[Lazarus] TCairoCanvas integration

[Mattias Gaertner]

On Thu, 11 Mar 2010 14:23:15 +0100 (CET)
Michael Van Canneyt <michael at freepascal.org> wrote:

> 
> 
> On Thu, 11 Mar 2010, petr.kristan at epos.cz wrote:
> 
> > On Wed, Mar 10, 2010 at 03:22:31PM +0100, petr.kristan at epos.cz wrote:
> >> Hi.
> >>
> >> Main work on TCairoCanvas = class(TPrinterCanvas) is almost done.
> >>
> >> My question is how to integrate it into LCL?
> >> IMHO user should have a choice which TPrinterCanvas implementation use.
> >> Now in TCUPSPrinter is hard coded TPostscriptPrinterCanvas:
> >>
> >> function TCUPSPrinter.GetCanvasRef: TPrinterCanvasRef;
> >> begin
> >>   Result:=TPostscriptPrinterCanvas;
> >> end;
> >>
> >> Petr
> >>
> > Nobody here, who can halp me to integrate TCairoCanvas into LCL?
> >
> > Were in LCL directory structure place cairocanvas.pas (depends only on
> > libcairo) and gdkcairocanvas.pas (depends extra on libgdk).
> >
> > How should programer select which implementation of TPrinterCanvas will
> > be created in TPrinter.GetCanvas.
> >
> > Now TCUPSPrinter implementation use hard coded TPostscriptPrinterCanvas
> > and needs access to TPostscriptPrinterCanvas(Canvas).OutputFileName.
> > My TCairoCanvas implementation has the same needs.
> >
> > I do not want to waste my time if comunity do not have an interest to
> > include CairoCanvas into lcl.
> 
> I think you should create an abstract TFilePrinterCanvas descendent of
> TPrinterCanvas (with the needed FileName property) and define a variable
> 
> Type
>    TFilePrinterCanvas = Class of TFilePrinterCanvas;
> 
> Var
>    CupsCanvasClass : TFilePrinterCanvas = TPostscriptPrinterCanvas;
> 
> which the programmer can set, if so desired. then the
> TCUPSPrinter.GetCanvasRef
> implementation checks the CupsCanvasClass variable. If it is set,
> it uses the class defined there, and if not, it uses
> TPostscriptPrinterCanvas.

Good idea.

Mattias