Cover browser: Add an option to view the central book by double clicking instead of single clicking (Preferences->Look & feel->Cover browser). Fixes #1937025 [[Enhancement] Single-clicking open book in Cover browser](https://bugs.launchpad.net/calibre/+bug/1937025)

src/calibre/gui2/__init__.py

@@ -175,6 +175,7 @@ def create_defs():
     defs['show_highlight_toggle_button'] = False
     defs['add_comments_to_email'] = False
     defs['cb_preserve_aspect_ratio'] = False
+    defs['cb_double_click_to_activate'] = False
     defs['gpm_template_editor_font_size'] = 10
     defs['show_emblems'] = False
     defs['emblem_size'] = 32

src/calibre/gui2/cover_flow.py

@@ -193,6 +193,8 @@ class CoverFlow(pictureflow.PictureFlow):
         self.setPreserveAspectRatio(gprefs['cb_preserve_aspect_ratio'])
         if not gprefs['cover_browser_reflections']:
             self.setShowReflections(False)
+        if gprefs['cb_double_click_to_activate']:
+            self.setActivateOnDoubleClick(True)
 
     def one_auto_scroll(self):
         if self.currentSlide() >= self.count() - 1:

src/calibre/gui2/pictureflow/pictureflow.cpp

@@ -371,6 +371,7 @@ public:
   int    pixelDistanceMoved;
   int    pixelsToMovePerSlide;
   bool   preserveAspectRatio;
+  bool   activateOnDoubleClick;
   QFont subtitleFont;
 
   void setImages(FlowImages *images);
@@ -426,6 +427,7 @@ PictureFlowPrivate::PictureFlowPrivate(PictureFlow* w, int queueLength_)
   fontSize = 10;
   doReflections = true;
   preserveAspectRatio = false;
+  activateOnDoubleClick = false;
 
   centerIndex = 0;
   queueLength = queueLength_;
@@ -1246,6 +1248,16 @@ void PictureFlow::setPreserveAspectRatio(bool preserve)
   clearCaches();
 }
 
+bool PictureFlow::activateOnDoubleClick() const
+{
+  return d->activateOnDoubleClick;
+}
+
+void PictureFlow::setActivateOnDoubleClick(bool on)
+{
+  d->activateOnDoubleClick = on;
+}
+
 void PictureFlow::setSubtitleFont(QFont font)
 {
   d->subtitleFont = font;
@@ -1468,7 +1480,7 @@ void PictureFlow::mouseReleaseEvent(QMouseEvent* event)
       showNext();
       accepted = true;
     } else {
-        if (event->button() == Qt::LeftButton) {
+        if (event->button() == Qt::LeftButton && !d->activateOnDoubleClick) {
             emit itemActivated(d->getTarget());
             accepted = true;
         }
@@ -1480,6 +1492,17 @@ void PictureFlow::mouseReleaseEvent(QMouseEvent* event)
   }
 }
 
+void PictureFlow::mouseDoubleClickEvent(QMouseEvent* event) {
+    if (event->button() == Qt::LeftButton && d->activateOnDoubleClick) {
+        int sideWidth = (d->buffer.width() - slideSize().width()) /2;
+        int x = (int)(event->x() * device_pixel_ratio());
+        if (sideWidth < x && x < sideWidth + slideSize().width() ) {
+            emit itemActivated(d->getTarget());
+            event->accept();
+        }
+    }
+}
+
 void PictureFlow::paintEvent(QPaintEvent* event)
 {
   Q_UNUSED(event);

src/calibre/gui2/pictureflow/pictureflow.h

@@ -94,6 +94,7 @@ Q_OBJECT
   Q_PROPERTY(QSize slideSize READ slideSize WRITE setSlideSize)
   Q_PROPERTY(QFont subtitleFont READ subtitleFont WRITE setSubtitleFont)
   Q_PROPERTY(bool preserveAspectRatio READ preserveAspectRatio WRITE setPreserveAspectRatio)
+  Q_PROPERTY(bool activateOnDoubleClick READ activateOnDoubleClick WRITE setActivateOnDoubleClick)
 
 public:
   /*!
@@ -168,6 +169,9 @@ public:
   */
   int currentSlide() const;
 
+  bool activateOnDoubleClick() const;
+  void setActivateOnDoubleClick(bool on);
+
 public slots:
 
   /*!
@@ -215,6 +219,7 @@ protected:
   void mouseMoveEvent(QMouseEvent* event);
   void mousePressEvent(QMouseEvent* event);
   void mouseReleaseEvent(QMouseEvent* event);
+  void mouseDoubleClickEvent(QMouseEvent* event);
   void resizeEvent(QResizeEvent* event);
   void timerEvent(QTimerEvent* event);
 

src/calibre/gui2/pictureflow/pictureflow.sip

@@ -41,6 +41,9 @@ public :
 
   void setSlideSize(QSize size);
 
+  bool activateOnDoubleClick() const;
+  void setActivateOnDoubleClick(bool on);
+
   bool preserveAspectRatio() const;
 
   void setPreserveAspectRatio(bool preserve);

src/calibre/gui2/preferences/look_feel.py

@@ -481,6 +481,7 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
         r('separate_cover_flow', config, restart_required=True)
         r('cb_fullscreen', gprefs)
         r('cb_preserve_aspect_ratio', gprefs)
+        r('cb_double_click_to_activate', gprefs)
 
         choices = [(_('Off'), 'off'), (_('Small'), 'small'),
             (_('Medium'), 'medium'), (_('Large'), 'large')]
@@ -806,6 +807,7 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
         gui.library_view.set_row_header_visibility()
         gui.cover_flow.setShowReflections(gprefs['cover_browser_reflections'])
         gui.cover_flow.setPreserveAspectRatio(gprefs['cb_preserve_aspect_ratio'])
+        gui.cover_flow.setActivateOnDoubleClick(gprefs['cb_double_click_to_activate'])
         gui.update_cover_flow_subtitle_font()
         gui.cover_flow.template_inited = False
         for view in 'library memory card_a card_b'.split():

src/calibre/gui2/preferences/look_feel.ui

@@ -1185,7 +1185,7 @@ using the mouse.&lt;/p&gt;</string>
          <property name="sizeHint" stdset="0">
           <size>
            <width>690</width>
-           <height>283</height>
+           <height>20</height>
           </size>
          </property>
         </spacer>
@@ -1277,6 +1277,13 @@ them to all have the same width and height</string>
          </property>
         </widget>
        </item>
+       <item row="6" column="0" colspan="2">
+        <widget class="QCheckBox" name="opt_cb_double_click_to_activate">
+         <property name="text">
+          <string>&amp;Double click to view the central book, instead of single click</string>
+         </property>
+        </widget>
+       </item>
       </layout>
      </widget>
      <widget class="QWidget" name="quickview_tab">