Add "Zoom" setting to the Help font settings

If the scrollWheelZooming is enabled, this
setting will get updated when using scroll wheel.
It will also be used when zooming in/out
by using keyboard shortcuts.

Fixes: QTCREATORBUG-25109
Fixes: QTCREATORBUG-25230
Fixes: QTCREATORBUG-23731
Change-Id: I9d22632b4c034ce236fa39dba074df4a2746ff84
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

20 files changed, 188 insertions, 230 deletions

diff --git a/src/plugins/help/generalsettingspage.cpp b/src/plugins/help/generalsettingspage.cpp
index 9d17efcee69..f42f6ac3164 100644
--- a/src/plugins/help/generalsettingspage.cpp
+++ b/src/plugins/help/generalsettingspage.cpp
@@ -70,6 +70,8 @@ QWidget *GeneralSettingsPage::widget()
         m_ui->styleComboBox->setEditable(false);
 
         m_font = LocalHelpManager::fallbackFont();
+        m_fontZoom = LocalHelpManager::fontZoom();
+        m_ui->zoomSpinBox->setValue(m_fontZoom);
 
         updateFontSizeSelector();
         updateFontStyleSelector();
@@ -92,6 +94,9 @@ QWidget *GeneralSettingsPage::widget()
         connect(m_ui->sizeComboBox, QOverload<int>::of(&QComboBox::currentIndexChanged),
                 this, &GeneralSettingsPage::updateFont);
 
+        connect(m_ui->zoomSpinBox, QOverload<int>::of(&QSpinBox::valueChanged),
+                this, [this](int value) { m_fontZoom = value; });
+
         m_homePage = LocalHelpManager::homePage();
         m_ui->homePageLineEdit->setText(m_homePage);
 
@@ -150,10 +155,11 @@ void GeneralSettingsPage::apply()
     if (!m_ui) // page was never shown
         return;
 
-    if (m_font != LocalHelpManager::fallbackFont()) {
+    if (m_font != LocalHelpManager::fallbackFont())
         LocalHelpManager::setFallbackFont(m_font);
-        emit fontChanged();
-    }
+
+    if (m_fontZoom != LocalHelpManager::fontZoom())
+        LocalHelpManager::setFontZoom(m_fontZoom);
 
     QString homePage = QUrl::fromUserInput(m_ui->homePageLineEdit->text()).toString();
     if (homePage.isEmpty())
diff --git a/src/plugins/help/generalsettingspage.h b/src/plugins/help/generalsettingspage.h
index b72168ec1c2..0c1353f267f 100644
--- a/src/plugins/help/generalsettingspage.h
+++ b/src/plugins/help/generalsettingspage.h
@@ -44,9 +44,6 @@ public:
     void apply() override;
     void finish() override;
 
-signals:
-    void fontChanged();
-
 private:
     void setCurrentPage();
     void setBlankPage();
@@ -61,6 +58,7 @@ private:
     int closestPointSizeIndex(int desiredPointSize) const;
 
     QFont m_font;
+    int m_fontZoom = 100;
     QFontDatabase m_fontDatabase;
 
     QString m_homePage;
diff --git a/src/plugins/help/generalsettingspage.ui b/src/plugins/help/generalsettingspage.ui
index 3738ccf7949..90936861cdb 100644
--- a/src/plugins/help/generalsettingspage.ui
+++ b/src/plugins/help/generalsettingspage.ui
@@ -6,8 +6,8 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>695</width>
-    <height>472</height>
+    <width>706</width>
+    <height>594</height>
    </rect>
   </property>
   <property name="windowTitle">
@@ -19,23 +19,23 @@
      <property name="title">
       <string>Font</string>
      </property>
-     <layout class="QVBoxLayout" name="verticalLayout_5">
-      <item>
+     <layout class="QGridLayout" name="gridLayout">
+      <item row="0" column="0">
+       <widget class="QLabel" name="familyLabel">
+        <property name="sizePolicy">
+         <sizepolicy hsizetype="Fixed" vsizetype="Fixed">
+          <horstretch>0</horstretch>
+          <verstretch>0</verstretch>
+         </sizepolicy>
+        </property>
+        <property name="text">
+         <string>Family:</string>
+        </property>
+       </widget>
+      </item>
+      <item row="0" column="1">
        <layout class="QHBoxLayout" name="horizontalLayout_2">
         <item>
-         <widget class="QLabel" name="familyLabel">
-          <property name="sizePolicy">
-           <sizepolicy hsizetype="Fixed" vsizetype="Fixed">
-            <horstretch>0</horstretch>
-            <verstretch>0</verstretch>
-           </sizepolicy>
-          </property>
-          <property name="text">
-           <string>Family:</string>
-          </property>
-         </widget>
-        </item>
-        <item>
          <widget class="QFontComboBox" name="familyComboBox"/>
         </item>
         <item>
@@ -123,7 +123,7 @@
           </property>
           <property name="sizeHint" stdset="0">
            <size>
-            <width>0</width>
+            <width>13</width>
             <height>20</height>
            </size>
           </property>
@@ -131,16 +131,65 @@
         </item>
        </layout>
       </item>
-      <item>
+      <item row="1" column="0" colspan="2">
        <widget class="QLabel" name="label">
         <property name="text">
-         <string>Note: This setting takes effect only if the HTML file does not use a style sheet.</string>
+         <string>Note: The above setting takes effect only if the HTML file does not use a style sheet.</string>
         </property>
         <property name="wordWrap">
          <bool>true</bool>
         </property>
        </widget>
       </item>
+      <item row="2" column="0">
+       <widget class="QLabel" name="zoomLabel">
+        <property name="sizePolicy">
+         <sizepolicy hsizetype="Fixed" vsizetype="Fixed">
+          <horstretch>0</horstretch>
+          <verstretch>0</verstretch>
+         </sizepolicy>
+        </property>
+        <property name="text">
+         <string>Zoom:</string>
+        </property>
+       </widget>
+      </item>
+      <item row="2" column="1">
+       <layout class="QHBoxLayout" name="horizontalLayout_3">
+        <item>
+         <widget class="QSpinBox" name="zoomSpinBox">
+          <property name="suffix">
+           <string>%</string>
+          </property>
+          <property name="minimum">
+           <number>10</number>
+          </property>
+          <property name="maximum">
+           <number>3000</number>
+          </property>
+          <property name="singleStep">
+           <number>10</number>
+          </property>
+          <property name="value">
+           <number>100</number>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <spacer name="spacer3_2">
+          <property name="orientation">
+           <enum>Qt::Horizontal</enum>
+          </property>
+          <property name="sizeHint" stdset="0">
+           <size>
+            <width>13</width>
+            <height>20</height>
+           </size>
+          </property>
+         </spacer>
+        </item>
+       </layout>
+      </item>
      </layout>
     </widget>
    </item>
diff --git a/src/plugins/help/helpplugin.cpp b/src/plugins/help/helpplugin.cpp
index 4e00c8b7890..00a1b28e5a1 100644
--- a/src/plugins/help/helpplugin.cpp
+++ b/src/plugins/help/helpplugin.cpp
@@ -412,7 +412,7 @@ HelpViewer *HelpPluginPrivate::externalHelpViewer()
     return m_externalWindow->currentViewer();
 }
 
-HelpViewer *HelpPlugin::createHelpViewer(qreal zoom)
+HelpViewer *HelpPlugin::createHelpViewer()
 {
     const HelpViewerFactory factory = LocalHelpManager::viewerBackend();
     QTC_ASSERT(factory.create, return nullptr);
@@ -424,7 +424,10 @@ HelpViewer *HelpPlugin::createHelpViewer(qreal zoom)
             viewer, &HelpViewer::setViewerFont);
 
     // initialize zoom
-    viewer->setScale(zoom);
+    viewer->setFontZoom(LocalHelpManager::fontZoom());
+    connect(LocalHelpManager::instance(), &LocalHelpManager::fontZoomChanged,
+            viewer, &HelpViewer::setFontZoom);
+
     viewer->setScrollWheelZoomingEnabled(LocalHelpManager::isScrollWheelZoomingEnabled());
     connect(LocalHelpManager::instance(), &LocalHelpManager::scrollWheelZoomingEnabledChanged,
             viewer, &HelpViewer::setScrollWheelZoomingEnabled);
diff --git a/src/plugins/help/helpplugin.h b/src/plugins/help/helpplugin.h
index c00cfd42e26..111ddb6b942 100644
--- a/src/plugins/help/helpplugin.h
+++ b/src/plugins/help/helpplugin.h
@@ -48,7 +48,7 @@ public:
     ~HelpPlugin() final;
 
     static void showHelpUrl(const QUrl &url, Core::HelpManager::HelpViewerLocation location);
-    static HelpViewer *createHelpViewer(qreal zoom);
+    static HelpViewer *createHelpViewer();
     static HelpWidget *modeHelpWidget();
 
 private:
diff --git a/src/plugins/help/helpviewer.cpp b/src/plugins/help/helpviewer.cpp
index e4eeffd5cda..806c73ab252 100644
--- a/src/plugins/help/helpviewer.cpp
+++ b/src/plugins/help/helpviewer.cpp
@@ -29,6 +29,7 @@
 
 #include <coreplugin/icore.h>
 
+#include <utils/fadingindicator.h>
 #include <utils/fileutils.h>
 #include <utils/temporarydirectory.h>
 
@@ -91,6 +92,11 @@ HelpViewer::~HelpViewer()
     restoreOverrideCursor();
 }
 
+void HelpViewer::setFontZoom(int percentage)
+{
+    setScale(percentage / 100.0);
+}
+
 void HelpViewer::setScrollWheelZoomingEnabled(bool enabled)
 {
     m_scrollWheelZoomingEnabled = enabled;
@@ -172,14 +178,45 @@ void HelpViewer::home()
     setSource(LocalHelpManager::homePage());
 }
 
+void HelpViewer::scaleUp()
+{
+    incrementZoom(1);
+}
+
+void HelpViewer::scaleDown()
+{
+    incrementZoom(-1);
+}
+
+void HelpViewer::resetScale()
+{
+    applyZoom(100);
+}
+
 void HelpViewer::wheelEvent(QWheelEvent *event)
 {
     if (m_scrollWheelZoomingEnabled && event->modifiers() == Qt::ControlModifier) {
         event->accept();
-        event->angleDelta().y() > 0 ? scaleUp() : scaleDown();
-    } else {
-        QWidget::wheelEvent(event);
+        const int deltaY = event->angleDelta().y();
+        if (deltaY != 0)
+            incrementZoom(deltaY / 120);
+        return;
     }
+    QWidget::wheelEvent(event);
+}
+
+void HelpViewer::incrementZoom(int steps)
+{
+    const int incrementPercentage = 10 * steps; // 10 percent increase by single step
+    const int previousZoom = LocalHelpManager::fontZoom();
+    applyZoom(previousZoom + incrementPercentage);
+}
+
+void HelpViewer::applyZoom(int percentage)
+{
+    const int newZoom = LocalHelpManager::setFontZoom(percentage);
+    Utils::FadingIndicator::showText(this, QCoreApplication::translate("Help::HelpViewer",
+                                     "Zoom: %1%").arg(newZoom), Utils::FadingIndicator::SmallText);
 }
 
 void HelpViewer::slotLoadStarted()
diff --git a/src/plugins/help/helpviewer.h b/src/plugins/help/helpviewer.h
index b1be6e1dfb9..4e0a7f7554b 100644
--- a/src/plugins/help/helpviewer.h
+++ b/src/plugins/help/helpviewer.h
@@ -54,9 +54,9 @@ public:
     virtual QFont viewerFont() const = 0;
     virtual void setViewerFont(const QFont &font) = 0;
 
-    virtual qreal scale() const = 0;
     virtual void setScale(qreal scale) = 0;
 
+    void setFontZoom(int percentage);
     void setScrollWheelZoomingEnabled(bool enabled);
     bool isScrollWheelZoomingEnabled() const;
 
@@ -87,9 +87,9 @@ public:
 
     void home();
 
-    virtual void scaleUp() = 0;
-    virtual void scaleDown() = 0;
-    virtual void resetScale() = 0;
+    void scaleUp();
+    void scaleDown();
+    void resetScale();
     virtual void copy() = 0;
     virtual void stop() = 0;
     virtual void forward() = 0;
@@ -117,6 +117,9 @@ protected:
     Actions m_visibleActions;
     bool m_scrollWheelZoomingEnabled = true;
     int m_loadOverrideStack = 0;
+private:
+    void incrementZoom(int steps);
+    void applyZoom(int percentage);
 };
 
 }   // namespace Internal
diff --git a/src/plugins/help/helpwidget.cpp b/src/plugins/help/helpwidget.cpp
index 65c468ac386..a72ff4c6b48 100644
--- a/src/plugins/help/helpwidget.cpp
+++ b/src/plugins/help/helpwidget.cpp
@@ -490,7 +490,7 @@ HelpWidget::HelpWidget(const Core::Context &context, WidgetStyle style, QWidget
     connect(reload, &QAction::triggered, this, [this]() {
         const int index = m_viewerStack->currentIndex();
         HelpViewer *previous = currentViewer();
-        insertViewer(index, previous->source(), previous->scale());
+        insertViewer(index, previous->source());
         removeViewerAt(index + 1);
         setCurrentIndex(index);
     });
@@ -711,15 +711,15 @@ void HelpWidget::setCurrentIndex(int index)
     emit currentIndexChanged(index);
 }
 
-HelpViewer *HelpWidget::addViewer(const QUrl &url, qreal zoom)
+HelpViewer *HelpWidget::addViewer(const QUrl &url)
 {
-    return insertViewer(m_viewerStack->count(), url, zoom);
+    return insertViewer(m_viewerStack->count(), url);
 }
 
-HelpViewer *HelpWidget::insertViewer(int index, const QUrl &url, qreal zoom)
+HelpViewer *HelpWidget::insertViewer(int index, const QUrl &url)
 {
     m_model.beginInsertRows({}, index, index);
-    HelpViewer *viewer = HelpPlugin::createHelpViewer(zoom);
+    HelpViewer *viewer = HelpPlugin::createHelpViewer();
     m_viewerStack->insertWidget(index, viewer);
     viewer->setFocus(Qt::OtherFocusReason);
     viewer->setActionVisible(HelpViewer::Action::NewPage, supportsPages());
@@ -900,19 +900,16 @@ void HelpWidget::saveState() const
 {
     // TODO generalize
     if (m_style == ModeWidget) {
-        QList<qreal> zoomFactors;
         QStringList currentPages;
         for (int i = 0; i < viewerCount(); ++i) {
             const HelpViewer *const viewer = viewerAt(i);
             const QUrl &source = viewer->source();
             if (source.isValid()) {
                 currentPages.append(source.toString());
-                zoomFactors.append(viewer->scale());
             }
         }
 
         LocalHelpManager::setLastShownPages(currentPages);
-        LocalHelpManager::setLastShownPagesZoom(zoomFactors);
         LocalHelpManager::setLastSelectedTab(currentIndex());
     }
 }
diff --git a/src/plugins/help/helpwidget.h b/src/plugins/help/helpwidget.h
index e79314d940c..55f90a8e566 100644
--- a/src/plugins/help/helpwidget.h
+++ b/src/plugins/help/helpwidget.h
@@ -87,7 +87,7 @@ public:
     HelpViewer *currentViewer() const;
     int currentIndex() const;
     void setCurrentIndex(int index);
-    HelpViewer *addViewer(const QUrl &url, qreal zoom = 0);
+    HelpViewer *addViewer(const QUrl &url);
     void removeViewerAt(int index);
 
     int viewerCount() const;
@@ -118,7 +118,7 @@ signals:
 
 private:
     int indexOf(HelpViewer *viewer) const;
-    HelpViewer *insertViewer(int index, const QUrl &url, qreal zoom);
+    HelpViewer *insertViewer(int index, const QUrl &url);
     void updateBackMenu();
     void updateForwardMenu();
     void updateWindowTitle();
diff --git a/src/plugins/help/litehtmlhelpviewer.cpp b/src/plugins/help/litehtmlhelpviewer.cpp
index dcc2673895f..30db13f5f26 100644
--- a/src/plugins/help/litehtmlhelpviewer.cpp
+++ b/src/plugins/help/litehtmlhelpviewer.cpp
@@ -99,26 +99,6 @@ void LiteHtmlHelpViewer::setViewerFont(const QFont &newFont)
     m_viewer->setDefaultFont(newFont);
 }
 
-void LiteHtmlHelpViewer::scaleUp()
-{
-    setScale(scale() * 1.1);
-}
-
-void LiteHtmlHelpViewer::scaleDown()
-{
-    setScale(scale() * .9);
-}
-
-void LiteHtmlHelpViewer::resetScale()
-{
-    m_viewer->setZoomFactor(1);
-}
-
-qreal LiteHtmlHelpViewer::scale() const
-{
-    return m_viewer->zoomFactor();
-}
-
 void LiteHtmlHelpViewer::setScale(qreal scale)
 {
     // interpret 0 as "default"
diff --git a/src/plugins/help/litehtmlhelpviewer.h b/src/plugins/help/litehtmlhelpviewer.h
index 0e35d79ddbd..99b1c723fe2 100644
--- a/src/plugins/help/litehtmlhelpviewer.h
+++ b/src/plugins/help/litehtmlhelpviewer.h
@@ -48,7 +48,6 @@ public:
     QFont viewerFont() const override;
     void setViewerFont(const QFont &font) override;
 
-    qreal scale() const override;
     void setScale(qreal scale) override;
 
     QString title() const override;
@@ -67,9 +66,6 @@ public:
     bool findText(const QString &text, Core::FindFlags flags,
                   bool incremental, bool fromSearch, bool *wrapped = nullptr) override;
 
-    void scaleUp() override;
-    void scaleDown() override;
-    void resetScale() override;
     void copy() override;
     void stop() override;
     void forward() override;
diff --git a/src/plugins/help/localhelpmanager.cpp b/src/plugins/help/localhelpmanager.cpp
index 404b5a9fdd7..4615e9716e6 100644
--- a/src/plugins/help/localhelpmanager.cpp
+++ b/src/plugins/help/localhelpmanager.cpp
@@ -83,16 +83,17 @@ static const char kHelpHomePageKey[] = "Help/HomePage";
 static const char kFontFamilyKey[] = "Help/FallbackFontFamily";
 static const char kFontStyleNameKey[] = "Help/FallbackFontStyleName";
 static const char kFontSizeKey[] = "Help/FallbackFontSize";
+static const char kFontZoomKey[] = "Help/FontZoom";
 static const char kStartOptionKey[] = "Help/StartOption";
 static const char kContextHelpOptionKey[] = "Help/ContextHelpOption";
 static const char kReturnOnCloseKey[] = "Help/ReturnOnClose";
 static const char kUseScrollWheelZooming[] = "Help/UseScrollWheelZooming";
 static const char kLastShownPagesKey[] = "Help/LastShownPages";
-static const char kLastShownPagesZoomKey[] = "Help/LastShownPagesZoom";
 static const char kLastSelectedTabKey[] = "Help/LastSelectedTab";
 static const char kViewerBackend[] = "Help/ViewerBackend";
 
 static const int kDefaultFallbackFontSize = 14;
+static const int kDefaultFontZoom = 100;
 const int kDefaultStartOption = LocalHelpManager::ShowLastPages;
 const int kDefaultContextHelpOption = Core::HelpManager::SideBySideIfPossible;
 const bool kDefaultReturnOnClose = false;
@@ -185,6 +186,22 @@ void LocalHelpManager::setFallbackFont(const QFont &font)
     emit m_instance->fallbackFontChanged(font);
 }
 
+int LocalHelpManager::fontZoom()
+{
+    return Core::ICore::settings()->value(kFontZoomKey, kDefaultFontZoom).toInt();
+}
+
+int LocalHelpManager::setFontZoom(int percentage)
+{
+    const int newZoom = qBound(10, percentage, 3000);
+    if (newZoom == fontZoom())
+        return newZoom;
+
+    Core::ICore::settings()->setValueWithDefault(kFontZoomKey, newZoom, kDefaultFontZoom);
+    emit m_instance->fontZoomChanged(newZoom);
+    return newZoom;
+}
+
 LocalHelpManager::StartOption LocalHelpManager::startOption()
 {
     const QVariant value = Core::ICore::settings()->value(kStartOptionKey, kDefaultStartOption);
@@ -284,22 +301,6 @@ void LocalHelpManager::setLastShownPages(const QStringList &pages)
                                                  pages.join(Constants::ListSeparator));
 }
 
-QList<float> LocalHelpManager::lastShownPagesZoom()
-{
-    const QVariant value = Core::ICore::settings()->value(kLastShownPagesZoomKey, QVariant());
-    const QStringList stringValues = value.toString().split(Constants::ListSeparator,
-                                                            Qt::SkipEmptyParts);
-    return Utils::transform(stringValues, [](const QString &str) { return str.toFloat(); });
-}
-
-void LocalHelpManager::setLastShownPagesZoom(const QList<qreal> &zoom)
-{
-    const QStringList stringValues = Utils::transform(zoom,
-                                                      [](qreal z) { return QString::number(z); });
-    Core::ICore::settings()->setValueWithDefault(kLastShownPagesZoomKey,
-                                                 stringValues.join(Constants::ListSeparator));
-}
-
 int LocalHelpManager::lastSelectedTab()
 {
     const QVariant value = Core::ICore::settings()->value(kLastSelectedTabKey, 0);
diff --git a/src/plugins/help/localhelpmanager.h b/src/plugins/help/localhelpmanager.h
index aac3a46871f..467987698b5 100644
--- a/src/plugins/help/localhelpmanager.h
+++ b/src/plugins/help/localhelpmanager.h
@@ -83,6 +83,9 @@ public:
     static QFont fallbackFont();
     static void setFallbackFont(const QFont &font);
 
+    static int fontZoom();
+    static int setFontZoom(int percentage);
+
     static StartOption startOption();
     static void setStartOption(StartOption option);
 
@@ -98,9 +101,6 @@ public:
     static QStringList lastShownPages();
     static void setLastShownPages(const QStringList &pages);
 
-    static QList<float> lastShownPagesZoom();
-    static void setLastShownPagesZoom(const QList<qreal> &zoom);
-
     static int lastSelectedTab();
     static void setLastSelectedTab(int index);
 
@@ -137,6 +137,7 @@ signals:
     void filterIndexChanged(int index);
 #endif
     void fallbackFontChanged(const QFont &font);
+    void fontZoomChanged(int percentage);
     void returnOnCloseChanged();
     void scrollWheelZoomingEnabledChanged(bool enabled);
     void contextHelpOptionChanged(Core::HelpManager::HelpViewerLocation option);
diff --git a/src/plugins/help/macwebkithelpviewer.h b/src/plugins/help/macwebkithelpviewer.h
index 1d1990ad331..98955cb070a 100644
--- a/src/plugins/help/macwebkithelpviewer.h
+++ b/src/plugins/help/macwebkithelpviewer.h
@@ -73,7 +73,6 @@ public:
     QFont viewerFont() const override;
     void setViewerFont(const QFont &font) override;
 
-    qreal scale() const override;
     void setScale(qreal scale) override;
 
     QString title() const override;
@@ -97,9 +96,6 @@ public:
     MacWebKitHelpWidget *widget() const { return m_widget; }
 
 public:
-    void scaleUp() override;
-    void scaleDown() override;
-    void resetScale() override;
     void copy() override;
     void stop() override;
     void forward() override;
diff --git a/src/plugins/help/macwebkithelpviewer.mm b/src/plugins/help/macwebkithelpviewer.mm
index ac2e721c12a..05433328137 100644
--- a/src/plugins/help/macwebkithelpviewer.mm
+++ b/src/plugins/help/macwebkithelpviewer.mm
@@ -553,34 +553,6 @@ void MacWebKitHelpViewer::setViewerFont(const QFont &font)
     }
 }
 
-void MacWebKitHelpViewer::scaleUp()
-{
-    @autoreleasepool {
-        m_widget->webView().textSizeMultiplier += 0.1f;
-    }
-}
-
-void MacWebKitHelpViewer::scaleDown()
-{
-    @autoreleasepool {
-        m_widget->webView().textSizeMultiplier = qMax(0.1f, m_widget->webView().textSizeMultiplier - 0.1f);
-    }
-}
-
-void MacWebKitHelpViewer::resetScale()
-{
-    @autoreleasepool {
-        m_widget->webView().textSizeMultiplier = 1.0f;
-    }
-}
-
-qreal MacWebKitHelpViewer::scale() const
-{
-    @autoreleasepool {
-        return m_widget->webView().textSizeMultiplier;
-    }
-}
-
 void MacWebKitHelpViewer::setScale(qreal scale)
 {
     m_widget->webView().textSizeMultiplier = (scale <= 0.0 ? 1.0 : scale);
diff --git a/src/plugins/help/openpagesmanager.cpp b/src/plugins/help/openpagesmanager.cpp
index 6fd3daf35a7..4fa96c341b7 100644
--- a/src/plugins/help/openpagesmanager.cpp
+++ b/src/plugins/help/openpagesmanager.cpp
@@ -137,15 +137,11 @@ void OpenPagesManager::setupInitialPages()
         const int pageCount = lastShownPageList.count();
 
         if (pageCount > 0) {
-            QList<float> zoomFactors = LocalHelpManager::lastShownPagesZoom();
-            while (zoomFactors.count() < pageCount)
-                zoomFactors.append(0.);
-
             initialPage = LocalHelpManager::lastSelectedTab();
             for (int curPage = 0; curPage < pageCount; ++curPage) {
                 const QString &curFile = lastShownPageList.at(curPage);
                 if (engine.findFile(curFile).isValid() || curFile == Help::Constants::AboutBlank) {
-                    m_helpWidget->addViewer(curFile, zoomFactors.at(curPage));
+                    m_helpWidget->addViewer(curFile);
                 } else if (curPage <= initialPage && initialPage > 0) {
                     --initialPage;
                 }
diff --git a/src/plugins/help/textbrowserhelpviewer.cpp b/src/plugins/help/textbrowserhelpviewer.cpp
index 3c84e94229e..e5e6db26b99 100644
--- a/src/plugins/help/textbrowserhelpviewer.cpp
+++ b/src/plugins/help/textbrowserhelpviewer.cpp
@@ -82,54 +82,22 @@ QFont TextBrowserHelpViewer::viewerFont() const
 
 void TextBrowserHelpViewer::setViewerFont(const QFont &newFont)
 {
-    m_textBrowser->forceFont = true;
-    m_textBrowser->setFont(newFont);
-    m_textBrowser->forceFont = false;
+    setFontAndScale(newFont, LocalHelpManager::fontZoom() / 100.0);
 }
 
-void TextBrowserHelpViewer::scaleUp()
+void TextBrowserHelpViewer::setFontAndScale(const QFont &font, qreal scale)
 {
-    m_textBrowser->scaleUp();
-}
-
-void TextBrowserHelpViewer::scaleDown()
-{
-    m_textBrowser->scaleDown();
-}
-
-void TextBrowserHelpViewer::resetScale()
-{
-    m_textBrowser->withFixedTopPosition([this] {
-        if (m_textBrowser->zoomCount != 0) {
-            m_textBrowser->forceFont = true;
-            m_textBrowser->zoomOut(m_textBrowser->zoomCount);
-            m_textBrowser->forceFont = false;
-        }
-        m_textBrowser->zoomCount = 0;
+    m_textBrowser->withFixedTopPosition([this, &font, scale] {
+        QFont newFont = font;
+        const float newSize = font.pointSizeF() * scale;
+        newFont.setPointSizeF(newSize);
+        m_textBrowser->setFont(newFont);
     });
 }
 
-qreal TextBrowserHelpViewer::scale() const
-{
-    return m_textBrowser->zoomCount;
-}
-
 void TextBrowserHelpViewer::setScale(qreal scale)
 {
-    m_textBrowser->withFixedTopPosition([this, &scale] {
-        m_textBrowser->forceFont = true;
-        if (scale > 10)
-            scale = 10;
-        else if (scale < -5)
-            scale = -5;
-        int diff = int(scale) - m_textBrowser->zoomCount;
-        if (diff > 0)
-            m_textBrowser->zoomIn(diff);
-        else if (diff < 0)
-            m_textBrowser->zoomOut(-diff);
-        m_textBrowser->zoomCount = int(scale);
-        m_textBrowser->forceFont = false;
-    });
+    setFontAndScale(LocalHelpManager::fallbackFont(), scale);
 }
 
 QString TextBrowserHelpViewer::title() const
@@ -302,8 +270,6 @@ void TextBrowserHelpViewer::goToHistoryItem()
 
 TextBrowserHelpWidget::TextBrowserHelpWidget(TextBrowserHelpViewer *parent)
     : QTextBrowser(parent)
-    , zoomCount(0)
-    , forceFont(false)
     , m_parent(parent)
 {
     installEventFilter(this);
@@ -350,30 +316,6 @@ void TextBrowserHelpWidget::scrollToTextPosition(int position)
     }
 }
 
-void TextBrowserHelpWidget::scaleUp()
-{
-    withFixedTopPosition([this] {
-        if (zoomCount < 10) {
-            zoomCount++;
-            forceFont = true;
-            zoomIn();
-            forceFont = false;
-        }
-    });
-}
-
-void TextBrowserHelpWidget::scaleDown()
-{
-    withFixedTopPosition([this] {
-        if (zoomCount > -5) {
-            zoomCount--;
-            forceFont = true;
-            zoomOut();
-            forceFont = false;
-        }
-    });
-}
-
 void TextBrowserHelpWidget::contextMenuEvent(QContextMenuEvent *event)
 {
     QMenu menu("", nullptr);
@@ -409,10 +351,7 @@ void TextBrowserHelpWidget::contextMenuEvent(QContextMenuEvent *event)
 bool TextBrowserHelpWidget::eventFilter(QObject *obj, QEvent *event)
 {
     if (obj == this) {
-        if (event->type() == QEvent::FontChange) {
-            if (!forceFont)
-                return true;
-        } else if (event->type() == QEvent::KeyPress) {
+        if (event->type() == QEvent::KeyPress) {
             auto keyEvent = static_cast<QKeyEvent *>(event);
             if (keyEvent->key() == Qt::Key_Slash) {
                 keyEvent->accept();
@@ -428,6 +367,21 @@ bool TextBrowserHelpWidget::eventFilter(QObject *obj, QEvent *event)
     return QTextBrowser::eventFilter(obj, event);
 }
 
+void TextBrowserHelpWidget::wheelEvent(QWheelEvent *e)
+{
+    // These two conditions should match those defined in QTextEdit::wheelEvent()
+    if (!(textInteractionFlags() & Qt::TextEditable)) {
+        if (e->modifiers() & Qt::ControlModifier) {
+            // Don't handle wheelEvent by the QTextEdit superclass, which zooms the
+            // view in a broken way. We handle it properly through the sequence:
+            // HelpViewer::wheelEvent() -> LocalHelpManager::setFontZoom() ->
+            // HelpViewer::setFontZoom() -> TextBrowserHelpViewer::setFontAndScale().
+            return;
+        }
+    }
+    QTextBrowser::wheelEvent(e);
+}
+
 void TextBrowserHelpWidget::mousePressEvent(QMouseEvent *e)
 {
     if (Utils::HostOsInfo::isLinuxHost() && m_parent->handleForwardBackwardMouseButtons(e))
diff --git a/src/plugins/help/textbrowserhelpviewer.h b/src/plugins/help/textbrowserhelpviewer.h
index b29517e61eb..60336635d19 100644
--- a/src/plugins/help/textbrowserhelpviewer.h
+++ b/src/plugins/help/textbrowserhelpviewer.h
@@ -46,7 +46,6 @@ public:
     QFont viewerFont() const override;
     void setViewerFont(const QFont &font) override;
 
-    qreal scale() const override;
     void setScale(qreal scale) override;
 
     QString title() const override;
@@ -65,9 +64,6 @@ public:
     bool findText(const QString &text, Core::FindFlags flags,
                   bool incremental, bool fromSearch, bool *wrapped = nullptr) override;
 
-    void scaleUp() override;
-    void scaleDown() override;
-    void resetScale() override;
     void copy() override;
     void stop() override;
     void forward() override;
@@ -76,6 +72,7 @@ public:
 
 private:
     void goToHistoryItem();
+    void setFontAndScale(const QFont &font, qreal scale);
 
     TextBrowserHelpWidget *m_textBrowser;
 };
@@ -89,14 +86,12 @@ public:
 
     QVariant loadResource(int type, const QUrl &name) override;
 
-    void scaleUp();
-    void scaleDown();
-
     void withFixedTopPosition(const std::function<void()> &action);
 
 protected:
     void contextMenuEvent(QContextMenuEvent *event) override;
     bool eventFilter(QObject *obj, QEvent *event) override;
+    void wheelEvent(QWheelEvent *e) override;
     void mousePressEvent(QMouseEvent *e) override;
     void mouseReleaseEvent(QMouseEvent *e) override;
     void resizeEvent(QResizeEvent *e) override;
@@ -105,8 +100,6 @@ private:
     QString linkAt(const QPoint &pos);
     void scrollToTextPosition(int position);
 
-    int zoomCount;
-    bool forceFont;
     TextBrowserHelpViewer *m_parent;
     friend class Help::Internal::TextBrowserHelpViewer;
 };
diff --git a/src/plugins/help/webenginehelpviewer.cpp b/src/plugins/help/webenginehelpviewer.cpp
index 6801bd9b535..3766e551620 100644
--- a/src/plugins/help/webenginehelpviewer.cpp
+++ b/src/plugins/help/webenginehelpviewer.cpp
@@ -173,11 +173,6 @@ void WebEngineHelpViewer::setViewerFont(const QFont &font)
     webSettings->setFontSize(QWebEngineSettings::DefaultFontSize, font.pointSize());
 }
 
-qreal WebEngineHelpViewer::scale() const
-{
-    return m_widget->zoomFactor();
-}
-
 void WebEngineHelpViewer::setScale(qreal scale)
 {
     m_widget->setZoomFactor(scale);
@@ -277,21 +272,6 @@ WebEngineHelpPage *WebEngineHelpViewer::page() const
     return static_cast<WebEngineHelpPage *>(m_widget->page());
 }
 
-void WebEngineHelpViewer::scaleUp()
-{
-    m_widget->setZoomFactor(m_widget->zoomFactor() + 0.1);
-}
-
-void WebEngineHelpViewer::scaleDown()
-{
-    m_widget->setZoomFactor(qMax(qreal(0.1), m_widget->zoomFactor() - qreal(0.1)));
-}
-
-void WebEngineHelpViewer::resetScale()
-{
-    m_widget->setZoomFactor(1.0);
-}
-
 void WebEngineHelpViewer::copy()
 {
     m_widget->triggerPageAction(QWebEnginePage::Copy);
diff --git a/src/plugins/help/webenginehelpviewer.h b/src/plugins/help/webenginehelpviewer.h
index 259bc571a92..1869ac67027 100644
--- a/src/plugins/help/webenginehelpviewer.h
+++ b/src/plugins/help/webenginehelpviewer.h
@@ -84,7 +84,6 @@ public:
 
     QFont viewerFont() const override;
     void setViewerFont(const QFont &font) override;
-    qreal scale() const override;
     void setScale(qreal scale) override;
     QString title() const override;
     QUrl source() const override;
@@ -99,9 +98,6 @@ public:
 
     WebEngineHelpPage *page() const;
 
-    void scaleUp() override;
-    void scaleDown() override;
-    void resetScale() override;
     void copy() override;
     void stop() override;
     void forward() override;