docs/latex/wx/boxsizer.tex

   1 \section{\class{wxBoxSizer}}\label{wxboxsizer}
   2
   3 The basic idea behind a box sizer is that windows will most often be laid out in rather
   4 simple basic geomerty, typically in a row or a column or several hierachies of either.
   5
   6 As an example, we will construct a dialog that will contain a text field at the top and
   7 two buttons at the bottom. This can be seen as a top-hierarchy column with the text at
   8 the top and buttons at the bottom and a low-hierchary row with an OK button to the left
   9 and a Cancel button to the right. In many cases (particulary dialogs under Unix and
  10 normal frames) the main window will be resizable by the user and this change of size
  11 will have to get propagated to its children. In our case, we want the text area to grow
  12 with the dialog, whereas the button shall have a fixed size. In addition, there will be
  13 a thin border around all controls to make the dialog look nice and - to make matter worse -
  14 the buttons shall be centred as the width of the dialog changes.
  15
  16 It is the unique feature of a box sizer, that it can grow in both directions (height and
  17 width) but can distribute its growth in the main direction (horizontal for a row) {\it unevenly}
  18 among its children. In our example case, the vertical sizer is supposed to propagate all its
  19 height changes to only the text area, not to the button area. This is determined by the {\it option} parameter
  20 when adding a window (or another sizer) to a sizer. It is interpreted
  21 as a weight factor, i.e. it can be zero, indicating that the window may not be resized
  22 at all, or above zero. If several windows have a value above zero, the value is interpreted
  23 relative to the sum of all weight factors of the sizer, so when adding two windows with
  24 a value of 1, they will both get resized equally much and each half as much as the sizer
  25 owning them. Then what do we do when a column sizer changes its width? This behaviour is
  26 controlled by {\it flags} (the second parameter of the Add() function): Zero or no flag
  27 indicates that the window will preserve it is original size, wxGROW flag (same as wxEXPAND)
  28 forces the window to grow with the sizer, and wxSHAPED flag tells the window to change it is
  29 size proportionally, preserving original aspect ratio.  When wxGROW flag is not used,
  30 the item can be aligned within available space.  wxALIGN\_LEFT, wxALIGN\_TOP, wxALIGN\_RIGHT,
  31 wxALIGN\_BOTTOM, wxALIGN\_CENTER\_HORIZONTAL and wxALIGN\_CENTER\_VERTICAL do what they say.
  32 wxALIGN\_CENTRE (same as wxALIGN\_CENTER) is defined as (wxALIGN\_CENTER\_HORIZONTAL |
  33 wxALIGN\_CENTER\_VERTICAL).  Default alignment is wxALIGN\_LEFT | wxALIGN\_TOP.
  34
  35 As mentioned above, any window belonging to a sizer may have border, and it can be specified
  36 which of the four sides may have this border, using the wxTOP, wxLEFT, wxRIGHT and wxBOTTOM
  37 constants or wxALL for all directions (and you may also use wxNORTH, wxWEST etc instead). These
  38 flags can be used in combination with the alignment flags above as the second parameter of the
  39 Add() method using the binary or operator |. The sizer of the border also must be made known,
  40 and it is the third parameter in the Add() method. This means, that the entire behaviour of
  41 a sizer and its children can be controlled by the three parameters of the Add() method.
  42
  43 \begin{verbatim}
  44 // we want to get a dialog that is stretchable because it
  45 // has a text ctrl at the top and two buttons at the bottom
  46
  47 MyDialog::MyDialog(wxFrame *parent, wxWindowID id, const wxString &title ) :
  48   wxDialog( parent, id, title, wxDefaultPosition, wxDefaultSize, wxDIALOG_STYLE | wxRESIZE_BORDER )
  49 {
  50   wxBoxSizer *topsizer = new wxBoxSizer( wxVERTICAL );
  51
  52   // create text ctrl with minimal size 100x60
  53   topsizer->Add(
  54     new wxTextCtrl( this, -1, "My text.", wxDefaultPosition, wxSize(100,60), wxTE_MULTILINE),
  55     1,            // make vertically stretchable
  56     wxEXPAND |    // make horizontally stretchable
  57     wxALL,        //   and make border all around
  58     10 );         // set border width to 10
  59
  60
  61   wxBoxSizer *button_sizer = new wxBoxSizer( wxHORIZONTAL );
  62   button_sizer->Add(
  63      new wxButton( this, wxID_OK, "OK" ),
  64      0,           // make horizontally unstretchable
  65      wxALL,       // make border all around (implicit top alignment)
  66      10 );        // set border width to 10
  67   button_sizer->Add(
  68      new wxButton( this, wxID_CANCEL, "Cancel" ),
  69      0,           // make horizontally unstretchable
  70      wxALL,       // make border all around (implicit top alignment)
  71      10 );        // set border width to 10
  72
  73   topsizer->Add(
  74      button_sizer,
  75      0,                // make vertically unstretchable
  76      wxALIGN_CENTER ); // no border and centre horizontally
  77
  78   SetAutoLayout( TRUE );     // tell dialog to use sizer
  79   SetSizer( topsizer );      // actually set the sizer
  80
  81   topsizer->Fit( this );            // set size to minimum size as calculated by the sizer
  82   topsizer->SetSizeHints( this );   // set size hints to honour mininum size
  83 }
  84 \end{verbatim}
  85
  86 \wxheading{Derived from}
  87
  88 \helpref{wxSizer}{wxsizer}\\
  89 \helpref{wxObject}{wxobject}
  90
  91 \membersection{wxBoxSizer::wxBoxSizer}\label{wxboxsizerwxboxsizer}
  92
  93 \func{}{wxBoxSizer}{\param{int }{orient}}
  94
  95 Constructor for a wxBoxSizer. {\it orient} may be either of wxVERTICAL
  96 or wxHORIZONTAL for creating either a column sizer or a row sizer.
  97
  98 \membersection{wxBoxSizer::RecalcSizes}\label{wxboxsizerrecalcsizes}
  99
 100 \func{void}{RecalcSizes}{\void}
 101
 102 Implements the calculation of a box sizer's dimensions and then sets
 103 the size of its its children (calling \helpref{wxWindow::SetSize}{wxwindowsetsize}
 104 if the child is a window). It is used internally only and must not be called
 105 by the user. Documented for information.
 106
 107 \membersection{wxBoxSizer::CalcMin}\label{wxboxsizercalcmin}
 108
 109 \func{wxSize}{CalcMin}{\void}
 110
 111 Implements the calculation of a box sizer's minimal. It is used internally
 112 only and must not be called by the user. Documented for information.
 113
 114 \membersection{wxBoxSizer::GetOrientation}\label{wxboxsizergetorientation}
 115
 116 \func{int}{GetOrientation}{\void}
 117
 118 Returns the orientation of the box sizer, either wxVERTICAL
 119 or wxHORIZONTAL.
 120