GetDeviceCaps to obtain printer margins

[kyledunn]

I need to access the Win32 GetDeviceCaps function to obtain the PHYSICALOFFSETX and PHYSICALOFFSETY values for a printer using C# and .NET or VB.NET. Can anyone share the code or give me a lead to pursue this problem? Thank you for any help you can offer.

Kyle

 

[jfrost10]

Hey Kyle,

Did you check the VisualStudio.NET help files? I checked the index, and they have a few headings for the GetDeviceCaps, and some code examples that I'm guessing are in C# (I havn't used the GEtDeviceCaps function before, so its all greek to me).

If you don't have the help files let me know and I can post what the articles were saying


Jack

 

[kyledunn]

Hey Jack,

As always, thanks for your help. I figured it out. It involves accessing the Win32 API, my first experience with unmanaged code from .NET. I'll list the code at the end of this post. Sorry it's in C# but it will be good conversion practice for you if you need the routine. The general idea is that the method (GetDeviceCaps) in the dll (gid32.dll) that gets the unprintable margin values from a printer can be called using the IneropServices assembly. You have to define constants so the GetDeviceCaps method knows what values to return. After prototyping the Win32 API method you can call it from your managed .NET code. The biggest stumbling block for me was figuring out that the graphics object would return the handle to the device context so I could pass that to the method. I just kind of stumbled around in the code and intellisense until I figured that out. The return value is in printer units so it must be divided by the printer resolution to know the value of the unprintable margin.

Take care and thanks again.

Here's the code:

// Reference InteropServices;
using System.Runtime.InteropServices;

// define constants for the physical offset values
private const int PHYSICALOFFSETX = 112;
private const int PHYSICALOFFSETY = 113;

// Define DLL and prototype the Win32 API method
[DllImport("gdi32&quot]
public static extern int GetDeviceCaps(IntPtr hdc, int cap);

// get the device context handle from the graphic object that is being printed
// call GetDeviceCaps to return the offsets
// release the handle to the device context
int unprintableleft, unprintabletop;
IntPtr hdc;
hdc = e.Graphics.GetHdc();
unprintableleft = GetDeviceCaps(hdc,PHYSICALOFFSETX);
unprintabletop = GetDeviceCaps(hdc,PHYSICALOFFSETY);
e.Graphics.ReleaseHdc(hdc);
MessageBox.Show("Unprintable: " + unprintableleft + " " + unprintabletop);