[Qgis-developer] Re: qgis minimal version

[Tim Sutton]

Hi


On Sat, Oct 1, 2011 at 10:06 AM, Mohammed Rashad
<mohammedrashadkm at gmail.com> wrote:
> Hell QGIS Developers,

Yes sometimes it is hell :-)

>
> I have couple of questions regarding QGIS and its vector rendering part. I
> had posted one mail titled "question on qgis rendering" now with more set of
> questions I am starting a new thread
> as the title says I need minimal qgis.
>
> does qgis  rasterise the vector data before rendering?
> does QGIS paint points to QPixMap and render the image or QGIS directly
> draws the point
> like painter->drawCircle/point
> because QGIS rendering is faster than direct rendering
> How to make a minimal qgis version which renders fast enough. I want to
> customize QGIS for my needs.
> first I want rendering engine of QGIS to be seperate.
> Which files are responsible for QGIS rendering a vector data (OGR) ?
> Which file opens OGR data?
> which is responsible for grabing chips from vector data?
> which is responsible for rendering to QGraphicsScene or QPainter?
> Does QGIS cache some data when rendering if yes how is done?
> I want all technical details of QGIS rendering?
> what I need is a custom QGIS with only vector RENDERING no labels, no
> attributes, no projection etc. I had made a small vector rendering system
> using Qt and GDAL
> please review this video
> http://www.youtube.com/watch?v=KTeYBpSe0kw
> I dont need to link my application to qgis_core and build a simple
> application on top of QGIS
> I need to know everything about QGIS Vector RENDERING and need to build a
> new rendering system for vectors. I know my requirement sounds like
> reinventing wheels but I need to do it
> please dont advice me to use qgis_core.so and build a GUI seperately. I need
> to have full control over the code written for rendering.
> The reason I am not using qgis_core is nothing but it is difficult for me to
> manage bugs if I use qgis_core. on the other hand if I build my own I can
> easily track bugs and fix the as soon as possible.
> managing qgis_core for a person like me without help of others is a pain!!!
>
>
> If you cant tell me how to make qgis minimal version, please point me to
> qgis very first version and also tell me how to build it...
>
> I hope everyone understandss my requirement. My english is not good so if
> you have any doubts please feel free to contact me and will surely reply
> back with your answers
> Anyone please help me...



Please take some time to examine the code before asking these
questions - most of what you want to know can be answered by simply
looking at classes like:

QgsMapRenderer
QgsMapCanvas
QgsVectorLayer

and so on. http://doc.qgis.org/head/ is a good place to start.

In general a few other tips to help you get helped:

- don't write to developers directly unless invited to do so - use the
developer mailing list rather
- we implemented QGIS libraries such as qgis_core to make it easy for
third parties to create new applications based on our codebase.
Separating the vector rendering stuff away from it is possible but its
not going to be trivial and you will be more or less on your own
support wise since it is going way off the mainstream.
- try to not write such long complicated series of questions in a
single email. You can imagine the time investment needed by a
developer to go through all the various things you ask. You would
probably get a better response asking one or two carefully crafted
questions and showing that you have done basic research before coming
to the list with your question.

Anyway hopefully the above will get you started....

Regards

Tim

8<---------snip---------------------


-- 
Tim Sutton - QGIS Project Steering Committee Member (Release  Manager)
==============================================
Please do not email me off-list with technical
support questions. Using the lists will gain
more exposure for your issues and the knowledge
surrounding your issue will be shared with all.

Visit http://linfiniti.com to find out about:
 * QGIS programming and support services
 * Mapserver and PostGIS based hosting plans
 * FOSS Consulting Services
Skype: timlinux
Irc: timlinux on #qgis at freenode.net
==============================================