]>
Commit | Line | Data |
---|---|---|
1 | ///////////////////////////////////////////////////////////////////////////// | |
2 | // Name: sizer.h | |
3 | // Purpose: topic overview | |
4 | // Author: wxWidgets team | |
5 | // RCS-ID: $Id$ | |
6 | // Licence: wxWindows licence | |
7 | ///////////////////////////////////////////////////////////////////////////// | |
8 | ||
9 | /** | |
10 | ||
11 | @page overview_sizer Sizers Overview | |
12 | ||
13 | @tableofcontents | |
14 | ||
15 | Sizers, as represented by the wxSizer class and its descendants in the | |
16 | wxWidgets class hierarchy, have become the method of choice to define the | |
17 | layout of controls in dialogs in wxWidgets because of their ability to create | |
18 | visually appealing dialogs independent of the platform, taking into account | |
19 | the differences in size and style of the individual controls. Unlike the | |
20 | original wxWidgets Dialog Editor, editors such as wxDesigner, DialogBlocks, | |
21 | XRCed and wxWorkshop create dialogs based exclusively on sizers, practically | |
22 | forcing the user to create platform independent layouts without compromises. | |
23 | ||
24 | The next section describes and shows what can be done with sizers. The | |
25 | following sections briefly describe how to program with individual sizer | |
26 | classes. | |
27 | ||
28 | For information about the wxWidgets resource system, which can describe | |
29 | sizer-based dialogs, see the @ref overview_xrc. | |
30 | ||
31 | @see wxSizer, wxBoxSizer, wxStaticBoxSizer, wxGridSizer, wxFlexGridSizer, | |
32 | wxGridBagSizer | |
33 | ||
34 | ||
35 | ||
36 | @section overview_sizer_idea The Idea Behind Sizers | |
37 | ||
38 | The layout algorithm used by sizers in wxWidgets is closely related to layout | |
39 | systems in other GUI toolkits, such as Java's AWT, the GTK toolkit or the Qt | |
40 | toolkit. It is based upon the idea of individual subwindows reporting their | |
41 | minimal required size and their ability to get stretched if the size of the | |
42 | parent window has changed. This will most often mean that the programmer does | |
43 | not set the start-up size of a dialog, the dialog will rather be assigned a | |
44 | sizer and this sizer will be queried about the recommended size. This sizer in | |
45 | turn will query its children (which can be normal windows, empty space or other | |
46 | sizers) so that a hierarchy of sizers can be constructed. Note that wxSizer | |
47 | does not derive from wxWindow and thus does not interfere with tab ordering and | |
48 | requires very few resources compared to a real window on screen. | |
49 | ||
50 | What makes sizers so well fitted for use in wxWidgets is the fact that every | |
51 | control reports its own minimal size and the algorithm can handle differences | |
52 | in font sizes or different window (dialog item) sizes on different platforms | |
53 | without problems. For example, if the standard font as well as the overall | |
54 | design of Linux/GTK widgets requires more space than on Windows, the initial | |
55 | dialog size will automatically be bigger on Linux/GTK than on Windows. | |
56 | ||
57 | There are currently five different kinds of sizers available in wxWidgets. Each | |
58 | represents either a certain way to lay out dialog items in a dialog or it | |
59 | fulfills a special task such as wrapping a static box around a dialog item (or | |
60 | another sizer). These sizers will be discussed one by one in the text below. | |
61 | For more detailed information on how to use sizers programmatically, please | |
62 | refer to the section @ref overview_sizer_box. | |
63 | ||
64 | ||
65 | @section overview_sizer_features Common Features | |
66 | ||
67 | All sizers are containers, that is, they are used to lay out one dialog item | |
68 | (or several dialog items), which they contain. Such items are sometimes | |
69 | referred to as the children of the sizer. Independent of how the individual | |
70 | sizers lay out their children, all children have certain features in common: | |
71 | ||
72 | <b>A minimal size</b>: This minimal size is usually identical to the initial | |
73 | size of the controls and may either be set explicitly in the wxSize field of | |
74 | the control constructor or may be calculated by wxWidgets, typically by setting | |
75 | the height and/or the width of the item to -1. Note that only some controls can | |
76 | calculate their size (such as a checkbox) whereas others (such as a listbox) | |
77 | don't have any natural width or height and thus require an explicit size. Some | |
78 | controls can calculate their height, but not their width (e.g. a single line | |
79 | text control): | |
80 | ||
81 | @image html overview_sizer_03.png | |
82 | ||
83 | @image html overview_sizer_04.png | |
84 | ||
85 | @image html overview_sizer_05.png | |
86 | ||
87 | <b>A border</b>: The border is just empty space and is used to separate dialog | |
88 | items in a dialog. This border can either be all around, or at any combination | |
89 | of sides such as only above and below the control. The thickness of this border | |
90 | must be set explicitly, typically 5 points. The following samples show dialogs | |
91 | with only one dialog item (a button) and a border of 0, 5, and 10 pixels around | |
92 | the button: | |
93 | ||
94 | @image html overview_sizer_00.png | |
95 | ||
96 | @image html overview_sizer_01.png | |
97 | ||
98 | @image html overview_sizer_02.png | |
99 | ||
100 | <b>An alignment</b>: Often, a dialog item is given more space than its minimal | |
101 | size plus its border. Depending on what flags are used for the respective | |
102 | dialog item, the dialog item can be made to fill out the available space | |
103 | entirely, i.e. it will grow to a size larger than the minimal size, or it will | |
104 | be moved to either the centre of the available space or to either side of the | |
105 | space. The following sample shows a listbox and three buttons in a horizontal | |
106 | box sizer; one button is centred, one is aligned at the top, one is aligned at | |
107 | the bottom: | |
108 | ||
109 | @image html overview_sizer_06.png | |
110 | ||
111 | <b>A stretch factor</b>: If a sizer contains more than one child and it is | |
112 | offered more space than its children and their borders need, the question | |
113 | arises how to distribute the surplus space among the children. For this | |
114 | purpose, a stretch factor may be assigned to each child, where the default | |
115 | value of 0 indicates that the child will not get more space than its requested | |
116 | minimum size. A value of more than zero is interpreted in relation to the sum | |
117 | of all stretch factors in the children of the respective sizer, i.e. if two | |
118 | children get a stretch factor of 1, they will get half the extra space each | |
119 | <em>independent of whether one control has a minimal sizer inferior to the | |
120 | other or not</em>. The following sample shows a dialog with three buttons, the | |
121 | first one has a stretch factor of 1 and thus gets stretched, whereas the other | |
122 | two buttons have a stretch factor of zero and keep their initial width: | |
123 | ||
124 | @image html overview_sizer_07.png | |
125 | ||
126 | Within wxDesigner, this stretch factor gets set from the @e Option menu. | |
127 | ||
128 | ||
129 | @section overview_sizer_hiding Hiding Controls Using Sizers | |
130 | ||
131 | You can hide controls contained in sizers the same way you would hide any | |
132 | control, using the wxWindow::Show method. However, wxSizer also offers a | |
133 | separate method which can tell the sizer not to consider that control in its | |
134 | size calculations. To hide a window using the sizer, call wxSizer::Show. You | |
135 | must then call Layout on the sizer to force an update. | |
136 | ||
137 | This is useful when hiding parts of the interface, since you can avoid removing | |
138 | the controls from the sizer and having to add them back later. | |
139 | ||
140 | @note This is supported only by wxBoxSizer and wxFlexGridSizer. | |
141 | ||
142 | @subsection overview_sizer_hiding_box wxBoxSizer | |
143 | ||
144 | wxBoxSizer can lay out its children either vertically or horizontally, | |
145 | depending on what flag is being used in its constructor. When using a vertical | |
146 | sizer, each child can be centered, aligned to the right or aligned to the left. | |
147 | Correspondingly, when using a horizontal sizer, each child can be centered, | |
148 | aligned at the bottom or aligned at the top. The stretch factor described in | |
149 | the last paragraph is used for the main orientation, i.e. when using a | |
150 | horizontal box sizer, the stretch factor determines how much the child can be | |
151 | stretched horizontally. The following sample shows the same dialog as in the | |
152 | last sample, only the box sizer is a vertical box sizer now: | |
153 | ||
154 | @image html overview_sizer_08.png | |
155 | ||
156 | @subsection overview_sizer_hiding_static wxStaticBoxSizer | |
157 | ||
158 | wxStaticBoxSixer is the same as a wxBoxSizer, but surrounded by a static box. | |
159 | Here is a sample: | |
160 | ||
161 | @image html overview_sizer_09.png | |
162 | ||
163 | @subsection overview_sizer_hiding_grid wxGridSizer | |
164 | ||
165 | wxGridSizer is a two-dimensional sizer. All children are given the same size, | |
166 | which is the minimal size required by the biggest child, in this case the text | |
167 | control in the left bottom border. Either the number of columns or the number | |
168 | or rows is fixed and the grid sizer will grow in the respectively other | |
169 | orientation if new children are added: | |
170 | ||
171 | @image html overview_sizer_10.png | |
172 | ||
173 | For programming information, see wxGridSizer. | |
174 | ||
175 | @subsection overview_sizer_hiding_flexgrid wxFlexGridSizer | |
176 | ||
177 | Another two-dimensional sizer derived from wxGridSizer. The width of each | |
178 | column and the height of each row are calculated individually according to the | |
179 | minimal requirements from the respectively biggest child. Additionally, columns | |
180 | and rows can be declared to be stretchable if the sizer is assigned a size | |
181 | different from the one it requested. The following sample shows the same dialog | |
182 | as the one above, but using a flex grid sizer: | |
183 | ||
184 | @image html overview_sizer_11.png | |
185 | ||
186 | ||
187 | @section overview_sizer_box Programming with wxBoxSizer | |
188 | ||
189 | The basic idea behind a wxBoxSizer is that windows will most often be laid out | |
190 | in rather simple basic geometry, typically in a row or a column or several | |
191 | hierarchies of either. | |
192 | ||
193 | As an example, we will construct a dialog that will contain a text field at the | |
194 | top and two buttons at the bottom. This can be seen as a top-hierarchy column | |
195 | with the text at the top and buttons at the bottom and a low-hierarchy row with | |
196 | an OK button to the left and a Cancel button to the right. In many cases | |
197 | (particularly dialogs under Unix and normal frames) the main window will be | |
198 | resizable by the user and this change of size will have to get propagated to | |
199 | its children. In our case, we want the text area to grow with the dialog, | |
200 | whereas the button shall have a fixed size. In addition, there will be a thin | |
201 | border around all controls to make the dialog look nice and - to make matter | |
202 | worse - the buttons shall be centred as the width of the dialog changes. | |
203 | ||
204 | It is the unique feature of a box sizer, that it can grow in both directions | |
205 | (height and width) but can distribute its growth in the main direction | |
206 | (horizontal for a row) @e unevenly among its children. In our example case, the | |
207 | vertical sizer is supposed to propagate all its height changes to only the text | |
208 | area, not to the button area. This is determined by the @e proportion parameter | |
209 | when adding a window (or another sizer) to a sizer. It is interpreted as a | |
210 | weight factor, i.e. it can be zero, indicating that the window may not be | |
211 | resized at all, or above zero. If several windows have a value above zero, the | |
212 | value is interpreted relative to the sum of all weight factors of the sizer, so | |
213 | when adding two windows with a value of 1, they will both get resized equally | |
214 | much and each half as much as the sizer owning them. Then what do we do when a | |
215 | column sizer changes its width? This behaviour is controlled by @e flags (the | |
216 | second parameter of the Add() function): Zero or no flag indicates that the | |
217 | window will preserve it is original size, wxGROW flag (same as wxEXPAND) forces | |
218 | the window to grow with the sizer, and wxSHAPED flag tells the window to change | |
219 | it is size proportionally, preserving original aspect ratio. When wxGROW flag | |
220 | is not used, the item can be aligned within available space. wxALIGN_LEFT, | |
221 | wxALIGN_TOP, wxALIGN_RIGHT, wxALIGN_BOTTOM, wxALIGN_CENTER_HORIZONTAL and | |
222 | wxALIGN_CENTER_VERTICAL do what they say. wxALIGN_CENTRE (same as | |
223 | wxALIGN_CENTER) is defined as (wxALIGN_CENTER_HORIZONTAL | | |
224 | wxALIGN_CENTER_VERTICAL). Default alignment is wxALIGN_LEFT | wxALIGN_TOP. | |
225 | ||
226 | As mentioned above, any window belonging to a sizer may have a border, and it | |
227 | can be specified which of the four sides may have this border, using the wxTOP, | |
228 | wxLEFT, wxRIGHT and wxBOTTOM constants or wxALL for all directions (and you may | |
229 | also use wxNORTH, wxWEST etc instead). These flags can be used in combination | |
230 | with the alignment flags above as the second parameter of the Add() method | |
231 | using the binary or operator |. The sizer of the border also must be made | |
232 | known, and it is the third parameter in the Add() method. This means, that the | |
233 | entire behaviour of a sizer and its children can be controlled by the three | |
234 | parameters of the Add() method. | |
235 | ||
236 | @code | |
237 | // We want to get a dialog that is stretchable because it | |
238 | // has a text ctrl at the top and two buttons at the bottom. | |
239 | ||
240 | MyDialog::MyDialog(wxFrame *parent, wxWindowID id, const wxString &title ) | |
241 | : wxDialog(parent, id, title, wxDefaultPosition, wxDefaultSize, | |
242 | wxDEFAULT_DIALOG_STYLE | wxRESIZE_BORDER) | |
243 | { | |
244 | wxBoxSizer *topsizer = new wxBoxSizer( wxVERTICAL ); | |
245 | ||
246 | // create text ctrl with minimal size 100x60 | |
247 | topsizer->Add( | |
248 | new wxTextCtrl( this, -1, "My text.", wxDefaultPosition, wxSize(100,60), wxTE_MULTILINE), | |
249 | 1, // make vertically stretchable | |
250 | wxEXPAND | // make horizontally stretchable | |
251 | wxALL, // and make border all around | |
252 | 10 ); // set border width to 10 | |
253 | ||
254 | wxBoxSizer *button_sizer = new wxBoxSizer( wxHORIZONTAL ); | |
255 | button_sizer->Add( | |
256 | new wxButton( this, wxID_OK, "OK" ), | |
257 | 0, // make horizontally unstretchable | |
258 | wxALL, // make border all around (implicit top alignment) | |
259 | 10 ); // set border width to 10 | |
260 | button_sizer->Add( | |
261 | new wxButton( this, wxID_CANCEL, "Cancel" ), | |
262 | 0, // make horizontally unstretchable | |
263 | wxALL, // make border all around (implicit top alignment) | |
264 | 10 ); // set border width to 10 | |
265 | ||
266 | topsizer->Add( | |
267 | button_sizer, | |
268 | 0, // make vertically unstretchable | |
269 | wxALIGN_CENTER ); // no border and centre horizontally | |
270 | ||
271 | SetSizerAndFit(topsizer); // use the sizer for layout and size window | |
272 | // accordingly and prevent it from being resized | |
273 | // to smaller size | |
274 | } | |
275 | @endcode | |
276 | ||
277 | Note that the new way of specifying flags to wxSizer is via wxSizerFlags. This | |
278 | class greatly eases the burden of passing flags to a wxSizer. | |
279 | ||
280 | Here's how you'd do the previous example with wxSizerFlags: | |
281 | ||
282 | @code | |
283 | // We want to get a dialog that is stretchable because it | |
284 | // has a text ctrl at the top and two buttons at the bottom. | |
285 | ||
286 | MyDialog::MyDialog(wxFrame *parent, wxWindowID id, const wxString &title ) | |
287 | : wxDialog(parent, id, title, wxDefaultPosition, wxDefaultSize, | |
288 | wxDEFAULT_DIALOG_STYLE | wxRESIZE_BORDER) | |
289 | { | |
290 | wxBoxSizer *topsizer = new wxBoxSizer( wxVERTICAL ); | |
291 | ||
292 | // create text ctrl with minimal size 100x60 that is horizontally and | |
293 | // vertically stretchable with a border width of 10 | |
294 | topsizer->Add( | |
295 | new wxTextCtrl( this, -1, "My text.", wxDefaultPosition, wxSize(100,60), wxTE_MULTILINE), | |
296 | wxSizerFlags(1).Align().Expand().Border(wxALL, 10)); | |
297 | ||
298 | wxBoxSizer *button_sizer = new wxBoxSizer( wxHORIZONTAL ); | |
299 | ||
300 | //create two buttons that are horizontally unstretchable, | |
301 | // with an all-around border with a width of 10 and implicit top alignment | |
302 | button_sizer->Add( | |
303 | new wxButton( this, wxID_OK, "OK" ), | |
304 | wxSizerFlags(0).Align().Border(wxALL, 10)); | |
305 | ||
306 | button_sizer->Add( | |
307 | new wxButton( this, wxID_CANCEL, "Cancel" ), | |
308 | wxSizerFlags(0).Align().Border(wxALL, 10)); | |
309 | ||
310 | //create a sizer with no border and centered horizontally | |
311 | topsizer->Add( | |
312 | button_sizer, | |
313 | wxSizerFlags(0).Center() ); | |
314 | ||
315 | SetSizerAndFit(topsizer); // use the sizer for layout and set size and hints | |
316 | } | |
317 | @endcode | |
318 | ||
319 | ||
320 | ||
321 | @section overview_sizer_types Other Types of Sizers | |
322 | ||
323 | wxGridSizer is a sizer which lays out its children in a two-dimensional table | |
324 | with all table fields having the same size, i.e. the width of each field is the | |
325 | width of the widest child, the height of each field is the height of the | |
326 | tallest child. | |
327 | ||
328 | wxFlexGridSizer is a sizer which lays out its children in a two-dimensional | |
329 | table with all table fields in one row having the same height and all fields in | |
330 | one column having the same width, but all rows or all columns are not | |
331 | necessarily the same height or width as in the wxGridSizer. | |
332 | ||
333 | wxStaticBoxSizer is a sizer derived from wxBoxSizer but adds a static box | |
334 | around the sizer. Note that this static box has to be created separately. | |
335 | ||
336 | wxGridBagSizer is a rather special kind of sizer which, unlike the other | |
337 | classes, allows to directly put the elements at the given position in the | |
338 | sizer. Please see its documentation for more details. | |
339 | ||
340 | @section overview_sizer_button CreateButtonSizer | |
341 | ||
342 | As a convenience, wxDialog::CreateButtonSizer(long flags) can be used to create a | |
343 | standard button sizer in which standard buttons are displayed. The following | |
344 | flags can be passed to this function: | |
345 | ||
346 | @code | |
347 | wxYES_NO // Add Yes/No subpanel | |
348 | wxYES // return wxID_YES | |
349 | wxNO // return wxID_NO | |
350 | wxNO_DEFAULT // make the wxNO button the default, | |
351 | // otherwise wxYES or wxOK button will be default | |
352 | ||
353 | wxOK // return wxID_OK | |
354 | wxCANCEL // return wxID_CANCEL | |
355 | wxHELP // return wxID_HELP | |
356 | ||
357 | wxFORWARD // return wxID_FORWARD | |
358 | wxBACKWARD // return wxID_BACKWARD | |
359 | wxSETUP // return wxID_SETUP | |
360 | wxMORE // return wxID_MORE | |
361 | @endcode | |
362 | ||
363 | */ |