Add basic drag and drop support in the model designer

[ValentinBuira]

Introduction

This PR add the new way to edit a model using a drag and drop interface. This is part of long waited improvements in the model designer capabilities.

The design is based of the Google Summer of code proposal I did last year, and that we discussed on the mailling list. Compared to the original proposal the UI looks more similar to the current modeler interface

I encourage anyone to open your existing models and give it a try !

Thanks to the Hauts-de-France region for sponsorising this work

How does it works ?

New sockets were added around each parameter and algorithm used in a model.

sockets.example.mp4

Those are interactive and are used to connect component between them. To connect component drag any output socket regardless of it's from a model parameter or a algorithm into an input socket. You can also remove a connection by dragging an edge out of the socket.

peek.drag.and.drop.mp4

Theses new capabilities have been added as part of the select/edit tool. No needs to switch to a new tool when you want to edit connection in your model.

This PR remain fully compatible with the previous user interface. When you connect sockets by drag and drop. The dialog used when opening an algorithm is updated as well.

retro.compatible.mp4

[github-actions]

🪟 Windows builds

Download Windows builds of this PR for testing.
Debug symbols for this build are available here.
(Built from commit bff841a)

🪟 Windows Qt6 builds

Download Windows Qt6 builds of this PR for testing.
(Built from commit bff841a)

[troopa81]

Good job! 👍

Please let me know when you have finished this work and the PR is not draft anymore, I would make a proper review.

[ValentinBuira]

I noticed that "input" types of node now have a little "+" icon, but while clicking on it it crashes and close. Below, a distance input node:

Seems to be working on my side ?

2025-04-08.mp4

I recall fixing something similar for algorithms, were you using the latest commit ?

[ValentinBuira]

I adressed all the comments and should be ready for a final review @nyalldawson

[jonathanlurie]

QgsModelComponentGraphicItem::fold

Hey @ValentinBuira , OK,my bad, you're right! Apologies for the false alarm, the error comes from a silly mistake of mine.

[ValentinBuira]

This PR was also impacted by #61528 so I had to add an extra check to make sure we properly return to the select tool

[nyalldawson]

Great work -- thanks for the responsive changes @ValentinBuira !!

[nyalldawson]

@ValentinBuira there's now a warning shown when opening the modeler - "signal not found in QgsModelGraphicsView". I also get a crash when attempting to unlink two components via drag.

[ValentinBuira]

there's now a warning shown when opening the modeler - "signal not found in QgsModelGraphicsView". I also get a crash when attempting to unlink two components via drag.

I'm looking into it thanks for the heads up

[qgis-bot]

@ValentinBuira
This pull request has been tagged as requiring documentation.

A documentation ticket will be opened at https://github.com/qgis/QGIS-Documentation when this PR is merged.

Please update the description (not the comments) with helpful description and screenshot to help the work from documentors.
Also, any commit having [needs-doc] or [Needs Documentation] in will see its message pushed to the issue, so please be as verbose as you can.

Thank you!

[qgis-bot]

@ValentinBuira
A documentation ticket has been opened at qgis/QGIS-Documentation#9849
It is your responsibility to visit this ticket and add as much detail as possible for the documentation team to correctly document this change.
Thank you!

[qgis-bot]

@ValentinBuira

This pull request has been tagged for the changelog.

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Thank you!

[ValentinBuira]

I also get a crash when attempting to unlink two components via drag.

Hi @nyalldawson #61758 was merged, can you confirm it fixed your issue ?