[lazarus] Printers unit

andrew johnson acjgenius at earthlink.net
Thu Nov 7 11:26:49 EST 2002

On Wed, 2002-11-06 at 23:31, Tony Maro wrote:
> Well, nobody has complained yet about small attachments so here:
> Another working printing example.  I did as requested and separated the
> TPostScript object from the printing system completely.  It still uses a
> TPostScriptCanvas for individual pages, to keep a similarity to the
> standard Delphi printing system so that it will interact more smoothly
> with it.
> So far it supports text with fonts and sizes, color, fills, rectangles,
> ellipses, lines and pies.  Stretching ellipses and pies was hard work,
> BTW.

Starting to look nicer. If you can encapsulate everything that doesn't
require a parent handle into these components, such that it doesn't
actually require any of the LCL code, I think this would make a nice
starting point for an FCL Printers unit. From there we can create a LCL
backend around it to hide the differences between a Printer Canvas and a
Canvas. cool.

> I then hacked together a TPrinter object that calls it.  The hacked
> TPrinter will print to postscript file, print to printer or print to
> PDF.  In OS's other than Linux all you get is print to postscript file.
> Here's my next question:  I've no experience with TPen or TBrush and I
> wonder if I need to use them to standardize the color selection
> methods.  However, I won't be supporting bitmaps yet, so TBrush may be
> the wrong thing...
> Do you think it needs to use the standard TPen and TBrush objects, or do
> you think my current approach of a FillColor and PenColor property will
> be fine?  I do need a Pattern property, but it will be postscript code,
> not bitmap, most likely.  I'm having problems figuring out embedding
> bitmaps.  But, considering I've only really been doing Postscript for
> about a week now, I guess this isn't bad.

yes you definitely should use Pen's and Brush's, but as I said before,
it would be nicer if none of this code required any LCL code, so that it
could become part of the FCL. I would suggest creating a TPSBrush and a
TPSPen wih callbacks on change, exactly like the Graphics versions. Then
in your code you could do a If Pen.Style = psNull else and so forth.
Something along the lines of this :

  TPSObject = class(TPersistent)
    procedure Changed; dynamic;
    Procedure Lock;
    Procedure UnLock;
    property OnChange: TNotifyEvent read FOnChange write FOnChange;

  TPSPen = class(TPSObject)
    procedure SetColor(Value : TColor);
    procedure SetStyle(Value : TPenStyle);
    procedure Setwidth(value : Integer);
    constructor Create;
    destructor Destroy; override;
    procedure Assign(Source: TPersistent); override;
    property Color: TColor read FPenData.Color write SetColor;
    property Style: TPenStyle read FPenData.Style write SetStyle default
    property Width: Integer read FPenData.Width write SetWidth default

we can slowly remove any dependencies on Graphics.pas this way, while
still retaining the Canvas look'n'feel. 

Just my thoughts.. others may have(probably do have) better ideas.


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