Thank you Ramon. At the very least, then, a separate button to 'Refresh Extent' 
in the composer. In ArcView it was really easy to add a button to the interface 
and associate a line or two of Avenue code with it. So in addition to 
suggesting that future versions should have a 'Refresh Extent' button already 
there, I'm saying that the ability to easily add a button (for whatever reason) 
would also be useful. And right now I'm wondering if someone can help me with 
the latter, as a way to make it easier to refresh the extent (as I say I did 
find a script but it's not precisely what I have in mind - it must simply 
refresh the extent of the active composer).

-----Original Message-----
From: Ramon Andinach [mailto:cust...@westnet.com.au] 
Sent: 15 May 2017 11:53 AM
To: Willem Coetzer
Cc: qgis-user@lists.osgeo.org
Subject: Re: [Qgis-user] script to simplify 'Set to Map Canvas Extent'

Hi Willem,

I can give you an example of where I really, really don’t want the extent to be 
updated with the refresh button.

One of the things I use QGIS for requires making a series of maps using two or 
more of a set of layers.
So I can have a composer set to a wide view to give a regional overview, and 
another composer set to a narrower more local view. I can then turn on one set 
of layers and generate maps at both scales with that set. After that I can 
change to set B, hit refresh to check it looks right (and I didn’t forget a 
layer) then have maps for set B straight up.
(I keep different QGIS projects, with a similar set of composers for each 
project area I work in. Once I’ve got the map extents set, then I don’t have to 
meddle with the composers too much. You sound a lot like you’re expecting to 
people to recreate maps on the fly over and over again - this is really time 
consuming.)

Another reason might be that you’ve got your composer set up and you zoom into 
somewhere on the map to check a detail, fix it and you want to see what it 
looks like on the map - but you don’t want to zoom back out. 

I really like that the extent for each composer is fixed - unless I choose to 
change it. It seems perfectly intuitive to me :)



On a slight tangent, I notice that Christine did answer the question you asked. 
Did you mean to ask, “Is there a way to automate creating a map?"
or,
"Can I create a button that combines functions in the Composer window?"
instead?
In current QGIS, the composer is pretty isolated from the rest of the program, 
as it’s not possible to directly make changes to composers through scripts. 
This is a limitation of the libraries used in the composer. I know there’s been 
a major overhaul of the Composer in the upcoming QGIS 3 release, and I’m pretty 
sure this is one of the changes.
I’m sure Nyall will correct me if I’m wrong.

Ramon.


> On 15 May 2017, at 16:00, Willem Coetzer <w.coet...@saiab.ac.za> wrote:
> 
> I was amazed that QGIS doesn't have a button to simplify this critical 
> function. Thank you Christine, I do appreciate the response. I found a script 
> that makes a new composer and then zooms to the extent of the map canvas in 
> the new composer, but the script is not ideal (dependent on objects that 
> won't always be present e.g. the filename of the QGIS template). Ideally one 
> should be able to create a new button on a toolbar and then simply associate 
> the 'Set to Map Canvas Extent' function with the button. If that is not 
> possible I guess the next best thing would be a python script that does the 
> same i.e. zooms to the extent of the map in the active composer.
> 
> I teach basic GIS skills to non-technical people and without this simple 
> function it will be very hard to make any progress. Even the default 
> procedure is too complex for them to remember.
> 
> I strongly suggest that QGIS developers look at this.
> 
> I really expected the 'Refresh' button to refresh the zoom extent as well. 
> Why wouldn't a user want to refresh the zoom extent when refreshing the 
> display of layers? It doesn't make sense to me.
> 
> If anyone can help with that script I'd be grateful.
> 
> 
> 
> Somerset StreetWillem Coetzer
> Grahamstown, 6139Biodiversity Information Manager Private Bag 
> 1015Tel:+27 46 603 5841 Grahamstown, 6140Fax:+27 46 622 2403 South 
> AfricaEmail:mailto:w.coet...@saiab.ac.za
> http://www.saiab.ac.za/
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> -----Original Message-----
> From: Qgis-user [mailto:qgis-user-boun...@lists.osgeo.org] On Behalf 
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>   1. refresh zoom extent in composer (Willem Coetzer)
>   2. Re: refresh zoom extent in composer (Christine)
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> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Sat, 13 May 2017 10:44:44 +0000
> From: Willem Coetzer <w.coet...@saiab.ac.za>
> To: "qgis-user@lists.osgeo.org" <qgis-user@lists.osgeo.org>
> Subject: [Qgis-user] refresh zoom extent in composer
> Message-ID: <5f079d395252426b9a6f1f0d6af33499@ZAGRH01EX02.saiab.local>
> Content-Type: text/plain; charset="utf-8"
> 
> If the zoom extent in the view changes, is there a way to update the composer 
> to reflect the same extent or do you need to create a new composer?
> 
> Thanks
> 
> 
> [cid:image40e5f3.PNG@44bf3bf6.42823550]<http://www.saiab.ac.za/>
> 
> 
> 
> 
> Somerset Street
>        Willem Coetzer
> 
> Grahamstown, 6139       Biodiversity Information Manager
> Private Bag 1015        Tel:    +27 46 603 5841
> Grahamstown, 6140       Fax:    +27 46 622 2403
> South Africa    Email:  w.coet...@saiab.ac.za<mailto:w.coet...@saiab.ac.za>
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> ------------------------------
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> Message: 2
> Date: Sat, 13 May 2017 06:42:50 -0700 (MST)
> From: Christine <geo.gu...@web.de>
> To: qgis-user@lists.osgeo.org
> Subject: Re: [Qgis-user] refresh zoom extent in composer
> Message-ID: <1494682970839-5320434.p...@n6.nabble.com>
> Content-Type: text/plain; charset=us-ascii
> 
> Willem Coetzer wrote
>> If the zoom extent in the view changes, is there a way to update the 
>> composer to reflect the same extent or do you need to create a new 
>> composer?
> 
> Dear Willem,
> you don't need to create a new composer. Procedure may depend on your QGIS 
> version, in elder versions the window to select an item may be missing.
> 
> First select the map item in the composer view (right column). In the item 
> properties tab (below) scroll to the extents section. There you can find the 
> two buttons "set to map canvas extent" and "view extent in map canvas".
> 
> Click the first one to transfer your map window extent coordinates 
> (your
> "view") to your composer map extents (your "composer"). That's what you 
> wanted to do as I understand it.
> 
> With the second button you might do the reverse: transfer the composer map 
> extent coordinates (your "composer") to your map window (your "view").
> 
> Regards, Christine
> 
> 
> 
> 
> --
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> Nabble.com.
> 
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