[Lazarus] TCairoCanvas integration

[Mattias Gaertner]

On Thu, 11 Mar 2010 14:54:48 +0100
petr.kristan at epos.cz wrote:

> On Thu, Mar 11, 2010 at 02:50:04PM +0100, Mattias Gaertner wrote:
> > On Thu, 11 Mar 2010 14:41:18 +0100
> > petr.kristan at epos.cz wrote:
> > 
> > > On Thu, Mar 11, 2010 at 02:23:15PM +0100, Michael Van Canneyt 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.
> > > Thanks.
> > > 
> > > This corresponds with my idea. 
> > > 
> > > Where is recommeded place for cairocanvas.pas and gdkcairocanvas.pas in
> > > lcl? CairoCanvas can work on Windows, Linux and Mac OS X. 
> > 
> > lcl/interfaces/gtk2
> I think this is good place for gdkcairocanvas.pas. But cairocanvas.pas
> needs only libcairo. It do not needs gtk. 

Well, it should be added to the fpc sources, but till this is in a
release we have to add this unit to the lazarus sources too.


Mattias