frontend: Fix checked control button color not changing in System theme

[shiina424]

Description

The control button colors do not change in the System theme.
I chose the button colors with consideration for the OS light and dark modes, but I don’t think they are perfect.
Given my current knowledge, it is difficult for me to make any further changes.
If a better solution exists, please feel free to close this PR.

This issue does not occur in version 31.0.4.
It appears to have been caused by the following changes:
76e1818 and 28960a4

Before (version 31.0.4)
Note: OBS does not switch to dark mode even when the OS is set to dark mode.

Before-31-0-4.mp4

Before (OS Color Light Mode)

Before-system-light.mp4

After (OS Color Light Mode)

rgb 203, 226, 248 (Before)

rgb 140, 181, 255

After-system-light.mp4

Before (OS Color Dark Mode)

Before-system-dark.mp4

After (OS Color Dark Mode)

rgb 203, 226, 248 (Before)

rgb 140, 181, 255

After-system-dark.mp4

Motivation and Context

I found a post mentioning that after updating OBS, the control buttons no longer change color. (I’m not sure whether the user was using the System theme.)
I’m not sure how many people are using the system theme, but I’ll fix it (even though I don’t use it myself).

How Has This Been Tested?

Windows 11 25H2
Tested in both Windows light and dark modes.

I changed the System.obt file.
I’m not sure if the code changes are correct.

You can test by changing the Theme in user.ini to Theme=com.obsproject.System.

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.