docs/doxygen/overviews/windowsizing.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        windowsizing.h
   3 // Purpose:     topic overview
   4 // Author:      wxWidgets team
   5 // Licence:     wxWindows licence
   6 /////////////////////////////////////////////////////////////////////////////
   7
   8 /**
   9
  10 @page overview_windowsizing Window Sizing Overview
  11
  12 @tableofcontents
  13
  14 It can sometimes be confusing to keep track of the various size-related
  15 attributes of a wxWindow, how they relate to each other, and how they interact
  16 with sizers. This document will attempt to clear the fog a little, and give
  17 some simple explanations of things.
  18
  19
  20
  21 @section overview_windowsizing_glossary Glossary
  22
  23 @li @b "Size": this is the current size of the window and it can be explicitly
  24     set or fetched with the wxWindow::SetSize() or wxWindow::GetSize() methods.
  25     This size value is the size that the widget is currently using on screen and is
  26     the way to change the size of something that is not being managed by a sizer.
  27
  28 @li @b "Client Size": the client size represents the widget's area inside of any
  29     borders belonging to the widget and is the area that can be drawn upon in a
  30     @c EVT_PAINT event. For wxFrame, the client size also excludes the frame
  31     menu, tool and status bars, if any. If a window doesn't have any border
  32     (and is not a wxFrame with some bars) then its client size is the same as
  33     its size.
  34
  35 @li @b "Best Size": the best size of a widget depends on what kind of widget it is,
  36     and usually also on the contents of the widget. For example a wxListBox's best
  37     size will be calculated based on how many items it has, up to a certain limit,
  38     or a wxButton's best size will be calculated based on its label size, but
  39     normally won't be smaller than the platform default button size (unless a style
  40     flag overrides that).
  41     There is a special virtual method in the C++ window classes called
  42     wxWindow::DoGetBestSize() that a class can override if it wants to calculate
  43     its own best size based on its content, however notice that usually it is
  44     more convenient to override DoGetBestClientSize(), see below.
  45
  46 @li @b "Best Client Size": this is simply the client size corresponding to the
  47     best window size. When the fitting size for the given contents is computed,
  48     it will usually be the client size and the size of the borders needs to be
  49     added to obtain the full best size. For this reason, it's preferable to
  50     override DoGetBestClientSize() and let DoGetBestSize() compute the full
  51     best size.
  52
  53 @li @b "Minimal Size": the minimal size of a widget is a size that is normally explicitly
  54     set by the programmer either with the wxWindow::SetMinSize() method or with the
  55     wxWindow::SetSizeHints() method.
  56     Most controls will also set the minimal size to the size given in the control's
  57     constructor if a non-default value is passed.
  58     Top-level windows such as wxFrame will not allow the user to resize the frame below
  59     the minimal size.
  60
  61 @li @b "Maximum Size": just like for the minimal size, the maximum size is normally
  62     explicitly set by the programmer with the wxWindow::SetMaxSize() method or
  63     with wxWindow::SetSizeHints().
  64     Top-level windows such as wxFrame will not allow the user to resize the frame above
  65     the maximum size.
  66
  67 @li @b "Initial Size": the initial size of a widget is the size given to the
  68     constructor of the widget, if any.
  69     As mentioned above most controls will also set this size value as the control's
  70     minimal size. If the size passed to the constructor is the default ::wxDefaultSize,
  71     or if the size is not fully specified (such as wxSize(150,-1)) then most controls
  72     will fill in the missing size components using the best size and will set the
  73     initial size of the control to the resulting size.
  74
  75 @li @b "Virtual Size": the virtual size is the size of the potentially viewable
  76     area of the widget.
  77     The virtual size of a widget may be larger than its actual size and in this
  78     case scrollbars will appear to the let the user 'explore' the full contents
  79     of the widget.
  80     See wxScrolled for more info.
  81
  82
  83 @section overview_windowsizing_func Functions related to sizing
  84
  85 @li wxWindow::GetEffectiveMinSize(): returns a blending of the widget's minimal size
  86     and best size, giving precedence to the minimal size.
  87     For example, if a widget's min size is set to (150, -1) and the best size is
  88     (80, 22) then the best fitting size is (150, 22). If the min size is (50, 20)
  89     then the best fitting size is (50, 20). This method is what is called by the
  90     sizers when determining what the requirements of each item in the sizer is,
  91     and is used for calculating the overall minimum needs of the sizer.
  92
  93 @li wxWindow::SetInitialSize(): this is a little different than the typical size
  94     setters. Rather than just setting an "initial size" attribute it actually sets
  95     the minimal size to the value passed in, blends that value with the best size,
  96     and then sets the size of the widget to be the result.
  97     So you can consider this method to be a "Smart SetSize". This method is what is
  98     called by the constructor of most controls to set the minimal size and the initial
  99     size of the control.
 100
 101 @li wxWindow::Fit(): this method sets the size of a window to fit around its children.
 102     If it has no children then nothing is done, if it does have children then the size
 103     of the window is set to the window's best size.
 104
 105 @li wxSizer::Fit(): this sets the size of the window to be large enough to
 106     accommodate the minimum size needed by the sizer, (along with a few other
 107     constraints...). If the sizer is the one that is assigned to the window then
 108     this should be equivalent to wxWindow::Fit().
 109
 110 @li wxSizer::Layout(): recalculates the minimum space needed by each item in the
 111     sizer, and then lays out the items within the space currently allotted to the sizer.
 112
 113 @li wxWindow::Layout(): if the window has a sizer then it sets the space given to
 114     the sizer to the current size of the window, which results in a call to
 115     wxSizer::Layout(). If the window has layout constraints instead of a sizer then
 116     the constraints algorithm is run. The @c Layout() method is what is called by
 117     the default @c EVT_SIZE handler for container windows.
 118
 119 */