DlgPrefMixer: add option to reset EQ kill switches on track load

[gary-gdbsystems]

Summary

Resolves #10684.

Previously "Reset equalizers on track load" also reset the EQ kill switches, so there was no way to reset the kill switches independently of the EQ knobs — the request in this issue.

Approach

Add a separate "Reset EQ kill switches on track load" option ([Mixer Profile]/EqKillAutoReset) and decouple the reset logic in BaseTrackPlayerImpl::slotLoadTrack():

• EqAutoReset → resets the EQ knobs
• EqAutoReset or EqKillAutoReset → resets the kill switches

Backward compatible: users who had EqAutoReset enabled still get their kill switches reset (via the ||), and the new key defaults off, so nothing changes until it is enabled.

UI coupling

Following @JosepMaJAZ's proposal in the thread (which @ronso0 endorsed), the kill-switch checkbox is forced on and disabled while "Reset equalizers on track load" is active, because resetting the equalizers inherently resets the kill switches. The user's own kill-switch setting is preserved and restored when equalizer reset is turned off again.

I chose the coupled variant over three fully independent checkboxes because it is backward compatible — a fully independent design would silently stop resetting kill switches for existing EqAutoReset users unless their config were migrated. Happy to adjust if maintainers prefer otherwise.

Changes

• src/mixer/basetrackplayer.cpp — decouple knob vs kill-switch reset; read the new config key.
• src/preferences/dialog/dlgprefmixer.{cpp,h} — new checkbox load/save/default wiring + coupling logic.
• src/preferences/dialog/dlgprefmixerdlg.ui — new checkbox.

Screenshots

Before — EQ / gain / stem reset options:

After (default) — new independent "Reset EQ kill switches on track load":

After (coupled) — with "Reset equalizers" enabled, the kill option is forced on and locked:

Testing

• Builds cleanly (incl. uic regeneration of the dialog).
• clang-format, clang-tidy, and the other pre-commit hooks pass.
• Verified the checkbox wiring, coupling behavior, and reset decoupling by code inspection; the existing reset-on-load behavior has no unit-test harness.

[cr7pt0gr4ph7]

Looks good to me, except for the small nitpick about option naming.

If the feature itself is desirable (and I don't see why not) then this should be ready for merging.

[cr7pt0gr4ph7]

For symmetry with "Reset equalizers on track load":

Suggested change

	<string>Reset EQ kill switches on track load</string>
	<string>Reset equalizer kill switches on track load</string>

[gary-gdbsystems]

Thanks. Renamed to "Reset equalizer kill switches on track load" and updated the tooltip to match. Screenshot updated.

[ronso0]

Is there a reason not to use m_eqAutoReset which is set above when the EQ checkbox is toggled?

Suggested change

	void DlgPrefMixer::updateEqKillAutoResetState() {
	const bool eqReset = CheckBoxEqAutoReset->isChecked();
	CheckBoxEqKillAutoReset->setEnabled(!eqReset);
	CheckBoxEqKillAutoReset->setChecked(eqReset || m_eqKillAutoReset);
	void DlgPrefMixer::updateEqKillAutoResetState() {
	CheckBoxEqKillAutoReset->setEnabled(!m_eqAutoReset);
	CheckBoxEqKillAutoReset->setChecked(m_eqAutoReset || m_eqKillAutoReset);

[ronso0]

Thank you for this nice addition @gary-gdbsystems
Code mostly LGTM (see my comment). Manual test still pending.

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