[Bug]: App icons don't show as black icons with the light theme selected

[arnowelzel]

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

Since at least Nextcloud 34 (maybe even earlier version), many app icons don't show as black icons when a light theme is used.

Light theme:

Dark theme:

Steps to reproduce

1. Open the list of active apps (.../settings/apps/enabled).
2. See the app list and check the icons - many are invisible since they are not black on a light background or not white on a dark backround.

Expected behavior

All icons appear black, when Nextcloud uses a light theme or white, when Nextcloud uses a dark theme.

Nextcloud Server version

34

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.4

Web server

Apache (supported)

Database engine version

MariaDB

Is this bug present after an update or on a fresh install?

Upgraded to a MAJOR version (ex. 31 to 32)

Are you using the Nextcloud Server Encryption module?

No response

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

system
{
    "system": {
        "htaccess.RewriteBase": "\/",
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "nextcloud-dev.0x0c.de"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "mysql",
        "version": "34.0.1.2",
        "overwrite.cli.url": "https:\/\/nextcloud-dev.0x0c.de\/",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "mysql.utf8mb4": true,
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "integrity.check.disabled": false,
        "maintenance": false,
        "loglevel": 2,
        "theme": "",
        "app_install_overwrite": {
            "0": "deck",
            "1": "dicomviewer",
            "3": "memories",
            "5": "bookmarks",
            "6": "theming_customcss"
        },
        "memories.db.triggers.fcu": true,
        "memories.exiftool": "\/var\/www\/clients\/client1\/web85\/web\/apps\/memories\/bin-ext\/exiftool-amd64-glibc",
        "memories.vod.path": "\/var\/www\/clients\/client1\/web85\/web\/apps\/memories\/bin-ext\/go-vod-amd64",
        "memories.gis_type": 1,
        "defaultapp": "files"
    }
}

List of activated Apps

Enabled:
  - activity: 7.0.0
  - app_api: 34.0.0
  - appstore: 1.0.0
  - bookmarks: 16.2.4
  - bruteforcesettings: 7.0.0
  - calendar: 6.5.1
  - circles: 34.0.0
  - cloud_federation_api: 1.18.0
  - collectives: 4.4.2
  - comments: 1.24.0
  - contacts: 8.7.4
  - contactsinteraction: 1.15.0
  - dashboard: 7.14.0
  - dav: 1.39.0
  - deck: 1.18.2
  - dicomviewer: 2.3.3
  - drawio: 4.3.5
  - federatedfilesharing: 1.24.0
  - federation: 1.24.0
  - files: 2.6.0
  - files_downloadlimit: 5.2.0-dev.0
  - files_lock: 34.0.0
  - files_pdfviewer: 7.0.0-dev.0
  - files_reminders: 1.7.0
  - files_sharing: 1.26.0
  - files_trashbin: 1.24.0
  - files_versions: 1.27.0
  - firstrunwizard: 7.0.0-dev.0
  - keeweb: 0.6.25
  - logreader: 7.0.0
  - lookup_server_connector: 1.22.0
  - memories: 8.1.0
  - nextcloud_announcements: 6.0.0
  - notes: 6.0.1
  - notifications: 7.0.0-dev.1
  - oauth2: 1.22.0
  - office: 1.0.0
  - password_policy: 6.0.0-dev.0
  - photos: 7.0.0
  - polls: 9.1.4
  - privacy: 6.0.0-dev.1
  - profile: 1.3.0
  - provisioning_api: 1.24.0
  - related_resources: 5.0.0-dev.0
  - serverinfo: 6.0.0
  - settings: 1.17.0
  - sharebymail: 1.24.0
  - spreed: 24.0.2
  - support: 6.0.0
  - survey_client: 6.0.0-dev.0
  - systemtags: 1.24.0
  - text: 8.0.0
  - theming: 2.9.0
  - theming_customcss: 1.20.0
  - twofactor_backupcodes: 1.23.0
  - twofactor_totp: 16.0.0
  - updatenotification: 1.24.0
  - user_status: 1.14.0
  - viewer: 7.0.0-dev.0
  - weather_status: 1.14.0
  - webhook_listeners: 1.6.0
  - workflowengine: 2.16.0
Disabled:
  - admin_audit: 1.24.0
  - encryption: 2.22.0
  - files_external: 1.26.0
  - recommendations: 7.0.0 (installed 2.0.0)
  - suspicious_login: 12.0.0-dev.0
  - testing: 1.23.0
  - twofactor_nextcloud_notification: 8.0.0
  - unroundedcorners: 1.1.5 (installed 1.1.5)
  - user_ldap: 1.25.0

Nextcloud Signing status

No errors have been found.

Nextcloud Logs

Additional info

Since I also maintain an app my self (Diagramming) I realized, that it seems to be crucial to provide an SVG image with black fillings and strokes and name that app_dark.svg, otherwise the UI seems not to know how to deal with it. Is this assumption correct and is there any documentation about this?

At least some of the affected apps provide a white icon and name it app.svg and not app_dark.svg - for example Contacts. In this case, the UI should reverse the color used for the final display if the current theme is not a dark theme.