added images for topic overviews

[wxWidgets.git] / docs / doxygen / overviews / windowsizing.h

/////////////////////////////////////////////////////////////////////////////
// Name:        windowsizing
// Purpose:     topic overview
// Author:      wxWidgets team
// RCS-ID:      $Id$
// Licence:     wxWindows license
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/*!

 @page overview_windowsizing Window Sizing Overview

 It can sometimes be confusing to keep track of the various
 size-related attributes of a #wxWindow, 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.
 @b BestSize: 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
 #wxListBox's best size will be calculated based on
 how many items it has, up to a certain limit, or a
 #wxButton'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). Get the
 picture? There is a special virtual method in the C++ window classes
 called @c DoGetBestSize() that a class needs to override if it
 wants to calculate its own best size based on its content. The default
 @c DoGetBestSize() is designed for use in container windows,
 such as #wxPanel, and works something like this:


   If the window has a sizer then it is used to calculate the best size.
   Otherwise if the window has layout constraints then that is used to calculate the best size.
   Otherwise if the window has children then the best size is set to be large enough to show all the children.
   Otherwise if there are no children then the window's min size will be used for the best size.
   Otherwise if there is no min size set, then the current size is used for the best size.


 @b MinSize: The min size of a widget is a size that is normally
 explicitly set by the programmer either with the @c SetMinSize()
 method or the @c SetSizeHints() method. Most controls will also
 set the min size to the size given in the control's constructor if a
 non-default value is passed. Top-level windows such as
 #wxFrame will not allow the user to resize the frame
 below the min size.
 @b Size: The size of a widget can be explicitly set or fetched with
 the @c SetSize() or @c 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.
 @b ClientSize: 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 @c EVT_PAINT event. If a widget doesn't have a
 border then its client size is the same as its size.
 @b InitialSize: 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 min size. If
 the size passed to the constructor is the default
 @c wxDefaultSize, or if the size is not fully specified (such as
 @c wxSize(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.
 @b GetEffectiveMinSize(): (formerly @c GetBestFittingSize) A
 blending of the widget's min size and best size, giving precedence to
 the min size. For example, if a widget's min size is set to (150, -1)
 and the best size is (80, 22) then the best fitting size is (150,
 22). If the min size is (50, 20) then the best fitting size is (50,
 20). This method is what is called by the sizers when determining what
 the requirements of each item in the sizer is, and is used for
 calculating the overall minimum needs of the sizer.
 @b SetInitialSize(size): (formerly @c SetBestFittingSize)
 This is a little different than the typical size setters. Rather than
 just setting an "initial size" attribute it actually sets the minsize
 to the value passed in, blends that value with the best size, and then
 sets the size of the widget to be the result. So you can consider this
 method to be a "Smart SetSize". This method is what is called by the
 constructor of most controls to set the minsize and initial size of
 the control.
 @b window.Fit(): The @c Fit() method sets the size of a
 window to fit around its children. If it has no children then nothing
 is done, if it does have children then the size of the window is set
 to the window's best size.
 @b sizer.Fit(window): This sets the size of the window to be large
 enough to accommodate the minimum size needed by the sizer, (along with
 a few other constraints...) If the sizer is the one that is assigned
 to the window then this should be equivalent to @c window.Fit().
 @b sizer.Layout(): Recalculates the minimum space needed by each
 item in the sizer, and then lays out the items within the space
 currently allotted to the sizer.
 @b window.Layout(): If the window has a sizer then it sets the
 space given to the sizer to the current size of the window, which
 results in a call to @c sizer.Layout(). If the window has layout
 constraints instead of a sizer then the constraints algorithm is
 run. The @c Layout() method is what is called by the default
 @c EVT_SIZE handler for container windows.

 */