docs/doxygen/overviews/windowsizing.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        windowsizing
   3 // Purpose:     topic overview
   4 // Author:      wxWidgets team
   5 // RCS-ID:      $Id$
   6 // Licence:     wxWindows license
   7 /////////////////////////////////////////////////////////////////////////////
   8
   9 /*!
  10
  11  @page overview_windowsizing Window Sizing Overview
  12
  13  It can sometimes be confusing to keep track of the various
  14  size-related attributes of a #wxWindow, how they
  15  relate to each other, and how they interact with sizers. This document
  16  will attempt to clear the fog a little, and give some simple
  17  explanations of things.
  18  @b BestSize: The best size of a widget depends on what kind of widget it
  19  is, and usually also on the contents of the widget. For example a
  20  #wxListBox's best size will be calculated based on
  21  how many items it has, up to a certain limit, or a
  22  #wxButton's best size will be calculated based on
  23  its label size, but normally won't be smaller than the platform
  24  default button size (unless a style flag overrides that). Get the
  25  picture? There is a special virtual method in the C++ window classes
  26  called @c DoGetBestSize() that a class needs to override if it
  27  wants to calculate its own best size based on its content. The default
  28  @c DoGetBestSize() is designed for use in container windows,
  29  such as #wxPanel, and works something like this:
  30
  31
  32    If the window has a sizer then it is used to calculate the best size.
  33    Otherwise if the window has layout constraints then that is used to calculate the best size.
  34    Otherwise if the window has children then the best size is set to be large enough to show all the children.
  35    Otherwise if there are no children then the window's min size will be used for the best size.
  36    Otherwise if there is no min size set, then the current size is used for the best size.
  37
  38
  39  @b MinSize: The min size of a widget is a size that is normally
  40  explicitly set by the programmer either with the @c SetMinSize()
  41  method or the @c SetSizeHints() method. Most controls will also
  42  set the min size to the size given in the control's constructor if a
  43  non-default value is passed. Top-level windows such as
  44  #wxFrame will not allow the user to resize the frame
  45  below the min size.
  46  @b Size: The size of a widget can be explicitly set or fetched with
  47  the @c SetSize() or @c GetSize() methods. This size value
  48  is the size that the widget is currently using on screen and is the
  49  way to change the size of something that is not being managed by a
  50  sizer.
  51  @b ClientSize: The client size represents the widget's area inside
  52  of any borders belonging to the widget and is the area that can be
  53  drawn upon in a @c EVT_PAINT event. If a widget doesn't have a
  54  border then its client size is the same as its size.
  55  @b InitialSize: The initial size of a widget is the size given to
  56  the constructor of the widget, if any.  As mentioned above most
  57  controls will also set this size value as the control's min size. If
  58  the size passed to the constructor is the default
  59  @c wxDefaultSize, or if the size is not fully specified (such as
  60  @c wxSize(150,-1)) then most controls will fill in the missing
  61  size components using the best size and will set the initial size of
  62  the control to the resulting size.
  63  @b GetEffectiveMinSize(): (formerly @c GetBestFittingSize) A
  64  blending of the widget's min size and best size, giving precedence to
  65  the min size. For example, if a widget's min size is set to (150, -1)
  66  and the best size is (80, 22) then the best fitting size is (150,
  67  22). If the min size is (50, 20) then the best fitting size is (50,
  68  20). This method is what is called by the sizers when determining what
  69  the requirements of each item in the sizer is, and is used for
  70  calculating the overall minimum needs of the sizer.
  71  @b SetInitialSize(size): (formerly @c SetBestFittingSize)
  72  This is a little different than the typical size setters. Rather than
  73  just setting an "initial size" attribute it actually sets the minsize
  74  to the value passed in, blends that value with the best size, and then
  75  sets the size of the widget to be the result. So you can consider this
  76  method to be a "Smart SetSize". This method is what is called by the
  77  constructor of most controls to set the minsize and initial size of
  78  the control.
  79  @b window.Fit(): The @c Fit() method sets the size of a
  80  window to fit around its children. If it has no children then nothing
  81  is done, if it does have children then the size of the window is set
  82  to the window's best size.
  83  @b sizer.Fit(window): This sets the size of the window to be large
  84  enough to accommodate the minimum size needed by the sizer, (along with
  85  a few other constraints...) If the sizer is the one that is assigned
  86  to the window then this should be equivalent to @c window.Fit().
  87  @b sizer.Layout(): Recalculates the minimum space needed by each
  88  item in the sizer, and then lays out the items within the space
  89  currently allotted to the sizer.
  90  @b window.Layout(): If the window has a sizer then it sets the
  91  space given to the sizer to the current size of the window, which
  92  results in a call to @c sizer.Layout(). If the window has layout
  93  constraints instead of a sizer then the constraints algorithm is
  94  run. The @c Layout() method is what is called by the default
  95  @c EVT_SIZE handler for container windows.
  96
  97  */
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