Re: [Tcl-soc2008] GSoC 2008 - printing support

[Clif F. <cl...@cf...>]

Hi,
  I apologize for being unclear.
  
  I believe that all 4 parts of the process are too much for a single
student (or experienced programmer) to complete.  The canvas export
portion alone could easily take more than a single summer, depending
on how much detail was added to it.

  I see the export facility as the required part of the project. 
Without no data to print, a printer interface doesn't do much. :)
  
  I'll be very happy to work with you on the project, and provide such
insight (and preliminary code) as I've gathered.

  I suggest that (if you work on this project), you start with the
canvas export problem and work on that until there is enough working
code to provide a good foundation for further work. Then start looking
at the print system interface.

  Here's my suggestion for the export section.
  
  I've got a library that generates output for canvases and selected
Tk widgets.  The basic structure is OK, but there are some glitches in
the the translation/scaling math for handling embedded windows.

  I'd suggest looking at that code, the other canvas export tools, and
the PDF manual (which is available online for free as a PDF document) and
deciding which portions of which existing tools to combine to make a new
package with the best features of the three existing libraries.

  To my mind, the good features in my code are:
  1) I split canvas extraction and PDF generation into two sections

  2) my code does a recursive step into subordinate windows, supporting
     the idea of exporting any Tk window to pdf.
     
  Shortcomings of my code are:

  1) I wasn't thinking of recursion when I started it, and the data
     structures need to be fixed.  Changing from global arrays to dicts
     will solve a lot of this problem.
     
  2) My library has no support for embedded fonts.

  A good thing about Tcl/Tk is that it is introspective in ways that
other languages (particularly compiled languages) are not.  This will
be a new thing for you to get used to.  A running application can query
the widgets to learn things like border width, font, and objects
displayed on a canvas.

  Some of the tricky parts are that all aspects of a widget can be
configured by an application.  The "normal" appearance of a button is
not necessarily what any given application uses.  For example, the
button widgets in an application may have no border at all, to make them
look like menu items instead of buttons.

  The Tk Font support will try to find a font on your system that 
supports the application's request.  The application might request
"17 point Times bold", but the system might only have a 16 and 24 point
font available.  In that case, the application would display text
using the 16 point font (I think).

  I think you saw other discussions on this list about the need for
direct Windows support.

  The PDF or Postscript export is great for Linux/Unix users, but we
really need to be able to print to a winPrinter on the windows boxes.

  I can help you a lot with the Tcl/Tk end and I can help with
architecture and design type questions.  You'll be largely on your own
for the implementation of the Windows/CUPS interface.

  Does this help?
  
  Clif
  

On Wed, Apr 02, 2008 at 10:11:05PM +0200, krzysztof blicharski wrote:
> Clif I'm sorry, I may mistook your letter. I thought you divided the project
> into 4 seperate parts and I could choose any of them. However, I've
> mentioned in my application (which I had written before you responsed me)
> that after finishing the part of project that I've choosen, I could work on
> another one.
> 
> I'll take a look on what you've written and reconsider the shape of my
> application.
> 
> 
> Thanks all for your comments and suggestions.
> 
> Best regards.
> Krzysiek

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-- 
.... Clif Flynt ... http://www.cflynt.com ... cl...@cf... ...
.. Tcl/Tk: A Developer's Guide (2nd edition) - Morgan Kauffman ..
... 15'th Annual Tcl/Tk Conference:  Oct 2008,  Somewhere, USA... 
.............  http://www.tcl.tk/community/tcl2008/  ............