cd8b0a9914
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@43537 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
103 lines
5.1 KiB
TeX
103 lines
5.1 KiB
TeX
\section{Window Sizing Overview}\label{windowsizingoverview}
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It can sometimes be confusing to keep track of the various
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size-related attributes of a \helpref{wxWindow}{wxwindow}, how they
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relate to each other, and how they interact with sizers. This document
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will attempt to clear the fog a little, and give some simple
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explanations of things.
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{\bf BestSize}: The best size of a widget depends on what kind of widget it
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is, and usually also on the contents of the widget. For example a
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\helpref{wxListBox}{wxlistbox}'s best size will be calculated based on
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how many items it has, up to a certain limit, or a
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\helpref{wxButton}{wxbutton}'s best size will be calculated based on
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its label size, but normally won't be smaller than the platform
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default button size (unless a style flag overrides that). Get the
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picture? There is a special virtual method in the C++ window classes
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called \texttt{DoGetBestSize()} that a class needs to override if it
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wants to calculate its own best size based on its content. The default
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\texttt{DoGetBestSize()} is designed for use in container windows,
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such as \helpref{wxPanel}{wxpanel}, and works something like this:
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\begin{enumerate}
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\item{If the window has a sizer then it is used to calculate the best size.}
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\item{Otherwise if the window has layout constraints then that is used to calculate the best size.}
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\item{Otherwise if the window has children then the best size is set to be large enough to show all the children.}
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\item{Otherwise if there are no children then the window's min size will be used for the best size.}
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\item{Otherwise if there is no min size set, then the current size is used for the best size.}
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\end{enumerate}
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{\bf MinSize}: The min size of a widget is a size that is normally
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explicitly set by the programmer either with the \texttt{SetMinSize()}
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method or the \texttt{SetSizeHints()} method. Most controls will also
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set the min size to the size given in the control's constructor if a
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non-default value is passed. Top-level windows such as
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\helpref{wxFrame}{wxframe} will not allow the user to resize the frame
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below the min size.
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{\bf Size}: The size of a widget can be explicitly set or fetched with
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the \texttt{SetSize()} or \texttt{GetSize()} methods. This size value
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is the size that the widget is currently using on screen and is the
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way to change the size of something that is not being managed by a
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sizer.
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{\bf ClientSize}: The client size represents the widget's area inside
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of any borders belonging to the widget and is the area that can be
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drawn upon in a \texttt{EVT\_PAINT} event. If a widget doesn't have a
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border then its client size is the same as its size.
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{\bf InitialSize}: The initial size of a widget is the size given to
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the constructor of the widget, if any. As mentioned above most
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controls will also set this size value as the control's min size. If
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the size passed to the constructor is the default
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\texttt{wxDefaultSize}, or if the size is not fully specified (such as
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\texttt{wxSize(150,-1)}) then most controls will fill in the missing
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size components using the best size and will set the initial size of
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the control to the resulting size.
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{\bf GetEffectiveMinSize()}: (formerly \texttt{GetBestFittingSize}) A
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blending of the widget's min size and best size, giving precedence to
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the min size. For example, if a widget's min size is set to (150, -1)
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and the best size is (80, 22) then the best fitting size is (150,
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22). If the min size is (50, 20) then the best fitting size is (50,
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20). This method is what is called by the sizers when determining what
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the requirements of each item in the sizer is, and is used for
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calculating the overall minimum needs of the sizer.
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{\bf SetInitialSize(size)}: (formerly \texttt{SetBestFittingSize})
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This is a little different than the typical size setters. Rather than
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just setting an "initial size" attribute it actually sets the minsize
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to the value passed in, blends that value with the best size, and then
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sets the size of the widget to be the result. So you can consider this
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method to be a "Smart SetSize". This method is what is called by the
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constructor of most controls to set the minsize and initial size of
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the control.
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{\bf window.Fit()}: The \texttt{Fit()} method sets the size of a
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window to fit around its children. If it has no children then nothing
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is done, if it does have children then the size of the window is set
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to the window's best size.
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{\bf sizer.Fit(window)}: This sets the size of the window to be large
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enough to accommodate the minimum size needed by the sizer, (along with
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a few other constraints...) If the sizer is the one that is assigned
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to the window then this should be equivalent to \texttt{window.Fit()}.
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{\bf sizer.Layout()}: Recalculates the minimum space needed by each
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item in the sizer, and then lays out the items within the space
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currently allotted to the sizer.
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{\bf window.Layout()}: If the window has a sizer then it sets the
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space given to the sizer to the current size of the window, which
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results in a call to \texttt{sizer.Layout()}. If the window has layout
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constraints instead of a sizer then the constraints algorithm is
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run. The \texttt{Layout()} method is what is called by the default
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\texttt{EVT\_SIZE} handler for container windows.
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