TPostScriptPrinterCanvas
lazarus / 31-LCL

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timppl · 2012-12-06 11:39

Hi all

Laz version svn 39445M , fpc version 2.7.1 on Mandriva Linux 2001

I am trying to implement the textRect function in the
TPostScriptPrinterCanvas. I dont know if my approach is correct: I
copied the TextRect code from TCanvas and am trying to modify it to
suit.

Note that TPostScriptPrinterCanvas uses a dummy handle ( ie Handle :=
1 );

I have tried the following:
Using the default DC for TPostScriptPrinterCanvas, I get a
segmentation fault in TGtk2WidgetSet.SetBkMode in gtk2winapi.inc with
the code
Code: [Select]  Result := DevCtx.BkMode;
Debugger tells me that this is because DevCtx is at address 0xd9. This
seems reasonable because it has no valid handle, so I then tried
getting a valid handle and using that.
Code: [Select]DC := CreateCompatibleDC( Self.Handle );
BMHandle := CreateCompatibleBitmap( DC,Self.Width,Self.Height );
SelectObject ( DC, BMHandle );

This seems to satisfy the SetBkMode, but  then DrawText is called and
now a segmentation fault is produced in  gtk2/gtk2winapi.inc at line
2558:
Code: [Select]    Result :=
(TGtkDeviceContext(DC).CurrentFont^.LogFont.lfOrientation <> 0) and

Here the debugger tells me that CurrentFont is nil.

So I have now got stuck.  I suspect that the DC is not correct but I
do not know where to go from here. Has anyone got any comments ,
pointers or advice ( preferably good   )

Regards

Tim

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jesusr · 2012-12-06 20:14

There is simply no DeviceContext in PostscriptPrinterCanvas all
graphic operations should "emit" or "translate to" the corresponding
postscript code

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timppl · 2012-12-07 06:22

Thanks. I was starting to come to that conclusion. I will do it all
within the unit.

Regards

Tim