This 'bug' was caused due to the way the dark mode was applied. The dark mode detection detects the preferred theme style from the client and then saves the preferred type with a cookie, all with JavaScript. Then a simple PHP if-else statement loads either the dark or light mode CSS theme, depending on the cookie.
The problem here was that the cookie would only be detected if the page was refreshed, so once the cookie was set, the dark mode was applied every time without a problem. But the first time a user visited the site and the preferred theme was set to dark mode, the page would still display the white version until the page was refreshed.
Now, I could have changed how the page applies the dark mode, however I decided against that and went with this commit instead.
Now I'm not really experienced with JavaScript at all, so this definitely could have been solved in a more elegant way, but this is what I did:
I added a bit to the JavaScript that sets and reads the cookie. When the page finished loading, a simple if statement is run that requires the following conditions:
The URL contains a '#' and the color scheme equals 'dark' and the cookie isn't set yet.
After these conditions are met, '#dark' is added to the URL and the page will be refreshed.
This refresh is only performed without the cookie, thus only refreshing the page on the first visit if the dark mode would be applied.
The '#dark' is only added to the URL to fail the first requirement of the if statement, preventing the page from being reloaded in an infinite loop. Otherwise, the '#dark' part of the URL fulfills no purpose and only the '#' part is required, so it doesn't even matter what comes after the hash. I just chose this for clarification.
If the dark mode cookie is blocked by the user, the page will be set to light mode and refreshed every time they visit but the '#dark' will still be added to the URL, preventing the infinite refresh-loop.
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