[Qgis-psc] Report on the grant for QEP 291

[Régis Haubourg]

This is great Mathieu !

Le ven. 15 nov. 2024 à 12:52, Mathieu Pellerin via QGIS-PSC <
qgis-psc at lists.osgeo.org> a écrit :

> Greetings PSC,
>
> I’m happy to report that the work for the above-mentioned QEP has been
> completed during the months of August and September 2024. The work includes:
>
> - A new “smart” network cache mode - enabled by default – which adopts
> modern browsers’ strategies to determine the on-disk network cache size
> based on users’ available space. Starting with QGIS, for the fast majority
> of users, this will increase the network cache size from 0.25gb to 1gb,
> which in turn will allow for greater space to cache XYZ raster tiles,
> including those served by openstreetmap.org. While a backport was made
> available, it was deemed – wisely :) - too risky to merge.
>
> - The following processing algorithms were modified to insure QGIS users
> do not accidentally breach the OSMF tile usage policy with regards to bulk
> downloads: the generate XYZ tiles (MBTiles) algorithm, the generate XYZ
> tiles (Directory) algorithm, and the convert map to raster algorithm. In
> all three algorithms, a check is now in place to insure that no more than
> 5,000 tiles will be fetched from openstreetmap.org. If the amount of
> tiles goes behind this threshold, users will be informed through a warning
> message in their processing algorithm dialog that the layer serving
> openstreetmap.org tiles has been removed from the set of layers being
> rendered. Below 5,000 tiles, we assume users are not aimed at bulk
> downloading tiles but rather preparing a map of reasonable extent for
> viewing. These changes have been backported to the current 3.34 LTR.
>
> - Additionally, further safeguards were put in place while researching
> other means through which bulk downloads could be achieved. The same 5,000
> tiles threshold when saving a XYZ raster layer through the browser panel as
> well as through the layers panel when those tiles are served through
> openstreetmap.org. As with the processing algorithms, when users
> surpasses the threshold, a message box will appear to inform them of the
> OSMF tile usage policy. These changes are available in 3.40 and have also
> been backported to the current 3.34 LTR.
>
> - Finally, I took the opportunity to apply an improvement to the default
> OpenStreetMap XYZ layer available through the browser panel. On fresh QGIS
> installations, this layer now now has its tile resolution set to 96DPI
> instead of unknown. The change results in a significant reduction in tiles
> being fetched when exporting a print layout in high DPI (e.g. 300). The
> benefits in terms of tile fetching reduction also impacts atlas and report
> layout exports. The change arguably improves layout exports by avoiding
> tiny, unreadable labels. Users can always manually change this tile
> resolution setting if desired. This change is available in 3.40 and has
> also been backported to the current 3.34 LTR.
>
> With those improvements in place, QGIS 3.40 has the safeguards in place to
> insure that bulk downloads - accidental or intentional - are prohibited.
> Furthermore, the network caching improvement and the adjusted configuration
> of the default OpenStreetMap XYZ layer shipped with QGIS are undoubtedly
> going to reduce any stress caused by normal usage’s fetching of tiles.
>
> Regards,
>
> Mathieu Pellerin
> OPENGIS.ch
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>
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