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/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information (qt-info@nokia.com)
**
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/*!
\example richtext/calendar
\title Calendar Example
The Calendar example shows how to create rich text content and display it using
a rich text editor.
\image calendar-example.png
Specifically, the example demonstrates the following:
\list
\o Use of a text editor with a text document
\o Insertion of tables and frames into a document
\o Navigation within a table
\o Insert text in different styles
\endlist
The rich text editor used to display the document is used within a main window
application.
\section1 MainWindow Class Definition
The \c MainWindow class provides a text editor widget and some controls to
allow the user to change the month and year shown. The font size used for the
text can also be adjusted.
\snippet examples/richtext/calendar/mainwindow.h 0
The private \c insertCalendar() function performs most of the work, relying on
the \c fontSize and \c selectedDate variables to write useful information to
the \c editor.
\section1 MainWindow Class Implementation
The \c MainWindow constructor sets up the user interface and initializes
variables used to generate a calendar for each month.
\snippet examples/richtext/calendar/mainwindow.cpp 0
We begin by setting default values for the selected date that will be highlighted
in the calendar and the font size to be used. Since we are using a QMainWindow
for the user interface, we construct a widget for use as the central widget.
The user interface will include a line of controls above the generated calendar;
we construct a label and a combobox to allow the month to be selected, and a
spin box for the year. These widgets are configured to provide a reasonable range
of values for the user to try:
\snippet examples/richtext/calendar/mainwindow.cpp 1
We use the \c selectedDate object to obtain the current month and year, and we
set these in the combobox and spin box:
The font size is displayed in a spin box which we restrict to a sensible range
of values:
\snippet examples/richtext/calendar/mainwindow.cpp 2
We construct an editor and use the \c insertCalendar() function to create
a calendar for it. Each calendar is displayed in the same text editor; in
this example we use a QTextBrowser since we do not allow the calendar to be
edited.
The controls used to set the month, year, and font size will not have any
effect on the appearance of the calendar unless we make some signal-slot
connections:
\snippet examples/richtext/calendar/mainwindow.cpp 3
The signals are connected to some simple slots in the \c MainWindow class
which we will describe later.
We create layouts to manage the widgets we constructed:
\snippet examples/richtext/calendar/mainwindow.cpp 4
Finally, the central widget is set for the window.
Each calendar is created for the editor by the \c insertCalendar() function
which uses the date and font size, defined by the private \a selectedDate
and \c fontSize variables, to produce a suitable plan for the specified
month and year.
\snippet examples/richtext/calendar/mainwindow.cpp 5
We begin by clearing the editor's rich text document, and obtain a text
cursor from the editor that we will use to add content. We also create a
QDate object based on the currently selected date.
The calendar is made up of a table with a gray background color that contains
seven columns: one for each day of the week. It is placed in the center of the
page with equal space to the left and right of it. All of these properties are
set in a QTextTableFormat object:
\snippet examples/richtext/calendar/mainwindow.cpp 6
Each cell in the table will be padded and spaced to make the text easier to
read.
We want the columns to have equal widths, so we provide a vector containing
percentage widths for each of them and set the constraints in the
QTextTableFormat:
\snippet examples/richtext/calendar/mainwindow.cpp 7
The constraints used for the column widths are only useful if the table has
an appropriate number of columns. With the format for the table defined, we
construct a new table with one row and seven columns at the current cursor
position:
\snippet examples/richtext/calendar/mainwindow.cpp 8
We only need one row to start with; more can be added as we need them. Using
this approach means that we do not need to perform any date calculations
until we add cells to the table.
When inserting objects into a document with the cursor's insertion functions,
the cursor is automatically moved inside the newly inserted object. This means
that we can immediately start modifying the table from within:
\snippet examples/richtext/calendar/mainwindow.cpp 9
Since the table has an outer frame, we obtain the frame and its format so that
we can customize it. After making the changes we want, we set the frame's format
using the modified format object. We have given the table an outer border one
pixel wide.
\snippet examples/richtext/calendar/mainwindow.cpp 10
In a similar way, we obtain the cursor's current character format and
create customized formats based on it.
We do not set the format on the cursor because this would change the default
character format; instead, we use the customized formats explicitly when we
insert text. The following loop inserts the days of the week into the table
as bold text:
\snippet examples/richtext/calendar/mainwindow.cpp 11
For each day of the week, we obtain an existing table cell in the first row
(row 0) using the table's \l{QTextTable::cellAt()}{cellAt()} function. Since
we start counting the days of the week at day 1 (Monday), we subtract 1 from
\c weekDay to ensure that we obtain the cell for the correct column of the
table.
Before text can be inserted into a cell, we must obtain a cursor with the
correct position in the document. The cell provides a function for this
purpose, and we use this cursor to insert text using the \c boldFormat
character format that we created earlier:
\snippet examples/richtext/calendar/mainwindow.cpp 12
Inserting text into document objects usually follows the same pattern.
Each object can provide a new cursor that corresponds to the first valid
position within itself, and this can be used to insert new content. We
continue to use this pattern as we insert the days of the month into the
table.
Since every month has more than seven days, we insert a single row to begin
and add days until we reach the end of the month. If the current date is
encountered, it is inserted with a special format (created earlier) that
makes it stand out:
\snippet examples/richtext/calendar/mainwindow.cpp 13
We add a new row to the table at the end of each week only if the next week
falls within the currently selected month.
For each calendar that we create, we change the window title to reflect the
currently selected month and year:
\snippet examples/richtext/calendar/mainwindow.cpp 14
The \c insertCalendar() function relies on up-to-date values for the month,
year, and font size. These are set in the following slots:
\snippet examples/richtext/calendar/mainwindow.cpp 15
The \c setFontSize() function simply changes the private \c fontSize variable
before updating the calendar.
\snippet examples/richtext/calendar/mainwindow.cpp 16
The \c setMonth slot is called when the QComboBox used to select the month is
updated. The value supplied is the currently selected row in the combobox.
We add 1 to this value to obtain a valid month number, and create a new QDate
based on the existing one. The calendar is then updated to use this new date.
\snippet examples/richtext/calendar/mainwindow.cpp 17
The \c setYear() slot is called when the QDateTimeEdit used to select the
year is updated. The value supplied is a QDate object; this makes
the construction of a new value for \c selectedDate simple. We update the
calendar afterwards to use this new date.
*/
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