mGBA uses disabled shader after fresh installation, causing high CPU usage and audio stuttering

[maniacnny]

Device: TrimUI Brick Hammer
NextUI: v6.11.2
Stock Firmware: v1.1.1

Steps to Reproduce

Perform a clean installation of NextUI.
Launch any GBA game using the mGBA core (Apotris, Metroid Zero Mission etc.
Leave the shader setting as Pixel Perfect Sharp (shown as OFF by default).

Expected Behavior

The shader should remain disabled, mGBA should run normally, CPU frequency should stay low, and audio should be smooth.

Actual Behavior

Although the shader is shown as OFF, it still appears to be applied in the background. This causes the CPU to stay at maximum frequency (1800), resulting in poor performance and noticeable audio stuttering.

Workaround

Select any other shader.
Turn the shader ON.
Turn it OFF again.

After doing this, mGBA runs smoothly, audio stuttering disappears, and CPU frequency returns to normal (1000-1200).

Possible Cause

It looks like the default shader configuration is not being initialized correctly after a fresh installation. An empty shader configuration by default may prevent this issue.

P.S. I know the gpSP core is available, but it has noticeably higher input latency. mGBA offers a more responsive experience, so I’d prefer to use it.

[pvaibhav]

Can confirm this issue appears on other cores also e.g. Picodrive. Instead of pixel-perfect-sharp, if the shader is changed to pixel-perfect-smooth does not exhibit this issue. However this might be because the underlying problem is jostled by changing the shader.