Class Device

  • All Implemented Interfaces:
    Drawable
    Direct Known Subclasses:
    Display, Printer

    public abstract class Device
    extends Object
    implements Drawable
    This class is the abstract superclass of all device objects, such as the Display device and the Printer device. Devices can have a graphics context (GC) created for them, and they can be drawn on by sending messages to the associated GC.
    See Also:
    Sample code and further information
    • Constructor Summary

      Constructors 
      Constructor Description
      Device()
      Constructs a new instance of this class.
      Device​(DeviceData data)
      Constructs a new instance of this class.
    • Method Summary

      All Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      protected void checkDevice()
      Throws an SWTException if the receiver can not be accessed by the caller.
      protected void create​(DeviceData data)
      Creates the device in the operating system.
      protected void destroy()
      Destroys the device in the operating system and releases the device's handle.
      void dispose()
      Disposes of the operating system resources associated with the receiver.
      Rectangle getBounds()
      Returns a rectangle describing the receiver's size and location.
      Rectangle getClientArea()
      Returns a rectangle which describes the area of the receiver which is capable of displaying data.
      int getDepth()
      Returns the bit depth of the screen, which is the number of bits it takes to represent the number of unique colors that the screen is currently capable of displaying.
      DeviceData getDeviceData()
      Returns a DeviceData based on the receiver.
      protected int getDeviceZoom()
      Gets the scaling factor from the device and calculates the zoom level.
      Point getDPI()
      Returns a point whose x coordinate is the logical horizontal dots per inch of the display, and whose y coordinate is the logical vertical dots per inch of the display.
      FontData[] getFontList​(String faceName, boolean scalable)
      Returns FontData objects which describe the fonts that match the given arguments.
      Color getSystemColor​(int id)
      Returns the matching standard color for the given constant, which should be one of the color constants specified in class SWT.
      Font getSystemFont()
      Returns a reasonable font for applications to use.
      boolean getWarnings()
      Returns true if the underlying window system prints out warning messages on the console, and setWarnings had previously been called with true.
      protected void init()
      Initializes any internal resources needed by the device.
      abstract void internal_dispose_GC​(long hDC, GCData data)
      Invokes platform specific functionality to dispose a GC handle.
      abstract long internal_new_GC​(GCData data)
      Invokes platform specific functionality to allocate a new GC handle.
      boolean isDisposed()
      Returns true if the device has been disposed, and false otherwise.
      boolean loadFont​(String path)
      Loads the font specified by a file.
      protected void release()
      Releases any internal resources back to the operating system and clears all fields except the device handle.
      void setWarnings​(boolean warnings)
      If the underlying window system supports printing warning messages to the console, setting warnings to false prevents these messages from being printed.
    • Field Detail

      • DEBUG

        public static boolean DEBUG
      • CurrentDevice

        protected static Device CurrentDevice
      • DeviceFinder

        protected static Runnable DeviceFinder
    • Method Detail

      • checkDevice

        protected void checkDevice()
        Throws an SWTException if the receiver can not be accessed by the caller. This may include both checks on the state of the receiver and more generally on the entire execution context. This method should be called by device implementors to enforce the standard SWT invariants.

        Currently, it is an error to invoke any method (other than isDisposed() and dispose()) on a device that has had its dispose() method called.

        In future releases of SWT, there may be more or fewer error checks and exceptions may be thrown for different reasons.

        Throws:
        SWTException -
        • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
      • create

        protected void create​(DeviceData data)
        Creates the device in the operating system. If the device does not have a handle, this method may do nothing depending on the device.

        This method is called before init.

        Subclasses are supposed to reimplement this method and not call the super implementation.

        Parameters:
        data - the DeviceData which describes the receiver
        See Also:
        init()
      • destroy

        protected void destroy()
        Destroys the device in the operating system and releases the device's handle. If the device does not have a handle, this method may do nothing depending on the device.

        This method is called after release.

        Subclasses are supposed to reimplement this method and not call the super implementation.

        See Also:
        dispose(), release()
      • dispose

        public void dispose()
        Disposes of the operating system resources associated with the receiver. After this method has been invoked, the receiver will answer true when sent the message isDisposed().
        See Also:
        release(), destroy(), checkDevice()
      • getBounds

        public Rectangle getBounds()
        Returns a rectangle describing the receiver's size and location.
        Returns:
        the bounding rectangle
        Throws:
        SWTException -
        • ERROR_DEVICE_DISPOSED - if the receiver has been disposed
      • getDeviceData

        public DeviceData getDeviceData()
        Returns a DeviceData based on the receiver. Modifications made to this DeviceData will not affect the receiver.
        Returns:
        a DeviceData containing the device's data and attributes
        Throws:
        SWTException -
        • ERROR_DEVICE_DISPOSED - if the receiver has been disposed
        See Also:
        DeviceData
      • getClientArea

        public Rectangle getClientArea()
        Returns a rectangle which describes the area of the receiver which is capable of displaying data.
        Returns:
        the client area
        Throws:
        SWTException -
        • ERROR_DEVICE_DISPOSED - if the receiver has been disposed
        See Also:
        getBounds()
      • getDepth

        public int getDepth()
        Returns the bit depth of the screen, which is the number of bits it takes to represent the number of unique colors that the screen is currently capable of displaying. This number will typically be one of 1, 8, 15, 16, 24 or 32.
        Returns:
        the depth of the screen
        Throws:
        SWTException -
        • ERROR_DEVICE_DISPOSED - if the receiver has been disposed
      • getDPI

        public Point getDPI()
        Returns a point whose x coordinate is the logical horizontal dots per inch of the display, and whose y coordinate is the logical vertical dots per inch of the display.
        Returns:
        the horizontal and vertical DPI
        Throws:
        SWTException -
        • ERROR_DEVICE_DISPOSED - if the receiver has been disposed
      • getFontList

        public FontData[] getFontList​(String faceName,
                                      boolean scalable)
        Returns FontData objects which describe the fonts that match the given arguments. If the faceName is null, all fonts will be returned.
        Parameters:
        faceName - the name of the font to look for, or null
        scalable - if true only scalable fonts are returned, otherwise only non-scalable fonts are returned.
        Returns:
        the matching font data
        Throws:
        SWTException -
        • ERROR_DEVICE_DISPOSED - if the receiver has been disposed
      • getSystemColor

        public Color getSystemColor​(int id)
        Returns the matching standard color for the given constant, which should be one of the color constants specified in class SWT. Any value other than one of the SWT color constants which is passed in will result in the color black. This color should not be freed because it was allocated by the system, not the application.
        Parameters:
        id - the color constant
        Returns:
        the matching color
        Throws:
        SWTException -
        • ERROR_DEVICE_DISPOSED - if the receiver has been disposed
        See Also:
        SWT
      • getSystemFont

        public Font getSystemFont()
        Returns a reasonable font for applications to use. On some platforms, this will match the "default font" or "system font" if such can be found. This font should not be freed because it was allocated by the system, not the application.

        Typically, applications which want the default look should simply not set the font on the widgets they create. Widgets are always created with the correct default font for the class of user-interface component they represent.

        Returns:
        a font
        Throws:
        SWTException -
        • ERROR_DEVICE_DISPOSED - if the receiver has been disposed
      • getWarnings

        public boolean getWarnings()
        Returns true if the underlying window system prints out warning messages on the console, and setWarnings had previously been called with true.
        Returns:
        trueif warnings are being handled, and false otherwise
        Throws:
        SWTException -
        • ERROR_DEVICE_DISPOSED - if the receiver has been disposed
      • init

        protected void init()
        Initializes any internal resources needed by the device.

        This method is called after create.

        If subclasses reimplement this method, they must call the super implementation.

        See Also:
        create(org.eclipse.swt.graphics.DeviceData)
      • internal_new_GC

        public abstract long internal_new_GC​(GCData data)
        Invokes platform specific functionality to allocate a new GC handle.

        IMPORTANT: This method is not part of the public API for Device. It is marked public only so that it can be shared within the packages provided by SWT. It is not available on all platforms, and should never be called from application code.

        Specified by:
        internal_new_GC in interface Drawable
        Parameters:
        data - the platform specific GC data
        Returns:
        the platform specific GC handle
        Restriction:
        This method is not intended to be referenced by clients.
      • internal_dispose_GC

        public abstract void internal_dispose_GC​(long hDC,
                                                 GCData data)
        Invokes platform specific functionality to dispose a GC handle.

        IMPORTANT: This method is not part of the public API for Device. It is marked public only so that it can be shared within the packages provided by SWT. It is not available on all platforms, and should never be called from application code.

        Specified by:
        internal_dispose_GC in interface Drawable
        Parameters:
        hDC - the platform specific GC handle
        data - the platform specific GC data
        Restriction:
        This method is not intended to be referenced by clients.
      • isDisposed

        public boolean isDisposed()
        Returns true if the device has been disposed, and false otherwise.

        This method gets the dispose state for the device. When a device has been disposed, it is an error to invoke any other method using the device.

        Returns:
        true when the device is disposed and false otherwise
      • loadFont

        public boolean loadFont​(String path)
        Loads the font specified by a file. The font will be present in the list of fonts available to the application.
        Parameters:
        path - the font file path
        Returns:
        whether the font was successfully loaded
        Throws:
        SWTException -
        • ERROR_NULL_ARGUMENT - if path is null
        • ERROR_DEVICE_DISPOSED - if the receiver has been disposed
        Since:
        3.3
        See Also:
        Font
      • release

        protected void release()
        Releases any internal resources back to the operating system and clears all fields except the device handle.

        When a device is destroyed, resources that were acquired on behalf of the programmer need to be returned to the operating system. For example, if the device allocated a font to be used as the system font, this font would be freed in release. Also,to assist the garbage collector and minimize the amount of memory that is not reclaimed when the programmer keeps a reference to a disposed device, all fields except the handle are zero'd. The handle is needed by destroy.

        This method is called before destroy.

        If subclasses reimplement this method, they must call the super implementation.

        See Also:
        dispose(), destroy()
      • setWarnings

        public void setWarnings​(boolean warnings)
        If the underlying window system supports printing warning messages to the console, setting warnings to false prevents these messages from being printed. If the argument is true then message printing is not blocked.
        Parameters:
        warnings - trueif warnings should be printed, and false otherwise
        Throws:
        SWTException -
        • ERROR_DEVICE_DISPOSED - if the receiver has been disposed
      • getDeviceZoom

        protected int getDeviceZoom()
        Gets the scaling factor from the device and calculates the zoom level.
        Returns:
        zoom in percentage
        Since:
        3.105
        Restriction:
        This method is not intended to be referenced by clients.
        Restriction:
        This method is not intended to be re-implemented or extended by clients.