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QStyle Class Reference

The QStyle class specifies the look and feel of a GUI. More...

#include <qstyle.h>

Inherits QObject.

Inherited by QCommonStyle.

List of all member functions.

Public Members

Static Public Members

Detailed Description

The QStyle class specifies the look and feel of a GUI.

A large number of GUI elements are common to many widgets. The QStyle class allows the look of these elements to be modified across all widgets that use the QStyle functions. It also provides two feel options: Motif and Windows.

Although it is not possible to fully enumerate the look of graphical elements and the feel of widgets in a GUI, QStyle provides a considerable amount of control and customisability.

In Qt 1.x the look and feel option for widgets was specified by a single value: the GUIStyle. Starting with Qt 2.0, this notion was expanded to allow the look to be specified by virtual drawing functions.

Derived classes may reimplement some or all of the drawing functions to modify the look of all widgets that use those functions.

Languages written from right to left (such as Arabic and Hebrew) usually also mirror the whole layout of widgets. If you design a style, you should take special care when drawing asymmetric elements to make sure that they also look correct in a mirrored layout. You can start your application with -reverse to check the mirrored layout. Also notice, that for a reversed layout, the light usually comes from top right instead of top left.

The actual reverse layout is performed automatically when possible. However, for the sake of flexibility, the translation cannot be performed everywhere. The documentation for each function in the QStyle API states whether the function expects/returns logical or screen coordinates. Using logical coordinates (in ComplexControls, for example) provides great flexibility in controlling the look of a widget. Use visualRect() when necessary to translate logical coordinates into screen coordinates for drawing.

In Qt versions prior to 3.0, if you wanted a low level route into changing the appearance of a widget, you would reimplement polish(). With the new 3.0 style engine the recommended approach is to reimplement the draw functions, for example drawItem(), drawPrimitive(), drawControl(), drawControlMask(), drawComplexControl() and drawComplexControlMask(). Each of these functions is called with a range of parameters that provide information that you can use to determine how to draw them, e.g. style flags, rectangle, color group, etc.

For information on changing elements of an existing style or creating your own style see the Style overview.

Styles can also be created as plugins.

See also Widget Appearance and Style.

Member Type Documentation

QStyle::ComplexControl

This enum represents a ComplexControl. ComplexControls have different behaviour depending upon where the user clicks on them or which keys are pressed.

See also SubControl and drawComplexControl().

QStyle::ContentsType

This enum represents a ContentsType. It is used to calculate sizes for the contents of various widgets.

See also sizeFromContents().

QStyle::ControlElement

This enum represents a ControlElement. A ControlElement is part of a widget that performs some action or displays information to the user.

See also drawControl().

QStyle::PixelMetric

This enum represents a PixelMetric. A PixelMetric is a style dependent size represented as a single pixel value.

See also pixelMetric().

QStyle::PrimitiveElement

This enum represents the PrimitiveElements of a style. A PrimitiveElement is a common GUI element, such as a checkbox indicator or pushbutton bevel.

See also drawPrimitive().

QStyle::StyleFlags

This enum represents flags for drawing PrimitiveElements. Not all primitives use all of these flags. Note that these flags may mean different things to different primitives. For an explanation of the relationship between primitives and their flags, as well as the different meanings of the flags, see the Style overview.

See also drawPrimitive().

QStyle::StyleHint

This enum represents a StyleHint. A StyleHint is a general look and/or feel hint.

See also styleHint().

QStyle::StylePixmap

This enum represents a StylePixmap. A StylePixmap is a pixmap that can follow some existing GUI style or guideline.

See also stylePixmap().

QStyle::SubControl

This enum represents a SubControl within a ComplexControl.

See also ComplexControl.

QStyle::SubRect

This enum represents a sub-area of a widget. Style implementations would use these areas to draw the different parts of a widget.

See also subRect().

Member Function Documentation

QStyle::QStyle ()

Constructs a QStyle.

QStyle::~QStyle () [virtual]

Destroys the style and frees all allocated resources.

int QStyle::defaultFrameWidth () const

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.

void QStyle::drawComplexControlMask ( ComplexControl control, QPainter * p, const QWidget * widget, const QRect & r, const QStyleOption & opt = QStyleOption::Default ) const [pure virtual]

Draw a bitmask for the ComplexControl control using the painter p in the area r. See drawComplexControl() for an explanation of the use of the widget and opt arguments.

The rect r should be in logical coordinates. Reimplementations of this function should use visualRect() to change the logical corrdinates into screen coordinates when using drawPrimitive() and drawControl().

See also drawComplexControl() and ComplexControl.

void QStyle::drawControl ( ControlElement element, QPainter * p, const QWidget * widget, const QRect & r, const QColorGroup & cg, SFlags how = Style_Default, const QStyleOption & opt = QStyleOption::Default ) const [pure virtual]

Draws the ControlElement element using the painter p in the area r. Colors are used from the color group cg.

The rect r should be in screen coordinates.

The how argument is used to control how the ControlElement is drawn. Multiple flags can be OR'ed together. See the table below for an explanation of which flags are used with the various ControlElements.

The widget argument is a pointer to a QWidget or one of its subclasses. The widget can be cast to the appropriate type based on the value of element. The opt argument can be used to pass extra information required when drawing the ControlElement. Note that opt may be the default value even for ControlElements that can make use of the extra options. See the table below for the appropriate widget and opt usage:

ControlElement
& Widget Cast 		Style Flags Notes Options Notes
CE_PushButton(const QPushButton *)

and

CE_PushButtonLabel(const QPushButton *)

Style_Enabled Set if the button is enabled. Unused.  
Style_HasFocus Set if the button has input focus.
Style_Raised Set if the button is not down, not on and not flat.
Style_On Set if the button is a toggle button and toggled on.
Style_Down Set if the button is down (i.e., the mouse button or space bar is pressed on the button).
Style_ButtonDefault Set if the button is a default button.
CE_CheckBox(const QCheckBox *)

and

CE_CheckBoxLabel(const QCheckBox *)

Style_Enabled Set if the checkbox is enabled. Unused.  
Style_HasFocus Set if the checkbox has input focus.
Style_On Set if the checkbox is checked.
Style_Off Set if the checkbox is not checked.
Style_NoChange Set if the checkbox is in the NoChange state.
Style_Down Set if the checkbox is down (i.e., the mouse button or space bar is pressed on the button).
CE_RadioButton(const QRadioButton *)

and

CE_RadioButtonLabel(const QRadioButton *)

Style_Enabled Set if the radiobutton is enabled. Unused.  
Style_HasFocus Set if the radiobutton has input focus.
Style_On Set if the radiobutton is checked.
Style_Off Set if the radiobutton is not checked.
Style_Down Set if the radiobutton is down (i.e., the mouse button or space bar is pressed on the radiobutton).
CE_TabBarTab(const QTabBar *)

and

CE_TabBarLabel(const QTabBar *)

Style_Enabled Set if the tabbar and tab is enabled. QStyleOption ( QTab *t ) t is the QTab being drawn.
Style_Selected Set if the tab is the current tab.
CE_ProgressBarGroove(const QProgressBar *)

and

CE_ProgressBarContents(const QProgressBar *)

and

CE_ProgressBarLabel(const QProgressBar *)

Style_Enabled Set if the progressbar is enabled. Unused.  
Style_HasFocus Set if the progressbar has input focus.
CE_PopupMenuItem(const QPopupMenu *) Style_Enabled Set if the menuitem is enabled. QStyleOption ( QMenuItem *mi, int tabwidth, int maxpmwidth ) mi is the menu item being drawn. QMenuItem is currently an internal class.
Style_Active Set if the menuitem is the current item. tabwidth is the width of the tab column where key accelerators are drawn.
Style_Down Set if the menuitem is down (i.e., the mouse button or space bar is pressed). maxpmwidth is the maximum width of the check column where checkmarks and iconsets are drawn.
CE_MenuBarItem(const QMenuBar *) Style_Enabled Set if the menuitem is enabled QStyleOption ( QMenuItem *mi ) mi is the menu item being drawn.
Style_Active Set if the menuitem is the current item.
Style_Down Set if the menuitem is down (i.e., a mouse button or the space bar is pressed).
Style_HasFocus Set if the menubar has input focus.
CE_ToolButtonLabel(const QToolButton *) Style_Enabled Set if the toolbutton is enabled. QStyleOption ( ArrowType t ) When the tool button only contains an arrow, t is the arrow's type.
Style_HasFocus Set if the toolbutton has input focus.
Style_Down Set if the toolbutton is down (i.e., a mouse button or the space is pressed).
Style_On Set if the toolbutton is a toggle button and is toggled on.
Style_AutoRaise Set if the toolbutton has auto-raise enabled.
Style_MouseOver Set if the mouse pointer is over the toolbutton.
Style_Raised Set if the button is not down, not on and doesn't contain the mouse when auto-raise is enabled.

See also ControlElement and StyleFlags.

void QStyle::drawControlMask ( ControlElement element, QPainter * p, const QWidget * widget, const QRect & r, const QStyleOption & opt = QStyleOption::Default ) const [pure virtual]

Draw a bitmask for the ControlElement element using the painter p in the area r. See drawControl() for an explanation of the use of the widget and opt arguments.

The rect r should be in screen coordinates.

See also drawControl() and ControlElement.

void QStyle::drawItem ( QPainter * p, const QRect & r, int flags, const QColorGroup & g, bool enabled, const QPixmap * pixmap, const QString & text, int len = -1, const QColor * penColor = 0 ) const [virtual]

Draws the text or pixmap in rectangle r using painter p and color group g. The pen color is specified with penColor. The enabled bool indicates whether or not the item is enabled; when reimplementing this bool should influence how the item is drawn. If len is -1 (the default) all the text is drawn; otherwise only the first len characters of text are drawn. The text is aligned and wrapped according to the alignment flags (see Qt::AlignmentFlags).

By default, if both the text and the pixmap are not null, the pixmap is drawn and the text is ignored.

void QStyle::drawPrimitive ( PrimitiveElement pe, QPainter * p, const QRect & r, const QColorGroup & cg, SFlags flags = Style_Default, const QStyleOption & opt = QStyleOption::Default ) const [pure virtual]

Draws the style PrimitiveElement pe using the painter p in the area r. Colors are used from the color group cg.

The rect r should be in screen coordinates.

The flags argument is used to control how the PrimitiveElement is drawn. Multiple flags can be OR'ed together.

For example, a pressed button would be drawn with the flags Style_Enabled and Style_Down.

The opt argument can be used to control how various PrimitiveElements are drawn. Note that opt may be the default value even for PrimitiveElements that make use of extra options. When opt is non-default, it is used as follows:

PrimitiveElement Options Notes
PE_FocusRect QStyleOption ( const QColor & bg ) bg is the background color on which the focus rect is being drawn.
PE_Panel QStyleOption ( int linewidth, int midlinewidth ) linewidth is the line width for drawing the panel.
midlinewidth is the mid-line width for drawing the panel.
PE_PanelPopup QStyleOption ( int linewidth, int midlinewidth ) linewidth is the line width for drawing the panel.
midlinewidth is the mid-line width for drawing the panel.
PE_PanelMenuBar QStyleOption ( int linewidth, int midlinewidth ) linewidth is the line width for drawing the panel.
midlinewidth is the mid-line width for drawing the panel.
PE_PanelDockWindow QStyleOption ( int linewidth, int midlinewidth ) linewidth is the line width for drawing the panel.
midlinewidth is the mid-line width for drawing the panel.
PE_GroupBoxFrame QStyleOption ( int linewidth, int midlinewidth, int shape, int shadow ) linewidth is the line width for the group box.
midlinewidth is the mid-line width for the group box.
shape is the frame shape for the group box.
shadow is the frame shadow for the group box.

For all other PrimitiveElements, opt is unused.

See also StyleFlags.

Example: themes/wood.cpp.

QRect QStyle::itemRect ( QPainter * p, const QRect & r, int flags, bool enabled, const QPixmap * pixmap, const QString & text, int len = -1 ) const [virtual]

Returns the appropriate area (see below) within rectangle r in which to draw the text or pixmap using painter p. If len is -1 (the default) all the text is drawn; otherwise only the first len characters of text are drawn. The text is aligned in accordance with the alignment flags (see Qt::AlignmentFlags). The enabled bool indicates whether or not the item is enabled.

If r is larger than the area needed to render the text the rectangle that is returned will be offset within r in accordance with the alignment flags. For example if flags is AlignCenter the returned rectangle will be centered within r. If r is smaller than the area needed the rectangle that is returned will be larger than r (the smallest rectangle large enough to render the text or pixmap).

By default, if both the text and the pixmap are not null, the pixmap is drawn and the text is ignored.

int QStyle::pixelMetric ( PixelMetric metric, const QWidget * widget = 0 ) const [pure virtual]

Returns the pixel metric for metric. The widget argument is a pointer to a QWidget or one of its subclasses. The widget can be cast to the appropriate type based on the value of metric. Note that widget may be zero even for PixelMetrics that can make use of widget. See the table below for the appropriate widget casts:

PixelMetric Widget Cast
PM_SliderControlThickness (const QSlider *)
PM_SliderLength (const QSlider *)
PM_SliderTickmarkOffset (const QSlider *)
PM_SliderSpaceAvailable (const QSlider *)
PM_TabBarTabOverlap (const QTabBar *)
PM_TabBarTabHSpace (const QTabBar *)
PM_TabBarTabVSpace (const QTabBar *)
PM_TabBarBaseHeight (const QTabBar *)
PM_TabBarBaseOverlap (const QTabBar *)

void QStyle::polish ( QWidget * ) [virtual]

Initializes the appearance of a widget.

This function is called for every widget at some point after it has been fully created but just before it is shown the very first time.

Reasonable actions in this function might be to call QWidget::setBackgroundMode() for the widget. An example of highly unreasonable use would be setting the geometry! Reimplementing this function gives you a back-door through which you can change the appearance of a widget. With Qt 3.0's style engine you will rarely need to write your own polish(); instead reimplement drawItem(), drawPrimitive(), etc.

The QWidget::inherits() function may provide enough information to allow class-specific customizations. But be careful not to hard-code things too much because new QStyle subclasses are expected to work reasonably with all current and future widgets.

See also unPolish().

Examples: themes/metal.cpp and themes/wood.cpp.

void QStyle::polish ( QApplication * ) [virtual]

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

Late initialization of the QApplication object.

See also unPolish().

void QStyle::polish ( QPalette & ) [virtual]

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

The style may have certain requirements for color palettes. In this function it has the chance to change the palette according to these requirements.

See also QPalette and QApplication::setPalette().

void QStyle::polishPopupMenu ( QPopupMenu * ) [pure virtual]

Polishes the popup menu according to the GUI style. This usually means setting the mouse tracking (QPopupMenu::setMouseTracking()) and whether the menu is checkable by default (QPopupMenu::setCheckable()).

SubControl QStyle::querySubControl ( ComplexControl control, const QWidget * widget, const QPoint & pos, const QStyleOption & opt = QStyleOption::Default ) const [pure virtual]

Returns the SubControl for widget at the point pos. The widget argument is a pointer to a QWidget or one of its subclasses. The widget can be cast to the appropriate type based on the value of control. The opt argument can be used to pass extra information required when drawing the ComplexControl. Note that opt may be the default value even for ComplexControls that can make use of the extra options. See drawComplexControl() for an explanation of the widget and opt arguments.

Note that pos is passed in screen coordinates. When using querySubControlMetrics() to check for hits and misses, use visualRect() to change the logical coordinates into screen coordinates.

See also drawComplexControl(), ComplexControl, SubControl, and querySubControlMetrics().

QRect QStyle::querySubControlMetrics ( ComplexControl control, const QWidget * widget, SubControl subcontrol, const QStyleOption & opt = QStyleOption::Default ) const [pure virtual]

Returns the rect for the SubControl subcontrol for widget in logical coordinates.

The widget argument is a pointer to a QWidget or one of its subclasses. The widget can be cast to the appropriate type based on the value of control. The opt argument can be used to pass extra information required when drawing the ComplexControl. Note that opt may be the default value even for ComplexControls that can make use of the extra options. See drawComplexControl() for an explanation of the widget and opt arguments.

See also drawComplexControl(), ComplexControl, and SubControl.

QSize QStyle::scrollBarExtent () const

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.

QSize QStyle::sizeFromContents ( ContentsType contents, const QWidget * widget, const QSize & contentsSize, const QStyleOption & opt = QStyleOption::Default ) const [pure virtual]

Returns the size of widget based on the contents size contentsSize.

The widget argument is a pointer to a QWidget or one of its subclasses. The widget can be cast to the appropriate type based on the value of contents. The opt argument can be used to pass extra information required when calculating the size. Note that opt may be the default value even for ContentsTypes that can make use of the extra options. See the table below for the appropriate widget and opt usage:

ContentsType Widget Cast Options Notes
CT_PushButton (const QPushButton *) Unused.  
CT_CheckBox (const QCheckBox *) Unused.  
CT_RadioButton (const QRadioButton *) Unused.  
CT_ToolButton (const QToolButton *) Unused.  
CT_ComboBox (const QComboBox *) Unused.  
CT_Splitter (const QSplitter *) Unused.  
CT_DockWindow (const QDockWindow *) Unused.  
CT_ProgressBar (const QProgressBar *) Unused.  
CT_PopupMenuItem (const QPopupMenu *) QStyleOption ( QMenuItem *mi ) mi is the menu item to use when calculating the size. QMenuItem is currently an internal class.

int QStyle::styleHint ( StyleHint stylehint, const QWidget * widget = 0, const QStyleOption & opt = QStyleOption::Default, QStyleHintReturn * returnData = 0 ) const [pure virtual]

Returns the style hint stylehint for widget. Currently, widget, opt, and returnData are unused; they're included to allow for future enhancements.

For an explanation of the return value see StyleHint.

QPixmap QStyle::stylePixmap ( StylePixmap stylepixmap, const QWidget * widget = 0, const QStyleOption & opt = QStyleOption::Default ) const [pure virtual]

Returns a pixmap for stylepixmap.

The opt argument can be used to pass extra information required when drawing the ControlElement. Note that opt may be the default value even for StylePixmaps that can make use of the extra options. Currently, the opt argument is unused.

The widget argument is a pointer to a QWidget or one of its subclasses. The widget can be cast to the appropriate type based on the value of stylepixmap. See the table below for the appropriate widget casts:

StylePixmap Widget Cast
SP_TitleBarMinButton (const QWidget *)
SP_TitleBarMaxButton (const QWidget *)
SP_TitleBarCloseButton (const QWidget *)
SP_TitleBarNormalButton (const QWidget *)
SP_TitleBarShadeButton (const QWidget *)
SP_TitleBarUnshadeButton (const QWidget *)
SP_DockWindowCloseButton (const QDockWindow *)

See also StylePixmap.

QRect QStyle::subRect ( SubRect subrect, const QWidget * widget ) const [pure virtual]

Returns the sub-area subrect for the widget in logical coordinates.

The widget argument is a pointer to a QWidget or one of its subclasses. The widget can be cast to the appropriate type based on the value of subrect. See the table below for the appropriate widget casts:

SubRect Widget Cast
SR_PushButtonContents (const QPushButton *)
SR_PushButtonFocusRect (const QPushButton *)
SR_CheckBoxIndicator (const QCheckBox *)
SR_CheckBoxContents (const QCheckBox *)
SR_CheckBoxFocusRect (const QCheckBox *)
SR_RadioButtonIndicator (const QRadioButton *)
SR_RadioButtonContents (const QRadioButton *)
SR_RadioButtonFocusRect (const QRadioButton *)
SR_ComboBoxFocusRect (const QComboBox *)
SR_DockWindowHandleRect (const QWidget *)
SR_ProgressBarGroove (const QProgressBar *)
SR_ProgressBarContents (const QProgressBar *)
SR_ProgressBarLabel (const QProgressBar *)

The tear-off handle (SR_DockWindowHandleRect) for QDockWindow is a private class. Use QWidget::parentWidget() to access the QDockWindow: 

        if ( !widget->parentWidget() )
            return;
        const QDockWindow *dw = (const QDockWindow *) widget->parentWidget();

See also SubRect.

void QStyle::tabbarMetrics ( const QWidget * t, int & hf, int & vf, int & ov ) const

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.

void QStyle::unPolish ( QWidget * ) [virtual]

Undoes the initialization of a widget's appearance.

This function is the counterpart to polish. It is called for every polished widget when the style is dynamically changed. The former style has to unpolish its settings before the new style can polish them again.

See also polish().

Examples: themes/metal.cpp and themes/wood.cpp.

void QStyle::unPolish ( QApplication * ) [virtual]

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

Undoes the application polish.

See also polish().

QRect QStyle::visualRect ( const QRect & logical, const QWidget * w ) [static]

Returns the rect logical in screen coordinates. The bounding rect for widget w is used to perform the translation. This function is provided to aid style implementors in supporting right-to-left mode.

See also QApplication::reverseLayout().

QRect QStyle::visualRect ( const QRect & logical, const QRect & bounding ) [static]

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

Returns the rect logical in screen coordinates. The rect bounding is used to perform the translation. This function is provided to aid style implementors in supporting right-to-left mode.

See also QApplication::reverseLayout().

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