[Qgis-developer] Meaning of "Canvas Units" in project properties?!?

Luigi Pirelli luipir at gmail.com
Mon Oct 19 01:08:01 PDT 2015

I suppose a side effect of introducing mapSettings?

On Sunday, 18 October 2015, Nyall Dawson <nyall.dawson at gmail.com> wrote:

> Hi all,
> I'm totally struggling to understand what the "Canvas Units" setting
> in project properties is there for, and what it's ACTUALLY supposed to
> do...
> Currently, it seems like a read-only property. Whatever you set it to
> (regardless of whether or not OTF is enabled or not), it's always
> reset whenever you reopen the properties dialog. But the broken
> behaviour goes a lot deeper than just this.... looking at the code
> it's very unclear what this setting is there for. I think it's
> *supposed* to allow users to override the map units for the current
> project CRS, but why would we want this? Changing it would result in
> totally meaningless measurements....!
> Unless I'm misunderstanding, this setting should be removed and
> replaced with a label showing what the units are for the current
> projection.
> I'm trying to get to the bottom of http://hub.qgis.org/issues/11986
> (Area calculation is wrong with OTF enabled), but even after reading
> the source I'm struggling to understand how QGIS is supposed to be
> handling this. And if a developer who CAN read the source has no idea,
> how are normal users supposed to understand this? ;)
> Any ideas on what the correct behaviour should be, please let me know
> ASAP and maybe I can get this sorted before release.
> Nyall
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Luigi Pirelli

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