GetDeviceCaps freezes everything

[Robert Gilland 5]

I borrowed the below function from jclPrint.pas using Delphi 10.4.2 

 

When function is called the entire process fails.

What could be wrong.

 

function GetPrinterResolution: TPoint;
begin
  Result.X := GetDeviceCaps(Printer.Handle, LogPixelsX);
  Result.Y := GetDeviceCaps(Printer.Handle, LogPixelsY);
end;

[PeterBelow 239]

If you put a breakpoint on the first GetDeviceCaps line, do you reach it when running under the debugger? If so, does Printer.Handle have a reasonable value? Are you dealing with a network printer here that may be offline?

 

So many questions, so little data...

[Robert Gilland 5]

By sheer exasperation, I removed the conditionals for FASTMM4 LogMemoryLeakDetailToFile and FullDebugMode.

And then GetDeviceCaps worked, no idea why.

Another day of banging my head against the wall ends miraculously, Thank God.

 

 

[Robert Gilland 5]

1 minute ago, PeterBelow said:

If you put a breakpoint on the first GetDeviceCaps line, do you reach it when running under the debugger? If so, does Printer.Handle have a reasonable value? Are you dealing with a network printer here that may be offline?

 

So many questions, so little data...

Yes I did that.

[eivindbakkestuen 47]

On 12/9/2024 at 9:55 PM, Robert Gilland said:

And then GetDeviceCaps worked

Probably the printer was offline or unreachable before; and then it was reachable.

 

This happens every day here when trying to print from many, even well known applications; they take forever to time out if the default printer wasn't turned on.

 

You could try using a worker thread for printing, then your application doesn't freeze and you have some control over what happens