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1 | \section{Sizer overview}\label{sizeroverview} |
2 | ||
3 | Classes: \helpref{wxSizer}{wxsizer}, \helpref{wxGridSizer}{wxgridsizer}, | |
4 | \helpref{wxFlexGridSizer}{wxflexgridsizer}, \helpref{wxBoxSizer}{wxboxsizer}, | |
5 | \helpref{wxStaticBoxSizer}{wxstaticboxsizer}, | |
6 | \helpref{wxNotebookSizer}{wxnotebooksizer} | |
7 | ||
8 | Sizers, as represented by the wxSizer class and its descendants in | |
9 | the wxWindows class hierarchy, have become the method of choice to | |
10 | define the layout of controls in dialogs in wxWindows because of | |
11 | their ability to create visually appealing dialogs independent of the | |
12 | platform, taking into account the differences in size and style of | |
13 | the individual controls. Unlike the original wxWindows Dialog Editor, | |
14 | editors such as wxDesigner, wxrcedit, XRCed and wxWorkshop create dialogs based exclusively on sizers, | |
15 | practically forcing the user to create platform independent layouts without compromises. | |
16 | ||
17 | The next section describes and shows what can be done with sizers. | |
18 | The following sections briefly describe how to program with individual sizer classes. | |
19 | ||
20 | For information about the new wxWindows resource system, which can describe | |
21 | sizer-based dialogs, see the \helpref{XML-based resource system overview}{xrcoverview}. | |
22 | ||
23 | \subsection{The idea behind sizers}\label{ideabehindsizers} | |
24 | ||
25 | The layout algorithm used by sizers in wxWindows is closely related to layout | |
26 | systems in other GUI toolkits, such as Java's AWT, the GTK toolkit or the Qt toolkit. It is | |
27 | based upon the idea of individual subwindows reporting their minimal required | |
28 | size and their ability to get stretched if the size of the parent window has changed. | |
29 | This will most often mean that the programmer does not set the start-up size of | |
30 | a dialog, the dialog will rather be assigned a sizer and this sizer | |
31 | will be queried about the recommended size. This sizer in turn will query its | |
32 | children (which can be normal windows, empty space or other sizers) so that | |
33 | a hierarchy of sizers can be constructed. Note that wxSizer does not derive from wxWindow | |
34 | and thus does not interfere with tab ordering and requires very few resources compared | |
35 | to a real window on screen. | |
36 | ||
37 | What makes sizers so well fitted for use in wxWindows is the fact that every control | |
38 | reports its own minimal size and the algorithm can handle differences in font sizes | |
39 | or different window (dialog item) sizes on different platforms without problems. For example, if | |
40 | the standard font as well as the overall design of Linux/GTK widgets requires more space than | |
41 | on Windows, the initial dialog size will automatically be bigger on Linux/GTK than on Windows. | |
42 | ||
43 | There are currently five different kinds of sizers available in wxWindows. Each represents | |
44 | either a certain way to lay out dialog items in a dialog or it fulfils a special task | |
45 | such as wrapping a static box around a dialog item (or another sizer). These sizers will | |
46 | be discussed one by one in the text below. For more detailed information on how to use sizers | |
47 | programmatically, please refer to the section \helpref{Programming with Sizers}{sizersprogramming}. | |
48 | ||
49 | \subsubsection{Common features}\label{sizerscommonfeatures} | |
50 | ||
51 | All sizers are containers, that is, they are used to lay out one dialog item (or several | |
52 | dialog items), which they contain. Such items are sometimes referred to as the children | |
53 | of the sizer. Independent of how the individual sizers lay out their children, all children | |
54 | have certain features in common: | |
55 | ||
56 | {\bf A minimal size:} This minimal size is usually identical to | |
57 | the initial size of the controls and may either be set explicitly in the wxSize field | |
58 | of the control constructor or may be calculated by wxWindows, typically by setting | |
59 | the height and/or the width of the item to -1. Note that only some controls can | |
60 | calculate their size (such as a checkbox) whereas others (such as a listbox) | |
61 | don't have any natural width or height and thus require an explicit size. Some controls | |
62 | can calculate their height, but not their width (e.g. a single line text control): | |
63 | ||
64 | \center{ | |
65 | \image{}{sizer03.gif} | |
66 | ||
67 | \image{}{sizer04.gif} | |
68 | ||
69 | \image{}{sizer05.gif} | |
70 | } | |
71 | ||
72 | {\bf A border:} The border is just empty space and is used to separate dialog items | |
73 | in a dialog. This border can either be all around, or at any combination of sides | |
74 | such as only above and below the control. The thickness of this border must be set | |
75 | explicitly, typically 5 points. The following samples show dialogs with only one | |
76 | dialog item (a button) and a border of 0, 5, and 10 pixels around the button: | |
77 | ||
78 | \center{ | |
79 | \image{}{sizer00.gif} | |
80 | ||
81 | \image{}{sizer01.gif} | |
82 | ||
83 | \image{}{sizer02.gif} | |
84 | } | |
85 | ||
86 | {\bf An alignment:} Often, a dialog item is given more space than its minimal size | |
87 | plus its border. Depending on what flags are used for the respective dialog | |
88 | item, the dialog item can be made to fill out the available space entirely, i.e. | |
89 | it will grow to a size larger than the minimal size, or it will be moved to either | |
90 | the centre of the available space or to either side of the space. The following | |
91 | sample shows a listbox and three buttons in a horizontal box sizer; one button | |
92 | is centred, one is aligned at the top, one is aligned at the bottom: | |
93 | ||
94 | \center{ | |
95 | \image{}{sizer06.gif} | |
96 | } | |
97 | ||
98 | {\bf A stretch factor:} If a sizer contains more than one child and it is offered | |
99 | more space than its children and their borders need, the question arises how to | |
100 | distribute the surplus space among the children. For this purpose, a stretch | |
101 | factor may be assigned to each child, where the default value of 0 indicates that the child | |
102 | will not get more space than its requested minimum size. A value of more than zero | |
103 | is interpreted in relation to the sum of all stretch factors in the children | |
104 | of the respective sizer, i.e. if two children get a stretch factor of 1, they will | |
105 | get half the extra space each {\it independent of whether one control has a minimal | |
106 | sizer inferior to the other or not}. The following sample shows a dialog with | |
107 | three buttons, the first one has a stretch factor of 1 and thus gets stretched, | |
108 | whereas the other two buttons have a stretch factor of zero and keep their | |
109 | initial width: | |
110 | ||
111 | \center{ | |
112 | \image{}{sizer07.gif} | |
113 | } | |
114 | ||
115 | Within wxDesigner, this stretch factor gets set from the {\it Option} menu. | |
116 | ||
117 | \wxheading{wxBoxSizer} | |
118 | ||
119 | \helpref{wxBoxSizer}{wxboxsizer} can lay out its children either vertically | |
120 | or horizontally, depending on what flag is being used in its constructor. | |
121 | When using a vertical sizer, each child can be centered, aligned to the | |
122 | right or aligned to the left. Correspondingly, when using a horizontal | |
123 | sizer, each child can be centered, aligned at the bottom or aligned at | |
124 | the top. The stretch factor described in the last paragraph is used | |
125 | for the main orientation, i.e. when using a horizontal box sizer, the | |
126 | stretch factor determines how much the child can be stretched horizontally. | |
127 | The following sample shows the same dialog as in the last sample, | |
128 | only the box sizer is a vertical box sizer now: | |
129 | ||
130 | \center{ | |
131 | \image{}{sizer08.gif} | |
132 | } | |
133 | ||
134 | \wxheading{wxStaticBoxSizer} | |
135 | ||
136 | \helpref{wxStaticBoxSixer}{wxstaticboxsizer} is the same as a wxBoxSizer, but surrounded by a | |
137 | static box. Here is a sample: | |
138 | ||
139 | \center{ | |
140 | \image{}{sizer09.gif} | |
141 | } | |
142 | ||
143 | \wxheading{wxGridSizer} | |
144 | ||
145 | \helpref{wxGridSizer}{wxgridsizer} is a two-dimensional sizer. All children are given the | |
146 | same size, which is the minimal size required by the biggest child, in | |
147 | this case the text control in the left bottom border. Either the number | |
148 | of columns or the number or rows is fixed and the grid sizer will grow | |
149 | in the respectively other orientation if new children are added: | |
150 | ||
151 | \center{ | |
152 | \image{}{sizer10.gif} | |
153 | } | |
154 | ||
155 | For programming information, see \helpref{wxGridSizer}{wxgridsizer}. | |
156 | ||
157 | \wxheading{wxFlexGridSizer} | |
158 | ||
159 | Another two-dimensional sizer derived from | |
160 | wxGridSizer. The width of each column and the height of each row | |
161 | are calculated individually according the minimal requirements | |
162 | from the respectively biggest child. Additionally, columns and | |
163 | rows can be declared to be stretchable if the sizer is assigned | |
164 | a size different from that which it requested. The following sample shows | |
165 | the same dialog as the one above, but using a flex grid sizer: | |
166 | ||
167 | \center{ | |
168 | \image{}{sizer11.gif} | |
169 | } | |
170 | ||
171 | \wxheading{wxNotebookSizer} | |
172 | ||
173 | \helpref{wxNotebookSizer}{wxnotebooksizer} can be used in | |
174 | connection with notebooks. It calculates the size of each | |
175 | notebook page and sets the size of the notebook to the size | |
176 | of the biggest page plus some extra space required for the | |
177 | notebook tabs and decorations. | |
178 | ||
179 | \subsection{Programming with wxBoxSizer}\label{boxsizerprogramming} | |
180 | ||
181 | The basic idea behind a \helpref{wxBoxSizer}{wxboxsizer} is that windows will most often be laid out in rather | |
182 | simple basic geometry, typically in a row or a column or several hierarchies of either. | |
183 | ||
184 | As an example, we will construct a dialog that will contain a text field at the top and | |
185 | two buttons at the bottom. This can be seen as a top-hierarchy column with the text at | |
186 | the top and buttons at the bottom and a low-hierarchy row with an OK button to the left | |
187 | and a Cancel button to the right. In many cases (particularly dialogs under Unix and | |
188 | normal frames) the main window will be resizable by the user and this change of size | |
189 | will have to get propagated to its children. In our case, we want the text area to grow | |
190 | with the dialog, whereas the button shall have a fixed size. In addition, there will be | |
191 | a thin border around all controls to make the dialog look nice and - to make matter worse - | |
192 | the buttons shall be centred as the width of the dialog changes. | |
193 | ||
194 | It is the unique feature of a box sizer, that it can grow in both directions (height and | |
195 | width) but can distribute its growth in the main direction (horizontal for a row) {\it unevenly} | |
196 | among its children. In our example case, the vertical sizer is supposed to propagate all its | |
197 | height changes to only the text area, not to the button area. This is determined by the {\it option} parameter | |
198 | when adding a window (or another sizer) to a sizer. It is interpreted | |
199 | as a weight factor, i.e. it can be zero, indicating that the window may not be resized | |
200 | at all, or above zero. If several windows have a value above zero, the value is interpreted | |
201 | relative to the sum of all weight factors of the sizer, so when adding two windows with | |
202 | a value of 1, they will both get resized equally much and each half as much as the sizer | |
203 | owning them. Then what do we do when a column sizer changes its width? This behaviour is | |
204 | controlled by {\it flags} (the second parameter of the Add() function): Zero or no flag | |
205 | indicates that the window will preserve it is original size, wxGROW flag (same as wxEXPAND) | |
206 | forces the window to grow with the sizer, and wxSHAPED flag tells the window to change it is | |
207 | size proportionally, preserving original aspect ratio. When wxGROW flag is not used, | |
208 | the item can be aligned within available space. wxALIGN\_LEFT, wxALIGN\_TOP, wxALIGN\_RIGHT, | |
209 | wxALIGN\_BOTTOM, wxALIGN\_CENTER\_HORIZONTAL and wxALIGN\_CENTER\_VERTICAL do what they say. | |
210 | wxALIGN\_CENTRE (same as wxALIGN\_CENTER) is defined as (wxALIGN\_CENTER\_HORIZONTAL | | |
211 | wxALIGN\_CENTER\_VERTICAL). Default alignment is wxALIGN\_LEFT | wxALIGN\_TOP. | |
212 | ||
213 | As mentioned above, any window belonging to a sizer may have border, and it can be specified | |
214 | which of the four sides may have this border, using the wxTOP, wxLEFT, wxRIGHT and wxBOTTOM | |
215 | constants or wxALL for all directions (and you may also use wxNORTH, wxWEST etc instead). These | |
216 | flags can be used in combination with the alignment flags above as the second parameter of the | |
217 | Add() method using the binary or operator |. The sizer of the border also must be made known, | |
218 | and it is the third parameter in the Add() method. This means, that the entire behaviour of | |
219 | a sizer and its children can be controlled by the three parameters of the Add() method. | |
220 | ||
221 | \begin{verbatim} | |
222 | // we want to get a dialog that is stretchable because it | |
223 | // has a text ctrl at the top and two buttons at the bottom | |
224 | ||
225 | MyDialog::MyDialog(wxFrame *parent, wxWindowID id, const wxString &title ) | |
226 | : wxDialog(parent, id, title, wxDefaultPosition, wxDefaultSize, | |
227 | wxDEFAULT_DIALOG_STYLE | wxRESIZE_BORDER) | |
228 | { | |
229 | wxBoxSizer *topsizer = new wxBoxSizer( wxVERTICAL ); | |
230 | ||
231 | // create text ctrl with minimal size 100x60 | |
232 | topsizer->Add( | |
233 | new wxTextCtrl( this, -1, "My text.", wxDefaultPosition, wxSize(100,60), wxTE_MULTILINE), | |
234 | 1, // make vertically stretchable | |
235 | wxEXPAND | // make horizontally stretchable | |
236 | wxALL, // and make border all around | |
237 | 10 ); // set border width to 10 | |
238 | ||
239 | ||
240 | wxBoxSizer *button_sizer = new wxBoxSizer( wxHORIZONTAL ); | |
241 | button_sizer->Add( | |
242 | new wxButton( this, wxID_OK, "OK" ), | |
243 | 0, // make horizontally unstretchable | |
244 | wxALL, // make border all around (implicit top alignment) | |
245 | 10 ); // set border width to 10 | |
246 | button_sizer->Add( | |
247 | new wxButton( this, wxID_CANCEL, "Cancel" ), | |
248 | 0, // make horizontally unstretchable | |
249 | wxALL, // make border all around (implicit top alignment) | |
250 | 10 ); // set border width to 10 | |
251 | ||
252 | topsizer->Add( | |
253 | button_sizer, | |
254 | 0, // make vertically unstretchable | |
255 | wxALIGN_CENTER ); // no border and centre horizontally | |
256 | ||
257 | SetAutoLayout( TRUE ); // tell dialog to use sizer | |
258 | SetSizer( topsizer ); // actually set the sizer | |
259 | ||
260 | topsizer->Fit( this ); // set size to minimum size as calculated by the sizer | |
261 | topsizer->SetSizeHints( this ); // set size hints to honour mininum size | |
262 | } | |
263 | \end{verbatim} | |
264 | ||
265 | \subsection{Programming with wxGridSizer}\label{gridsizerprogramming} | |
266 | ||
267 | \helpref{wxGridSizer}{wxgridsizer} is a sizer which lays out its children in a two-dimensional | |
268 | table with all table fields having the same size, | |
269 | i.e. the width of each field is the width of the widest child, | |
270 | the height of each field is the height of the tallest child. | |
271 | ||
272 | \subsection{Programming with wxFlexGridSizer}\label{flexgridsizerprogramming} | |
273 | ||
274 | \helpref{wxFlexGridSizer}{wxflexgridsizer} is a sizer which lays out its children in a two-dimensional | |
275 | table with all table fields in one row having the same | |
276 | height and all fields in one column having the same width, but all | |
277 | rows or all columns are not necessarily the same height or width as in | |
278 | the \helpref{wxGridSizer}{wxgridsizer}. | |
279 | ||
280 | \subsection{Programming with wxNotebookSizer}\label{notebooksizerprogramming} | |
281 | ||
282 | \helpref{wxNotebookSizer}{wxnotebooksizer} is a specialized sizer to make sizers work in connection | |
283 | with using notebooks. This sizer is different from any other sizer as | |
284 | you must not add any children to it - instead, it queries the notebook class itself. | |
285 | The only thing this sizer does is to determine the size of the biggest | |
286 | page of the notebook and report an adjusted minimal size to a more toplevel | |
287 | sizer. | |
288 | ||
289 | In order to query the size of notebook page, this page needs to have its | |
290 | own sizer, otherwise the wxNotebookSizer will ignore it. Notebook pages | |
291 | get there sizer by assiging one to them using \helpref{wxWindow::SetSizer}{wxwindowsetsizer} | |
292 | and setting the auto-layout option to TRUE using | |
293 | \helpref{wxWindow::SetAutoLayout}{wxwindowsetautolayout}. Here is one | |
294 | example showing how to add a notebook page that the notebook sizer is | |
295 | aware of: | |
296 | ||
297 | \begin{verbatim} | |
298 | wxNotebook *notebook = new wxNotebook( &dialog, -1 ); | |
299 | wxNotebookSizer *nbs = new wxNotebookSizer( notebook ); | |
300 | ||
301 | // Add panel as notebook page | |
302 | wxPanel *panel = new wxPanel( notebook, -1 ); | |
303 | notebook->AddPage( panel, "My Notebook Page" ); | |
304 | ||
305 | wxBoxSizer *panelsizer = new wxBoxSizer( wxVERTICAL ); | |
306 | ||
307 | // Add controls to panel and panelsizer here... | |
308 | ||
309 | panel->SetAutoLayout( TRUE ); | |
310 | panel->SetSizer( panelsizer ); | |
311 | \end{verbatim} | |
312 | ||
313 | \subsection{Programming with wxStaticBoxSizer}\label{staticboxsizerprogramming} | |
314 | ||
315 | \helpref{wxStaticBoxSizer}{wxstaticboxsizer} is a sizer derived from wxBoxSizer but adds a static | |
316 | box around the sizer. Note that this static box has to be created | |
317 | separately. | |
318 |