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/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** 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
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** information use the contact form at https://www.qt.io/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: https://www.gnu.org/licenses/fdl-1.3.html.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\example textfinder
\ingroup examples-qtuitools
\title Text Finder Example
\brief Dynamically processing forms using Qt UI Tools.
Dynamic form processing enables a form to
be processed at run-time only by changing the UI file for the project.
The program allows the user to look up a particular word within the
contents of a text file. This text file is included in the project's
resource and is loaded into the display at startup.
\table
\row \li \inlineimage textfinder-example-find.png
\li \inlineimage textfinder-example-find2.png
\endtable
\section1 Setting Up The Resource File
The resources required for Text Finder are:
\list
\li \e{textfinder.ui} - the user interface file created in QtDesigner
\li \e{input.txt} - a text file containing some text to be displayed
in the QTextEdit
\endlist
\e{textfinder.ui} contains all the necessary QWidget objects for the
Text Finder. A QLineEdit is used for the user input, a QTextEdit is
used to display the contents of \e{input.txt}, a QLabel is used to
display the text "Keyword", and a QPushButton is used for the "Find"
button. The screenshot below shows the preview obtained in QtDesigner.
\image textfinder-example-userinterface.png
A \e{textfinder.qrc} file is used to store both the \e{textfinder.ui}
and \e{input.txt} in the application's executable. The file contains
the following code:
\quotefile textfinder/textfinder.qrc
For more information on resource files, see \l{The Qt Resource System}.
To generate a form at run-time, the example is linked against the
QtUiTools module library. This is done in the \c{textfinder.pro} file
that contains the following lines:
\snippet textfinder/doc_src_examples_textfinder.pro 0
\section1 TextFinder Class Definition
The \c TextFinder class is a subclass of QWidget and it hosts the
\l{QWidget}s we need to access in the user interface. The QLabel in the
user interface is not declared here as we do not need to access it.
\snippet textfinder/textfinder.h 0
The slot \c{on_findButton_clicked()} is a slot named according to the
\l{Using a Designer UI File in Your Application#Automatic Connections}
{Automatic Connection} naming convention required
by \c uic.
\section1 TextFinder Class Implementation
The \c TextFinder class's constructor calls the \c loadUiFile() function
and then uses \c qFindChild() to access the user interface's
\l{QWidget}s.
\snippet textfinder/textfinder.cpp 0
We then use QMetaObject's system to enable signal and slot connections.
\snippet textfinder/textfinder.cpp 2
The loadTextFile() function is called to load \c{input.txt} into
QTextEdit to displays its contents.
\snippet textfinder/textfinder.cpp 3a
The \c{TextFinder}'s layout is set with \l{QWidget::}{setLayout()}.
\snippet textfinder/textfinder.cpp 3b
Finally, the window title is set to \e {Text Finder} and \c isFirstTime is
set to true.
\c isFirstTime is used as a flag to indicate whether the search operation
has been performed more than once. This is further explained with the
\c{on_findButton_clicked()} function.
The \c{loadUiFile()} function is used to load the user interface file
previously created in QtDesigner. The QUiLoader class is instantiated
and its \c load() function is used to load the form into \c{formWidget}
that acts as a place holder for the user interface. The function then
returns \c{formWidget} to its caller.
\snippet textfinder/textfinder.cpp 4
As mentioned earlier, the loadTextFile() function loads \e{input.txt}
into QTextEdit to display its contents. Data is read using QTextStream
into a QString object, \c line with the QTextStream::readAll() function.
The contents of \c line are then appended to \c{ui_textEdit}.
\snippet textfinder/textfinder.cpp 5
The \c{on_findButton_clicked()} function is a slot that is connected to
\c{ui_findButton}'s \c clicked() signal. The \c searchString is extracted
from the \c ui_lineEdit and the \c document is extracted from \c textEdit.
In event there is an empty \c searchString, a QMessageBox is used,
requesting the user to enter a word. Otherwise, we traverse through the
words in \c ui_textEdit, and highlight all ocurrences of the
\c searchString . Two QTextCursor objects are used: One to traverse through
the words in \c line and another to keep track of the edit blocks.
\snippet textfinder/textfinder.cpp 7
The \c isFirstTime flag is set to false the moment \c findButton is
clicked. This is necessary to undo the previous text highlight before
highlighting the user's next search string. Also, the \c found flag
is used to indicate if the \c searchString was found within the contents
of \c ui_textEdit. If it was not found, a QMessageBox is used
to inform the user.
\snippet textfinder/textfinder.cpp 9
\section1 \c main() Function
\snippet textfinder/main.cpp 0
The \c main() function initialises the \e{textfinder.qrc} resource file
and instantiates as well as displays \c TextFinder.
\sa {Calculator Builder Example}, {World Time Clock Builder Example}
*/
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