[Qgis-developer] Dropping the "render" checkbox

[Germán Carrillo]

Hi All,


I use mapCanvas().setRenderFlag( False ) before loading a (potentially)
large number of layers using the 'Load Them All' plugin [1]. I acknowledge
I needed to toggle such flag years ago (the plugin was mainly developed in
2012) and still use it.

For another plugin (private according to requirements from a company), I
use heavy PostGIS layers in a Processing workflow. As I don't want the
canvas to show anything in the meantime (I'm only interested in getting
progress bar updates in QgsMessageBar), I use the setRenderFlag(False) and
only ask canvas to show all needed layers, including results, after all
processing is done.

Does it make sense or could I avoid toggling the flag?


Regards,

Germán
----
[1] http://plugins.qgis.org/plugins/loadthemall/


2017-02-28 6:49 GMT-05:00 Tim Sutton <tim at kartoza.com>:

> Hi
>
> On 28 Feb 2017, at 12:00 PM, Matthias Kuhn <matthias at opengis.ch> wrote:
>
> Hi Tim
>
> On 02/28/2017 10:42 AM, Tim Sutton wrote:
>
> One reason to keep it: For us the use case has often been when you are
> doing first set up of a project and you are dropping a bunch of large
> layers yet. You want to set up scale dependent visibility and rules
> first without waiting for time consuming renders, then enable rendering
> when everything is added. I know we can also use the option to make
> layers not visible when they are first added to the canvas so I reckon
> that use case can be worked around easily enough.
>
>
> Sorry if I'm missing something, but why is it important that in this
> case nothing is rendered? I imagine you can just configure scale
> dependent rendering, while ignoring that something is rendered in the
> background. And once you apply the changed config, rendering will
> restart with the same net-time and net-result (but less clicks).
>
>
>
> Hmm probably not so important if it is rendering nicely in a side thread
> and esc cancels rendering efficiently. Anyway it seems that others like
> Giovanni and Denis are quite invested in the feature so probably it is more
> useful to understand their needs as I could easily see it go and not be too
> worried...
>
> Regards
>
> Tim
>
>
>
> Matthias
>
>
> —
>
>
>
>
>
>
>
>
>
> *Tim Sutton*
>
> *Co-founder:* Kartoza
> *Project chair:* QGIS.org
>
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