Gui: set minimum width of preferences dialog to avoid to truncate or hide controls

src/Gui/DlgPreferencesImp.cpp

@@ -329,6 +329,7 @@ void DlgPreferencesImp::createPageInGroup(PreferencesPageItem *groupItem, const
         }
 
         pages->addWidget(page);
+        addSizeHint(page);
     }
     catch (const Base::Exception& e) {
         Base::Console().Error("Base exception thrown for '%s'\n", pageName.c_str());
@@ -339,6 +340,29 @@ void DlgPreferencesImp::createPageInGroup(PreferencesPageItem *groupItem, const
     }
 }
 
+void DlgPreferencesImp::addSizeHint(QWidget* page)
+{
+    _sizeHintOfPages = _sizeHintOfPages.expandedTo(page->minimumSizeHint());
+}
+
+int DlgPreferencesImp::minimumPageWidth() const
+{
+    return _sizeHintOfPages.width();
+}
+
+int DlgPreferencesImp::minimumDialogWidth(int pageWidth) const
+{
+    QSize size = ui->groupWidgetStack->sizeHint();
+    int diff = pageWidth - size.width();
+    int dw = width();
+    if (diff > 0) {
+        const int offset = 2;
+        dw += diff + offset;
+    }
+
+    return dw;
+}
+
 void DlgPreferencesImp::updatePageDependentWidgets()
 {
     auto currentPageItem = getCurrentPage();
@@ -734,6 +758,12 @@ void DlgPreferencesImp::showEvent(QShowEvent* ev)
         resize(width(), maxStartHeight);
         move(x(), heightDifference / 2);
     }
+
+    // if the expanded dialog occupies less than 50% of the screen
+    int mw = minimumDialogWidth(minimumPageWidth());
+    if (availableSize.width() > 2 * mw) {
+        resize(mw, height());
+    }
 }
 
 void DlgPreferencesImp::onPageSelected(const QModelIndex& index)

src/Gui/DlgPreferencesImp.h

@@ -181,6 +181,10 @@ private:
     void updatePageDependentWidgets();
 
     QPixmap loadIconForGroup(const std::string& name) const;
+
+    void addSizeHint(QWidget*);
+    int minimumPageWidth() const;
+    int minimumDialogWidth(int) const;
     //@}
 
 private:
@@ -189,6 +193,7 @@ private:
     static std::list<TGroupPages> _pages; /**< Name of all registered preference pages */
 
     QStandardItemModel _model;
+    QSize _sizeHintOfPages;
 
     struct Group {
         std::string iconName;