Implement iconic live previews/iconic thumbnail icons.

[ChangeLog][QWinThumbnailToolBar] Added pixmap properties
and change notifications for thumbnail icons and live
preview.

Task-number: QTBUG-36730
Change-Id: I31ad0ff347235bc7933c1c14dece359ec0c36b39
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>

5 files changed, 310 insertions, 12 deletions

diff --git a/src/winextras/qwinfunctions_p.cpp b/src/winextras/qwinfunctions_p.cpp
index 1bb0d32..452685f 100644
--- a/src/winextras/qwinfunctions_p.cpp
+++ b/src/winextras/qwinfunctions_p.cpp
@@ -66,6 +66,14 @@ void QtDwmApiDll::resolve()
             (DwmIsCompositionEnabled) GetProcAddress(dwmapi, "DwmIsCompositionEnabled");
         dwmEnableComposition =
             (DwmEnableComposition) GetProcAddress(dwmapi, "DwmEnableComposition");
+        if (QSysInfo::windowsVersion() >= QSysInfo::WV_WINDOWS7) {
+            dwmSetIconicThumbnail =
+                (DwmSetIconicThumbnail) GetProcAddress(dwmapi, "DwmSetIconicThumbnail");
+            dwmSetIconicLivePreviewBitmap =
+                (DwmSetIconicLivePreviewBitmap) GetProcAddress(dwmapi, "DwmSetIconicLivePreviewBitmap");
+            dwmInvalidateIconicBitmaps =
+                (DwmInvalidateIconicBitmaps) GetProcAddress(dwmapi, "DwmInvalidateIconicBitmaps");
+        }
     }
 }
 
diff --git a/src/winextras/qwinfunctions_p.h b/src/winextras/qwinfunctions_p.h
index 744eae9..0cbd0ec 100644
--- a/src/winextras/qwinfunctions_p.h
+++ b/src/winextras/qwinfunctions_p.h
@@ -99,11 +99,15 @@ struct QtDwmApiDll
     typedef HRESULT (STDAPICALLTYPE *DwmEnableBlurBehindWindow)(HWND, const qt_DWM_BLURBEHIND *);
     typedef HRESULT (STDAPICALLTYPE *DwmIsCompositionEnabled)(BOOL *);
     typedef HRESULT (STDAPICALLTYPE *DwmEnableComposition)(UINT);
+    typedef HRESULT (STDAPICALLTYPE *DwmSetIconicThumbnail)(HWND, HBITMAP, DWORD);
+    typedef HRESULT (STDAPICALLTYPE *DwmSetIconicLivePreviewBitmap)(HWND, HBITMAP, POINT *, DWORD);
+    typedef HRESULT (STDAPICALLTYPE *DwmInvalidateIconicBitmaps)(HWND);
 
     QtDwmApiDll()
         : dwmGetColorizationColor(0), dwmSetWindowAttribute(0), dwmGetWindowAttribute(0)
         , dwmExtendFrameIntoClientArea(0), dwmEnableBlurBehindWindow(0)
         , dwmIsCompositionEnabled(0), dwmEnableComposition(0)
+        , dwmSetIconicThumbnail(0), dwmSetIconicLivePreviewBitmap(0), dwmInvalidateIconicBitmaps(0)
     {}
 
     void init()
@@ -130,6 +134,9 @@ struct QtDwmApiDll
     DwmEnableBlurBehindWindow dwmEnableBlurBehindWindow;
     DwmIsCompositionEnabled dwmIsCompositionEnabled;
     DwmEnableComposition dwmEnableComposition;
+    DwmSetIconicThumbnail dwmSetIconicThumbnail;
+    DwmSetIconicLivePreviewBitmap dwmSetIconicLivePreviewBitmap;
+    DwmInvalidateIconicBitmaps dwmInvalidateIconicBitmaps;
 };
 
 struct QtShell32Dll
diff --git a/src/winextras/qwinthumbnailtoolbar.cpp b/src/winextras/qwinthumbnailtoolbar.cpp
index baa4d7c..2748b7a 100644
--- a/src/winextras/qwinthumbnailtoolbar.cpp
+++ b/src/winextras/qwinthumbnailtoolbar.cpp
@@ -45,6 +45,7 @@
 #include "qwinthumbnailtoolbutton.h"
 #include "qwinthumbnailtoolbutton_p.h"
 #include "windowsguidsdefs_p.h"
+#include "qwinfunctions.h"
 
 #include <QWindow>
 #include <QCoreApplication>
@@ -53,14 +54,25 @@
 
 #include "qwinevent.h"
 #include "qwinfunctions.h"
+#include "qwinfunctions_p.h"
 #include "qwineventfilter_p.h"
 
 #ifndef THBN_CLICKED
 #  define THBN_CLICKED 0x1800
 #endif
 
+#ifndef WM_DWMSENDICONICLIVEPREVIEWBITMAP
+#  define WM_DWMSENDICONICLIVEPREVIEWBITMAP 0x0326
+#endif
+
+#ifndef WM_DWMSENDICONICTHUMBNAIL
+#  define WM_DWMSENDICONICTHUMBNAIL 0x0323
+#endif
+
 QT_BEGIN_NAMESPACE
 
+enum { dWM_SIT_DISPLAYFRAME = 1 , dWMWA_FORCE_ICONIC_REPRESENTATION = 7, dWMWA_HAS_ICONIC_BITMAP = 10 };
+
 static const int windowsLimitedThumbbarSize = 7;
 
 /*!
@@ -117,7 +129,10 @@ void QWinThumbnailToolBar::setWindow(QWindow *window)
     if (d->window != window) {
         if (d->window) {
             d->window->removeEventFilter(d);
-            d->clearToolbar();
+            if (d->window->handle()) {
+                d->clearToolbar();
+                setIconicPixmapNotificationsEnabled(false);
+            }
         }
         d->window = window;
         if (d->window) {
@@ -209,6 +224,196 @@ int QWinThumbnailToolBar::count() const
     return d->buttonList.size();
 }
 
+void QWinThumbnailToolBarPrivate::updateIconicPixmapsEnabled(bool invalidate)
+{
+    Q_Q(QWinThumbnailToolBar);
+    qtDwmApiDll.init();
+    const HWND hwnd = handle();
+    if (!hwnd) {
+         qWarning() << Q_FUNC_INFO << "invoked with hwnd=0";
+         return;
+    }
+    if (!qtDwmApiDll.dwmInvalidateIconicBitmaps)
+        return;
+    const bool enabled = iconicThumbnail || iconicLivePreview;
+    q->setIconicPixmapNotificationsEnabled(enabled);
+    if (enabled && invalidate) {
+        const HRESULT hr = qtDwmApiDll.dwmInvalidateIconicBitmaps(hwnd);
+        if (FAILED(hr))
+            qWarning() << QWinThumbnailToolBarPrivate::msgComFailed("DwmInvalidateIconicBitmaps", hr);
+    }
+}
+
+/*
+    QWinThumbnailToolBarPrivate::IconicPixmapCache caches a HBITMAP of for one of
+    the iconic thumbnail or live preview pixmaps. When the messages
+    WM_DWMSENDICONICLIVEPREVIEWBITMAP or WM_DWMSENDICONICTHUMBNAIL are received
+    (after setting the DWM window attributes accordingly), the bitmap matching the
+    maximum size is constructed on demand.
+ */
+
+void QWinThumbnailToolBarPrivate::IconicPixmapCache::deleteBitmap()
+{
+    if (m_bitmap) {
+        DeleteObject(m_bitmap);
+        m_size = QSize();
+        m_bitmap = 0;
+    }
+}
+
+bool QWinThumbnailToolBarPrivate::IconicPixmapCache::setPixmap(const QPixmap &pixmap)
+{
+    if (pixmap.cacheKey() == m_pixmap.cacheKey())
+        return false;
+    deleteBitmap();
+    m_pixmap = pixmap;
+    return true;
+}
+
+HBITMAP QWinThumbnailToolBarPrivate::IconicPixmapCache::bitmap(const QSize &maxSize)
+{
+    if (m_pixmap.isNull())
+        return 0;
+    if (m_bitmap && m_size.width() <= maxSize.width() && m_size.height() <= maxSize.height())
+        return m_bitmap;
+    deleteBitmap();
+    QPixmap pixmap = m_pixmap;
+    if (pixmap.width() >= maxSize.width() || pixmap.height() >= maxSize.width())
+        pixmap = pixmap.scaled(maxSize, Qt::KeepAspectRatio, Qt::SmoothTransformation);
+    if (const HBITMAP bitmap = QtWin::toHBITMAP(pixmap, QtWin::HBitmapAlpha)) {
+        m_size = pixmap.size();
+        m_bitmap = bitmap;
+    }
+    return m_bitmap;
+}
+
+/*!
+    \fn  QWinThumbnailToolBar::iconicThumbnailPixmapRequested()
+
+    This signal is emitted when the operating system requests a new iconic thumbnail pixmap,
+    typically when the thumbnail is shown.
+
+    \since 5.4
+    \sa iconicThumbnailPixmap
+*/
+
+/*!
+    \fn QWinThumbnailToolBar::iconicLivePreviewPixmapRequested()
+
+    This signal is emitted when the operating system requests a new iconic live preview pixmap,
+    typically when the user ALT-tabs to the application.
+
+    \since 5.4
+    \sa iconicLivePreviewPixmap
+*/
+
+/*!
+    \property QWinThumbnailToolBar::iconicPixmapNotificationsEnabled
+    \brief whether signals iconicThumbnailPixmapRequested() and iconicLivePreviewPixmapRequested()
+     will be emitted
+
+    \since 5.4
+    \sa QWinThumbnailToolBar::iconicThumbnailPixmap, QWinThumbnailToolBar::iconicLivePreviewPixmap
+ */
+
+bool QWinThumbnailToolBar::iconicPixmapNotificationsEnabled() const
+{
+    Q_D(const QWinThumbnailToolBar);
+    const HWND hwnd = d->handle();
+    if (!hwnd || !qtDwmApiDll.dwmGetWindowAttribute)
+        return false;
+    qtDwmApiDll.init();
+    return qtDwmApiDll.dwmGetWindowAttribute && hwnd
+        && QtDwmApiDll::booleanWindowAttribute(hwnd, dWMWA_FORCE_ICONIC_REPRESENTATION);
+}
+
+void QWinThumbnailToolBar::setIconicPixmapNotificationsEnabled(bool enabled)
+{
+    Q_D(const QWinThumbnailToolBar);
+    const HWND hwnd = d->handle();
+    if (!hwnd) {
+        qWarning() << Q_FUNC_INFO << "invoked with hwnd=0";
+        return;
+    }
+    qtDwmApiDll.init();
+    if (!qtDwmApiDll.dwmSetWindowAttribute || iconicPixmapNotificationsEnabled() == enabled)
+        return;
+    QtDwmApiDll::setBooleanWindowAttribute(hwnd, dWMWA_FORCE_ICONIC_REPRESENTATION, enabled);
+    QtDwmApiDll::setBooleanWindowAttribute(hwnd, dWMWA_HAS_ICONIC_BITMAP, enabled);
+}
+
+/*!
+    \property QWinThumbnailToolBar::iconicThumbnailPixmap
+    \brief the pixmap for use as a thumbnail representation
+
+    \since 5.4
+    \sa QWinThumbnailToolBar::iconicPixmapNotificationsEnabled
+ */
+
+void QWinThumbnailToolBar::setIconicThumbnailPixmap(const QPixmap &pixmap)
+{
+    Q_D(QWinThumbnailToolBar);
+    const bool changed = d->iconicThumbnail.setPixmap(pixmap);
+    if (d->hasHandle()) // Potentially 0 when invoked from QML loading, see _q_updateToolbar()
+        d->updateIconicPixmapsEnabled(changed && !d->withinIconicThumbnailRequest);
+}
+
+QPixmap QWinThumbnailToolBar::iconicThumbnailPixmap() const
+{
+    Q_D(const QWinThumbnailToolBar);
+    return d->iconicThumbnail.pixmap();
+}
+
+/*!
+    \property QWinThumbnailToolBar::iconicLivePreviewPixmap
+    \brief the pixmap for use as a live (peek) preview when tabbing into the application
+
+    \since 5.4
+ */
+
+void QWinThumbnailToolBar::setIconicLivePreviewPixmap(const QPixmap &pixmap)
+{
+    Q_D(QWinThumbnailToolBar);
+    const bool changed = d->iconicLivePreview.setPixmap(pixmap);
+    if (d->hasHandle()) // Potentially 0 when invoked from QML loading, see _q_updateToolbar()
+        d->updateIconicPixmapsEnabled(changed && !d->withinIconicLivePreviewRequest);
+}
+
+QPixmap QWinThumbnailToolBar::iconicLivePreviewPixmap() const
+{
+    Q_D(const QWinThumbnailToolBar);
+    return d->iconicLivePreview.pixmap();
+}
+
+inline void QWinThumbnailToolBarPrivate::updateIconicThumbnail(const MSG *message)
+{
+    qtDwmApiDll.init();
+    if (!qtDwmApiDll.dwmSetIconicThumbnail || !iconicThumbnail)
+        return;
+    const QSize maxSize(HIWORD(message->lParam), LOWORD(message->lParam));
+    if (const HBITMAP bitmap = iconicThumbnail.bitmap(maxSize)) {
+        const HRESULT hr = qtDwmApiDll.dwmSetIconicThumbnail(message->hwnd, bitmap, dWM_SIT_DISPLAYFRAME);
+        if (FAILED(hr))
+            qWarning() << QWinThumbnailToolBarPrivate::msgComFailed("DwmSetIconicThumbnail", hr);
+    }
+}
+
+inline void QWinThumbnailToolBarPrivate::updateIconicLivePreview(const MSG *message)
+{
+    qtDwmApiDll.init();
+    if (!qtDwmApiDll.dwmSetIconicLivePreviewBitmap || !iconicLivePreview)
+        return;
+    RECT rect;
+    GetClientRect(message->hwnd, &rect);
+    const QSize maxSize(rect.right, rect.bottom);
+    POINT offset = {0, 0};
+    if (const HBITMAP bitmap = iconicLivePreview.bitmap(maxSize)) {
+        const HRESULT hr = qtDwmApiDll.dwmSetIconicLivePreviewBitmap(message->hwnd, bitmap, &offset, dWM_SIT_DISPLAYFRAME);
+        if (FAILED(hr))
+            qWarning() << QWinThumbnailToolBarPrivate::msgComFailed("DwmSetIconicLivePreviewBitmap", hr);
+    }
+}
+
 /*!
     Removes all buttons from the thumbnail toolbar.
  */
@@ -239,7 +444,8 @@ static inline ITaskbarList4 *createTaskbarList()
 }
 
 QWinThumbnailToolBarPrivate::QWinThumbnailToolBarPrivate() :
-    QObject(0), updateScheduled(false), window(0), pTbList(createTaskbarList()), q_ptr(0)
+    QObject(0), updateScheduled(false), window(0), pTbList(createTaskbarList()), q_ptr(0),
+    withinIconicThumbnailRequest(false), withinIconicLivePreviewRequest(false)
 {
     buttonList.reserve(windowsLimitedThumbbarSize);
     QCoreApplication::instance()->installNativeEventFilter(this);
@@ -252,6 +458,16 @@ QWinThumbnailToolBarPrivate::~QWinThumbnailToolBarPrivate()
     QCoreApplication::instance()->removeNativeEventFilter(this);
 }
 
+inline bool QWinThumbnailToolBarPrivate::hasHandle() const
+{
+    return window && window->handle();
+}
+
+inline HWND QWinThumbnailToolBarPrivate::handle() const
+{
+    return hasHandle() ? reinterpret_cast<HWND>(window->winId()) : HWND(0);
+}
+
 void QWinThumbnailToolBarPrivate::initToolbar()
 {
 #if !defined(_MSC_VER) || _MSC_VER >= 1600
@@ -259,7 +475,7 @@ void QWinThumbnailToolBarPrivate::initToolbar()
         return;
     THUMBBUTTON buttons[windowsLimitedThumbbarSize];
     initButtons(buttons);
-    HRESULT hresult = pTbList->ThumbBarAddButtons(reinterpret_cast<HWND>(window->winId()), windowsLimitedThumbbarSize, buttons);
+    HRESULT hresult = pTbList->ThumbBarAddButtons(handle(), windowsLimitedThumbbarSize, buttons);
     if (FAILED(hresult))
         qWarning() << msgComFailed("ThumbBarAddButtons", hresult);
 #else
@@ -274,7 +490,7 @@ void QWinThumbnailToolBarPrivate::clearToolbar()
         return;
     THUMBBUTTON buttons[windowsLimitedThumbbarSize];
     initButtons(buttons);
-    HRESULT hresult = pTbList->ThumbBarUpdateButtons(reinterpret_cast<HWND>(window->winId()), windowsLimitedThumbbarSize, buttons);
+    HRESULT hresult = pTbList->ThumbBarUpdateButtons(handle(), windowsLimitedThumbbarSize, buttons);
     if (FAILED(hresult))
         qWarning() << msgComFailed("ThumbBarUpdateButtons", hresult);
 }
@@ -301,9 +517,10 @@ void QWinThumbnailToolBarPrivate::_q_updateToolbar()
             buttons[i].szTip[button->toolTip().left(sizeof(buttons[i].szTip)/sizeof(buttons[i].szTip[0]) - 1).toWCharArray(buttons[i].szTip)] = 0;
         }
     }
-    HRESULT hresult = pTbList->ThumbBarUpdateButtons(reinterpret_cast<HWND>(window->winId()), windowsLimitedThumbbarSize, buttons);
+    HRESULT hresult = pTbList->ThumbBarUpdateButtons(handle(), windowsLimitedThumbbarSize, buttons);
     if (FAILED(hresult))
         qWarning() << msgComFailed("ThumbBarUpdateButtons", hresult);
+    updateIconicPixmapsEnabled(false);
     freeButtonResources(buttons);
 }
 
@@ -327,13 +544,30 @@ bool QWinThumbnailToolBarPrivate::eventFilter(QObject *object, QEvent *event)
 
 bool QWinThumbnailToolBarPrivate::nativeEventFilter(const QByteArray &, void *message, long *result)
 {
-    MSG *msg = static_cast<MSG *>(message);
-    if (window && msg->message == WM_COMMAND && HIWORD(msg->wParam) == THBN_CLICKED && msg->hwnd == reinterpret_cast<HWND>(window->winId())) {
-        int buttonId = LOWORD(msg->wParam);
-        buttonId = buttonId - (windowsLimitedThumbbarSize - qMin(windowsLimitedThumbbarSize, buttonList.size()));
-        buttonList.at(buttonId)->click();
-        if (result)
-            *result = 0;
+    const MSG *msg = static_cast<const MSG *>(message);
+    if (handle() != msg->hwnd)
+        return false;
+    switch (msg->message) {
+    case WM_COMMAND:
+        if (HIWORD(msg->wParam) == THBN_CLICKED) {
+            const int buttonId = LOWORD(msg->wParam) - (windowsLimitedThumbbarSize - qMin(windowsLimitedThumbbarSize, buttonList.size()));
+            buttonList.at(buttonId)->click();
+            if (result)
+                *result = 0;
+            return true;
+        }
+        break;
+    case WM_DWMSENDICONICTHUMBNAIL:
+        withinIconicThumbnailRequest = true;
+        emit q_func()->iconicThumbnailPixmapRequested();
+        withinIconicThumbnailRequest = false;
+        updateIconicThumbnail(msg);
+        return true;
+    case WM_DWMSENDICONICLIVEPREVIEWBITMAP:
+        withinIconicLivePreviewRequest = true;
+        emit q_func()->iconicLivePreviewPixmapRequested();
+        withinIconicLivePreviewRequest = false;
+        updateIconicLivePreview(msg);
         return true;
     }
     return false;
diff --git a/src/winextras/qwinthumbnailtoolbar.h b/src/winextras/qwinthumbnailtoolbar.h
index c048298..09dfc34 100644
--- a/src/winextras/qwinthumbnailtoolbar.h
+++ b/src/winextras/qwinthumbnailtoolbar.h
@@ -48,6 +48,7 @@
 
 QT_BEGIN_NAMESPACE
 
+class QPixmap;
 class QWindow;
 class QWinThumbnailToolButton;
 class QWinThumbnailToolBarPrivate;
@@ -57,6 +58,9 @@ class Q_WINEXTRAS_EXPORT QWinThumbnailToolBar : public QObject
     Q_OBJECT
     Q_PROPERTY(int count READ count STORED false)
     Q_PROPERTY(QWindow *window READ window WRITE setWindow)
+    Q_PROPERTY(bool iconicPixmapNotificationsEnabled READ iconicPixmapNotificationsEnabled WRITE setIconicPixmapNotificationsEnabled)
+    Q_PROPERTY(QPixmap iconicThumbnailPixmap READ iconicThumbnailPixmap WRITE setIconicThumbnailPixmap)
+    Q_PROPERTY(QPixmap iconicLivePreviewPixmap READ iconicLivePreviewPixmap WRITE setIconicLivePreviewPixmap)
 
 public:
     explicit QWinThumbnailToolBar(QObject *parent = 0);
@@ -71,8 +75,20 @@ public:
     QList<QWinThumbnailToolButton *> buttons() const;
     int count() const;
 
+    bool iconicPixmapNotificationsEnabled() const;
+    void setIconicPixmapNotificationsEnabled(bool enabled);
+
+    QPixmap iconicThumbnailPixmap() const;
+    QPixmap iconicLivePreviewPixmap() const;
+
 public Q_SLOTS:
     void clear();
+    void setIconicThumbnailPixmap(const QPixmap &);
+    void setIconicLivePreviewPixmap(const QPixmap &);
+
+Q_SIGNALS:
+    void iconicThumbnailPixmapRequested();
+    void iconicLivePreviewPixmapRequested();
 
 private:
     Q_DISABLE_COPY(QWinThumbnailToolBar)
diff --git a/src/winextras/qwinthumbnailtoolbar_p.h b/src/winextras/qwinthumbnailtoolbar_p.h
index b799d7c..b7d8eff 100644
--- a/src/winextras/qwinthumbnailtoolbar_p.h
+++ b/src/winextras/qwinthumbnailtoolbar_p.h
@@ -47,6 +47,7 @@
 #include <QtCore/QHash>
 #include <QtCore/QList>
 #include <QtGui/QIcon>
+#include <QtGui/QPixmap>
 #include <QtCore/QAbstractNativeEventFilter>
 
 #include "winshobjidl_p.h"
@@ -56,6 +57,27 @@ QT_BEGIN_NAMESPACE
 class QWinThumbnailToolBarPrivate : public QObject, QAbstractNativeEventFilter
 {
 public:
+    class IconicPixmapCache
+    {
+    public:
+        IconicPixmapCache() : m_bitmap(0) {}
+        ~IconicPixmapCache() { deleteBitmap(); }
+
+        operator bool() const { return !m_pixmap.isNull(); }
+
+        QPixmap pixmap() const { return m_pixmap; }
+        bool setPixmap(const QPixmap &p);
+
+        HBITMAP bitmap(const QSize &maxSize);
+
+    private:
+        void deleteBitmap();
+
+        QPixmap m_pixmap;
+        QSize m_size;
+        HBITMAP m_bitmap;
+    };
+
     QWinThumbnailToolBarPrivate();
     ~QWinThumbnailToolBarPrivate();
     void initToolbar();
@@ -77,9 +99,20 @@ public:
     QWindow *window;
     ITaskbarList4 * const pTbList;
 
+    IconicPixmapCache iconicThumbnail;
+    IconicPixmapCache iconicLivePreview;
+
 private:
+    bool hasHandle() const;
+    HWND handle() const;
+    void updateIconicPixmapsEnabled(bool invalidate);
+    void updateIconicThumbnail(const MSG *message);
+    void updateIconicLivePreview(const MSG *message);
+
     QWinThumbnailToolBar *q_ptr;
     Q_DECLARE_PUBLIC(QWinThumbnailToolBar)
+    bool withinIconicThumbnailRequest;
+    bool withinIconicLivePreviewRequest;
 };
 
 QT_END_NAMESPACE