network(networkmanager): rebuild the Wi-Fi list once per scan (#3818)

core/internal/server/network/backend_networkmanager.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"maps"
 	"sync"
+	"time"
 
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/log"
 	"github.com/Wifx/gonetworkmanager/v2"
@@ -80,6 +81,10 @@ type NetworkManagerBackend struct {
 	sigWG    sync.WaitGroup
 	stopChan chan struct{}
 
+	wifiRefreshTimer *time.Timer
+	wifiRefreshMu    sync.Mutex
+	wifiRefreshWG    sync.WaitGroup
+
 	secretAgent  *SecretAgent
 	promptBroker PromptBroker
 

core/internal/server/network/backend_networkmanager_signals.go

@@ -1,6 +1,8 @@
 package network
 
 import (
+	"time"
+
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/log"
 	"github.com/Wifx/gonetworkmanager/v2"
 	"github.com/godbus/dbus/v5"
@@ -10,6 +12,8 @@ const (
 	dbusNMSettingsPath                = "/org/freedesktop/NetworkManager/Settings"
 	dbusNMSettingsInterface           = "org.freedesktop.NetworkManager.Settings"
 	dbusNMSettingsConnectionInterface = "org.freedesktop.NetworkManager.Settings.Connection"
+
+	wifiNetworksUpdateDelay = 500 * time.Millisecond
 )
 
 func (b *NetworkManagerBackend) startSignalPump() error {
@@ -287,7 +291,8 @@ func (b *NetworkManagerBackend) stopSignalPump() {
 	}
 
 	b.sigWG.Wait()
-
+	b.cancelWiFiNetworksUpdate()
+	b.wifiRefreshWG.Wait()
 }
 
 func (b *NetworkManagerBackend) handleDBusSignal(sig *dbus.Signal) {
@@ -537,7 +542,7 @@ func (b *NetworkManagerBackend) handleWiFiChange(changes map[string]dbus.Variant
 			needsStateUpdate = true
 			needsNetworkUpdate = true
 		case "AccessPoints":
-			needsNetworkUpdate = true
+			b.scheduleWiFiNetworksUpdate()
 		default:
 			continue
 		}
@@ -547,6 +552,7 @@ func (b *NetworkManagerBackend) handleWiFiChange(changes map[string]dbus.Variant
 		b.updateWiFiState()
 	}
 	if needsNetworkUpdate {
+		b.cancelWiFiNetworksUpdate()
 		b.updateWiFiNetworks()
 	}
 	if needsStateUpdate || needsNetworkUpdate {
@@ -556,6 +562,41 @@ func (b *NetworkManagerBackend) handleWiFiChange(changes map[string]dbus.Variant
 	}
 }
 
+// A scan announces each new access point on its own, so rebuild the list
+// once per burst instead of once per access point.
+func (b *NetworkManagerBackend) scheduleWiFiNetworksUpdate() {
+	b.wifiRefreshMu.Lock()
+	defer b.wifiRefreshMu.Unlock()
+
+	if b.wifiRefreshTimer != nil {
+		return
+	}
+	b.wifiRefreshWG.Add(1)
+	b.wifiRefreshTimer = time.AfterFunc(wifiNetworksUpdateDelay, func() {
+		defer b.wifiRefreshWG.Done()
+
+		b.wifiRefreshMu.Lock()
+		b.wifiRefreshTimer = nil
+		b.wifiRefreshMu.Unlock()
+
+		b.updateWiFiNetworks()
+		if b.onStateChange != nil {
+			b.onStateChange()
+		}
+	})
+}
+
+func (b *NetworkManagerBackend) cancelWiFiNetworksUpdate() {
+	b.wifiRefreshMu.Lock()
+	defer b.wifiRefreshMu.Unlock()
+
+	if b.wifiRefreshTimer == nil || !b.wifiRefreshTimer.Stop() {
+		return
+	}
+	b.wifiRefreshTimer = nil
+	b.wifiRefreshWG.Done()
+}
+
 func (b *NetworkManagerBackend) handleAccessPointChange(changes map[string]dbus.Variant) {
 	_, hasStrength := changes["Strength"]
 	if !hasStrength {

core/internal/server/network/backend_networkmanager_signals_test.go

@@ -1,7 +1,9 @@
 package network
 
 import (
+	"sync/atomic"
 	"testing"
+	"time"
 
 	mock_gonetworkmanager "github.com/AvengeMedia/DankMaterialShell/core/internal/mocks/github.com/Wifx/gonetworkmanager/v2"
 	"github.com/Wifx/gonetworkmanager/v2"
@@ -98,3 +100,33 @@ func TestNetworkManagerBackend_HandleDeviceChange_UnmanagedRefreshesHotspotState
 	defer backend.stateMutex.RUnlock()
 	assert.False(t, backend.state.HotspotAvailable, "availability must be recomputed when the only AP-capable radio becomes unmanaged")
 }
+
+func TestNetworkManagerBackend_HandleWiFiChange_CoalescesAccessPointBurst(t *testing.T) {
+	mockNM := mock_gonetworkmanager.NewMockNetworkManager(t)
+	mockWiFi := mock_gonetworkmanager.NewMockDeviceWireless(t)
+
+	backend, err := NewNetworkManagerBackend(mockNM)
+	assert.NoError(t, err)
+	backend.settings = emptySettingsMock(t)
+	backend.wifiDevice = mockWiFi
+	backend.wifiDev = mockWiFi
+
+	var stateChangeCalls atomic.Int32
+	backend.onStateChange = func() {
+		stateChangeCalls.Add(1)
+	}
+
+	mockWiFi.EXPECT().GetAccessPoints().Return([]gonetworkmanager.AccessPoint{}, nil).Once()
+
+	changes := map[string]dbus.Variant{
+		"AccessPoints": dbus.MakeVariant([]dbus.ObjectPath{}),
+	}
+	for range 5 {
+		backend.handleWiFiChange(changes)
+	}
+	assert.Zero(t, stateChangeCalls.Load(), "the list must not be rebuilt per access point")
+
+	assert.Eventually(t, func() bool {
+		return stateChangeCalls.Load() == 1
+	}, 4*wifiNetworksUpdateDelay, 10*time.Millisecond)
+}