/// <summary>
/// Implements EndPrint for generating print preview information.
/// </summary>
public override void OnEndPrint(PrintDocument document, PrintEventArgs e)
{
if (_dc != null)
{
_dc.Dispose();
_dc = null;
}
base.OnEndPrint(document, e);
}
/// <summary>
/// Implements StartPrint for generating print preview information.
/// </summary>
public override void OnStartPrint(PrintDocument document, PrintEventArgs e)
{
base.OnStartPrint(document, e);
if (!document.PrinterSettings.IsValid)
{
throw new InvalidPrinterException(document.PrinterSettings);
}
// We need a DC as a reference; we don't actually draw on it.
// We make sure to reuse the same one to improve performance.
_dc = document.PrinterSettings.CreateInformationContext(_modeHandle !);
}
public override bool Equals(object?obj)
{
DeviceContext?other = obj as DeviceContext;
if (other == this)
{
return(true);
}
if (other == null)
{
return(false);
}
// Note: Use property instead of field so the HDC is initialized. Also, this avoid serialization issues (the obj could be a proxy that does not have access to private fields).
return(other.Hdc == Hdc);
}
/// <summary>
/// Implements StartPrint for printing to a physical printer.
/// </summary>
public override void OnStartPrint(PrintDocument document, PrintEventArgs e)
{
Debug.Assert(_dc == null && _graphics == null, "PrintController methods called in the wrong order?");
Debug.Assert(_modeHandle != null);
base.OnStartPrint(document, e);
// the win32 methods below SuppressUnmanagedCodeAttributes so assertin on UnmanagedCodePermission is redundant
if (!document.PrinterSettings.IsValid)
{
throw new InvalidPrinterException(document.PrinterSettings);
}
_dc = document.PrinterSettings.CreateDeviceContext(_modeHandle);
Interop.Gdi32.DOCINFO info = new Interop.Gdi32.DOCINFO();
info.lpszDocName = document.DocumentName;
if (document.PrinterSettings.PrintToFile)
{
info.lpszOutput = document.PrinterSettings.OutputPort; //This will be "FILE:"
}
else
{
info.lpszOutput = null;
}
info.lpszDatatype = null;
info.fwType = 0;
int result = Interop.Gdi32.StartDoc(new HandleRef(_dc, _dc.Hdc), info);
if (result <= 0)
{
int error = Marshal.GetLastPInvokeError();
if (error == SafeNativeMethods.ERROR_CANCELLED)
{
e.Cancel = true;
}
else
{
throw new Win32Exception(error);
}
}
}
/// <summary>
/// Implements EndPrint for printing to a physical printer.
/// </summary>
public override void OnEndPrint(PrintDocument document, PrintEventArgs e)
{
Debug.Assert(_dc != null && _graphics == null, "PrintController methods called in the wrong order?");
if (_dc != null)
{
try
{
int result = (e.Cancel) ? Interop.Gdi32.AbortDoc(new HandleRef(_dc, _dc.Hdc)) : Interop.Gdi32.EndDoc(new HandleRef(_dc, _dc.Hdc));
if (result <= 0)
{
throw new Win32Exception();
}
}
finally
{
_dc.Dispose();
_dc = null;
}
}
base.OnEndPrint(document, e);
}