os/graphics/windowing/windowserver/inc/Graphics/openwfc/wselement.h
changeset 0 bde4ae8d615e
     1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/os/graphics/windowing/windowserver/inc/Graphics/openwfc/wselement.h	Fri Jun 15 03:10:57 2012 +0200
     1.3 @@ -0,0 +1,498 @@
     1.4 +// Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
     1.5 +// All rights reserved.
     1.6 +// This component and the accompanying materials are made available
     1.7 +// under the terms of "Eclipse Public License v1.0"
     1.8 +// which accompanies this distribution, and is available
     1.9 +// at the URL "http://www.eclipse.org/legal/epl-v10.html".
    1.10 +//
    1.11 +// Initial Contributors:
    1.12 +// Nokia Corporation - initial contribution.
    1.13 +//
    1.14 +// Contributors:
    1.15 +//
    1.16 +// Description:
    1.17 +// Interface for Scene Elements
    1.18 +// 
    1.19 +//
    1.20 +
    1.21 +/**
    1.22 + @publishedPartner
    1.23 + @prototype
    1.24 +*/
    1.25 +
    1.26 +#ifndef WSELEMENT_H
    1.27 +#define WSELEMENT_H
    1.28 +
    1.29 +#include <w32std.h>
    1.30 +#include <graphics/wsgraphicdrawerinterface.h>
    1.31 +#include <graphics/surface.h>
    1.32 +
    1.33 +/**
    1.34 + * @brief Window Server Scene Element Interface Definition
    1.35 + *
    1.36 + * This interface allows Image Sources to be associated with meta-data
    1.37 + * to define how the Image Source must be presented within a Scene.
    1.38 + *
    1.39 + * For a conceptual overview of Scenes, refer to the @c MWsScene Interface.
    1.40 + *
    1.41 + * The following aspects of Image Source presentation may be controlled:
    1.42 + * @li Source rectangular region
    1.43 + * @li Destination rectangular region
    1.44 + * @li Rotation and flipping
    1.45 + * @li Opacity
    1.46 + * @li Relative z-order (ordinal position)
    1.47 + * @li Tags to descriminate the UI from other Elements
    1.48 + *
    1.49 + * All co-ordinates are pixels offsets from (0,0) representing the
    1.50 + * top level of the Image Source or Destination Target (the screen
    1.51 + * or an off-screen buffer representing the screen), moving rightwards
    1.52 + * and downwards in x and y co-ordinates respectively.
    1.53 + *
    1.54 + * Elements can be marked with flags.  There are two different consumers
    1.55 + * of flags: Target Renderers and Render Stage Plug-ins.
    1.56 + * 
    1.57 + * Target Renderers are sub-systems which actually do composition and
    1.58 + * rendering on a particular display device or off-screen buffer.
    1.59 + * The EElementTransparencySource flag tells the Target Renderer that 
    1.60 + * alpha blending must use the alpha channel in the Surface connected to
    1.61 + * the Element.
    1.62 + * 
    1.63 + * On the other hand, Render Stage Plug-ins need flags to implement
    1.64 + * specific policies such as "UI always on top".  To facilitate this,
    1.65 + * Elements have a EElementIsIndirectlyRenderedUserInterface or a
    1.66 + * EElementIsDirectlyRenderedUserInterface optionally set.  This
    1.67 + * flag allows Render Stage Plug-ins to keep the relative z-order
    1.68 + * of Elements aligned to this policy.
    1.69 + * 
    1.70 + * To allow compatible updates to be made to flags, all Render Stage
    1.71 + * Plug-ins must preserve the flags in Elements which they do not operate
    1.72 + * upon.  Target Renderers may ignore the flags in Elements which they
    1.73 + * do not operate on.
    1.74 + *
    1.75 + * <h2>Intial State</h2>
    1.76 + * 
    1.77 + * The initial state for an Element is:
    1.78 + * @li Fully opaque
    1.79 + * @li No rotation, nor flipped
    1.80 + * @li Not part of the Committed Scene
    1.81 + * @li No connected Surface
    1.82 + * @li All flags reset
    1.83 + * @li Local error value set as KErrNone
    1.84 + * @li Source Rectangle and Destination Rectangle is (0,0,0,0)
    1.85 + * @il Destination Clipping Rectangle is (0,0,0,0)
    1.86 + * 
    1.87 + * When an Image Source is connected, the initial state becomes:
    1.88 + * @li Source Rectangle is the extent of the Image Source
    1.89 + * @li Destination Rectangle is set at origin (0,0), whose sized equals the
    1.90 + *     Image Source size truncated the the target screen size.
    1.91 + * @li Destination Clipping Rectangle is (0,0,0,0) to represent the entire
    1.92 + *     area of the target screen.
    1.93 + * 
    1.94 + * <h2>Special Rectangle Values</h2>
    1.95 + * 
    1.96 + * Sometimes it is desirable to reset a Source, Destination, or Clipping
    1.97 + * Rectangle so that the actual value used matches the corresponding Source
    1.98 + * Image or Target Screen size.  In such cases rectangle (0,0,0,0) is used to
    1.99 + * represent this.
   1.100 + * 
   1.101 + * <h2>Extending this interface</h2>
   1.102 + * 
   1.103 + * This interface can be extended in two different ways
   1.104 + * @li Creating optional extension interfaces with 
   1.105 + *       MWsElement::MWsObjectProvider::ResolveObjectInterface()
   1.106 + * @li Defining new TElementFlags flag settings; Render Stage Plug-ins
   1.107 + *       preserve the value of these across the Render Stage Pipeline.
   1.108 + *
   1.109 + * <h2>Committed Elements versus Pending Elements</h2>
   1.110 + * 
   1.111 + * This interface allows Elements to be modified in terms of their
   1.112 + * own flag settings, and rotation, as well as their relative position
   1.113 + * with other Elements.  Queries return the pending values for such
   1.114 + * Elements.  Any modifications are marked Pending, and affect the Scene
   1.115 + * according to the rules described by "Rendering" in @c MWsScene.
   1.116 + * 
   1.117 + * <h2>Order in which transformations are applied</h2>
   1.118 + * 
   1.119 + * A number of different transformations may be specified for an Element.
   1.120 + * The order in which these are applied to arrive at the view seen in
   1.121 + * the target is:
   1.122 + * -# SetSourceRectangle              (Cropping)
   1.123 + * -# SetSourceFlipping               (Flipping)
   1.124 + * -# SetSourceRotation               (Rotation)
   1.125 + * -# SetDestinationRectangle         (Scaling and Positioning)
   1.126 + * -# SetDestinationClippingRectangle (Scaling and Positioning)
   1.127 + * -# SetGlobalAlpha                  (Blending)
   1.128 + */
   1.129 +class MWsElement : public MWsObjectProvider
   1.130 +    {
   1.131 +public:
   1.132 +    
   1.133 +    /**
   1.134 +     * @brief Flags used by Target Renderers.
   1.135 +     */
   1.136 +    enum TElementTargetRendererFlags
   1.137 +        {
   1.138 +        /**
   1.139 +         * Target renderer must treat the Element as Opaque.
   1.140 +         */
   1.141 +        EElementTransparencyNone                 = 0,
   1.142 +        /**
   1.143 +         * Target renderer must use the Global Alpha Transparency value
   1.144 +         * from the Element
   1.145 +         */
   1.146 +        EElementTransparencyGlobalAlpha          = (1 << 0),
   1.147 +        /**
   1.148 +         * Target renderer must use the Alpha Transparency Channel from
   1.149 +         * the Element
   1.150 +         */
   1.151 +        EElementTransparencySource               = (1 << 1),
   1.152 +        /**
   1.153 +         * Reserved flag value; this must not be set.
   1.154 +         */
   1.155 +        EElementTargetRendererReserved           = (1 << 2)
   1.156 +        };
   1.157 +    
   1.158 +    /**
   1.159 +     * @brief Flags used by Render Stages.
   1.160 +     */
   1.161 +    enum TElementRenderStageFlags
   1.162 +        {
   1.163 +        /**
   1.164 +         * No flag value set for Render Stage Plug-in
   1.165 +         */
   1.166 +        EElementRenderStageNone                   = 0,
   1.167 +        /**
   1.168 +         * Indirectly Rendered User Interface, i.e. rendering via 
   1.169 +         * MWsGraphicsContext calls originating from client CWindowGc
   1.170 +         * commands
   1.171 +         */
   1.172 +        EElementIsIndirectlyRenderedUserInterface = (1 << 0),
   1.173 +        /**
   1.174 +         * Directly Render User Interface, i.e. rendering where Window
   1.175 +         * Server does not see the graphics commands, as is the case for
   1.176 +         * Direct Screen Access clients.
   1.177 +         */
   1.178 +        EElementIsDirectlyRenderedUserInterface   = (1 << 1),
   1.179 +        /**
   1.180 +         * Reserved values for future Render Stage Plug-in usage
   1.181 +         */
   1.182 +        EElementRenderStageReserved               = (1 << 2)
   1.183 +        };
   1.184 +    
   1.185 +    /**
   1.186 +     * Amount of rotation of pixel data to apply to the Image Source
   1.187 +     * to obtain the Target Image
   1.188 +     */
   1.189 +    enum TElementRotation
   1.190 +        {
   1.191 +        EElementAntiClockwise0   = 0, /** No rotation */
   1.192 +        EElementAntiClockwise90  = 1, /** 90 Degrees Anti-clockwise in target */
   1.193 +        EElementAntiClockwise180 = 2, /** 180 Degrees Anti-clockwise in target */
   1.194 +        EElementAntiClockwise270 = 3  /** 270 Degrees Anti-clockwise in target */
   1.195 +        };
   1.196 +    
   1.197 +public:
   1.198 +    /**
   1.199 +     * @brief Set which portion of the image source is used.
   1.200 +     *
   1.201 +     * Set which rectangular portion of the connected image source
   1.202 +     * will be used when displaying this Element.
   1.203 +     *
   1.204 +     * @param aSrc  The source rectangle of pixels from the connected Image Source.
   1.205 +     *              This rectangle must not include any pixels outside the Image
   1.206 +     *              Source.  (0,0,0,0) means the entire size of the Image Source.
   1.207 +     * @pre     An Image Source must have been connected; @see ConnectSurface()
   1.208 +     * @return  One of the system-wide error codes.  
   1.209 +     *          KErrGeneral, if there is no image source connected.
   1.210 +     *          KErrArgument, if the source rectangle includes pixels not in the 
   1.211 +     *          connected image source, or has negative width or height.  
   1.212 +     *          KErrNone, if successful.
   1.213 +     */
   1.214 +    virtual TInt SetSourceRectangle(const TRect& aSrc) = 0;
   1.215 +    
   1.216 +    /**
   1.217 +     * @brief Get the portion of the Image Source being used.
   1.218 +     *
   1.219 +     * Get the portion of the connected Image Source being used.  The default
   1.220 +     * value is the entire extent of the connected Image Source.
   1.221 +     *
   1.222 +     * @param aSrc  The source rectangle is updated with the current rectangular
   1.223 +     *              region being used within the Image Source.
   1.224 +     * @pre     An Image Source must have been connected; @see ConnectSurface()
   1.225 +     * @return  One of the system-wide error codes.  
   1.226 +     *          KErrGeneral, if no Image Source has been connected.  
   1.227 +     *          KErrNone, if successful.
   1.228 +     */
   1.229 +    virtual TInt GetSourceRectangle(TRect& aSrc) = 0;
   1.230 +    
   1.231 +    /**
   1.232 +     * @brief Set the target area where the Image Source should appear.
   1.233 +     * 
   1.234 +     * Set the target area in the target screen (or off-screen buffer)
   1.235 +     * where the Image Source should appear.  Scaling may result if
   1.236 +     * the source and destination rectangles differ.  A platform specific
   1.237 +     * algorithm will be used to interpolate the scaled image.
   1.238 +     * 
   1.239 +     * @param aDest  The destination rectangle in the target.
   1.240 +     * @pre     An Image Source must have been connected; @see ConnectSurface()
   1.241 +     * @return  One of the system-wide error codes.  
   1.242 +     *          KErrGeneral, if there is no image source connected. 
   1.243 +     *          KErrArgument, if the destination rectangle has negative width or 
   1.244 +     *          height.  
   1.245 +     *          KErrNone, if successful.
   1.246 +     */
   1.247 +    virtual TInt SetDestinationRectangle(const TRect& aDest) = 0;
   1.248 +    
   1.249 +    /**
   1.250 +     * @brief Get the target area where the Image Source would appear.
   1.251 +     * 
   1.252 +     * Get the target area where the Image Source would appear.  The default
   1.253 +     * value is at (0,0) sized to the Image Source clipped to the size
   1.254 +     * of the target.
   1.255 +     * 
   1.256 +     * @param aDest  The destination rectangle is updated with the current
   1.257 +     *               region used in the target screen. 
   1.258 +     * @pre     An Image Source must have been connected; @see ConnectSurface()
   1.259 +     * @return  One of the system-wide error codes.  
   1.260 +     *          KErrGeneral, if no Image Source has been connected.  
   1.261 +     *          KErrNone, if successful.
   1.262 +     */
   1.263 +    virtual TInt GetDestinationRectangle(TRect& aDest) const = 0;
   1.264 +    
   1.265 +    /**
   1.266 +     * @brief Clip the target area where the Image Source would appear.
   1.267 +     * 
   1.268 +     * Set clipping area where the Image Source would appear.  The default
   1.269 +     * value is the area of the target screen.
   1.270 +     * 
   1.271 +     * @param aDestClipRect  The clipping rectangle in the target.  (0,0,0,0)
   1.272 +     *                       means the entire size of the Target Screen.
   1.273 +     * @return  One of the system-wide error codes.  
   1.274 +     *          KErrGeneral, if no Image Source has been connected. 
   1.275 +     *          KErrArgument, if the rectangle has negative width or height  
   1.276 +     *          KErrNone, if successful.
   1.277 +     */
   1.278 +    virtual TInt SetDestinationClippingRect(const TRect& aDestClipRect) = 0;
   1.279 +    
   1.280 +    /**
   1.281 +     * @brief Get the clipping area in the target.
   1.282 +     * 
   1.283 +     * Get the clipping area which limits where in the target screen the
   1.284 +     * element may appear.
   1.285 +     * 
   1.286 +     * @param aDestClipRect  The clipping rectangle is updated with the current
   1.287 +     *                       clipping area used in the target screen.
   1.288 +     * @return  One of the system-wide error codes.  KErrGeneral means no Image
   1.289 +     *          Source has been connected.  KErrNone is returned upon success.      
   1.290 +     */
   1.291 +    virtual TInt GetDestinationClippingRect(TRect& aDestClipRect) const = 0;
   1.292 +    
   1.293 +    /**
   1.294 +     * @brief Set the rotation that should appear in the target for the
   1.295 +     * Image Source.
   1.296 +     * 
   1.297 +     * Set the rotation which describes how the connected Image Source
   1.298 +     * should be rotated to appear in the target.
   1.299 +     * 
   1.300 +     * @param aElementRotation  The amount of rotation in the target.
   1.301 +     * @pre     An Image Source must have been connected; @see ConnectSurface()
   1.302 +     * @return  One of the system-wide error codes.  
   1.303 +     *          KErrGeneral, if no Image Source has been connected.  
   1.304 +     *          KErrArgument, if an out of bounds rotation value has been 
   1.305 +     *          supplied.  
   1.306 +     *          KErrNone, if successful.
   1.307 +     */
   1.308 +    virtual TInt SetSourceRotation(const TElementRotation aElementRotation) = 0;
   1.309 +    
   1.310 +    /**
   1.311 +     * @brief Get the pending rotation setting as it would appear in the target.
   1.312 +     * 
   1.313 +     * Get the pending rotation setting for the connected Image Source.
   1.314 +     * By default, the rotation is EElementAntiClockwise0 and this is returned
   1.315 +     * if there is no connected Image Source.
   1.316 +     * 
   1.317 +     * @return  The pending rotation setting.
   1.318 +     */
   1.319 +    virtual TElementRotation SourceRotation() const = 0 ;
   1.320 +    
   1.321 +    /**
   1.322 +     * @brief Set flipping about the image horizontal centerline.
   1.323 +     * 
   1.324 +     * Set the pending flipping setting for the connected Image Source.
   1.325 +     * When flipped, the Image Source appears in the target as inverted
   1.326 +     * about its horizontal centerline.  This effect can be combined
   1.327 +     * with rotation effects.
   1.328 +     * By default, the Image Source is not flipped.
   1.329 +     * 
   1.330 +     * @param aFlip  If ETrue, the connected Image is flipped, else
   1.331 +     *               it is not flipped.
   1.332 +     * @pre     An Image Source must have been connected; @see ConnectSurface()
   1.333 +     * @return  One of the system-wide error codes.  
   1.334 +     *          KErrGeneral, if no Image Source has been connceted.  
   1.335 +     *          KErrNotSupported, if the platform does not support the feature.  
   1.336 +     *          KErrNone, if successful.
   1.337 +     */
   1.338 +    virtual TInt SetSourceFlipping(const TBool aFlip) = 0;
   1.339 +    
   1.340 +    /**
   1.341 +     * @brief Get the pending flipping setting.
   1.342 +     * 
   1.343 +     * Get the pending flipping setting for the connected Image Source.
   1.344 +     * By default, the image is not flipped.
   1.345 +     * 
   1.346 +     * @return  The pending flipping setting.  If no Image is connected, return
   1.347 +     *          EFalse.
   1.348 +     */
   1.349 +    virtual TBool SourceFlipping() const = 0 ;
   1.350 +    
   1.351 +    /**
   1.352 +     * @brief Set Target Renderer Flags associated with this Element
   1.353 +     * 
   1.354 +     * Set the Target Renderer flags to be associated with this Element.
   1.355 +     * 
   1.356 +     * @note    Flags which are not recognised by an implementation must
   1.357 +     *          be kept to allow the interface to be extended in a 
   1.358 +     *          compatible manner.
   1.359 +     * @param aTargetRendererFlags  Flags to set for Target Renderer;
   1.360 +     *                              @see TElementTargetRendererFlags
   1.361 +     * @return  One of the system-wide error codes.  
   1.362 +     *          KErrNotSupported, if the platform does not support the given 
   1.363 +     *          flags.  
   1.364 +     *          KErrArgument, if incompatible flag settings have been made.  
   1.365 +     *          KErrNone, if successful.
   1.366 +     */
   1.367 +    virtual TInt SetTargetRendererFlags(const TUint32& aTargetRendererFlags) = 0;
   1.368 +    
   1.369 +    /**
   1.370 +     * @brief Set Render Stage Flags associated with this Element
   1.371 +     * 
   1.372 +     * Set the Render Stage flags to be associated with this Element.
   1.373 +     * 
   1.374 +     * @note    Flags which are not recognised by an implementation must
   1.375 +     *          be kept to allow the interface to be extended in a 
   1.376 +     *          compatible manner.
   1.377 +     * @param aRenderStageFlags  Flags to set for Render Stage Plug-ins;
   1.378 +     *                           @see TElementRenderStageFlags
   1.379 +     * @return  One of the system-wide error codes.  
   1.380 +     *          KErrNotSupported, if the platform does not support the given 
   1.381 +     *          flags.  
   1.382 +     *          KErrArgument, if incompatible flag settings have been requested.  
   1.383 +     *          KErrNone, if successful.
   1.384 +     */
   1.385 +    virtual TInt SetRenderStageFlags(const TUint32& aRenderStageFlags) = 0;
   1.386 +    
   1.387 +    /**
   1.388 +     * @brief Get Target Renderer Flags associated with this Element
   1.389 +     * 
   1.390 +     * Get the Target Renderer flags associated with this Element.
   1.391 +     *   
   1.392 +     * @note    Flags which are not recognised by an implementation must
   1.393 +     *          be kept to allow the interface to be extended in a 
   1.394 +     *          compatible manner.
   1.395 +     * @param aTargetRendererFlags  Variable to receive TElementTargetRendererFlags
   1.396 +     */
   1.397 +    virtual void GetTargetRendererFlags(TUint32& aTargetRendererFlags) const = 0;
   1.398 +
   1.399 +    /**
   1.400 +      * @brief Get Render Stage Flags associated with this Element
   1.401 +      * 
   1.402 +      * Get the Render Stage flags associated with this Element.
   1.403 +      *   
   1.404 +      * @note    Flags which are not recognised by an implementation must
   1.405 +      *          be kept to allow the interface to be extended in a 
   1.406 +      *          compatible manner.
   1.407 +      * @param aRenderStageFlags  Variable to receive TElementRenderStageFlags
   1.408 +      */
   1.409 +     virtual void GetRenderStageFlags(TUint32& aRenderStageFlags) const = 0;   
   1.410 +     
   1.411 +    /**
   1.412 +     * @brief Get the Element above this Element.
   1.413 +     * 
   1.414 +     * Get the Element which is above this Element in the Pending Scene.
   1.415 +     * If the Element is the top-most element, NULL is returned.  If the
   1.416 +     * Element is not in the Scene, NULL is returned.
   1.417 +     * 
   1.418 +     * @return Element above, or NULL.
   1.419 +     */
   1.420 +    virtual MWsElement *ElementAbove() = 0;
   1.421 +    
   1.422 +    /**
   1.423 +     * @brief Get the Element below this Element.
   1.424 +     * 
   1.425 +     * Get the Element which is below this Element in the Pending Scene.
   1.426 +     * If the Element is the bottom-most element, NULL is returned.  If the
   1.427 +     * Element is not in the Scene, NULL is returned.
   1.428 +     * 
   1.429 +     * @return Element below, or NULL.
   1.430 +     */
   1.431 +    virtual MWsElement *ElementBelow() = 0;
   1.432 +    
   1.433 +    /**
   1.434 +     * @brief Connect or re-Connect a Surface to this Element.
   1.435 +     * 
   1.436 +     * Connect the given Surface to this Element, or re-Connect a new
   1.437 +     * Surface to this Element which already has a connected Surface.
   1.438 +     * The Element does not need to be in the Scene when this call is made.
   1.439 +     * 
   1.440 +     * @note    The Source Rectangle of the Element is updated to correspond
   1.441 +     *          to match the Source Rectangle of the Surface.  Thus any
   1.442 +     *          prior Source Rectangle setting will be overwritten.
   1.443 +     * 
   1.444 +     * @param aSurface  Surface to connect to.  If this is the Null
   1.445 +     *                  Surface, then the Source Rectangle of the
   1.446 +     *                  Element is set to (0,0,0,0).
   1.447 +     * @return  One of the system-wide error codes.  
   1.448 +     *          KErrArgument, if supplied Surface cannot be connected.  For 
   1.449 +     *          example the Element has a flag indicating it has an Alpha 
   1.450 +     *          Channel but the Surface does not.  
   1.451 +     *          KErrNone, if successful.
   1.452 +     */
   1.453 +    virtual TInt ConnectSurface(const TSurfaceId& aSurface) = 0;
   1.454 +    
   1.455 +    /**
   1.456 +     * @brief Get the Surface connected to this Element
   1.457 +     * 
   1.458 +     * @return  The Surface Identifier of the Connected Surface.  This
   1.459 +     *          identifier may represent the Null Surface Id if there
   1.460 +     *          was no Surface connected in the Pending Scene for this
   1.461 +     *          Element.
   1.462 +     */
   1.463 +    virtual const TSurfaceId& ConnectedSurface() const = 0;
   1.464 +    
   1.465 +    /**
   1.466 +     * @brief Set the Global Alpha Transparency value
   1.467 +     * 
   1.468 +     * Sets the Global Alpha Transparency value for this Element.  Elements
   1.469 +     * are by default fully opaque, represented by opacity 255.  On platforms
   1.470 +     * that support it, the Alpha Transparency value can be reduced down
   1.471 +     * to 0 representing fully transparent.  The purpose of this is to
   1.472 +     * allow the fading in and fading out of Elements into the Scene.
   1.473 +     * 
   1.474 +     * @param aAlpha  The Alpha Transparency value desired.  Values
   1.475 +     *                are clamped to be within the range [0, 255] where 0
   1.476 +     *                represents fully transparent, and 255 represents
   1.477 +     *                fully opaque.
   1.478 +     * @note    This setting has no effect unless the flag
   1.479 +     *          Target Renderer flag EElementTransparencyGlobalAlpha
   1.480 +     *          is set; @see SetTargetRendererFlags()
   1.481 +     * @note    Out of range values are clamped silently, and do not cause
   1.482 +     *          error conditions.
   1.483 +     * @return  One of the system-wide error codes.  
   1.484 +     *          KErrNotSupported, if the supplied value, once clamped, is not 
   1.485 +     *          supported on the platform.
   1.486 +     *          KErrNone, if successful.
   1.487 +     */
   1.488 +    virtual TInt SetGlobalAlpha(const TInt aAlpha) = 0;
   1.489 +    
   1.490 +    /**
   1.491 +     * @brief Get the Global Alpha Transparency value
   1.492 +     * 
   1.493 +     * Gets the Global Alpha Transparency value for this Element.  Elements
   1.494 +     * are by default fully opaque, represented by opacity 255.
   1.495 +     * 
   1.496 +     * @param aAlpha  Variable which receives the Global Alpha Transparency
   1.497 +     *                value.
   1.498 +     */
   1.499 +    virtual void GlobalAlpha(TInt& aAlpha) const = 0;
   1.500 +    };
   1.501 +#endif // WSELEMENT_H