Relayout ctkThumbnailListWidget when thumbnails become visible

ctkThumbnailListWidget controls it's own scrollarea internal widget size.
The size is manually computed from the layout (ctkFlowLayout).
However, it fails at computing a correct size if the added widgets are
not visible at the time of the relayout.
ctkThumbnailListWidget now observes the showevent of such widgets to
trigger a relayout.
Closes #272

Libs/Widgets/ctkThumbnailListWidget.cpp

@@ -21,6 +21,7 @@
 // Qt include
 #include <QDateTime>
 #include <QDir>
+#include <QEvent>
 #include <QFile>
 #include <QFileInfo>
 #include <QGridLayout>
@@ -28,6 +29,7 @@
 #include <QPushButton>
 #include <QResizeEvent>
 #include <QScrollBar>
+#include <QTimer>
 
 // ctk includes
 #include "ctkLogger.h"
@@ -52,6 +54,7 @@ static ctkLogger logger("org.commontk.Widgets.ctkThumbnailListWidget");
 ctkThumbnailListWidgetPrivate
 ::ctkThumbnailListWidgetPrivate(ctkThumbnailListWidget* parent)
   : q_ptr(parent)
+  , RequestRelayout(false)
 {
 }
 
@@ -98,6 +101,8 @@ void ctkThumbnailListWidgetPrivate::addThumbnail(ctkThumbnailLabel* thumbnail)
   Q_Q(ctkThumbnailListWidget);
 
   this->ScrollAreaContentWidget->layout()->addWidget(thumbnail);
+  thumbnail->installEventFilter(q);
+  this->RequestRelayout = true;
 
   q->connect(thumbnail, SIGNAL(selected(ctkThumbnailLabel)),
     q, SLOT(onThumbnailSelected(ctkThumbnailLabel)));
@@ -302,6 +307,24 @@ void ctkThumbnailListWidget::resizeEvent(QResizeEvent* event)
   d->updateScrollAreaContentWidgetSize(event->size());
 }
 
+//----------------------------------------------------------------------------
+bool ctkThumbnailListWidget::eventFilter(QObject* watched, QEvent* event)
+{
+  Q_D(ctkThumbnailListWidget);
+  if (d->RequestRelayout &&
+      qobject_cast<ctkThumbnailLabel*>(watched) &&
+      event->type() == QEvent::Show)
     {
+    d->RequestRelayout = false;
+    watched->removeEventFilter(this);
+    QTimer::singleShot(0, this, SLOT(updateLayout()));
     }
+  return this->Superclass::eventFilter(watched, event);
+}
+
+//----------------------------------------------------------------------------
+void ctkThumbnailListWidget::updateLayout()
+{
+  Q_D(ctkThumbnailListWidget);
+  d->updateScrollAreaContentWidgetSize(this->size());
 }

Libs/Widgets/ctkThumbnailListWidget.h

@@ -66,6 +66,8 @@ public:
   /// Get thumbnail width
   QSize thumbnailSize()const;
 
+  virtual bool eventFilter(QObject* watched, QEvent* event);
+
 public Q_SLOTS:
   /// Set thumbnail width
   void setThumbnailSize(QSize size);
@@ -76,6 +78,7 @@ Q_SIGNALS:
 
 protected Q_SLOTS:
   void onThumbnailSelected(const ctkThumbnailLabel& widget);
+  void updateLayout();
 
 protected:
   explicit ctkThumbnailListWidget(ctkThumbnailListWidgetPrivate* ptr, QWidget* parent=0);

Libs/Widgets/ctkThumbnailListWidget_p.h

@@ -45,6 +45,7 @@ public:
 
   int CurrentThumbnail;
   QSize ThumbnailSize;
+  bool RequestRelayout;
 
 protected:
   ctkThumbnailListWidget* const q_ptr;