phoenix_title Window Sizing Overview

It can sometimes be confusing to keep track of the various size-related attributes of a wx.Window, how they relate to each other, and how they interact with sizers.

This document will attempt to clear the fog a little, and give some simple explanations of things.


  • “Best Size”: the best size of a widget depends on what kind of widget it is, and usually also on the contents of the widget. For example a wx.ListBox ‘s best size will be calculated based on how many items it has, up to a certain limit, or a wx.Button ‘s best size will be calculated based on its label size, but normally won’t be smaller than the platform default button size (unless a style flag overrides that). There is a special method in the wxPython window classes called wx.Window.DoGetBestSize that a class needs to override if it wants to calculate its own best size based on its content.

  • “Minimal Size”: the minimal size of a widget is a size that is normally explicitly set by the programmer either with the wx.Window.SetMinSize method or with the wx.Window.SetSizeHints method. Most controls will also set the minimal size to the size given in the control’s constructor if a non-default value is passed. Top-level windows such as wx.Frame will not allow the user to resize the frame below the minimal size.

  • “Maximum Size”: just like for the minimal size, the maximum size is normally explicitly set by the programmer with the wx.Window.SetMaxSize method or with wx.Window.SetSizeHints. Top-level windows such as wx.Frame will not allow the user to resize the frame above the maximum size.

  • “Size”: the size of a widget can be explicitly set or fetched with the wx.Window.SetSize or wx.Window.GetSize methods. This size value is the size that the widget is currently using on screen and is the way to change the size of something that is not being managed by a sizer.

  • “Client Size”: the client size represents the widget’s area inside of any borders belonging to the widget and is the area that can be drawn upon in a wx.EVT_PAINT event. If a widget doesn’t have a border then its client size is the same as its size.

  • “Initial Size”: the initial size of a widget is the size given to the constructor of the widget, if any. As mentioned above most controls will also set this size value as the control’s minimal size. If the size passed to the constructor is the default wx.DefaultSize, or if the size is not fully specified (such as wx.Size(150, -1)) then most controls will fill in the missing size components using the best size and will set the initial size of the control to the resulting size.

  • “Virtual Size”: the virtual size is the size of the potentially viewable area of the widget. The virtual size of a widget may be larger than its actual size and in this case scrollbars will appear to the let the user ‘explore’ the full contents of the widget. See wx.Scrolled for more info.