteLine ("Display Size is {0} x {1}", w, h);
    return r;
}