Re: AppKit (Win32) generals questions

[Gregory John Casamento]

Richard,

We should probably put this in the FAQ someplace since the question regarding 
using Win32 controls comes up relatively often.   

I've found it necessary to explain this to a number of people in the past.

Later, GJC

 Gregory Casamento -- Principal Consultant - OLC, Inc 
# GNUstep Chief Maintainer


----- Original Message ----
From: Richard Frith-Macdonald <address@hidden>
To: Thierry DELHAISE <address@hidden>
Cc: Gregory John Casamento <address@hidden>; address@hidden
Sent: Thursday, May 8, 2008 1:16:24 PM
Subject: Re: AppKit (Win32) generals questions


On 8 May 2008, at 15:04, Thierry DELHAISE wrote:

> Gregory John Casamento a écrit :
>> Thierry,
>>
>> GNUstep can be made to have a native win32 look through the use of  
>> themes.
>>
> Great ! But ... this is not enought and this is my fault (sorry)  
> since  I've asked about look and should not have to. What I want is  
> that my Application be a Native win32 application using MS Windows  
> application recommendations : using of standards panel, alowing  
> interaction with clipboard, and Windows services (ODBC, COM, OLE) ,  
> Windows toolbar's, etc ...So what I want , is that GNUstep be a  
> layer between my application code and Win32.

That's roughly what GNUstep is supposed to be ... but it's a little  
more complex than that

>
>> Currently there is no plan for using the standard panels.   This  
>> would be a welcome change, since it would help GS blend into the OS  
>> better.
>>
> Yes, I saw, and this is where I can may be contribute to the project  
> but with the directions/recommendations of some old steppers ;-)  
> (let call them gurus ! ;-) ).
>
> After spending my morning time to dig into GNUstep implementation  
> I've some (certainly stupid) questions about  how  is  port  GNUstep  
> on Win32 :
>
> So on Win32, the concept of  DisplayServer have been port ? What was  
> the functionnal need for this, I mean for Win32 ? It seems to me  
> (but may be I'm wrong) that the display server have the functionnal  
> job to draw all (GNUstep) windows inside an application. So,  
> DisplayServer is in charge of drawing low level window letting  
> gnustep gui drawing all controls with the look of GNUsetp since gui  
> don't use native control on win32 (?). It seems too that it have to  
> handle drag and drop operations and may be clipboard interaction ?  
> Why not have let this jobs to operating system ? Since on win32  
> windows could do the jobs ? (I know that win32 do mostly bad job ;-)  
> but this one, since it do it since so many years, we can hope it  
> will do it mostly correctly ;-), no ?

The GNUstep GUI code is divided into two library ... the gui proper  
(gnustep-gui), which handles most of the work of implementing the  
AppKit API, and the backend (gnustep-back) which handles the interface  
to the native operating system.  The display server (GSDispalyServer)  
is the class which provides the main interface between the two parts.  
So code in gnustep-gui calls methods in the display server, and code  
in gnustep-back translates them to native calls of the system you are  
running on.

This means that application developers use the OpenStep/GNUstep/MacOS- 
X AppKit API to write their applications, and the gnustep-back library  
uses the native functionality to do the job where possible.
For instance, you do cut and paste or DnD using the OpenStep API for  
that, and the actual calls to perform the operations are the native  
windows ones.  ie we do leave the job to the operating system.
Of course, where the two APIs (OpenStep and win32) operate in very  
different ways, the conversion between the two is hard, but often the  
layer between the two is quite thin.

One area where there is not much scope for overlap is drawing within a  
window ... the way that the OpenStep API operates is so different that  
high level code for drawing things inside a windows using the native  
operating system generally cannot fit with OpenStep, so the gui  
library does all the drawing inside the window with quite low level  
code rather than trying to map OpenStep 'controls' to native 'widgets'.

> In this area, does controls in the spirit of GNUstep have to be draw  
> by GNUstep or could those be the native one's ? This questions since  
> I pretty sure that developping a Win32 theme could spent a lot of  
> time to recreate the exact look and feel (and function) of an  
> allready existing control under the native platform. And I'm not  
> sure (but may be I'm wrong) that Mac's users, or *nix one's want to  
> have a win32 native look on their host platform ? I know that *Step  
> one's want to remember the good day's ... so I understand why there  
> is a need to draw controls or windows or menus with *Step look and  
> feel in mind ;-) (my Sun's OpenStep workstation died last  
> years ... ;-) )

Well, the amount of use of native controls can be quite variable.  The  
basic design of the two libraries is, to draw OpenStep controls rather  
than try to map to native controls, because that's generally easier.  
However, a theme engine is free to try to draw parts of a window using  
the native controls where that's a practical solution.



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