| 1 | /****************************************************************************
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| 2 | **
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| 3 | ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
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| 4 | ** All rights reserved.
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| 5 | ** Contact: Nokia Corporation ([email protected])
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| 6 | **
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| 7 | ** This file is part of the documentation of the Qt Toolkit.
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| 8 | **
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| 9 | ** $QT_BEGIN_LICENSE:FDL$
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| 10 | ** Commercial Usage
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| 11 | ** Licensees holding valid Qt Commercial licenses may use this file in
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| 12 | ** accordance with the Qt Commercial License Agreement provided with the
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| 13 | ** Software or, alternatively, in accordance with the terms contained in a
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| 14 | ** written agreement between you and Nokia.
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| 15 | **
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| 16 | ** GNU Free Documentation License
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| 17 | ** Alternatively, this file may be used under the terms of the GNU Free
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| 18 | ** Documentation License version 1.3 as published by the Free Software
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| 19 | ** Foundation and appearing in the file included in the packaging of this
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| 20 | ** file.
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| 21 | **
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| 22 | ** If you have questions regarding the use of this file, please contact
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| 23 | ** Nokia at [email protected].
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| 24 | ** $QT_END_LICENSE$
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| 25 | **
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| 26 | ****************************************************************************/
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| 27 |
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| 28 | /*!
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| 29 | \example widgets/shapedclock
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| 30 | \title Shaped Clock Example
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| 31 |
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| 32 | The Shaped Clock example shows how to apply a widget mask to a top-level
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| 33 | widget to produce a shaped window.
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| 34 |
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| 35 | \image shapedclock-example.png
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| 36 |
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| 37 | Widget masks are used to customize the shapes of top-level widgets by restricting
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| 38 | the available area for painting. On some window systems, setting certain window flags
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| 39 | will cause the window decoration (title bar, window frame, buttons) to be disabled,
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| 40 | allowing specially-shaped windows to be created. In this example, we use this feature
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| 41 | to create a circular window containing an analog clock.
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| 42 |
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| 43 | Since this example's window does not provide a \gui File menu or a close
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| 44 | button, we provide a context menu with an \gui Exit entry so that the example
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| 45 | can be closed. Click the right mouse button over the window to open this menu.
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| 46 |
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| 47 | \section1 ShapedClock Class Definition
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| 48 |
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| 49 | The \c ShapedClock class is based on the \c AnalogClock class defined in the
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| 50 | \l{Analog Clock Example}{Analog Clock} example. The whole class definition is
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| 51 | presented below:
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| 52 |
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| 53 | \snippet examples/widgets/shapedclock/shapedclock.h 0
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| 54 |
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| 55 | The \l{QWidget::paintEvent()}{paintEvent()} implementation is the same as that found
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| 56 | in the \c AnalogClock class. We implement \l{QWidget::sizeHint()}{sizeHint()}
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| 57 | so that we don't have to resize the widget explicitly. We also provide an event
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| 58 | handler for resize events. This allows us to update the mask if the clock is resized.
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| 59 |
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| 60 | Since the window containing the clock widget will have no title bar, we provide
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| 61 | implementations for \l{QWidget::mouseMoveEvent()}{mouseMoveEvent()} and
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| 62 | \l{QWidget::mousePressEvent()}{mousePressEvent()} to allow the clock to be dragged
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| 63 | around the screen. The \c dragPosition variable lets us keep track of where the user
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| 64 | last clicked on the widget.
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| 65 |
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| 66 | \section1 ShapedClock Class Implementation
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| 67 |
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| 68 | The \c ShapedClock constructor performs many of the same tasks as the \c AnalogClock
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| 69 | constructor. We set up a timer and connect it to the widget's update() slot:
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| 70 |
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| 71 | \snippet examples/widgets/shapedclock/shapedclock.cpp 0
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| 72 |
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| 73 | We inform the window manager that the widget is not to be decorated with a window
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| 74 | frame by setting the Qt::FramelessWindowHint flag on the widget. As a result, we need
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| 75 | to provide a way for the user to move the clock around the screen.
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| 76 |
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| 77 | Mouse button events are delivered to the \c mousePressEvent() handler:
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| 78 |
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| 79 | \snippet examples/widgets/shapedclock/shapedclock.cpp 1
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| 80 |
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| 81 | If the left mouse button is pressed over the widget, we record the displacement in
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| 82 | global (screen) coordinates between the top-left position of the widget's frame (even
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| 83 | when hidden) and the point where the mouse click occurred. This displacement will be
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| 84 | used if the user moves the mouse while holding down the left button. Since we acted
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| 85 | on the event, we accept it by calling its \l{QEvent::accept()}{accept()} function.
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| 86 |
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| 87 | \image shapedclock-dragging.png
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| 88 |
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| 89 | The \c mouseMoveEvent() handler is called if the mouse is moved over the widget.
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| 90 |
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| 91 | \snippet examples/widgets/shapedclock/shapedclock.cpp 2
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| 92 |
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| 93 | If the left button is held down while the mouse is moved, the top-left corner of the
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