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/****************************************************************************
**
** Copyright (C) 2012 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
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** Documentation License version 1.3 as published by the Free Software
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** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
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****************************************************************************/
/*!
\title Calendar Widget Example
\example widgets/calendarwidget
\brief The Calendar Widget example shows use of \c QCalendarWidget.
\image calendarwidgetexample.png
QCalendarWidget displays one calendar month
at a time and lets the user select a date.
The calendar consists of four components: a navigation
bar that lets the user change the month that is
displayed, a grid where each cell represents one day
in the month, and two headers that display weekday names
and week numbers.
The Calendar Widget example displays a QCalendarWidget and lets the user
configure its appearance and behavior using
\l{QComboBox}es, \l{QCheckBox}es, and \l{QDateEdit}s. In
addition, the user can influence the formatting of individual dates
and headers.
The properties of the QCalendarWidget are summarized in the table
below.
\table
\header \o Property
\o Description
\row \o \l{QCalendarWidget::}{selectedDate}
\o The currently selected date.
\row \o \l{QCalendarWidget::}{minimumDate}
\o The earliest date that can be selected.
\row \o \l{QCalendarWidget::}{maximumDate}
\o The latest date that can be selected.
\row \o \l{QCalendarWidget::}{firstDayOfWeek}
\o The day that is displayed as the first day of the week
(usually Sunday or Monday).
\row \o \l{QCalendarWidget::}{gridVisible}
\o Whether the grid should be shown.
\row \o \l{QCalendarWidget::}{selectionMode}
\o Whether the user can select a date or not.
\row \o \l{QCalendarWidget::}{horizontalHeaderFormat}
\o The format of the day names in the horizontal header
(e.g., "M", "Mon", or "Monday").
\row \o \l{QCalendarWidget::}{verticalHeaderFormat}
\o The format of the vertical header.
\row \o \l{QCalendarWidget::}{navigationBarVisible}
\o Whether the navigation bar at the top of the calendar
widget is shown.
\endtable
The example consists of one class, \c Window, which creates and
lays out the QCalendarWidget and the other widgets that let the
user configure the QCalendarWidget.
\section1 Window Class Definition
Here is the definition of the \c Window class:
\snippet examples/widgets/calendarwidget/window.h 0
\dots
\snippet examples/widgets/calendarwidget/window.h 1
As is often the case with classes that represent self-contained
windows, most of the API is private. We will review the private
members as we stumble upon them in the implementation.
\section1 Window Class Implementation
Let's now review the class implementation, starting with the constructor:
\snippet examples/widgets/calendarwidget/window.cpp 0
We start by creating the four \l{QGroupBox}es and their child
widgets (including the QCalendarWidget) using four private \c
create...GroupBox() functions, described below. Then we arrange
the group boxes in a QGridLayout.
We set the grid layout's resize policy to QLayout::SetFixedSize to
prevent the user from resizing the window. In that mode, the
window's size is set automatically by QGridLayout based on the
size hints of its contents widgets.
To ensure that the window isn't automatically resized every time
we change a property of the QCalendarWidget (e.g., hiding the
navigation bar, trhe vertical header, or the grid), we set the
minimum height of row 0 and the minimum width of column 0 to the
initial size of the QCalendarWidget.
Let's move on to the \c createPreviewGroupBox() function:
\snippet examples/widgets/calendarwidget/window.cpp 9
The \gui Preview group box contains only one widget: the
QCalendarWidget. We set it up, connect its
\l{QCalendarWidget::}{currentPageChanged()} signal to our \c
reformatCalendarPage() slot to make sure that every new page gets
the formatting specified by the user.
The \c createGeneralOptionsGroupBox() function is somewhat large
and several widgets are set up the same way; we look at parts of
its implementation here and skip the rest:
\snippet examples/widgets/calendarwidget/window.cpp 10
\dots
We start with the setup of the \gui{Week starts on} combobox.
This combobox controls which day should be displayed as the first
day of the week.
The QComboBox class lets us attach user data as a QVariant to
each item. The data can later be retrieved with QComboBox's
\l{QComboBox::}{itemData()} function. QVariant doesn't directly
support the Qt::DayOfWeek data type, but it supports \c int, and
C++ will happily convert any enum value to \c int.
\dots
\snippet examples/widgets/calendarwidget/window.cpp 11
\dots
After creating the widgets, we connect the signals and slots. We
connect the comboboxes to private slots of \c Window or to
public slots provided by QComboBox.
\dots
\snippet examples/widgets/calendarwidget/window.cpp 12
At the end of the function, we call the slots that update the calendar to ensure
that the QCalendarWidget is synchronized with the other widgets on startup.
Let's now take a look at the \c createDatesGroupBox() private function:
\snippet examples/widgets/calendarwidget/window.cpp 13
In this function, we create the \gui {Minimum Date}, \gui {Maximum Date},
and \gui {Current Date} editor widgets,
which control the calendar's minimum, maximum, and selected dates.
The calendar's minimum and maximum dates have already been
set in \c createPrivewGroupBox(); we can then set the widgets
default values to the calendars values.
\snippet examples/widgets/calendarwidget/window.cpp 14
\dots
\snippet examples/widgets/calendarwidget/window.cpp 15
We connect the \c currentDateEdit's
\l{QDateEdit::}{dateChanged()} signal directly to the calendar's
\l{QCalendarWidget::}{setSelectedDate()} slot. When the calendar's
selected date changes, either as a result of a user action or
programmatically, our \c selectedDateChanged() slot updates
the \gui {Current Date} editor. We also need to react when the user
changes the \gui{Minimum Date} and \gui{Maximum Date} editors.
Here is the \c createTextFormatsGroup() function:
\snippet examples/widgets/calendarwidget/window.cpp 16
We set up the \gui {Weekday Color} and \gui {Weekend Color} comboboxes
using \c createColorCombo(), which instantiates a QComboBox and
populates it with colors ("Red", "Blue", etc.).
\snippet examples/widgets/calendarwidget/window.cpp 17
The \gui {Header Text Format} combobox lets the user change the
text format (bold, italic, or plain) used for horizontal and
vertical headers. The \gui {First Friday in blue} and \gui {May 1
in red} check box affect the rendering of specific dates.
\snippet examples/widgets/calendarwidget/window.cpp 18
We connect the check boxes and comboboxes to various private
slots. The \gui {First Friday in blue} and \gui {May 1 in red}
check boxes are both connected to \c reformatCalendarPage(),
which is also called when the calendar switches month.
\dots
\snippet examples/widgets/calendarwidget/window.cpp 19
At the end of \c createTextFormatsGroupBox(), we call private
slots to synchronize the QCalendarWidget with the other widgets.
We're now done reviewing the four \c create...GroupBox()
functions. Let's now take a look at the other private functions
and slots.
\snippet examples/widgets/calendarwidget/window.cpp 20
In \c createColorCombo(), we create a combobox and populate it with
standard colors. The second argument to QComboBox::addItem()
is a QVariant storing user data (in this case, QColor objects).
This function was used to set up the \gui {Weekday Color}
and \gui {Weekend Color} comboboxes.
\snippet examples/widgets/calendarwidget/window.cpp 1
When the user changes the \gui {Week starts on} combobox's
value, \c firstDayChanged() is invoked with the index of the
combobox's new value. We retrieve the custom data item
associated with the new current item using
\l{QComboBox::}{itemData()} and cast it to a Qt::DayOfWeek.
\c selectionModeChanged(), \c horizontalHeaderChanged(), and \c
verticalHeaderChanged() are very similar to \c firstDayChanged(),
so they are omitted.
\snippet examples/widgets/calendarwidget/window.cpp 2
The \c selectedDateChanged() updates the \gui{Current Date}
editor to reflect the current state of the QCalendarWidget.
\snippet examples/widgets/calendarwidget/window.cpp 3
When the user changes the minimum date, we tell the
QCalenderWidget. We also update the \gui {Maximum Date} editor,
because if the new minimum date is later than the current maximum
date, QCalendarWidget will automatically adapt its maximum date
to avoid a contradicting state.
\snippet examples/widgets/calendarwidget/window.cpp 4
\c maximumDateChanged() is implemented similarly to \c
minimumDateChanged().
\snippet examples/widgets/calendarwidget/window.cpp 5
Each combobox item has a QColor object as user data corresponding to the
item's text. After fetching the colors from the comboboxes, we
set the text format of each day of the week.
The text format of a column in the calendar is given as a
QTextCharFormat, which besides the foreground color lets us
specify various character formatting information. In this
example, we only show a subset of the possibilities.
\snippet examples/widgets/calendarwidget/window.cpp 6
\c weekendFormatChanged() is the same as \c
weekdayFormatChanged(), except that it affects Saturday and
Sunday instead of Monday to Friday.
\snippet examples/widgets/calendarwidget/window.cpp 7
The \c reformatHeaders() slot is called when the user
changes the text format of
the headers. We compare the current text of the \gui {Header Text Format}
combobox to determine which format to apply. (An alternative would
have been to store \l{QTextCharFormat} values alongside the combobox
items.)
\snippet examples/widgets/calendarwidget/window.cpp 8
In \c reformatCalendarPage(), we set the text format of the first
Friday in the month and May 1 in the current year. The text
formats that are actually used depend on which check boxes are
checked.
QCalendarWidget lets us set the text format of individual dates
with the \l{QCalendarWidget::}{setDateTextFormat()}. We chose to
set the dates when the calendar page changes, i.e., a new month is
displayed. We check which of the \c mayFirstCheckBox and \c
firstDayCheckBox, if any, are checked
and set the text formats accordingly.
*/
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