[Qgis-user] Options: General tab - questions about QGIS 1.8

[Etienne Tourigny]

Hi,

I introduced these options but unfortunately they were not documented...
I am making some changes to the layout in the options dialog as well
as some other related changes to the dev version, will push soon.

On Wed, Nov 21, 2012 at 10:00 AM, Larissa Junek <junek at gbd-consult.de> wrote:
> Hi all,
>
> I have some questions concerning the General tab in the QGIS options.
> There are 3 entries we cannot describe properly in the QGIS 1.8 user
> manual.
>
> "Prompt for raster sublayers"
> When is this option used? When to create raster sublayers?

Some rasters support sublayers - they are called subdatasets in gdal.
An example is netcdf files - if there are many netcdf variables, gdal
sees every variable as a subdataset.

The option is to control how to deal with sublayers when a file with
sublayers is opened (through commandline or through "Add Raster Layer"
action

from QgisApp::shouldAskUserForGDALSublayers() the options mean:

Always -> always ask (if there are existing sublayers)
If needed -> ask if layer has no bands, but has sublayers
Never -> never prompt, will not load anything
Load all -> never prompt, but load all sublayers

>
> "Scan for valid items in the browser dock"
> When is this option used? What is Check file contents?
> What's the deal with the option to check extension?

This is only used in the browser. It controls which files the browser will show.
"Check file contents" tries to open each file (but doesn't read the
data) to see if it is valid, whereas check extension lists the files
which extension is supported by a driver.
For example, files like "sample.tif" will be listed, even if the file
is invalid (for whatever reason).

This option was designed to speed up the loading of a directory, which
can be time-consuming when "Check file contents" is activated and
there are many files (tens or hundreds).

>
> "Scan for contents of compresses files (.zip) in browser dock"
> What's the difference between Basic scan and Full scan?
> I've seen that in the Passthru layer also visible only that they are
> presented with a kind of database icon and that they can be embedded.
> Then what is the functional difference to Basic Scan and
> Full scan?

Similar to above question.
Basic Scan just checks that the extension is supported by one of the
drivers, whereas Full Scan opens every file to check it is valid.
Passthru just lets gdal/ogr try to open the file, which works for some
cases.  This option has been dropped from the dev version and should
not be used.

>
> Furthermore, we would like to know if the "Attribute table row cache"
> defines the storage capacity of the cache or the amount of rows.

Can't help you there.

Please let me know if I can help in the writting of the manual. And if
you have any suggestions for rewording, please do so and the dev
version will be changed accordingly...
I realize the choice of words may not be the most intuitive.


Etienne

>
> Thank you.
>
> Kind regards,
> Larissa
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