Canvas / image does not allow drawing

rbuser

Hi,
I have created some new reports and test them on my PC, everything OK.
After this, I installed them on a terminal server. Over an internet
application (Webterminal) (!!!!LOCAL Computer!!!!) the reports are call
up. If I press the button on the local machine to create the report, a
error application is popping up. Error message: "Canvas / image does not
allow drawing".
On of my colleague got the same error and he could not reproduce the
error, too.
Is the problem in the PDF export or on the terminal server?

...
David

nardmoseley

The exception 'Canvas does not allow drawing' is a Delphi exception that is
raised when an application cannot get a valid handle to a Canvas associated
with a bitmap, screen, or printer.

If you are generating PDF's you might check whether the machine has a
default printer installed. If it does not, try installing one. Another thing
you could try is setting Report.PrinterSetup.PrinterName to 'Screen'.

ReportBuilder uses the printer device context (i.e. canvas) to measure text,
wrap text etc. If a machine does not have a printer driver installed, RB
should be automatically defaulting to 'Screen'.

We don't have experience with Windows Terminal Services here, but we have
customers using it successfully. In theory the apps should just work, but in
reality I think there are many difference versions of Terminal Services and
different ways to configure it.


-
Nard Moseley
Digital Metaphors
www.digital-metaphors.com

rbuser

Hello David,

PDF export of reports with lots of text elements leaks GDI resources. In the unit ppPDFRendererCustomText method TppPDFRendererCustomText.RenderToPDF add a lBitmap.Free to the end and checkout if the problem is gone. You can check the GDIObjects in the Taskmanager (before and after the patch ;-) ).
Terminalservers - especially older ones - do have less resources than local machines. So you will sooner run into any kind of resource problems.

Regards,
Michael

Am 29.08.2012 09:51, schrieb David Wolf:

rbuser

Hi Nard,
after hours of testing I got the same error on my computer, too.
But I don't understand why it works via Delphi but not about the
Webapplication. (both on the same computer).

I've set the propertie PrinterName to Screen but the error is still
there. A default printer has already installed, too.
Can the error may be raise up because of a component?
I use this components:
Header:
Label
Line
DbText
Variable
Group:
Header:
Footer:
Subreport2
Title:
Group:
Header:
Footer:
Region1
Label
Line
DBText
Variable
Detail:
Summary:
Detail:
Line
DBText
Variable
Footer:
Image
Label
Systemvariable
Label

I don't have any more ideas and the customer is waiting ...
Are there any more things I could try?

rbuser

Hi Michael,
i can't find the line where the bitmap is created?


@{@TppPDFRendererCustomText.RenderToPDF }

procedure TppPDFRendererCustomText.RenderToPDF;
var
lbTrueType: Boolean;
begin

inherited;

FFont := DrawTextCommand.Font;
FTextMetric := TppPDFUtils.PopulateTextMetric(FFont, Printer.Canvas);

{Check if font is TrueType}
lbTrueType := (FTextMetric.tmPitchAndFamily and TMPF_TRUETYPE) =
TMPF_TRUETYPE;
FFontName := TppPDFUtils.ProcessFontName(FFont, lbTrueType);

StartText;

end;

nardmoseley

There is a patch available for RB 14.06 that fixes the memory leak in
TppPDFRendereCustomText. Registered customers can email support@ and request
the patch.

-
Nard Moseley
Digital Metaphors
www.digital-metaphors.com