Screen Resolution not matching Screen.Bounds

Question

I am seeing an interesting difference between the resolution that is set through Control Panel and the output of Screen.Bounds for my widescreen laptop. The screen is 15.5" and the resolution set through Control Panel is 1920x1080. However when I run some code like this.

Screen[] screens = Screen.AllScreens;
foreach (Screen scr in screens)
{
    Console.WriteLine("Width: " + scr.Bounds.Width + ", Height: " + scr.Bounds.Width);
}

The output shows my resolution being 1536x864. I have done some looking around, and I thought it may be related to a DPI issue, and when I look at my display settings, the slider (I am on Windows 8.1) is in the middle, and the checkbox that states "Let me choose one scaling level for all my displays" is unchecked. I ran this little code to get the current DPI setting.

float dpiX, dpiY;
Graphics graphics = new System.Windows.Forms.Form().CreateGraphics();
Console.WriteLine("DPI: " + graphics.DpiX);

The DPI that is returned is 96.0 which by my understanding is the 100% DPI setting (so no enlargement or whatever it is called). What seems odd to me is that the bounds returned by Screen is exactly 80% of my actual resolution, which would make me think my DPI is set to 100 (or 125%) but it is not. I am only having this issue with my laptop screen, as my secondary monitor has bounds that are equal to resolution through Control Panel. Is this due to the fact that my DPI setting is not set to have the displays independent of eachother (that checkbox checked)? For a little bit of background, I am writing a tool that takes the current screens and gets pictures from reddit and fits them to the screens independently of each other, so whatever solution I have, it has to correctly get the resolution of each display.

Answer 1

I had same problem also for screen shot tool. I found solution and it works for me.

private enum ProcessDPIAwareness
{
  ProcessDPIUnaware = 0,
  ProcessSystemDPIAware = 1,
  ProcessPerMonitorDPIAware = 2
}

[DllImport("shcore.dll")]
private static extern int SetProcessDpiAwareness(ProcessDPIAwareness value);

private static void SetDpiAwareness()
{
  try
  {
    if (Environment.OSVersion.Version.Major >= 6)
    {
      SetProcessDpiAwareness(ProcessDPIAwareness.ProcessPerMonitorDPIAware);
    }
  }
  catch (EntryPointNotFoundException)//this exception occures if OS does not implement this API, just ignore it.
  {
  }
}

You should call SetDpiAwareness() method before call functions to get system resolution, etc. Also if you have some UI in your application now it is your responsibility to scale your UI in screen with high DPI.

Hope this helps.

Answer 2

I believe you have to notify the operating system that your application is DPI aware. Otherwise the OS pretends that everything is just fine, leading to the behaviour you're observing - the OS handles the resizing.

You can find some information about writing DPI aware applications here - http://msdn.microsoft.com/cs-cz/library/dd464646.aspx Of course, you should make sure your application actually is DPI aware - if not, you better stick with the default. It's not as nice, but at least it will work.

The main difference that Windows 8.1 brought to this is that you can have different DPI on different monitors, and you can query the monitor DPI API. .NET (and especially WPF) by default handles DPI awareness automatically, but only based on system DPI. If your monitors have different DPI settings, it will behave as non-DPI-aware (more precisely, system-DPI-aware, but the end result is your applications graphics are going to be virtualized by Windows). I'd expect that if you disconnect your second display, your application would behave as expected on your sole display (at least after manually setting the DPI, whatever the value).