[Qgis-developer] qgis minimal version

[Mohammed Rashad]

Hell QGIS Developers,


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...


On Wed, Sep 28, 2011 at 5:38 PM, Mohammed Rashad <mohammedrashadkm at gmail.com
> wrote:

> does QGIS paint points to QPixMap and render the image or QGIS directly
> draws the point
> like painter->drawCircle/point
>
>
> On Tue, Sep 27, 2011 at 9:34 PM, Mohammed Rashad <
> mohammedrashadkm at gmail.com> wrote:
>
>>
>>
>> On Tue, Sep 27, 2011 at 8:25 PM, Marco Hugentobler <
>> marco.hugentobler at sourcepole.ch> wrote:
>>
>>> Hi Mohammed
>>>
>>> > How came this time gap?
>>>
>>> A possible reason could be the following:
>>> In QGIS, most point renderers do some caching of the point symbols as
>>> QImage.
>>> So in case you invoke a QPainter->drawCircle/drawRectangle etc. command
>>> for
>>> every point, it helps a lot do do the rasterisation only once.
>>>
>> the point is not clear for me maybe because of my misunderstanding
>> will you please eloborate??
>>
>>>
>>>
>>> Regards,
>>> Marco
>>>
>>>
>>> Am Dienstag, 27. September 2011, 16.18:25 schrieb Mohammed Rashad:
>>> > Hi All,
>>> > I am developing tiled vector rendering in OSSIM. I like the Qgis vector
>>> > rendering system
>>> >
>>> > point.shp contains 9,99,999 points which are generated by grass for
>>> using
>>> > v.random and ~27MB in size
>>> > roads.shp contains 2,28,068 linestrings and is ~50MB in size
>>> >
>>> > these point.shp and roads.shp data gets rendered in ~10 sec
>>> >
>>> > When I read vector using ogr and parse feature and draw
>>> point/linestring my
>>> > application taking about 40 sec to render point.shp
>>> > and
>>> >
>>> > I am using Qt4 with QPainter not QGraphicsView
>>> >
>>> > How came this time gap?
>>> >
>>> > i see Rtree and pal libs in src/core source code
>>> > Does they have any role in rendering?
>>> >
>>> > Does QGIS Rendering uses threading?
>>> >
>>> > How to get a minimal of QGIS code to hack it and build a new vector
>>> > rendering because I need it to make it tiled rendering vectors?
>>> >
>>> > How to improve performance in rendering without qgis?
>>> > ---
>>> > Regards,
>>> >    Mohammed Rashad K M
>>> >    M.S. (By Research) student
>>> >    Lab for Spatial Informatics
>>> >    Department of CSE
>>> >    International Institute of Information Technology
>>> >    Hyderabad, India
>>>
>>>
>>
>>
>> --
>> Regards,
>>    Mohammed Rashad K M
>>    M.S. (By Research) student
>>    Lab for Spatial Informatics
>>    Department of CSE
>>    International Institute of Information Technology
>>    Hyderabad, India
>>
>>
>
>
> --
> Regards,
>    Mohammed Rashad K M
>    M.S. (By Research) student
>    Lab for Spatial Informatics
>    Department of CSE
>    International Institute of Information Technology
>    Hyderabad, India
>
>


-- 
Regards,
   Mohammed Rashad K M
   M.S. (By Research) student
   Lab for Spatial Informatics
   Department of CSE
   International Institute of Information Technology
   Hyderabad, India
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