feat: restore xml parsing to avoid postgis request

[jmkerloch]

Even with the use of flags QgsProject.FlagDontResolveLayers | QgsProject.FlagDontLoadLayouts | QgsProject.FlagTrustLayerMetadata | QgsProject.FlagDontStoreOriginalStyles we still see some request to postgis if there are postgis layer in the project.

If the number of layer is big this really increase project load time.

To avoid that this PR restore the use of xml parsing for project menu configuration definition.

• A new class QgsDomManager is created to store all the loaded xml projects (was previously in plugin main):
  • This allow us to use this class in other part of plugin that the plugin main.
• Full refactoring of project_read.py to use xml parsing.

[Guts]

@xcaeag woa so fast! Did you really review it before? I had not time to set up my local test environment!

[xcaeag]

not familiar with reviews. I trust, I integrate, I test then!

[jmkerloch]

@xcaeag Wasn't expecting a merge this quick !

If anything turns out to be wrong I will quickly do a fix.

[xcaeag]

well, it rocks!
tests passed on different test menus:

• our big projects / postgis
• geoplatform big project
• project with relations between layers
• project with joins
• project with relative layers
• project with vector tiles
• tooltip "layer note"
• web project (https://adour-garonne.eaufrance.fr/upload/DATA/SIG/aeag-web.qgz)

all loaded in.. 2s

[Guts]

@jmkerloch can you remember me the related issue upstream on QGIS project please?

[jmkerloch]

@jmkerloch can you remember me the related issue upstream on QGIS project please?

I created an issue about layer notes that should be corrected in master : qgis/QGIS#58818

But if we wan't to be as fast as xml parsing there are other optimization needed in Qgis core.

[Guts]

But if we wan't to be as fast as xml parsing there are other optimization needed in Qgis core.

Can you develop a bit please?

[Guts]

I created an issue about layer notes that should be corrected in master : qgis/QGIS#58818

It has been backported to 3.34.

[jmkerloch]

But if we wan't to be as fast as xml parsing there are other optimization needed in Qgis core.

Can you develop a bit please?

I need to do some tests but this wasn't as fast as xml parsing. I remember for instance query to database in case of postgis layer.