1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
|
/****************************************************************************
**
** Copyright (C) 2012 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Digia. For licensing terms and
** conditions see http://qt.digia.com/licensing. For further information
** use the contact form at http://qt.digia.com/contact-us.
**
** GNU Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: http://www.gnu.org/copyleft/fdl.html.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\example widgets/windowflags
\title Window Flags Example
\brief The Window Flags example shows how to use the window flags
available in Qt.
A window flag is either a type or a hint. A type is used to
specify various window-system properties for the widget. A widget
can only have one type, and the default is Qt::Widget. However, a
widget can have zero or more hints. The hints are used to
customize the appearance of top-level windows.
A widget's flags are stored in a Qt::WindowFlags type which stores
an OR combination of the flags.
\image windowflags-example.png Screenshot of the Window Flags example
The example consists of two classes:
\list
\o \c ControllerWindow is the main application widget that allows
the user to choose among the available window flags, and displays
the effect on a separate preview window.
\o \c PreviewWindow is a custom widget displaying the name of
its currently set window flags in a read-only text editor.
\endlist
We will start by reviewing the \c ControllerWindow class, then we
will take a look at the \c PreviewWindow class.
\section1 ControllerWindow Class Definition
\snippet examples/widgets/windowflags/controllerwindow.h 0
The \c ControllerWindow class inherits QWidget. The widget allows
the user to choose among the available window flags, and displays
the effect on a separate preview window.
We declare a private \c updatePreview() slot to refresh the
preview window whenever the user changes the window flags.
We also declare several private functions to simplify the
constructor: We call the \c createTypeGroupBox() function to
create a radio button for each available window type, using the
private \c createButton() function, and gather them within a group
box. In a similar way we use the \c createHintsGroupBox() function
to create a check box for each available hint, using the private
\c createCheckBox() function.
In addition to the various radio buttons and checkboxes, we need
an associated \c PreviewWindow to show the effect of the currently
chosen window flags.
\image windowflags_controllerwindow.png Screenshot of the Controller Window
\section1 ControllerWindow Class Implementation
\snippet examples/widgets/windowflags/controllerwindow.cpp 0
In the constructor we first create the preview window. Then we
create the group boxes containing the available window flags using
the private \c createTypeGroupBox() and \c createHintsGroupBox()
functions. In addition we create a \gui Quit button. We put the
button and a stretchable space in a separate layout to make the
button appear in the \c WindowFlag widget's right bottom corner.
Finally, we add the button's layout and the two goup boxes to a
QVBoxLayout, set the window title and refresh the preview window
using the \c updatePreview() slot.
\snippet examples/widgets/windowflags/controllerwindow.cpp 1
\snippet examples/widgets/windowflags/controllerwindow.cpp 2
The \c updatePreview() slot is called whenever the user changes
any of the window flags. First we create an empty Qt::WindowFlags
\c flags, then we determine which one of the types that is checked
and add it to \c flags.
\snippet examples/widgets/windowflags/controllerwindow.cpp 3
We also determine which of the hints that are checked, and add
them to \c flags using an OR operator. We use \c flags to set the
window flags for the preview window.
\snippet examples/widgets/windowflags/controllerwindow.cpp 4
We adjust the position of the preview window. The reason we do
that, is that playing around with the window's frame may on some
platforms cause the window's position to be changed behind our
back. If a window is located in the upper left corner of the
screen, parts of the window may not be visible. So we adjust the
widget's position to make sure that, if this happens, the window
is moved within the screen's boundaries. Finally, we call
QWidget::show() to make sure the preview window is visible.
\omit
\skipto pos
\printuntil /^\}/
\endomit
\snippet examples/widgets/windowflags/controllerwindow.cpp 5
The private \c createTypeGroupBox() function is called from the
constructor.
First we create a group box, and then we create a radio button
(using the private \c createRadioButton() function) for each of
the available types among the window flags. We make Qt::Window the
initially applied type. We put the radio buttons into a
QGridLayout and install the layout on the group box.
We do not include the default Qt::Widget type. The reason is that
it behaves somewhat different than the other types. If the type is
not specified for a widget, and it has no parent, the widget is a
window. However, if it has a parent, it is a standard child
widget. The other types are all top-level windows, and since the
hints only affect top-level windows, we abandon the Qt::Widget
type.
\snippet examples/widgets/windowflags/controllerwindow.cpp 6
The private \c createHintsGroupBox() function is also called from
the constructor.
Again, the first thing we do is to create a group box. Then we
create a checkbox, using the private \c createCheckBox() function,
for each of the available hints among the window flags. We put the
checkboxes into a QGridLayout and install the layout on the group
box.
\snippet examples/widgets/windowflags/controllerwindow.cpp 7
The private \c createCheckBox() function is called from \c
createHintsGroupBox().
We simply create a QCheckBox with the provided text, connect it to
the private \c updatePreview() slot, and return a pointer to the
checkbox.
\snippet examples/widgets/windowflags/controllerwindow.cpp 8
In the private \c createRadioButton() function it is a
QRadioButton we create with the provided text, and connect to the
private \c updatePreview() slot. The function is called from \c
createTypeGroupBox(), and returns a pointer to the button.
\section1 PreviewWindow Class Definition
\snippet examples/widgets/windowflags/previewwindow.h 0
The \c PreviewWindow class inherits QWidget. It is a custom widget
that displays the names of its currently set window flags in a
read-only text editor. It is also provided with a QPushbutton that
closes the window.
We reimplement the constructor to create the \gui Close button and
the text editor, and the QWidget::setWindowFlags() function to
display the names of the window flags.
\image windowflags_previewwindow.png Screenshot of the Preview Window
\section1 PreviewWindow Class Implementation
\snippet examples/widgets/windowflags/previewwindow.cpp 0
In the constructor, we first create a QTextEdit and make sure that
it is read-only.
We also prohibit any line wrapping in the text editor using the
QTextEdit::setLineWrapMode() function. The result is that a
horizontal scrollbar appears when a window flag's name exceeds the
width of the editor. This is a reasonable solution since we
construct the displayed text with built-in line breaks. If no line
breaks were guaranteed, using another QTextEdit::LineWrapMode
would perhaps make more sense.
Then we create the \gui Close button, and put both the widgets
into a QVBoxLayout before we set the window title.
\snippet examples/widgets/windowflags/previewwindow.cpp 1
In our reimplementation of the \c setWindowFlags() function, we
first set the widgets flags using the QWidget::setWindowFlags()
function. Then we run through the available window flags, creating
a text that contains the names of the flags that matches the \c
flags parameter. Finally, we display the text in the widgets text
editor.
*/
|
