qt: Port Windows taskbar progress to native Windows API

Replace QtWinExtras (removed in Qt6) with native Windows ITaskbarList3
COM API. This makes the Windows taskbar progress feature compatible
with both Qt5 and Qt6.

Changes:
- Replace QtWinExtras with direct ITaskbarList3 COM interface
- Create new WinTaskbarProgress class using Windows COM API
- Use consistent Q_OS_WIN macro for Windows platform detection
- Update CMakeLists.txt to link ole32 instead of Qt WinExtras

The new implementation maintains full feature parity with the Qt5
version while working with both Qt5 and Qt6 without requiring
QtWinExtras.

Author: kwsantiago

src/qt/CMakeLists.txt

@@ -257,6 +257,8 @@ add_library(bitcoinqt STATIC EXCLUDE_FROM_ALL
   utilitydialog.h
   $<$<PLATFORM_ID:Windows>:winshutdownmonitor.cpp>
   $<$<PLATFORM_ID:Windows>:winshutdownmonitor.h>
+  $<$<PLATFORM_ID:Windows>:wintaskbarprogress.cpp>
+  $<$<PLATFORM_ID:Windows>:wintaskbarprogress.h>
   bitcoin.qrc
   ${CMAKE_CURRENT_BINARY_DIR}/bitcoin_locale.qrc
   ${CMAKE_CURRENT_BINARY_DIR}/bitcoin_rendered.qrc
@@ -366,8 +368,8 @@ endif()
 if(WITH_TASKBAR_PROGRESS)
   target_link_libraries(bitcoinqt
     PRIVATE
-      "Qt${WITH_QT_VERSION}::WinExtras"
-      $<$<PLATFORM_ID:Windows>:dwmapi>
+      # Using native Windows API (ITaskbarList3), requires ole32 for COM
+      $<$<PLATFORM_ID:Windows>:ole32>
   )
 endif()
 

src/qt/bitcoingui.cpp

@@ -35,8 +35,7 @@
 #include <qt/macdockiconhandler.h>
 #endif
 #ifdef BITCOIN_QT_WIN_TASKBAR
-#include <QWinTaskbarButton>
-#include <QWinTaskbarProgress>
+#include <qt/wintaskbarprogress.h>
 #endif
 
 #include <chain.h>
@@ -232,7 +231,10 @@ BitcoinGUI::BitcoinGUI(interfaces::Node& node, const PlatformStyle *_platformSty
     m_app_nap_inhibitor = new CAppNapInhibitor;
 #endif
 #ifdef BITCOIN_QT_WIN_TASKBAR
-    m_taskbar_button = new QWinTaskbarButton(this);
+    m_taskbar_progress = new WinTaskbarProgress();
+    if (windowHandle()) {
+        m_taskbar_progress->setWindow(windowHandle());
+    }
 #endif
 
     GUIUtil::handleCloseWindowShortcut(this);
@@ -251,6 +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;
@@ -1235,11 +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_button->setWindow(windowHandle());
-    QWinTaskbarProgress* taskbar_progress = m_taskbar_button->progress();
-#endif
-
     // Set icon state: spinning if catching up, tick otherwise
     if (secs < MAX_BLOCK_TIME_GAP) {
         tooltip = tr("Up to date") + QString(".<br>") + tooltip;
@@ -1256,7 +1256,7 @@ void BitcoinGUI::setNumBlocks(int count, const QDateTime& blockDate, double nVer
         progressBarLabel->setVisible(false);
         progressBar->setVisible(false);
 #ifdef BITCOIN_QT_WIN_TASKBAR
-        taskbar_progress->setVisible(false);
+        m_taskbar_progress->setVisible(false);
 #endif
     }
     else
@@ -1273,8 +1273,8 @@ void BitcoinGUI::setNumBlocks(int count, const QDateTime& blockDate, double nVer
         progressBar->setValue(nVerificationProgress * 1000000000.0 + 0.5);
         progressBar->setVisible(true);
 #ifdef BITCOIN_QT_WIN_TASKBAR
-        taskbar_progress->setValue(qRound(nVerificationProgress * 100.0));
-        taskbar_progress->setVisible(true);
+        m_taskbar_progress->setValue(qRound(nVerificationProgress * 100.0));
+        m_taskbar_progress->setVisible(true);
 #endif
 
         tooltip = tr("Catching up…") + QString("<br>") + tooltip;
@@ -1445,6 +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/bitcoingui.h

@@ -55,9 +55,12 @@ class QComboBox;
 class QDateTime;
 class QProgressBar;
 class QProgressDialog;
-class QWinTaskbarButton;
 QT_END_NAMESPACE
 
+#ifdef BITCOIN_QT_WIN_TASKBAR
+class WinTaskbarProgress;
+#endif
+
 namespace GUIUtil {
 class ClickableLabel;
 class ClickableProgressBar;
@@ -180,7 +183,7 @@ class BitcoinGUI : public QMainWindow
     RPCConsole* rpcConsole = nullptr;
     HelpMessageDialog* helpMessageDialog = nullptr;
 #ifdef BITCOIN_QT_WIN_TASKBAR
-    QWinTaskbarButton* m_taskbar_button = nullptr;
+    WinTaskbarProgress* m_taskbar_progress = nullptr;
 #endif
     ModalOverlay* modalOverlay = nullptr;
     MempoolStats* mempoolStats = nullptr;

src/qt/wintaskbarprogress.cpp

@@ -0,0 +1,140 @@
+// 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 <QWindow>
+
+#include <windows.h>
+#include <shobjidl.h>
+
+WinTaskbarProgress::WinTaskbarProgress()
+{
+}
+
+WinTaskbarProgress::~WinTaskbarProgress()
+{
+    releaseTaskbar();
+}
+
+void WinTaskbarProgress::setWindow(QWindow* window)
+{
+    m_window = window;
+}
+
+void WinTaskbarProgress::initializeTaskbar()
+{
+    if (m_initialized || !m_window) {
+        return;
+    }
+
+    HWND winId = reinterpret_cast<HWND>(m_window->winId());
+    if (!winId) {
+        return;
+    }
+
+    HRESULT hr = CoCreateInstance(
+        CLSID_TaskbarList,
+        nullptr,
+        CLSCTX_INPROC_SERVER,
+        IID_ITaskbarList3,
+        reinterpret_cast<void**>(&m_taskbarList)
+    );
+
+    if (SUCCEEDED(hr) && m_taskbarList) {
+        hr = m_taskbarList->HrInit();
+        if (SUCCEEDED(hr)) {
+            m_initialized = true;
+        } else {
+            m_taskbarList->Release();
+            m_taskbarList = nullptr;
+        }
+    }
+}
+
+void WinTaskbarProgress::releaseTaskbar()
+{
+    if (m_taskbarList) {
+        // Clear progress state before releasing
+        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)
+{
+    // 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(winId, value, 100);
+}
+
+void WinTaskbarProgress::setVisible(bool visible)
+{
+    if (!m_initialized || !m_taskbarList || !m_window) {
+        return;
+    }
+
+    HWND winId = reinterpret_cast<HWND>(m_window->winId());
+    if (!winId) {
+        return;
+    }
+
+    if (visible && !m_visible) {
+        // Show normal progress
+        m_taskbarList->SetProgressState(winId, TBPF_NORMAL);
+        m_visible = true;
+    } else if (!visible && m_visible) {
+        // Hide progress
+        m_taskbarList->SetProgressState(winId, TBPF_NOPROGRESS);
+        m_visible = false;
+    }
+}
+
+void WinTaskbarProgress::reset()
+{
+    setVisible(false);
+}
+
+#endif // Q_OS_WIN

src/qt/wintaskbarprogress.h

@@ -0,0 +1,54 @@
+// 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 Q_OS_WIN
+#include <QWindow>
+
+#include <windows.h>
+
+// Forward declarations for COM interfaces
+struct ITaskbarList3;
+
+/**
+ * Native Windows taskbar progress indicator
+ * Uses ITaskbarList3 COM interface for Windows 7+ compatibility
+ * Works with both Qt5 and Qt6
+ */
+class WinTaskbarProgress
+{
+public:
+    WinTaskbarProgress();
+    ~WinTaskbarProgress();
+
+    /** Set the window handle to attach progress to */
+    void setWindow(QWindow* window);
+
+    /** Get the window handle */
+    QWindow* window() const { return m_window; }
+
+    /** Set progress value (0-100) */
+    void setValue(int value);
+
+    /** Show or hide the progress indicator */
+    void setVisible(bool visible);
+
+    /** Reset progress state */
+    void reset();
+
+private:
+    QWindow* m_window{nullptr};
+    ITaskbarList3* m_taskbarList{nullptr};
+    bool m_initialized{false};
+    bool m_visible{false};
+
+    void initializeTaskbar();
+    void releaseTaskbar();
+};
+
+#endif // Q_OS_WIN
+
+#endif // BITCOIN_QT_WINTASKBARPROGRESS_H