System-wide Dark Mode has been one of the highlight features of Android 10. Dark mode had been a long-requested feature from the Android community, especially from AMOLED smartphone users. Several app developers had independently adopted Dark themes for their apps prior to Google's adoption; but with the rollout of Google's system-wide dark mode, many others jumped on the opportunity and offered their users an alternative darker theme. But there were still others that seemed curiously hesitant in offering a Dark mode, taking their own sweet time to implement the same (we're looking at you, WhatsApp). Despite dark mode options being well-received by users, there are apps that continue to roll around with predominantly light themes, either out of stubbornness or out of apathy. Android 10 also comes with an option to force blanket dark themes across all apps, but that is not an ideal option for all apps. OEMs thus have to consider providing their users with an option of selectively enforcing this mode, and OnePlus appears to be moving towards the same as it tests out a new forced dark mode for more apps, within OxygenOS.
We found strings (h/t XDA Senior Member Some_Random_Username for the tip!) within the Settings app in the latest OxygenOS Open Beta 11 that was released for the OnePlus 7 and OnePlus 7 Pro. These strings suggest that OnePlus is looking to bring over a forced dark mode for certain apps:
<string name="oneplus_global_dark_mode_description">"Make apps that don't support dark theme also appear as dark tone. Some apps may not perform as expected, you can disable them in the list below."</string>
<string name="oneplus_global_dark_mode_only_valid_in_dark_mode">This feature is only available under dark tone</string>
<string name="oneplus_global_dark_mode_summary">Make more apps that do not adapt to dark mode turn into dark automatically when dark tone is turned on</string>
<string name="oneplus_global_dark_mode_title">Enable dark tone in more apps</string>
We managed to surface the Settings page for the feature, but we were unable to ascertain which apps will be supported under the feature.
The idea behind this feature appears to be similar to DarQ. DarQ allows users to enable Android 10's built-in forced dark mode on a per-app basis, so you can choose which apps you wish to darken. This lets you retain light themes on apps that do not react well with enforced dark themes, while still darkening apps that react well with enforced dark themes but where developers have not implemented a dark theme yet. We hope to see the feature rolled out soon.