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,
  49                    wxDEFAULT_DIALOG_STYLE | wxRESIZE_BORDER)
  50 {
  51   wxBoxSizer *topsizer = new wxBoxSizer( wxVERTICAL );
  52
  53   // create text ctrl with minimal size 100x60
  54   topsizer->Add(
  55     new wxTextCtrl( this, -1, "My text.", wxDefaultPosition, wxSize(100,60), wxTE_MULTILINE),
  56     1,            // make vertically stretchable
  57     wxEXPAND |    // make horizontally stretchable
  58     wxALL,        //   and make border all around
  59     10 );         // set border width to 10
  60
  61
  62   wxBoxSizer *button_sizer = new wxBoxSizer( wxHORIZONTAL );
  63   button_sizer->Add(
  64      new wxButton( this, wxID_OK, "OK" ),
  65      0,           // make horizontally unstretchable
  66      wxALL,       // make border all around (implicit top alignment)
  67      10 );        // set border width to 10
  68   button_sizer->Add(
  69      new wxButton( this, wxID_CANCEL, "Cancel" ),
  70      0,           // make horizontally unstretchable
  71      wxALL,       // make border all around (implicit top alignment)
  72      10 );        // set border width to 10
  73
  74   topsizer->Add(
  75      button_sizer,
  76      0,                // make vertically unstretchable
  77      wxALIGN_CENTER ); // no border and centre horizontally
  78
  79   SetAutoLayout( TRUE );     // tell dialog to use sizer
  80   SetSizer( topsizer );      // actually set the sizer
  81
  82   topsizer->Fit( this );            // set size to minimum size as calculated by the sizer
  83   topsizer->SetSizeHints( this );   // set size hints to honour mininum size
  84 }
  85 \end{verbatim}
  86
  87 \wxheading{Derived from}
  88
  89 \helpref{wxSizer}{wxsizer}\\
  90 \helpref{wxObject}{wxobject}
  91
  92 \membersection{wxBoxSizer::wxBoxSizer}\label{wxboxsizerwxboxsizer}
  93
  94 \func{}{wxBoxSizer}{\param{int }{orient}}
  95
  96 Constructor for a wxBoxSizer. {\it orient} may be either of wxVERTICAL
  97 or wxHORIZONTAL for creating either a column sizer or a row sizer.
  98
  99 \membersection{wxBoxSizer::RecalcSizes}\label{wxboxsizerrecalcsizes}
 100
 101 \func{void}{RecalcSizes}{\void}
 102
 103 Implements the calculation of a box sizer's dimensions and then sets
 104 the size of its its children (calling \helpref{wxWindow::SetSize}{wxwindowsetsize}
 105 if the child is a window). It is used internally only and must not be called
 106 by the user. Documented for information.
 107
 108 \membersection{wxBoxSizer::CalcMin}\label{wxboxsizercalcmin}
 109
 110 \func{wxSize}{CalcMin}{\void}
 111
 112 Implements the calculation of a box sizer's minimal. It is used internally
 113 only and must not be called by the user. Documented for information.
 114
 115 \membersection{wxBoxSizer::GetOrientation}\label{wxboxsizergetorientation}
 116
 117 \func{int}{GetOrientation}{\void}
 118
 119 Returns the orientation of the box sizer, either wxVERTICAL
 120 or wxHORIZONTAL.
 121