## wxSizer

wxSizer is the abstract base class used for laying out subwindows in a window. You cannot use wxSizer directly; instead, you will have to use one of the sizer classes derived from it. Currently there are wxBoxSizer, wxStaticBoxSizer, wxNotebookSizer, wxGridSizer and wxFlexGridSizer.

The layout algorithm used by sizers in wxWindows is closely related to layout in other GUI toolkits, such as Java's AWT, the GTK toolkit or the Qt toolkit. It is based upon the idea of the individual subwindows reporting their minimal required size and their ability to get stretched if the size of the parent window has changed. This will most often mean, that the programmer does not set the original size of a dialog in the beginning, rather the dialog will assigned a sizer and this sizer will be queried about the recommended size. The sizer in turn will query its children, which can be normal windows, empty space or other sizers, so that a hierarchy of sizers can be constructed. Note that wxSizer does not derive from wxWindow and thus do not interfere with tab ordering and requires very little resources compared to a real window on screen.

What makes sizers so well fitted for use in wxWindows is the fact that every control reports its own minimal size and the algorithm can handle differences in font sizes or different window (dialog item) sizes on different platforms without problems. If e.g. the standard font as well as the overall design of Motif widgets requires more space than on Windows, the initial dialog size will automatically be bigger on Motif than on Windows.

wxPython note: If you wish to create a sizer class in wxPython you should derive the class from `wxPySizer` in order to get Python-aware capabilities for the various virtual methods.

Derived from

wxObject

See also

Sizer overview

Members

wxSizer::wxSizer
wxSizer::~wxSizer
wxSizer::Add
wxSizer::CalcMin
wxSizer::Fit
wxSizer::FitInside
wxSizer::GetSize
wxSizer::GetPosition
wxSizer::GetMinSize
wxSizer::Layout
wxSizer::Prepend
wxSizer::RecalcSizes
wxSizer::Remove
wxSizer::SetDimension
wxSizer::SetMinSize
wxSizer::SetItemMinSize
wxSizer::SetSizeHints
wxSizer::SetVirtualSizeHints
wxSizer::Show

### wxSizer::wxSizer

wxSizer()

The constructor. Note that wxSizer is an abstract base class and may not be instantiated.

### wxSizer::~wxSizer

~wxSizer()

The destructor.

### wxSizer::Add

void Add(wxWindow* window, int proportion = 0,int flag = 0, int border = 0, wxObject* userData = NULL)

void Add(wxSizer* sizer, int proportion = 0, int flag = 0, int border = 0, wxObject* userData = NULL)

void Add(int width, int height, int proportion = 0, int flag = 0, int border = 0, wxObject* userData = NULL)

Adds the window to the sizer. As wxSizer itself is an abstract class, the parameters have no meaning in the wxSizer class itself, but as there currently is only one class deriving directly from wxSizer and this class does not override these methods, the meaning of the parameters is described here:

window

The window to be added to the sizer. Its initial size (either set explicitly by the user or calculated internally when using wxDefaultSize) is interpreted as the minimal and in many cases also the initial size. This is particularly useful in connection with SetSizeHints.

sizer

The (child-)sizer to be added to the sizer. This allows placing a child sizer in a sizer and thus to create hierarchies of sizers (typically a vertical box as the top sizer and several horizontal boxes on the level beneath).

width and height

The dimension of a spacer to be added to the sizer. Adding spacers to sizers gives more flexibility in the design of dialogs; imagine for example a horizontal box with two buttons at the bottom of a dialog: you might want to insert a space between the two buttons and make that space stretchable using the proportion flag and the result will be that the left button will be aligned with the left side of the dialog and the right button with the right side - the space in between will shrink and grow with the dialog.

proportion

Although the meaning of this parameter is undefined in wxSizer, it is used in wxBoxSizer to indicate if a child of a sizer can change its size in the main orientation of the wxBoxSizer - where 0 stands for not changeable and a value of more than zero is interpreted relative to the value of other children of the same wxBoxSizer. For example, you might have a horizontal wxBoxSizer with three children, two of which are supposed to change their size with the sizer. Then the two stretchable windows would get a value of 1 each to make them grow and shrink equally with the sizer's horizontal dimension.

flag

This parameter can be used to set a number of flags which can be combined using the binary OR operator |. Two main behaviours are defined using these flags. One is the border around a window: the border parameter determines the border width whereas the flags given here determine where the border may be (wxTOP, wxBOTTOM, wxLEFT, wxRIGHT or wxALL). The other flags determine the child window's behaviour if the size of the sizer changes. However this is not - in contrast to the proportion flag - in the main orientation, but in the respectively other orientation. So if you created a wxBoxSizer with the wxVERTICAL option, these flags will be relevant if the sizer changes its horizontal size. A child may get resized to completely fill out the new size (using either wxGROW or wxEXPAND), it may get proportionally resized (wxSHAPED), it may get centered (wxALIGN_CENTER or wxALIGN_CENTRE) or it may get aligned to either side (wxALIGN_LEFT and wxALIGN_TOP are set to 0 and thus represent the default, wxALIGN_RIGHT and wxALIGN_BOTTOM have their obvious meaning). With proportional resize, a child may also be centered in the main orientation using wxALIGN_CENTER_VERTICAL (same as wxALIGN_CENTRE_VERTICAL) and wxALIGN_CENTER_HORIZONTAL (same as wxALIGN_CENTRE_HORIZONTAL) flags. Finally, you can also specify wxADJUST_MINSIZE flag to make the minimal size of the control dynamically adjust to the value returned by its GetAdjustedBestSize() method - this allows, for example, for correct relayouting of a static text control even if its text is changed during run-time.

border

Determines the border width, if the flag parameter is set to any border.

userData

Allows an extra object to be attached to the sizer item, for use in derived classes when sizing information is more complex than the proportion and flag will allow for.

### wxSizer::CalcMin

wxSize CalcMin()

This method is abstract and has to be overwritten by any derived class. Here, the sizer will do the actual calculation of its children minimal sizes.

### wxSizer::Fit

wxSize Fit(wxWindow* window)

Tell the sizer to resize the window to match the sizer's minimal size. This is commonly done in the constructor of the window itself, see sample in the description of wxBoxSizer. Returns the new size.

### wxSizer::FitInside

void FitInside(wxWindow* window)

Tell the sizer to resize the virtual size of the window to match the sizer's minimal size. This will not alter the on screen size of the window, but may cause the addition/removal/alteration of scrollbars required to view the virtual area in windows which manage it.

See also

wxScrolledWindow::SetScrollbars, wxSizer::SetVirtualSizeHints

### wxSizer::GetSize

wxSize GetSize()

Returns the current size of the sizer.

### wxSizer::GetPosition

wxPoint GetPosition()

Returns the current position of the sizer.

### wxSizer::GetMinSize

wxSize GetMinSize()

Returns the minimal size of the sizer. This is either the combined minimal size of all the children and their borders or the minimal size set by SetMinSize, depending on which is bigger.

### wxSizer::Layout

void Layout()

Call this to force layout of the children anew, e.g. after having added a child to or removed a child (window, other sizer or space) from the sizer while keeping the current dimension.

### wxSizer::Prepend

void Prepend(wxWindow* window, int proportion = 0, int flag = 0, int border = 0, wxObject* userData = NULL)

void Prepend(wxSizer* sizer, int proportion = 0, int flag = 0, int border = 0, wxObject* userData = NULL)

void Prepend(int width, int height, int proportion = 0, int flag = 0, int border= 0, wxObject* userData = NULL)

Same as wxSizer::Add, but prepends the items to the beginning of the list of items (windows, subsizers or spaces) owned by this sizer.

### wxSizer::RecalcSizes

void RecalcSizes()

This method is abstract and has to be overwritten by any derived class. Here, the sizer will do the actual calculation of its children's positions and sizes.

### wxSizer::Remove

bool Remove(wxWindow* window)

bool Remove(wxSizer* sizer)

bool Remove(int nth)

Removes a child from the sizer. window is the window to be removed, sizer is the equivalent sizer and nth is the position of the child in the sizer, typically 0 for the first item. This method does not cause any layout or resizing to take place and does not delete the window itself. Call wxSizer::Layout to update the layout "on screen" after removing a child from the sizer.

Returns TRUE if the child item was found and removed, FALSE otherwise.

### wxSizer::SetDimension

void SetDimension(int x, int y, int width, int height)

Call this to force the sizer to take the given dimension and thus force the items owned by the sizer to resize themselves according to the rules defined by the parameter in the Add and Prepend methods.

### wxSizer::SetMinSize

void SetMinSize(int width, int height)

void SetMinSize(wxSize size)

Call this to give the sizer a minimal size. Normally, the sizer will calculate its minimal size based purely on how much space its children need. After calling this method GetMinSize will return either the minimal size as requested by its children or the minimal size set here, depending on which is bigger.

### wxSizer::SetItemMinSize

void SetItemMinSize(wxWindow* window, int width, int height)

void SetItemMinSize(wxSizer* sizer, int width, int height)

void SetItemMinSize(int pos, int width, int height)

Set an item's minimum size by window, sizer, or position. The item will be found recursively in the sizer's descendants. This function enables an application to set the size of an item after initial creation.

### wxSizer::SetSizeHints

void SetSizeHints(wxWindow* window)

Tell the sizer to set (and Fit) the minimal size of the window to match the sizer's minimal size. This is commonly done in the constructor of the window itself, see sample in the description of wxBoxSizer if the window is resizable (as are many dialogs under Unix and frames on probably all platforms).

### wxSizer::SetVirtualSizeHints

void SetVirtualSizeHints(wxWindow* window)

Tell the sizer to set the minimal size of the window virtual area to match the sizer's minimal size. For windows with managed scrollbars this will set them appropriately.

See also

wxScrolledWindow::SetScrollbars

### wxSizer::Show

void Show(wxWindow* window, bool show = TRUE)

void Show(wxSizer* sizer, bool show = TRUE)

Shows or hides a window or sizer. To make a sizer item disappear or reappear, use Show() followed by Layout().