[Lazarus] GetTextMetrics in TCanvas proposal

[petr.kristan at epos.cz]

On Wed, Mar 24, 2010 at 10:32:31AM +0100, petr.kristan at epos.cz wrote:
> Hallo.
> 
> I suggest to add function function GetTextMetrics(var TM: TTextMetric): boolean; into TCanvas class.
> 
> If user wants to work with text on Canvas and mix different fonts on one
> line, he needs minimally to know Ascent and Descent metrics of the font.
> But TCanvas has only TextExtent function. If user renders text on the
> screen (or printer in Win), then uses lclintf.GetTextMetrics.
> But if renders on TPoscriptCanvas or upcoming TCairoCanvas he must use 
> some TCairoCanvas.GetTextMetrics or still non existing
> TPoscriptCanvas.GetTextMetrics.
> 
> It cause ugly non oop construction like:
> 
> {$IFDEF USE_CAIRO}
> if Canvas is TCairoCanvas then 
>   (Canvas as TCairoCanvas).GetTextMetrics(tm)
> else
>   GetTextMetrics(tm);
> {$ELSE}
>   GetTextMetrics(tm);
> {$ENDIF}
> 
> For that reason I propose to add virtual function GetTextMetrics into
> TCanvas.
> 
> Is this proposal acceptable?
> 
> If it is, how to move ahead to reach this goal.

Thanks all for their reactions :(

Is another place where I can discuss? Is another place where LCL core developers response
my few questions?

I have done my work on cairo canvas. It can be used as separate package.
Where should I put it? Certainly if comunity have an interest.

Petr

-- 
Petr Kristan
.
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