qt: Port Windows taskbar progress to Qt6

Replace QtWinExtras (removed in Qt6) with native Windows ITaskbarList3
COM API. The new WinTaskbarProgress class uses Windows ITaskbarList3
directly, maintaining full feature parity with the Qt5 implementation
while working with both Qt5 and Qt6.

Changes:
- Replace QtWinExtras with direct ITaskbarList3 COM interface
- Use consistent Q_OS_WIN macro for Windows platform detection
- Update copyright to Bitcoin Knots

Author: kwsantiago

src/qt/bitcoingui.cpp

@@ -232,6 +232,9 @@ BitcoinGUI::BitcoinGUI(interfaces::Node& node, const PlatformStyle *_platformSty
 #endif
 #ifdef BITCOIN_QT_WIN_TASKBAR
     m_taskbar_progress = new WinTaskbarProgress();
+    if (windowHandle()) {
+        m_taskbar_progress->setWindow(windowHandle());
+    }
 #endif
 
     GUIUtil::handleCloseWindowShortcut(this);
@@ -250,6 +253,9 @@ BitcoinGUI::~BitcoinGUI()
     delete m_app_nap_inhibitor;
     MacDockIconHandler::cleanup();
 #endif
+#ifdef BITCOIN_QT_WIN_TASKBAR
+    delete m_taskbar_progress;
+#endif
 
     delete NetWatch;
     delete rpcConsole;
@@ -1234,10 +1240,6 @@ void BitcoinGUI::setNumBlocks(int count, const QDateTime& blockDate, double nVer
 
     tooltip = tr("Processed %n block(s) of transaction history.", "", count);
 
-#ifdef BITCOIN_QT_WIN_TASKBAR
-    m_taskbar_progress->setWindow(this);
-#endif
-
     // Set icon state: spinning if catching up, tick otherwise
     if (secs < MAX_BLOCK_TIME_GAP) {
         tooltip = tr("Up to date") + QString(".<br>") + tooltip;
@@ -1443,6 +1445,13 @@ void BitcoinGUI::showEvent(QShowEvent *event)
     showMempoolStatsAction->setEnabled(true);
     aboutAction->setEnabled(true);
     optionsAction->setEnabled(true);
+
+#ifdef BITCOIN_QT_WIN_TASKBAR
+    // If window handle wasn't available during construction, set it now
+    if (m_taskbar_progress && !m_taskbar_progress->window() && windowHandle()) {
+        m_taskbar_progress->setWindow(windowHandle());
+    }
+#endif
 }
 
 #ifdef ENABLE_WALLET

src/qt/wintaskbarprogress.cpp

@@ -1,48 +1,41 @@
-// Copyright (c) 2025 The Bitcoin Core developers
+// Copyright (c) 2025 The Bitcoin Knots developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <qt/wintaskbarprogress.h>
 
 #if defined(Q_OS_WIN)
 
-#include <QWidget>
 #include <QWindow>
 
 #include <windows.h>
 #include <shobjidl.h>
 
 WinTaskbarProgress::WinTaskbarProgress()
 {
-    // COM will be initialized by Qt or the application
 }
 
 WinTaskbarProgress::~WinTaskbarProgress()
 {
     releaseTaskbar();
 }
 
-void WinTaskbarProgress::setWindow(QWidget* window)
+void WinTaskbarProgress::setWindow(QWindow* window)
 {
-    if (!window) {
-        return;
-    }
-
-    // Get the native window handle
-    QWindow* qwindow = window->windowHandle();
-    if (qwindow) {
-        m_winId = reinterpret_cast<HWND>(qwindow->winId());
-        initializeTaskbar();
-    }
+    m_window = window;
 }
 
 void WinTaskbarProgress::initializeTaskbar()
 {
-    if (m_initialized || !m_winId) {
+    if (m_initialized || !m_window) {
+        return;
+    }
+
+    HWND winId = reinterpret_cast<HWND>(m_window->winId());
+    if (!winId) {
         return;
     }
 
-    // Create ITaskbarList3 instance
     HRESULT hr = CoCreateInstance(
         CLSID_TaskbarList,
         nullptr,
@@ -66,41 +59,76 @@ void WinTaskbarProgress::releaseTaskbar()
 {
     if (m_taskbarList) {
         // Clear progress state before releasing
-        if (m_winId) {
-            m_taskbarList->SetProgressState(m_winId, TBPF_NOPROGRESS);
+        if (m_window) {
+            HWND winId = reinterpret_cast<HWND>(m_window->winId());
+            if (winId) {
+                m_taskbarList->SetProgressState(winId, TBPF_NOPROGRESS);
+            }
         }
         m_taskbarList->Release();
         m_taskbarList = nullptr;
     }
     m_initialized = false;
+    m_visible = false;
 }
 
 void WinTaskbarProgress::setValue(int value)
 {
-    if (!m_initialized || !m_taskbarList || !m_winId) {
+    // Lazy initialization on first use
+    if (!m_initialized) {
+        initializeTaskbar();
+    }
+
+    if (!m_initialized || !m_taskbarList || !m_window) {
+        return;
+    }
+
+    HWND winId = reinterpret_cast<HWND>(m_window->winId());
+    if (!winId) {
         return;
     }
 
     // Clamp value to 0-100
     if (value < 0) value = 0;
     if (value > 100) value = 100;
 
+    // Use indeterminate mode for very low progress (< 1%) to show activity
+    // Otherwise progress of 0 is invisible on the taskbar
+    if (value < 1) {
+        m_taskbarList->SetProgressState(winId, TBPF_INDETERMINATE);
+        m_visible = true;
+        return;
+    }
+
+    // Switch to normal mode if not already visible
+    if (!m_visible) {
+        m_taskbarList->SetProgressState(winId, TBPF_NORMAL);
+        m_visible = true;
+    }
+
     // Set progress value (current, maximum)
-    m_taskbarList->SetProgressValue(m_winId, value, 100);
+    m_taskbarList->SetProgressValue(winId, value, 100);
 }
 
 void WinTaskbarProgress::setVisible(bool visible)
 {
-    if (!m_initialized || !m_taskbarList || !m_winId) {
+    if (!m_initialized || !m_taskbarList || !m_window) {
+        return;
+    }
+
+    HWND winId = reinterpret_cast<HWND>(m_window->winId());
+    if (!winId) {
         return;
     }
 
-    if (visible) {
+    if (visible && !m_visible) {
         // Show normal progress
-        m_taskbarList->SetProgressState(m_winId, TBPF_NORMAL);
-    } else {
+        m_taskbarList->SetProgressState(winId, TBPF_NORMAL);
+        m_visible = true;
+    } else if (!visible && m_visible) {
         // Hide progress
-        m_taskbarList->SetProgressState(m_winId, TBPF_NOPROGRESS);
+        m_taskbarList->SetProgressState(winId, TBPF_NOPROGRESS);
+        m_visible = false;
     }
 }
 

src/qt/wintaskbarprogress.h

@@ -1,12 +1,14 @@
-// Copyright (c) 2025 The Bitcoin Core developers
+// Copyright (c) 2025 The Bitcoin Knots developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #ifndef BITCOIN_QT_WINTASKBARPROGRESS_H
 #define BITCOIN_QT_WINTASKBARPROGRESS_H
 
-#ifdef WIN32
-#include <QWidget>
+#ifdef Q_OS_WIN
+#include <QWindow>
+
+#include <windows.h>
 
 // Forward declarations for COM interfaces
 struct ITaskbarList3;
@@ -23,7 +25,10 @@ class WinTaskbarProgress
     ~WinTaskbarProgress();
 
     /** Set the window handle to attach progress to */
-    void setWindow(QWidget* window);
+    void setWindow(QWindow* window);
+
+    /** Get the window handle */
+    QWindow* window() const { return m_window; }
 
     /** Set progress value (0-100) */
     void setValue(int value);
@@ -35,14 +40,15 @@ class WinTaskbarProgress
     void reset();
 
 private:
+    QWindow* m_window{nullptr};
     ITaskbarList3* m_taskbarList{nullptr};
-    HWND m_winId{nullptr};
     bool m_initialized{false};
+    bool m_visible{false};
 
     void initializeTaskbar();
     void releaseTaskbar();
 };
 
-#endif // WIN32
+#endif // Q_OS_WIN
 
 #endif // BITCOIN_QT_WINTASKBARPROGRESS_H