[Taskbar Fluent Media Player] Windows Security Update (presumably) prevents tray widget from initializing

[helios-kc]

modlogs.txt

Mod author: @Salyts
Mod: Taskbar Fluent Media Player

New Windows Security Update (KB5129195) (26200.9457) broke mod from initializing. Logs show it initializing and then exiting. Widget will not appear in the tray or taskbar. Restarting explorer seems to have no effect. Could be an issue / conflict with Taskbar Styler that also seemed to have some conflicts with the new security update.

[helios-kc]

More info: Seems to appear and work fine with fluent media player set to the taskbar overlay or inlay, but will not appear in the system tray in any position. (Works if the position is in or on the taskbar, but not if placed in the tray)

[Kendosiy]

+1. Changing the widget position using the tray block fails completely, while selecting the taskbar position causes it to blink briefly and disappear.

[nolan0612]

Found the root cause and a working fix (tested on Windows 11 26200.9550, Windhawk 1.7.3, mod 1.6.0).

Disclosure: this investigation and patch were written by Claude Opus 5.5 (Anthropic's AI model), working on behalf of the user posting this comment, who tested it on their machine.

Root cause

In these builds, SystemTrayFrameGrid is no longer a Grid — it's now a StackPanel. All tray elements (NotifyIconStack, NotificationAreaIcons, ControlCenterButton, NotificationCenterButton, ShowDesktopStack, …) are its direct children, and they all have Grid.Column = 0. Dump of the new tray:

[SystemTray.SystemTrayFrame]
  [StackPanel] name='SystemTrayFrameGrid'
    [SystemTray.Stack] name='NotifyIconStack'
    [SystemTray.NotificationAreaIcons] name='NotificationAreaIcons'
    [SystemTray.Stack] name='MainStack'
    [SystemTray.Stack] name='NonActivatableStack'
    [SystemTray.Stack] name='SecondaryClockStack'
    [SystemTray.OmniButton] name='ControlCenterButton'
    [SystemTray.OmniButton] name='NotificationCenterButton'
    [SystemTray.Stack] name='ShowDesktopStack'

ResolveInjectionTarget() does trayFrame.try_as<Grid>(), which now returns null, so every tray_* position silently returns an empty target and nothing gets injected. That's why there's no error in the logs. Symbols and the TaskbarHost::FrameHeight pattern still resolve fine.

There's a second, smaller issue: on explorer startup, the injection can run before the target taskbar exists (secondary monitors) or before the tray is rebuilt, so the player gets lost. That may be related to the "blinks and disappears" report above.

Fix

1. If SystemTrayFrameGrid is a StackPanel, resolve the position to a child index (same anchors as before: before/after NotificationCenterButton, ControlCenterButton, NotifyIconStack, …) and use Children().InsertAt(index, playerGrid). Visibility then goes through the existing g_playerColumn == -1 path.
2. RemovePlayerGridChildren / RemoveAnchorDebugOverlays take a Panel so cleanup works for both layouts, and the column cleanup in RemovePlayerGrid is guarded by targetGrid.
3. A lightweight watchdog in TimerThreadProc (every ~2s): if the taskbar for the configured monitor changed, or the player is no longer attached to the live taskbar tree, it re-injects. Verified: after explorer.exe restarts, the player comes back on the configured monitor within a few seconds.

The old Grid path is unchanged, so older builds keep working.

Patch against 1.6.0 (click to expand)

--- a/mods/taskbar-fluent-media-player.wh.cpp
+++ b/mods/taskbar-fluent-media-player.wh.cpp
@@ -4303,6 +4303,8 @@
 static void RemovePlayerGrid();
 static bool InjectPlayerGrid();
 static std::atomic<bool> g_themeChangePending{false};
+static void ApplySettings();
+static bool IsPlayerInjected();
 static DWORD WINAPI TimerThreadProc(void*) {
     static bool lastThemeWasLight = IsSystemLightTheme();
     HKEY hKey = nullptr;
@@ -4345,6 +4347,33 @@
                 }, nullptr);
             }
         }
+        // Watchdog: the configured taskbar may appear after startup (secondary
+        // monitors), and newer builds rebuild the tray after injection,
+        // dropping the player. Re-check every ~2 seconds.
+        static ULONGLONG lastWatchdog = 0;
+        if (GetTickCount64() - lastWatchdog >= 2000) {
+            lastWatchdog = GetTickCount64();
+            HWND desired = FindCurrentProcessTaskbarWnd();
+            if (desired && desired != hWnd) {
+                Wh_Log(L"Watchdog: taskbar for configured monitor changed, moving player");
+                RunFromWindowThread(hWnd, [](void*) {
+                    if (!g_unloading && !g_applyingSettings) RemovePlayerGrid();
+                }, nullptr);
+                g_taskbarWnd = desired;
+                hWnd = desired;
+            }
+            RunFromWindowThread(hWnd, [](void*) {
+                if (g_unloading || g_applyingSettings) return;
+                if (!IsPlayerInjected()) {
+                    Wh_Log(L"Watchdog: player missing from taskbar, re-injecting");
+                    ApplySettings();
+                    if (g_playerGrid) {
+                        RefreshPlayerContents();
+                        UpdateVisibility();
+                    }
+                }
+            }, nullptr);
+        }
         bool needsUpdate = g_needsUiUpdate.exchange(false);
         if (g_settings.idleHideSeconds > 0) {
             bool playing = false;
@@ -8440,8 +8469,12 @@
 struct InjectionTarget {
     Grid grid;
     int  insertCol = 0;
+    // Newer Windows builds (26200.9457+) turned SystemTrayFrameGrid into a
+    // StackPanel; in that case the player is inserted by child index.
+    StackPanel panel{nullptr};
+    int  insertIndex = 0;
 };
-static int RemovePlayerGridChildren(Grid const& targetGrid) {
+static int RemovePlayerGridChildren(Panel const& targetGrid) {
     if (!targetGrid) return -1;
     int firstCol = -1;
     for (int i = (int)targetGrid.Children().Size() - 1; i >= 0; --i) {
@@ -8453,7 +8486,7 @@
     }
     return firstCol;
 }
-static void RemoveAnchorDebugOverlays(Grid const& targetGrid) {
+static void RemoveAnchorDebugOverlays(Panel const& targetGrid) {
     if (!targetGrid) return;
     for (int i = (int)targetGrid.Children().Size() - 1; i >= 0; --i) {
         auto fe = targetGrid.Children().GetAt(i).try_as<FrameworkElement>();
@@ -8640,11 +8673,71 @@
         return 0.0;
     }
 }
+// Index of the direct child of `panel` that is (or contains) the element named
+// `name`, or -1.
+static int FindPanelChildIndexByName(StackPanel const& panel, const wchar_t* name) {
+    auto elem = FindChildByName(panel, name);
+    if (!elem) return -1;
+    DependencyObject cur = elem;
+    while (cur) {
+        auto parent = VisualTreeHelper::GetParent(cur);
+        if (!parent) return -1;
+        if (parent == panel) {
+            uint32_t index = 0;
+            if (auto ui = cur.try_as<UIElement>(); ui && panel.Children().IndexOf(ui, index))
+                return (int)index;
+            return -1;
+        }
+        cur = parent;
+    }
+    return -1;
+}
+static InjectionTarget ResolveTrayStackPanelTarget(StackPanel const& panel,
+                                                   std::wstring_view position) {
+    const int size = (int)panel.Children().Size();
+    auto before = [&](const wchar_t* name) { return FindPanelChildIndexByName(panel, name); };
+    auto after = [&](const wchar_t* name) {
+        int i = FindPanelChildIndexByName(panel, name);
+        return i >= 0 ? i + 1 : -1;
+    };
+    int index = -1;
+    if      (position == L"tray_right")                   index = size;
+    else if (position == L"tray_left")                    index = 0;
+    else if (position == L"tray_before_clock")            index = before(L"NotificationCenterButton");
+    else if (position == L"tray_after_clock")             index = before(L"ShowDesktopStack");
+    else if (position == L"tray_before_omni_left")        index = before(L"ControlCenterButton");
+    else if (position == L"tray_before_omni_right")       index = after(L"ControlCenterButton");
+    else if (position == L"tray_language_left")           index = before(L"NonActivatableStack");
+    else if (position == L"tray_language_right")          index = after(L"NonActivatableStack");
+    else if (position == L"tray_hidden_icons_left")       index = before(L"NotifyIconStack");
+    else if (position == L"tray_hidden_icons_right")      index = after(L"NotifyIconStack");
+    else if (position == L"tray_icons_left")              index = before(L"NotificationAreaIcons");
+    else if (position == L"tray_icons_right")             index = after(L"NotificationAreaIcons");
+    else if (position == L"tray_after_showdesktop_left")  index = before(L"ShowDesktopStack");
+    else if (position == L"tray_after_showdesktop_right") {
+        index = after(L"ShowDesktopStack");
+        if (index < 0) index = size;
+    }
+    else return {};
+    if (index < 0) {
+        Wh_Log(L"ResolveTrayStackPanelTarget: anchor for '%.*s' not found, appending",
+               (int)position.size(), position.data());
+        index = size;
+    }
+    InjectionTarget target;
+    target.panel = panel;
+    target.insertIndex = std::min(index, size);
+    return target;
+}
 static InjectionTarget ResolveInjectionTarget(
     FrameworkElement const& root,
     std::wstring_view position)
 {
     auto trayFrame = FindChildByName(root, L"SystemTrayFrameGrid");
+    if (auto trayPanel = trayFrame ? trayFrame.try_as<StackPanel>() : nullptr) {
+        auto target = ResolveTrayStackPanelTarget(trayPanel, position);
+        if (target.panel) return target;
+    }
     if (auto trayGrid = trayFrame ? trayFrame.try_as<Grid>() : nullptr) {
         int col = -1;
         if      (position == L"tray_right")
@@ -8762,8 +8855,45 @@
                 }
             }
         }
-        auto [targetGrid, insertCol] = ResolveInjectionTarget(root, g_settings.position);
+        auto target = ResolveInjectionTarget(root, g_settings.position);
+        if (auto trayPanel = target.panel) {
+            Grid playerGrid = BuildPlayerGrid();
+            if (!playerGrid) return false;
+            RemovePlayerGridChildren(trayPanel);
+            RemoveAnchorDebugOverlays(trayPanel);
+            playerGrid.Margin({(double)g_settings.playerMarginLeft, 0,
+                               (double)g_settings.playerMarginRight, 0});
+            playerGrid.VerticalAlignment(VerticalAlignment::Center);
+            int index = std::min(target.insertIndex, (int)trayPanel.Children().Size());
+            Wh_Log(L"InjectPlayerGrid: tray StackPanel, inserting at %d of %u",
+                   index, trayPanel.Children().Size());
+            trayPanel.Children().InsertAt((uint32_t)index, playerGrid);
+            g_playerColumn = -1;
+            g_playerGrid      = playerGrid;
+            g_injectionParent = trayPanel;
+            RefreshPlayerContents();
+            g_playerGrid.Visibility(Visibility::Visible);
+            g_playerGrid.UpdateLayout();
+            trayPanel.UpdateLayout();
+            if (auto dispatcher = g_playerGrid.Dispatcher()) {
+                try {
+                    dispatcher.RunAsync(winrt::Windows::UI::Core::CoreDispatcherPriority::Low, [=]() {
+                        if (!g_unloading && g_playerGrid) RefreshThemeColors();
+                    });
+                } catch (...) {
+                    Wh_Log(L"InjectPlayerGrid: Failed to dispatch RefreshThemeColors");
+                }
+            }
+            OnSessionsChanged();
+            g_needsUiUpdate = true;
+            if (g_timerUpdateEvent) SetEvent(g_timerUpdateEvent);
+            return true;
+        }
+        Grid targetGrid = target.grid;
+        int insertCol = target.insertCol;
         if (!targetGrid) {
+            Wh_Log(L"InjectPlayerGrid: no injection target for position '%ls'",
+                   g_settings.position.c_str());
             if (g_settings.enableTreeDump) {
                 DumpXamlTree(root, 0, 8);
             }
@@ -9038,9 +9168,10 @@
         g_hasTrackedElementOriginalMargin = false;
         g_trackPosition = L"";
         auto targetGrid = g_injectionParent.try_as<Grid>();
+        auto targetPanel = g_injectionParent.try_as<Panel>();
         int playerCol = -1;
-        RemoveAnchorDebugOverlays(targetGrid);
-        playerCol = RemovePlayerGridChildren(targetGrid);
+        RemoveAnchorDebugOverlays(targetPanel);
+        playerCol = RemovePlayerGridChildren(targetPanel);
         bool isTrackingPosition = (g_settings.position == L"taskbar_left_edge" ||
                                 g_settings.position == L"taskbar_center_edge" ||
                                 g_settings.position == L"taskbar_right_edge" ||
@@ -9052,7 +9183,7 @@
                                 g_settings.position == L"taskbar_after_taskview_right" ||
                                 g_settings.position == L"taskbar_after_widgets_left" ||
                                 g_settings.position == L"taskbar_after_widgets_right");
-        if (!isTrackingPosition && playerCol >= 0 && playerCol < (int)targetGrid.ColumnDefinitions().Size()) {
+        if (!isTrackingPosition && targetGrid && playerCol >= 0 && playerCol < (int)targetGrid.ColumnDefinitions().Size()) {
             for (uint32_t i = 0; i < targetGrid.Children().Size(); ++i) {
                 auto child = targetGrid.Children().GetAt(i).try_as<FrameworkElement>();
                 if (child) {
@@ -10043,6 +10174,25 @@
         try { InjectPlayerGrid(); } catch (...) { Wh_Log(L"ApplySettings: Exception in InjectPlayerGrid"); }
     }
 }
+// True when the player grid is still attached to the live taskbar tree.
+static bool IsPlayerInjected() {
+    try {
+        if (!g_playerGrid || !g_injectionParent || !g_taskbarWnd) return false;
+        if (!VisualTreeHelper::GetParent(g_playerGrid)) return false;
+        auto xamlRoot = GetTaskbarXamlRoot(g_taskbarWnd);
+        if (!xamlRoot) return true;  // Can't tell; don't thrash.
+        auto root = xamlRoot.Content().try_as<FrameworkElement>();
+        if (!root) return true;
+        DependencyObject cur = g_playerGrid;
+        while (cur) {
+            if (cur == root) return true;
+            cur = VisualTreeHelper::GetParent(cur);
+        }
+        return false;
+    } catch (...) {
+        return false;
+    }
+}
 static void ApplySettingsWithRetry(FrameworkElement xamlRootContent, int retryCount = 0) {
     static constexpr int kMaxRetries = 50;
     auto retry = [&]() {