## 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, wxGridSizer wxFlexGridSizer and wxGridBagSizer.

The layout algorithm used by sizers in wxWidgets 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 be 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 does 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 wxWidgets 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.

Sizers may also be used to control the layout of custom drawn items on the window. The Add, Insert, and Prepend functions return a pointer to the newly added wxSizerItem. Just add empty space of the desired size and attributes, and then use the wxSizerItem::GetRect method to determine where the drawing operations should take place.

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
wxClientDataContainer

Include files

<wx/sizer.h>

See also

Sizer overview

Members

wxSizer::wxSizer
wxSizer::~wxSizer
wxSizer::Add
wxSizer::AddSpacer
wxSizer::AddStretchSpacer
wxSizer::CalcMin
wxSizer::Detach
wxSizer::Fit
wxSizer::FitInside
wxSizer::GetItem
wxSizer::GetSize
wxSizer::GetPosition
wxSizer::GetMinSize
wxSizer::Insert
wxSizer::InsertSpacer
wxSizer::InsertStretchSpacer
wxSizer::Layout
wxSizer::Prepend
wxSizer::PrependSpacer
wxSizer::PrependStretchSpacer
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

wxSizerItem* Add(wxWindow* window, const wxSizerFlags& flags)

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

wxSizerItem* Add(wxSizer* sizer, const wxSizerFlags& flags)

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

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

Appends a child to the sizer. wxSizer itself is an abstract class, but the parameters are equivalent in the derived classes that you will instantiate to use it so they are 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 which side(s) of the item that the border will be added. The other flags determine how the sizer item behaves when the space allotted to the sizer changes, and is somewhat dependent on the specific kind of sizer used.

wxTOP wxBOTTOM wxLEFT wxRIGHT wxALL | These flags are used to specify which side(s) of the sizer item the border width will apply to.

wxEXPAND | The item will be expanded to fill the space assigned to the item.
wxSHAPED | The item will be expanded as much as possible while also maintaining its aspect ratio
wxFIXED_MINSIZE | Normally wxSizers will use GetAdjustedBestSize to determine what the minimal size of window items should be, and will use that size to calculate the layout. This allows layouts to adjust when an item changes and its best size becomes different. If you would rather have a window item stay the size it started with then use wxFIXED_MINSIZE.
wxALIGN_CENTER wxALIGN_LEFT wxALIGN_RIGHT wxALIGN_TOP wxALIGN_BOTTOM wxALIGN_CENTER_VERTICAL wxALIGN_CENTER_HORIZONTAL | The wxALIGN flags allow you to specify the alignment of the item within the space allotted to it by the sizer, adjusted for the border if any.

border

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

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.

flags

A wxSizerFlags object that enables you to specify most of the above parameters more conveniently.

### wxSizer::AddSpacer

wxSizerItem* AddSpacer(int size)

Adds non-stretchable space to the sizer. More readable way of calling Add(size, size, 0).

### wxSizer::AddStretchSpacer

wxSizerItem* AddStretchSpacer(int prop = 1)

Adds stretchable space to the sizer. More readable way of calling Add(0, 0, prop).

### 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::Detach

bool Detach(wxWindow* window)

bool Detach(wxSizer* sizer)

bool Detach(size_t index)

Detach a child from the sizer without destroying it. window is the window to be detached, sizer is the equivalent sizer and index 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, call wxSizer::Layout to update the layout "on screen" after detaching a child from the sizer.

Returns true if the child item was found and detached, false otherwise.

See also

wxSizer::Remove

### 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.

For a top level window this is the total window size, not client 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::GetItem

wxSizerItem * GetItem(wxWindow* window, bool recursive = false)

wxSizerItem * GetItem(wxSizer* sizer, bool recursive = false)

wxSizerItem * GetItem(size_t index)

Finds item of the sizer which holds given window, sizer or is located in sizer at position index. Use parameter recursive to search in subsizers too.

Returns pointer to item or NULL.

### 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::Insert

wxSizerItem* Insert(size_t index, wxWindow* window, const wxSizerFlags& flags)

wxSizerItem* Insert(size_t index, wxWindow* window, int proportion = 0,int flag = 0, int border = 0, wxObject* userData = NULL)

wxSizerItem* Insert(size_t index, wxSizer* sizer, const wxSizerFlags& flags)

wxSizerItem* Insert(size_t index, wxSizer* sizer, int proportion = 0, int flag = 0, int border = 0, wxObject* userData = NULL)

wxSizerItem* Insert(size_t index, int width, int height, int proportion = 0, int flag = 0, int border = 0, wxObject* userData = NULL)

Insert a child into the sizer before any existing item at index.

index

The position this child should assume in the sizer.

See wxSizer::Add for the meaning of the other parameters.

### wxSizer::InsertSpacer

wxSizerItem* InsertSpacer(size_t index, int size)

Inserts non-stretchable space to the sizer. More readable way of calling Insert(size, size, 0).

### wxSizer::InsertStretchSpacer

wxSizerItem* InsertStretchSpacer(size_t index, int prop = 1)

Inserts stretchable space to the sizer. More readable way of calling Insert(0, 0, prop).

### 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

wxSizerItem* Prepend(wxWindow* window, const wxSizerFlags& flags)

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

wxSizerItem* Prepend(wxSizer* sizer, const wxSizerFlags& flags)

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

wxSizerItem* 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::PrependSpacer

wxSizerItem* PrependSpacer(int size)

Prepends non-stretchable space to the sizer. More readable way of calling Prepend(size, size, 0).

### wxSizer::PrependStretchSpacer

wxSizerItem* PrependStretchSpacer(int prop = 1)

Prepends stretchable space to the sizer. More readable way of calling Prepend(0, 0, prop).

### 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(size_t index)

Removes a child from the sizer and destroys it. sizer is the wxSizer to be removed, index 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, call wxSizer::Layout to update the layout "on screen" after removing a child from the sizer.

NB: The method taking a wxWindow* parameter is deprecated. For historical reasons it does not destroy the window as would usually be expected from Remove. You should use wxSizer::Detach in new code instead. There is currently no wxSizer method that will both detach and destroy a wxWindow item.

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(size_t index, 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

bool Show(wxWindow* window, bool show = true, bool recursive = false)

bool Show(wxSizer* sizer, bool show = true, bool recursive = false)

bool Show(size_t index, bool show = true)

Shows or hides the window, sizer, or item at index. To make a sizer item disappear or reappear, use Show() followed by Layout(). Use parameter recursive to show or hide elements found in subsizers.

Returns true if the child item was found, false otherwise.

Note that this only works with wxBoxSizer and wxFlexGridSizer, since they are the only two sizer classes that can size rows/columns independently.