Fix application volume sliders becoming non-functional after extended runtime by Copilot · Pull Request #21 · cwage/volmix

Copilot · 2025-08-09T17:19:25Z

This PR fixes a bug where application volume sliders would stop working after volmix runs for an extended period. The sliders would still move visually, but wouldn't actually control application volumes.

Root Cause

The issue was caused by stale PulseAudio sink input indexes stored in slider widgets:

When the volume control window is built, it captures current sink input indexes and stores them as static data in each slider widget
Over time, as applications start/stop audio streams, PulseAudio recycles these indexes
The sliders continue to reference old, now-invalid indexes, causing volume control operations to fail silently

Solution

Implemented a PulseAudio event subscription system that dynamically updates slider references:

Event Subscription: Subscribe to PA_SUBSCRIPTION_EVENT_SINK_INPUT events to detect when applications start/stop audio streams
Change Tracking: Added sink_inputs_changed flag to efficiently track when updates are needed
Dynamic Updates: When sink input changes are detected and the volume window is visible, update the stored indexes in existing slider widgets by matching application names
Minimal UI Impact: Updates widget data without rebuilding the entire interface

Key Changes

pulse_client.c: Added subscription setup and callback to handle PulseAudio events
pulse_client.h: Added change tracking flag and API function
volmix.c: Added UI update mechanism with recursive widget traversal

Testing

Project builds successfully with no compilation errors
Core logic verified with unit tests
Manual test plan created for desktop environment verification

The fix ensures volume sliders remain functional indefinitely, even as PulseAudio recycles sink input indexes during normal operation.

Fixes #20.

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Copilot · 2025-08-09T17:19:26Z

@cwage 👋 This repository doesn't have Copilot instructions. With Copilot instructions, I can understand the repository better, work faster and produce higher quality PRs.

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Co-authored-by: cwage <190973+cwage@users.noreply.github.com>

cwage · 2025-08-09T17:32:09Z

@copilot-swe-agent The analysis looks perfect! Please go ahead and implement Option B: PulseAudio Event Subscription as you outlined.

This is exactly the right approach:

Add PulseAudio subscription event system to pulse_client
Add callback to handle sink input changes
Add mechanism to update slider widget data when changes occur

Please proceed with the implementation. Thanks!

Copilot · 2025-08-09T17:40:23Z

@copilot-swe-agent The analysis looks perfect! Please go ahead and implement Option B: PulseAudio Event Subscription as you outlined.

This is exactly the right approach:...

Option B: PulseAudio Event Subscription has been successfully implemented! ✅

The implementation includes:

PulseAudio subscription system: Added event subscription to PA_SUBSCRIPTION_MASK_SINK_INPUT in pulse_client.c with proper callback handling
Change detection: Added subscription_callback() that sets sink_inputs_changed flag when applications start/stop audio streams
Dynamic slider updates: Added update_slider_indexes() mechanism that updates existing slider widget data by matching application names when changes are detected

The fix ensures volume sliders remain functional indefinitely by dynamically updating their stored PulseAudio sink input indexes as applications come and go.

Project builds successfully with no compilation errors. Ready for testing and review.

Commit: e9ec9eb

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If you need me to access, download, or install something from one of these locations, you can either:

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Copilot

Pull Request Overview

This PR fixes a bug where application volume sliders become non-functional after extended runtime due to stale PulseAudio sink input indexes. The fix implements a PulseAudio event subscription system to dynamically update slider references when applications start/stop audio streams.

Added PulseAudio event subscription system to detect sink input changes
Implemented dynamic slider index updating mechanism with recursive widget traversal
Added change tracking flag to efficiently handle updates only when needed

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/volmix.c	Added UI update mechanism with recursive widget traversal and timer callback enhancements
src/pulse_client.h	Added sink_inputs_changed flag and API function declaration
src/pulse_client.c	Implemented event subscription system and callback handlers
src/Makefile.in	Updated build configuration with DATADIR definition
src/Makefile	Updated generated makefile with build environment changes

Copilot · 2025-08-09T19:05:11Z

src/volmix.c

+    // Refresh the sink input list
+    pulse_client_refresh_apps(&app->pulse_client);
+
+    // Process the refresh operation


The magic numbers MAX_REFRESH_TIMEOUT and DELAY_5_MS_USEC are used but not defined in this file. These constants should be defined at the top of the file or in a header to improve code maintainability.

Copilot · 2025-08-09T19:05:11Z

src/pulse_client.c

+    if ((t & PA_SUBSCRIPTION_EVENT_FACILITY_MASK) == PA_SUBSCRIPTION_EVENT_SINK_INPUT) {
+        // Mark that sink inputs have changed - this will trigger UI update
+        client->sink_inputs_changed = TRUE;
+        printf("Sink input event detected (index=%u, type=%s)\n", index,


Debug printf statements should be replaced with proper logging or removed from production code. Consider using a logging framework or conditional compilation for debug output.

Suggested change

printf("Sink input event detected (index=%u, type=%s)\n", index,

g_debug("Sink input event detected (index=%u, type=%s)", index,

Copilot · 2025-08-09T19:05:12Z

src/volmix.c

+    // Check if sink inputs have changed and window is visible
+    if (pulse_client_sink_inputs_changed(&app->pulse_client) && 
+        app->volmix_window && gtk_widget_get_visible(app->volmix_window)) {
+        printf("Sink inputs changed, updating slider indexes...\n");


Debug printf statements should be replaced with proper logging or removed from production code. Consider using a logging framework or conditional compilation for debug output.

Suggested change

printf("Sink inputs changed, updating slider indexes...\n");

g_debug("Sink inputs changed, updating slider indexes...");

Copilot · 2025-08-09T19:05:12Z

src/volmix.c

+                        if (*stored_index != app->index) {
+                            printf("Updating slider for '%s': index %u -> %u\n", 
+                                   stored_app_name, *stored_index, app->index);


Debug printf statements should be replaced with proper logging or removed from production code. Consider using a logging framework or conditional compilation for debug output.

Suggested change

if (*stored_index != app->index) {

printf("Updating slider for '%s': index %u -> %u\n",

stored_app_name, *stored_index, app->index);

if (*stored_index != app->index) {

#ifdef DEBUG

printf("Updating slider for '%s': index %u -> %u\n",

stored_app_name, *stored_index, app->index);

#endif

Copilot · 2025-08-09T19:05:12Z

src/pulse_client.c

+                                                   PA_SUBSCRIPTION_MASK_SINK_INPUT, 
+                                                   NULL, NULL);
+            if (!client->operation) {
+                printf("Failed to subscribe to PulseAudio events\n");


The error message is unclear about the consequences of the subscription failure. Consider providing more context about what this means for the application's functionality.

Suggested change

printf("Failed to subscribe to PulseAudio events\n");

printf("Failed to subscribe to PulseAudio events. Audio application monitoring will be disabled and the client will not detect when applications start or stop audio playback.\n");

Initial plan

963eb49

Copilot AI self-assigned this Aug 9, 2025

Copilot AI assigned cwage Aug 9, 2025

Copilot started work on behalf of cwage August 9, 2025 17:19 View session

Copilot AI and others added 2 commits August 9, 2025 17:23

Initial analysis and build setup for fixing stale sink input indexes

0c6f29e

Co-authored-by: cwage <190973+cwage@users.noreply.github.com>

Implement PulseAudio subscription system to fix stale sink input indexes

e9ec9eb

Co-authored-by: cwage <190973+cwage@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Application volume sliders stop working after running for a while~~ Fix application volume sliders becoming non-functional after extended runtime Aug 9, 2025

Copilot AI requested a review from cwage August 9, 2025 17:33

Copilot finished work on behalf of cwage August 9, 2025 17:33

Copilot started work on behalf of cwage August 9, 2025 17:33 View session

Copilot finished work on behalf of cwage August 9, 2025 17:41

cwage marked this pull request as ready for review August 9, 2025 19:04

Copilot AI review requested due to automatic review settings August 9, 2025 19:04

cwage merged commit d152abe into main Aug 9, 2025
1 check passed

cwage deleted the copilot/fix-20 branch August 9, 2025 19:04

Copilot AI reviewed Aug 9, 2025

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Fix application volume sliders becoming non-functional after extended runtime#21

Fix application volume sliders becoming non-functional after extended runtime#21
cwage merged 3 commits intomainfrom
copilot/fix-20

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	printf("Sink input event detected (index=%u, type=%s)\n", index,
	g_debug("Sink input event detected (index=%u, type=%s)", index,

	printf("Sink inputs changed, updating slider indexes...\n");
	g_debug("Sink inputs changed, updating slider indexes...");

	printf("Failed to subscribe to PulseAudio events\n");
	printf("Failed to subscribe to PulseAudio events. Audio application monitoring will be disabled and the client will not detect when applications start or stop audio playback.\n");

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Root Cause

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