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Dettmer, A. L. · Guest

Hello:

I would like to build a descendant from TCanvas that would create
a PDF file. I need a TCanvas descendant because inside our apps we
use a "universal" report engine that can output to: screen, printer,
metafile and so on.

My BIG problem: nearly everything that TCanvas publish is static and
can't override the original methods, so if I have:

type
TPDFCanvas = class(TCanvas)
private
...
protected
...
end;

And try something like code below I'm in trouble:

procedure SomeMethod(aCanvas : TCanvas);
begin
....
aCanvas.rectangle(x1,x2,y1,y2); //<- call TCanvas.rectangle and not TPDFCanvas.rectangle
....
end;

var
pdfCanvas : TPDFCanvas;

begin
pdfCanvas:= TPDFCanvas.create;
....
someMethod(pdfCanvas);
....
end;

I just couldn't override the inherited methods.

Any idea ?

Thanks

Yahia El-Qasem · Guest

For PDF I would recommend using some of the available products - one very
good one is wPDF and AFAIK it provides a canvas.

Yahia

Dettmer, A. L. · Guest

Yahia El-Qasem wrote:

Yahia El-Qasem · Guest

that's true <g>

Yahia

Alexander Bauer · Guest

Hi,

I would say TCanves is the implementation of a DC of the Windows GUI system.
Not only Windows DCs also Printer DC and stuff. A Bitmap has a Canvas (DC)
too but no window at all.

Anyway... would it be possible to react on changes to the Canvas for you?
TCanvas offers two Events OnChange and OnChaniging. May be you can use them
to get informed about changes - drawings on the Canvas and the copy these
changes to your PDF.
To be able to profide these Events to the component user simply override
them and set the inherited to call a OnChange procedure where you first copy
the Canvas to the PDF and then fire the event of the user if assigned. If
you need to do the drawing like Ellipse and stuff to your PDF directly
simply write drawing methods as public and call the inherited before drawing
to the PDF. I think this should work.

You cannot override a static method - thats right, but you can write a new
one. Calls from the original TCanvas would alway be to the original version
but call from you TPDFCanvas would use your version.

Regards,
Alexnader Bauer

"Dettmer, A. L." <armando.die (AT) spam (DOT) die.eps.ufsc.br> schrieb im Newsbeitrag
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Danny Thorpe · Guest

"Dettmer, A. L." <armando.die (AT) spam (DOT) die.eps.ufsc.br> wrote

Danny Thorpe · Guest

"Dettmer, A. L." <armando.die (AT) spam (DOT) die.eps.ufsc.br> wrote

Grega Loboda · Guest

Hello

I was wondering. TCanvas is good, but when you come to enummetafile, things
become complicated. There is even a bug in metafile (search graphics group).
So, I'm developing my own metafile (it's a file, where you store your calls
to circle, rectangle,...). It's faster than metafile. I'm planing to use in
report engine at my work. I will store all those data into my metafile and
that just playback my metafile to screen canvas, printer canvas, or to any
file type. Are you interested?

Grega

"Dettmer, A. L." <armando.die (AT) spam (DOT) die.eps.ufsc.br> wrote

Graham Murt · Guest

Hi Grega,

In case you're interested... This is exactly what GmPrintSuite does, plus a
whole lot more!

The best part is that the Lite version is completely free for personal or
commercial use.

If you're interested, download it from here...
http://www.murtsoft.co.uk/downloads.html

Kind regards,
Graham Murt

--
GmPrintSuite Print & Print Preview Components
http://www.murtsoft.co.uk/

"Grega Loboda" <grega.loboda (AT) email (DOT) si> wrote