use wxEmptyString as default value to return from GetAttribute()

[wxWidgets.git] / interface / bitmap.h

/////////////////////////////////////////////////////////////////////////////
// Name:        bitmap.h
// Purpose:     interface of wxBitmap* classes
// Author:      wxWidgets team
// RCS-ID:      $Id$
// Licence:     wxWindows license
/////////////////////////////////////////////////////////////////////////////


/**
    In wxBitmap and wxBitmapHandler context this value means: "use the screen depth".
*/
#define wxBITMAP_SCREEN_DEPTH       (-1)

/**
    @class wxBitmapHandler
    @wxheader{bitmap.h}

    This is the base class for implementing bitmap file loading/saving, and
    bitmap creation from data.
    It is used within wxBitmap and is not normally seen by the application.

    If you wish to extend the capabilities of wxBitmap, derive a class from
    wxBitmapHandler and add the handler using wxBitmap::AddHandler in your
    application initialisation.

    @library{wxcore}
    @category{misc}

    @see @ref overview_bitmap, wxBitmap, wxIcon, wxCursor
*/
class wxBitmapHandler : public wxObject
{
public:
    /**
        Default constructor.

        In your own default constructor, initialise the members m_name,
        m_extension and m_type.
    */
    wxBitmapHandler();

    /**
        Destroys the wxBitmapHandler object.
    */
    ~wxBitmapHandler();

    /**
        Creates a bitmap from the given data, which can be of arbitrary type.
        The wxBitmap object @a bitmap is manipulated by this function.

        @param bitmap
            The wxBitmap object.
        @param width
            The width of the bitmap in pixels.
        @param height
            The height of the bitmap in pixels.
        @param depth
            The depth of the bitmap in pixels.
            If this is ::wxBITMAP_SCREEN_DEPTH, the screen depth is used.
        @param data
            Data whose type depends on the value of type.
        @param type
            A bitmap type identifier - see ::wxBitmapType for a list
            of possible values.

        @returns @true if the call succeeded, @false otherwise (the default).
    */
    virtual bool Create(wxBitmap* bitmap, const void* data, wxBitmapType type,
                        int width, int height, int depth = wxBITMAP_SCREEN_DEPTH);

    /**
        Gets the file extension associated with this handler.
    */
    const wxString& GetExtension() const;

    /**
        Gets the name of this handler.
    */
    const wxString& GetName() const;

    /**
        Gets the bitmap type associated with this handler.
    */
    wxBitmapType GetType() const;

    /**
        Loads a bitmap from a file or resource, putting the resulting data into
        @a bitmap.

        @param bitmap
            The bitmap object which is to be affected by this operation.
        @param name
            Either a filename or a Windows resource name.
            The meaning of name is determined by the type parameter.
        @param type
            See ::wxBitmapType for values this can take.

        @returns @true if the operation succeeded, @false otherwise.

        @see wxBitmap::LoadFile, wxBitmap::SaveFile, SaveFile()
    */
    bool LoadFile(wxBitmap* bitmap, const wxString& name, wxBitmapType type);

    /**
        Saves a bitmap in the named file.

        @param bitmap
            The bitmap object which is to be affected by this operation.
        @param name
            A filename. The meaning of name is determined by the type parameter.
        @param type
            See ::wxBitmapType for values this can take.
        @param palette
            An optional palette used for saving the bitmap.

        @returns @true if the operation succeeded, @false otherwise.

        @see wxBitmap::LoadFile, wxBitmap::SaveFile, LoadFile()
    */
    bool SaveFile(wxBitmap* bitmap, const wxString& name, wxBitmapType type,
                  wxPalette* palette = NULL);

    /**
        Sets the handler extension.

        @param extension
            Handler extension.
    */
    void SetExtension(const wxString& extension);

    /**
        Sets the handler name.

        @param name
            Handler name.
    */
    void SetName(const wxString& name);

    /**
        Sets the handler type.

        @param type
            Handler type.
    */
    void SetType(wxBitmapType type);
};


/**
    @class wxBitmap
    @wxheader{bitmap.h}

    This class encapsulates the concept of a platform-dependent bitmap,
    either monochrome or colour or colour with alpha channel support.

    @note
    Many wxBitmap functions take a @e type parameter, which is a value of the
    ::wxBitmapType enumeration.
    The validity of those values depends however on the platform where your program
    is running and from the wxWidgets configuration.
    If all possible wxWidgets settings are used, the Windows platform supports BMP file,
    BMP resource, XPM data, and XPM.
    Under wxGTK, the available formats are BMP file, XPM data, XPM file, and PNG file.
    Under wxMotif, the available formats are XBM data, XBM file, XPM data, XPM file.
    In addition, wxBitmap can load and save all formats that wxImage; see wxImage for
    more info. Of course, you must have wxImage handlers loaded.

    @library{wxcore}
    @category{gdi}

    @stdobjects
    ::wxNullBitmap

    @see @ref overview_bitmap, @ref overview_bitmap_supportedformats,
         wxDC::Blit, wxIcon, wxCursor, wxBitmap, wxMemoryDC
*/
class wxBitmap : public wxGDIObject
{
public:
    /**
        Default constructor.

        Constructs a bitmap object with no data; an assignment or another member
        function such as Create() or LoadFile() must be called subsequently.
    */
    wxBitmap();

    /**
        Copy constructor, uses @ref overview_refcount "reference counting".
        To make a real copy, you can use:

        @code
        wxBitmap newBitmap = oldBitmap.GetSubBitmap(
                             wxRect(0, 0, oldBitmap.GetWidth(), oldBitmap.GetHeight()));
        @endcode
    */
    wxBitmap(const wxBitmap& bitmap);


    /*
        Creates a bitmap from the given @a data which is interpreted in
        platform-dependent manner.

        @param data
            Specifies the bitmap data in a platform-dependent format.
        @param type
            May be one of the ::wxBitmapType values and indicates which type of
            bitmap does @a data contains. See the note in the class
            detailed description.
        @param width
            Specifies the width of the bitmap.
        @param height
            Specifies the height of the bitmap.
        @param depth
            Specifies the depth of the bitmap.
            If this is omitted, the display depth of the screen is used.
    wxBitmap(const void* data, int type, int width, int height, int depth = -1);


        NOTE: this ctor is not implemented by all port, is somewhat useless
              without further description of the "data" supported formats and
              uses 'int type' instead of wxBitmapType, so don't document it.
    */

    /**
        Creates a bitmap from the given array @a bits.
        You should only use this function for monochrome bitmaps (depth 1) in
        portable programs: in this case the bits parameter should contain an XBM image.

        For other bit depths, the behaviour is platform dependent: under Windows,
        the data is passed without any changes to the underlying CreateBitmap() API.
        Under other platforms, only monochrome bitmaps may be created using this
        constructor and wxImage should be used for creating colour bitmaps from
        static data.

        @param bits
            Specifies an array of pixel values.
        @param width
            Specifies the width of the bitmap.
        @param height
            Specifies the height of the bitmap.
        @param depth
            Specifies the depth of the bitmap.
            If this is omitted, then a value of 1 (monochrome bitmap) is used.
    */
    wxBitmap(const char bits[], int width, int height, int depth = 1);

    /**
        Creates a new bitmap. A depth of ::wxBITMAP_SCREEN_DEPTH indicates the
        depth of the current screen or visual.
        Some platforms only support 1 for monochrome and ::wxBITMAP_SCREEN_DEPTH for
        the current colour setting.

        A depth of 32 including an alpha channel is supported under MSW, Mac and GTK+.
    */
    wxBitmap(int width, int height, int depth = wxBITMAP_SCREEN_DEPTH);

    /**
        Creates a bitmap from XPM data.
    */
    wxBitmap(const char* const* bits);

    /**
        Loads a bitmap from a file or resource.

        @param name
            This can refer to a resource name or a filename under MS Windows and X.
            Its meaning is determined by the @a type parameter.
        @param type
            May be one of the ::wxBitmapType values and indicates which type of
            bitmap should be loaded. See the note in the class detailed description.

        @see LoadFile()
    */
    wxBitmap(const wxString& name, wxBitmapType type = wxBITMAP_TYPE_XPM);

    /**
        Creates this bitmap object from the given image.
        This has to be done to actually display an image as you cannot draw an
        image directly on a window.

        The resulting bitmap will use the provided colour depth (or that of the
        current system if depth is ::wxBITMAP_SCREEN_DEPTH) which entails that a
        colour reduction may take place.

        When in 8-bit mode (PseudoColour mode), the GTK port will use a color cube
        created on program start-up to look up colors. This ensures a very fast conversion,
        but the image quality won't be perfect (and could be better for photo images using
        more sophisticated dithering algorithms).

        On Windows, if there is a palette present (set with SetPalette), it will be
        used when creating the wxBitmap (most useful in 8-bit display mode).
        On other platforms, the palette is currently ignored.

        @param img
            Platform-independent wxImage object.
        @param depth
            Specifies the depth of the bitmap.
            If this is omitted, the display depth of the screen is used.
    */
    wxBitmap(const wxImage& img, int depth = wxBITMAP_SCREEN_DEPTH);

    /**
        Destructor.
        See @ref overview_refcount_destruct for more info.

        If the application omits to delete the bitmap explicitly, the bitmap will be
        destroyed automatically by wxWidgets when the application exits.

        @warning
        Do not delete a bitmap that is selected into a memory device context.
    */
    ~wxBitmap();

    /**
        Adds a handler to the end of the static list of format handlers.

        @param handler
            A new bitmap format handler object. There is usually only one instance
            of a given handler class in an application session.

        @see wxBitmapHandler
    */
    static void AddHandler(wxBitmapHandler* handler);

    /**
        Deletes all bitmap handlers.
        This function is called by wxWidgets on exit.
    */
    static void CleanUpHandlers();

    /**
        Creates an image from a platform-dependent bitmap. This preserves
        mask information so that bitmaps and images can be converted back
        and forth without loss in that respect.
    */
    wxImage ConvertToImage();

    /**
        Creates the bitmap from an icon.
    */
    bool CopyFromIcon(const wxIcon& icon);

    /**
        Creates a fresh bitmap.
        If the final argument is omitted, the display depth of the screen is used.

        This overload works on all platforms.
    */
    virtual bool Create(int width, int height, int depth = wxBITMAP_SCREEN_DEPTH);

    /*
        Creates a bitmap from the given data, which can be of arbitrary type.

        @param data
            Data whose type depends on the value of type.
        @param type
            A bitmap type identifier; see ::wxBitmapType for the list of values.
            See the note in the class detailed description for more info.
        @param width
            The width of the bitmap in pixels.
        @param height
            The height of the bitmap in pixels.
        @param depth
            The depth of the bitmap in pixels. If this is -1, the screen depth is used.

        @returns @true if the call succeeded, @false otherwise.

        This overload depends on the @a type of data.

    virtual bool Create(const void* data, int type, int width,
                        int height, int depth = -1);

        NOTE: leave this undoc for the same reason of the relative ctor.
    */

    /**
        Finds the handler with the given @a name.

        @returns A pointer to the handler if found, @NULL otherwise.
    */
    static wxBitmapHandler* FindHandler(const wxString& name);

    /**
        Finds the handler associated with the given @a extension and @a type.

        @param extension
            The file extension, such as "bmp" (without the dot).
        @param bitmapType
            The bitmap type managed by the handler, see ::wxBitmapType.

        @returns A pointer to the handler if found, @NULL otherwise.
    */
    static wxBitmapHandler* FindHandler(const wxString& extension,
                                        wxBitmapType bitmapType);

    /**
        Finds the handler associated with the given bitmap type.

        @param bitmapType
            The bitmap type managed by the handler, see ::wxBitmapType.

        @returns A pointer to the handler if found, @NULL otherwise.

        @see wxBitmapHandler
    */

    static wxBitmapHandler* FindHandler(wxBitmapType bitmapType);

    /**
        Gets the colour depth of the bitmap.
        A value of 1 indicates a monochrome bitmap.
    */
    int GetDepth() const;

    /**
        Returns the static list of bitmap format handlers.

        @see wxBitmapHandler
    */
    static wxList GetHandlers();

    /**
        Gets the height of the bitmap in pixels.
    */
    int GetHeight() const;

    /**
        Gets the associated mask (if any) which may have been loaded from a file
        or set for the bitmap.

        @see SetMask(), wxMask
    */
    wxMask* GetMask() const;

    /**
        Gets the associated palette (if any) which may have been loaded from a file
        or set for the bitmap.

        @see wxPalette
    */
    wxPalette* GetPalette() const;

    /**
        Returns a sub bitmap of the current one as long as the rect belongs entirely to
        the bitmap. This function preserves bit depth and mask information.
    */
    wxBitmap GetSubBitmap(const wxRect& rect) const;

    /**
        Gets the width of the bitmap in pixels.

        @see GetHeight()
    */
    int GetWidth() const;

    /**
        Adds the standard bitmap format handlers, which, depending on wxWidgets
        configuration, can be handlers for Windows bitmap, Windows bitmap resource,
        and XPM.

        This function is called by wxWidgets on startup.

        @see wxBitmapHandler
    */
    static void InitStandardHandlers();

    /**
        Adds a handler at the start of the static list of format handlers.

        @param handler
            A new bitmap format handler object. There is usually only one instance
            of a given handler class in an application session.

        @see wxBitmapHandler
    */
    static void InsertHandler(wxBitmapHandler* handler);

    /**
        Returns @true if bitmap data is present.
    */
    bool IsOk() const;

    /**
        Loads a bitmap from a file or resource.

        @param name
            Either a filename or a Windows resource name.
            The meaning of name is determined by the @a type parameter.
        @param type
            One of the ::wxBitmapType values; see the note in the class
            detailed description.

        @returns @true if the operation succeeded, @false otherwise.

        @remarks A palette may be associated with the bitmap if one exists
                 (especially for colour Windows bitmaps), and if the
                 code supports it. You can check if one has been created
                 by using the GetPalette() member.

        @see SaveFile()
    */
    bool LoadFile(const wxString& name, wxBitmapType type);

    /**
        Finds the handler with the given name, and removes it.
        The handler is not deleted.

        @param name
            The handler name.

        @returns @true if the handler was found and removed, @false otherwise.

        @see wxBitmapHandler
    */
    static bool RemoveHandler(const wxString& name);

    /**
        Saves a bitmap in the named file.

        @param name
            A filename. The meaning of name is determined by the type parameter.
        @param type
            One of the ::wxBitmapType values; see the note in the class
            detailed description.
        @param palette
            An optional palette used for saving the bitmap.

        @returns @true if the operation succeeded, @false otherwise.

        @remarks Depending on how wxWidgets has been configured, not all formats
                 may be available.

        @see LoadFile()
    */
    bool SaveFile(const wxString& name, wxBitmapType type,
                  const wxPalette* palette = NULL);

    /**
        Sets the depth member (does not affect the bitmap data).

        @todo since these functions do not affect the bitmap data,
              why they exist??

        @param depth
            Bitmap depth.
    */
    void SetDepth(int depth);

    /**
        Sets the height member (does not affect the bitmap data).

        @param height
            Bitmap height in pixels.
    */
    void SetHeight(int height);

    /**
        Sets the mask for this bitmap.

        @remarks The bitmap object owns the mask once this has been called.

        @see GetMask(), wxMask
    */
    void SetMask(wxMask* mask);

    /**
        Sets the associated palette. (Not implemented under GTK+).

        @param palette
            The palette to set.

        @see wxPalette
    */
    void SetPalette(const wxPalette& palette);

    /**
        Sets the width member (does not affect the bitmap data).

        @param width
            Bitmap width in pixels.
    */
    void SetWidth(int width);

    /**
        Assignment operator, using @ref overview_refcount "reference counting".

        @param bitmap
            Bitmap to assign.
    */
    wxBitmap operator =(const wxBitmap& bitmap);
};

/**
    An empty wxBitmap object.
*/
wxBitmap wxNullBitmap;




/**
    @class wxMask
    @wxheader{bitmap.h}

    This class encapsulates a monochrome mask bitmap, where the masked area is
    black and the unmasked area is white.

    When associated with a bitmap and drawn in a device context, the unmasked
    area of the bitmap will be drawn, and the masked area will not be drawn.

    @library{wxcore}
    @category{gdi}

    @see wxBitmap, wxDC::Blit, wxMemoryDC
*/
class wxMask : public wxObject
{
public:

    /**
        Default constructor.
    */
    wxMask();

    /**
        Constructs a mask from a bitmap and a palette index that indicates the
        background.
        Not yet implemented for GTK.

        @param bitmap
            A valid bitmap.
        @param index
            Index into a palette, specifying the transparency colour.
    */
    wxMask(const wxBitmap& bitmap, int index);

    /**
        Constructs a mask from a monochrome bitmap.

        @beginWxPythonOnly
        This is the default constructor for wxMask in wxPython.
        @endWxPythonOnly
    */
    wxMask(const wxBitmap& bitmap);

    /**
        Constructs a mask from a bitmap and a colour that indicates the background.

        @beginWxPythonOnly
        wxPython has an alternate wxMask constructor matching this form called wxMaskColour.
        @endWxPythonOnly
    */
    wxMask(const wxBitmap& bitmap, const wxColour& colour);

    /**
        Destroys the wxMask object and the underlying bitmap data.
    */
    ~wxMask();

    /**
        Constructs a mask from a bitmap and a palette index that indicates the
        background.
        Not yet implemented for GTK.

        @param bitmap
            A valid bitmap.
        @param index
            Index into a palette, specifying the transparency colour.
    */
    bool Create(const wxBitmap& bitmap, int index);

    /**
        Constructs a mask from a monochrome bitmap.
    */
    bool Create(const wxBitmap& bitmap);

    /**
        Constructs a mask from a bitmap and a colour that indicates the background.
    */
    bool Create(const wxBitmap& bitmap, const wxColour& colour);
};