docs/latex/wx/twinsizes.tex

   1 \section{Window Sizing Overview}\label{windowsizingoverview}
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   6 It can sometimes be confusing to keep track of the various
   7 size-related attribtes of a \helpref{wxWindow}{wxwindow}, how they
   8 relate to each other, and how they interact with sizers. This document
   9 will attempt to clear the fog a little, and give some simple
  10 explainations of things.
  11
  12 {\bf BestSize}: The best size of a widget depends on what kind of widget it
  13 is, and usually also on the contents of the widget. For example a
  14 \helpref{wxListBox}{wxlistbox}'s best size will be calculated based on
  15 how many items it has, up to a certain limit, or a
  16 \helpref{wxButton}{wxbutton}'s best size will be calculated based on
  17 its label size, but normally won't be smaller than the platform
  18 deafult button size (unless a style flag overrides that). Get the
  19 picture? There is a special virtual method in the C++ window classes
  20 called \texttt{DoGetBestSize()} that a class needs to override if it
  21 wants to calculate its own best size based on its content. The default
  22 \texttt{DoGetBestSize()} is designed for use in container windows,
  23 such as wx.Panel, and works something like this:
  24
  25 \begin{enumerate}
  26   \item{If the window has a sizer then it is used to calculate the best size.}
  27   \item{Otherwise if the window has layout constraints then that is used to calculate the best size.}
  28   \item{Otherwise if the window has children then the best size is set to be large enough to show all the children.}
  29   \item{Otherwise if there are no children then the window's min size will be used for the best size.}
  30   \item{Otherwise if there is no min size set, then the current size is used for the best size.}
  31 \end{enumerate}
  32
  33 {\bf MinSize}: The min size of a widget is a size that is normally
  34 explicitly set by the programmer either with the \texttt{SetMinSize()}
  35 method or the \texttt{SetSizeHints()} method. Most controls will also
  36 set the min size to the size given in the control's contstructor if a
  37 non-default value is passed. Top-level windows such as
  38 \helpref{wxFrame}{wxframe} will not allow the user to resize the frame
  39 below the min size.
  40
  41 {\bf Size}: The size of a widget can be explicitly set or fetched with
  42 the \texttt{SetSize()} or \texttt{GetSize()} methods. This size value
  43 is the size that the widget is currently using on screen and is the
  44 way to change the size of something that is not being managed by a
  45 sizer.
  46
  47 {\bf ClientSize}: The client size represents the widget's area inside
  48 of any borders belonging to the widget and is the area that can be
  49 drawn upon in a \texttt{EVT\_PAINT} event. If a widget doesn't have a
  50 border then its client size is the same as its size.
  51
  52 {\bf InitialSize}: The initial size of a widget is the size given to
  53 the constructor of the widget, if any.  As mentioned above most
  54 controls will also set this size value as the control's min size. If
  55 the size passed to the constructor is the default
  56 \texttt{wxDefaultSize}, or if the size is not fully specified (such as
  57 \texttt{wxSize(150,-1)}) then most controls will fill in the missing
  58 size components using the best size and will set the initial size of
  59 the control to the resulting size.
  60
  61 {\bf GetEffectiveMinSize()}: (formerly \texttt{GetBestFittingSize}) A
  62 blending of the widget's min size and best size, giving precedence to
  63 the min size. For example, if a widget's min size is set to (150, -1)
  64 and the best size is (80, 22) then the best fitting size is (150,
  65 22). If the min size is (50, 20) then the best fitting size is (50,
  66 20). This method is what is called by the sizers when determining what
  67 the requirements of each item in the sizer is, and is used for
  68 calculating the overall minimum needs of the sizer.
  69
  70 {\bf SetInitialSize(size)}: (formerly \texttt{SetBestFittingSize})
  71 This is a little different than the typical size setters. Rather than
  72 just setting an "initial size" attribute it actually sets the minsize
  73 to the value passed in, blends that value with the best size, and then
  74 sets the size of the widget to be the result. So you can consider this
  75 method to be a "Smart SetSize". This method is what is called by the
  76 constructor of most controls to set the minsize and initial size of
  77 the control.
  78
  79 {\bf window.Fit()}: The \texttt{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
  84 {\bf sizer.Fit(window)}: This sets the size of the window to be large
  85 enough to accomodate the minimum size needed by the sizer, (along with
  86 a few other constraints...) If the sizer is the one that is assigned
  87 to the window then this should be equivalent to \texttt{window.Fit()}.
  88
  89 {\bf sizer.Layout()}: Recalcualtes the minimum space needed by each
  90 item in the sizer, and then lays out the items within the space
  91 currently allotted to the sizer.
  92
  93 {\bf window.Layout()}: If the window has a sizer then it sets the
  94 space given to the sizer to the current size of the window, which
  95 results in a call to \texttt{sizer.Layout()}. If the window has layout
  96 constraints instead of a sizer then the constraints algorithm is
  97 run. The \texttt{Layout()} method is what is called by the default
  98 \texttt{EVT\_SIZE} handler for container windows.
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