Add O3DVisualizer API to enable collapse control of verts in the side panel

[EwingKang]

Add API SetCollapsableVertOpen to control the toggling of the verts in the side panel

Type

• Bug fix (non-breaking change which fixes an issue): Fixes #
• New feature (non-breaking change which adds functionality). Resolves #
• Breaking change (fix or feature that would cause existing functionality to not work as expected) Resolves #

Motivation and Context

When we have start the viewer with side panel ("show settings"), the default toggle vert (pane) in the side panel defaults to ON for the "Mouse Controls" and "Scene", but no "Lighting". These default on panels took a lot of space and I find myself always collapsing the settings since I mostly want to control the visibility of objects in "Geometries". This becomes quite annoying very soon.

Checklist:

• I have run python util/check_style.py --apply to apply Open3D code style
  to my code.
• This PR changes Open3D behavior or adds new functionality.
  • Both C++ (Doxygen) and Python (Sphinx / Google style) documentation is
    updated accordingly.
  • I have added or updated C++ and / or Python unit tests OR included test
    results (e.g. screenshots or numbers) here.
• I will follow up and update the code if CI fails.
• For fork PRs, I have selected Allow edits from maintainers.

Description

Before: Side vert "Mouse Controls" and "Scene" always defaults to ON

After The displayed result after calling the new API

O3DVisualizer::SetCollapsableVertOpen("Mouse Controls", false);

[update-docs]

Thanks for submitting this pull request! The maintainers of this repository would appreciate if you could update the CHANGELOG.md based on your changes.

[ssheorey]

Hi @EwingKang thanks for this PR.

One suggestion to simplify this is to addCollapsableVert::GetText() in Layout.cpp. This way, there is no need to store the text -> pointer map. You can instead iterate through all the children of the vert panel and just match the text.

Also, please add python bindings.

[EwingKang]

Hi @ssheorey
Thanks for your reply. I'll add the Python bindings (not sure how to do that exactly, but I'll try)
Also, adding CollapsableVert::GetText() in Layout.cpp is not a problem.

However, for the pointers suggestion, do you suggest having a std::vector<CollapsableVert *> instead of a map here? Does that mean the removal of CollapsableVert *mouse_panel, CollapsableVert *scene_panel, CollapsableVert *light_panel, and CollapsableVert *geometries_panel?
The upside is the simplification of members. We'll only have one pointer per object.
The downside is the increasing difficulties of using the object and slower speed if there are a lot of panels. For example, if someone wants to use geometries_panel within the O3DVisualizer.cpp, they would now have to find the pointer to that CollapsableVert * through the same look API with a key string. The API would have O(N) instead of O(logN). Of course, the former might still be faster, considering we have only 4 panels now.

[EwingKang]

Add GetText() and SetText() to CollapsableVert
Here are some test screenshots of setting the text (the "hahahaha#" was originally "Advanced lighting")

[ssheorey]

Looks good after a few minor updates. Thanks @EwingKang

[ssheorey]

Thanks @EwingKang Looks good!