Fix Windows paint on resize issue. Automatically resize to fit tabs and button content

src/slic3r/GUI/Widgets/StaticBox.cpp

@@ -7,6 +7,7 @@ BEGIN_EVENT_TABLE(StaticBox, wxWindow)
 
 // catch paint events
 //EVT_ERASE_BACKGROUND(StaticBox::eraseEvent)
+EVT_SIZE(StaticBox::sizeEvent)
 EVT_PAINT(StaticBox::paintEvent)
 
 END_EVENT_TABLE()
@@ -140,6 +141,12 @@ void StaticBox::eraseEvent(wxEraseEvent& evt)
 #endif
 }
 
+void StaticBox::sizeEvent(wxSizeEvent& evt)
+{
+    Refresh();
+    evt.Skip();
+}
+
 void StaticBox::paintEvent(wxPaintEvent& evt)
 {
     // depending on your system you may need to look at double-buffered dcs

src/slic3r/GUI/Widgets/StaticBox.hpp

@@ -46,6 +46,8 @@ public:
 protected:
     void eraseEvent(wxEraseEvent& evt);
 
+    void sizeEvent(wxSizeEvent& evt);
+
     void paintEvent(wxPaintEvent& evt);
 
     void render(wxDC& dc);

src/slic3r/GUI/Widgets/TabCtrl.cpp

@@ -295,6 +295,15 @@ void TabCtrl::relayout()
     Layout();
 }
 
+int TabCtrl::buttons_best_width() const
+{
+    // Mirrors relayout(): a 10px leading spacer plus every button's min width and spacing.
+    int width = 10;
+    for (const Button *btn : btns)
+        width += btn->GetMinSize().x + TAB_BUTTON_SPACE * 2;
+    return width;
+}
+
 void TabCtrl::buttonClicked(wxCommandEvent &event)
 {
     SetFocus();

src/slic3r/GUI/Widgets/TabCtrl.hpp

@@ -73,6 +73,8 @@ private:
 
     void relayout();
 
+    int buttons_best_width() const;
+
     void buttonClicked(wxCommandEvent & event);
     void keyDown(wxKeyEvent &event);