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/*!
\page helpsystem-example.html
\ingroup examples
\title Helpsystem
This example demonstrates the different Qt classes
that can be used to provide context sensitive help
in an application.
It uses QToolTip and QWhatsThis to provide both static and
dynamic balloon help for the widgets in the application, and
QToolTipGroup to display extended information for each tooltip
in the statusbar. QAssistantClient is used to display help
pages using Qt Assistant.
The application has a user interface based on a
QMainWindow with a menubar, statusbar and a toolbar, and uses
a QTable as the central widget.
\quotefile helpsystem/tooltip.h
\skipto : public QToolTip
\printuntil };
Two QToolTip subclasses implement dynamic tooltips for
QHeader and QTable by reimplementing maybeTip(). The
constructors differ from the QToolTip constructor in having a
QHeader and a QTable respectively as the first parameter for
the constructor instead of a QWidget. This is because
we want to ensure that only headers and tables can be
passed as arguments. A QToolTipGroup can be provided as the
second argument to show tooltips in, for example a statusbar.
\printuntil };
The TableToolTip class keeps a reference to the QTable
as a member for easier access of the QTable object later on.
\quotefile helpsystem/tooltip.cpp
\skipto HeaderToolTip::HeaderToolTip
\printuntil }
The HeaderToolTip constructor propagates the parameters
to the QToolTip constructor.
\printuntil }
The implementation of maybeTip() uses the QHeader API
to get the section at the requested position and uses
QToolTip::tip() to display the section's label in a
tooltip. The second string is used by QToolTipGroup and will
show up in the statusbar.
\printuntil }
Since QTable is a QScrollView all user interaction
happens on QTable's viewport() . The TableToolTip
constructor passes the viewport() and the tooltip
group to the QToolTip constructor, and initializes the table
member with the QTable pointer itself.
\printto moveTopLeft
The implementation of maybeTip() uses the QTable API
to get information about the cell at the requested position.
The QTable API expects contents coordinates, and since the
requested point is relative to the viewport we need to translate
the coordinates before we can use QTable's functions.
\printuntil }
\quotefile helpsystem/whatsthis.h
\skipto class WhatsThis
We translate the cell's geometry back to viewport coordinates
so that the tooltip disappears when the mouse cursor leaves
the cell, and use QToolTip::tip() to display the cell's label
in a tooltip and to provide text for the QToolTipGroup as before.
\printuntil };
\quotefile helpsystem/whatsthis.cpp
\skipto WhatsThis::WhatsThis
The WhatsThis class is a subclass of both QObject and
QWhatsThis and serves as a base class for the HeaderWhatsThis
and TableWhatsThis classes. \footnote Note that moc requires that QObject
is the first base class. \endfootnote WhatsThis
reimplements clicked() which will be called when the user clicks
inside the "What's this?" window. It also declares a signal
linkClicked() which will be emitted when a hyperlink is clicked.
\printuntil }
The WhatsThis constructor takes two parameters, the first is the
widget we want to provide WhatsThis for, and the second is the
one which receives the events. Normally this is the same widget,
but some widgets, like QTable, are more complex and have a
viewport() widget which receives the events. If such a widget
is passed to the constructor it will propagate the parameter to
the QWhatsThis constructor and store the QWidget pointer itself
in it's member variable to allow easier use of the QWidget API
later on.
\skipto bool WhatsThis::clicked
\printuntil }
\quotefile helpsystem/whatsthis.h
\skipto class HeaderWhatsThis
The implementation of clicked() emits the linkClicked() signal
if a hyperlink has been clicked.
\printuntil };
\printuntil };
\quotefile helpsystem/whatsthis.cpp
\skipto HeaderWhatsThis::HeaderWhatsThis
The HeaderWhatsThis and TableWhatsThis classes reimplement
text() to make it possible to return texts depending on the
mouse click's position. All the other functionality is
already provided by the generic WhatsThis base class. We ensure
type safety here in the same manner as in the tooltip classes.
\printuntil }
The HeaderWhatsThis constructor propagates the parameter to the
WhatsThis constructor.
\printto TableWhatsThis::TableWhatsThis
The implementation of text() uses the QHeader API to determine
whether we have a horizontal or a vertical header and returns
a string which states the header's orientation and section.
\footnote
Note that we have to explicitly scope the orientation
(QObject or QWhatsThis) since HeaderWhatsThis uses multiple
inheritance. \endfootnote
\printuntil }
Since QTable is a scrollview and has a viewport() which receives
the events, we propagate the table itself and the table's
viewport() to the WhatsThis constructor.
\printuntil }
\printuntil }
\printuntil }
\printuntil }
The implementation of text() uses the QTable API to get
information about the cell at the requested position.
The QTable API expects contents coordinates, so we need to
translate the point as shown earlier for the tooltip classes.
We use the rtti() function to figure out the item's type
and return a string accordingly.
\quotefile helpsystem/mainwindow.h
\skipto class MainWindow
\printuntil };
A QMainWindow is used to create a user interface that uses the
above classes in addition to Qt Assistant to provide context
sensitive help in the application.
The MainWindow class declares a slot called assistantSlot()
which creates an instance of Qt Assistant when it is called.
The class keeps references to the tooltip classes as members
because they are not QObjects and need to be deleted explicitly.
The class has a reference to QAssistantClient as a
member as well, to allow easier access to Qt Assistant later on.
\quotefile helpsystem/mainwindow.cpp
\skipto MainWindow::MainWindow
\printuntil assistant
The MainWindow constructor creates an instance of
QAssistantClient using QString::null as the first argument
so that the system path is used.
\printto QWhatsThis::whatsThisButton
A QTable is used as the central widget and the table, the menus
and the toolbar are populated.
\printto // create
The static function whatsThisButton() creates a QToolButton
which will enter "What's this?" mode when clicked.
\printto // set up
A QToolTipGroup is created and will show and remove tooltips
in the statusbar as the tooltips are displayed on the widgets.
\printto // set up whats this
The tooltips are set up. The static function add() sets up a
tooltip on the Assistant toolbutton. Tooltip objects are created
using the QToolTip subclasses, the constructor's first parameter
specifies the widget we want to add dynamic tooltips for and the
second argument specifies the QToolTipGroup they should belong
to.
\printto // connections
The WhatsThis help is set up. The static function add() adds
What's This? help for the toolbutton which opens Assistant.
Instances of the two WhatsThis subclasses are created for the
headers and the table. What's This? help is also added for the
menu items.
\printto MainWindow::~MainWindow
Signals and slots are connected, so that the relevant pages will
be displayed in Qt Assistant when clicking on a hyperlink or on
the assistant button.
\printuntil }
The destructor deletes the tooltips. We need to delete the
tooltips explicitly since QToolTip is, as mentioned above, not
a subclass of QObject and the instances of QToolTip not will be
deleted when the widget is deleted.
\printuntil }
The assistantSlot() uses applicationDirPath() to find the
location of the documentation files and shows the specified page
in Qt Assistant.
\quotefile helpsystem/main.cpp
\skipto #include
\printuntil }
The main function is a standard implementation opening
the application main window.
To build the example go to the helpsystem directory
(QTDIR/examples/helpsystem) run qmake to generate the makefile,
and use the make tool to build the library.
*/
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