Re: Cairo drawing on Windows and integration of Opal

[David Chisnall]

Hi Gregory,

As I'm sure you are aware, Eric is working on Opal as part of the GSoC.  He 
started late, due to prior commitments, but is now working.

Windows support is a priority in Opal, and Eric is currently working on porting 
the font code from the Windows back end so that we can use Windows fonts with 
Cairo via Opal.  I also plan on working on a CoreText implementation over the 
summer.  I have implemented lots of random typesetting algorithms from Knuth et 
al, and need to tidy them up for inclusion.

Both of these frameworks are important if we want to be able to support porting 
iPhone / iPad applications.  UIKit is very simple - a few improvements on 
AppKit (in particular, in action methods) and a lot of feature cuts.  In 
particular, there is no equivalent of the AppKit text system - the only way of 
drawing nontrivial strings (e.g. paragraphs of text, attributed strings with 
more than one font) is via CoreText. 

With regard to how to integrate Cairo, I think the best way is likely to be to 
provide implementations of the DPS* functions that call their CG* equivalents 
as inline functions in a header.  We can then switch to using Cairo or using 
-back with a single switch.  

David

On 3 Jun 2010, at 20:49, Gregory Casamento wrote:

> All,
> 
> I wanted to remind everyone of this discussion now that we've finished
> our last release.
> 
> One of the things that was being discussed/considered for a future
> release is the refactoring of the existing backend using Opal so that,
> like CoreGraphics, it becomes more interoperable with AppKit.  I
> realize that there is a version of the existing Cairo backend on
> Windows, it's currently experimental only.
> 
> One other thing I'd like to push is the use of Cairo on Windows.  Up
> until now we've used GDI which is, officially, deprecated by Microsoft
> (http://en.wikipedia.org/wiki/Graphics_Device_Interface).   Cairo on
> Windows uses GDI+.
> 
> I'm not simply pushing this change because Cairo is popular, but
> because it eliminates a number of issues on Windows for us
> automatically.  Right now we can't do certain types of compositing on
> Windows due to limitations of the existing backend.  Cairo would give
> us this automatically.   Additionally, the deprecated GDI API which
> are currently using will not be updated with new features, nor is it
> hardware accelerated on Windows versions later than Vista.  Cairo,
> using GDI+, on Windows WILL have hardware acceleration.
> 
> Please let me know if you guys have any thoughts about this.
> 
> GC
> -- 
> Gregory Casamento - GNUstep Lead/Principal Consultant, OLC, Inc.
> yahoo/skype: greg_casamento, aol: gjcasa
> (240)274-9630 (Cell)
> 
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