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// Copyright (C) 2017 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
/*!
\example textfinder
\examplecategory {Desktop}
\meta tags {widgets,designer}
\ingroup examples-qtuitools
\title Text Finder
\brief Dynamically loading .ui files using QUiLoader.
The TextFinder example shows how to load and setup a \c{.ui} file
dynamically using the \l{QUiLoader} class that is part of the
\l{Qt UI Tools} library.
The program allows the user to look up a particular word within the
contents of a text. The visual elements and layout of the user interface is
loaded at runtime, from a the program resources.
\table
\row \li \inlineimage textfinder-example-find.webp
\li \inlineimage textfinder-example-find2.webp
\endtable
\section1 Setting Up The Resource File
The resources required for the example are:
\list
\li \c{textfinder.ui} - the user interface file created in
\l{Qt Widgets Designer}
\li \c{input.txt} - a text file containing some text to be displayed in
a QTextEdit
\endlist
\c 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 \c input.txt, a QLabel is used to display the text
"Keyword", and a QPushButton is used for the \uicontrol Find button. Note
that all the widgets have sensible \c{objectName}'s assigned. These are
used in code to identify them.
The screenshot below shows the preview obtained in \l{Qt Widgets Designer}.
\image doc/images/textfinder-example-userinterface.webp
In this example, we store both resources in the applicaton's executable by
including the \c{textfinder.qrc} file. Alternatively, the files could also
be loaded at runtime from the file system, or from an external binary
resource \c{.rcc} file. For more information on resource files, see
\l{The Qt Resource System}.
The \c{textfinder.qrc} file lists all files that should be included as a
resource:
\quotefile textfinder/textfinder.qrc
To generate a form at run-time, the example is linked against the
\l{Qt Ui Tools} library. This is done in the \c{textfinder.pro} file:
\snippet textfinder/textfinder.pro 0
\section1 TextFinder Class Definition
The \c TextFinder class contains the main user interface. It declares
pointers to the QPushButton, QTextEdit and QLineEdit elements described
above. The QLabel in the user interface is not declared here as we do
not need to access it from code.
\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 Loading the Resources
We use QFile to load the data from the program resources at runtime. The
code for this is in two method methods on top of \c{textfinder.cpp}:
\c{loadUiFile} and \c{loadTextFile}.
The \c{loadUiFile} function loads the user interface file previously
created in \l{Qt Widgets Designer}. First, the content of the \c{textfinder.ui}
file is loaded from the resource system. Then a QUiLoader instance is
created, and the QUiLoader::load() function is called, with the first
argument being the open file, and the second argument being the pointer of
the widget that should be set as the parent. The created QWidget is
returned.
\snippet textfinder/textfinder.cpp 4
In a similar vein, the \c loadTextFile function loads \c{input.txt} from
the resources. Data is read using QTextStream into a QString with the
QTextStream::readAll() function. We explicitly set the encoding to
\e{UTF-8}, because QTextStream by default uses the current system locale.
Finally, the loaded text is returned.
\snippet textfinder/textfinder.cpp 5
\section1 TextFinder Class Implementation
The \c TextFinder class's constructor does not instantiate any child widgets
directly. Instead, it calls the \c loadUiFile() function, and then uses
QObject::findChild() to locate the created \l{QWidget}s by object name.
\snippet textfinder/textfinder.cpp 0
We then use QMetaObject::connectSlotsByName() to enable the automatic
calling of the \c on_findButton_clicked() slot.
\snippet textfinder/textfinder.cpp 2
The \c loadTextFile function is called to get the text to be shown in the
QTextEdit.
\snippet textfinder/textfinder.cpp 3a
The dynamically loaded user interface in \c formWidget is now properly set
up. We now embed \c formWidget through a \c QVBoxLayout.
\snippet textfinder/textfinder.cpp 3b
At the end of the constructor we set a window title.
\snippet textfinder/textfinder.cpp 3c
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 ui_textEdit. If 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 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
The \c main() function instantiates and shows \c TextFinder.
\snippet textfinder/main.cpp 0
There are various approaches to include forms into applications. Using
QUILoader is just one of them. See \l{Using a Designer UI File in Your
Application} for more information on the other approaches available.
\sa {Calculator Builder}
*/
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