wxWidgets/docs/latex/wx/bmpdatob.tex
1999-01-31 11:42:58 +00:00

112 lines
4.1 KiB
TeX

\section{\class{wxBitmapDataObject}}\label{wxbitmapdataobject}
wxBitmapDataObject is a specialization of wxDataObject for bitmap data. It can be
used without change to paste data into the \helpref{wxClipboard}{wxclipboard}
or a \helpref{wxDropSource}{wxdropsource}. A user may wish to derive a new class
from this class for providing a bitmap on-demand in order to minimize memory consumption
when offering data in several formats, such as a bitmap and GIF.
In order to offer bitmap data on-demand \helpref{GetSize}{wxbitmapdataobjectgetsize}
and \helpref{WriteData}{wxbitmapdataobjectwritedata} will have to be overridden.
\wxheading{Derived from}
\helpref{wxDataObject}{wxdataobject}
\wxheading{See also}
\helpref{wxDataObject}{wxdataobject}
\latexignore{\rtfignore{\wxheading{Members}}}
\membersection{wxBitmapDataObject::wxBitmapDataObject}\label{wxbitmapdataobjectwxbitmapdataobject}
\func{}{wxBitmapDataObject}{\void}
Default constructor. Call \helpref{SetBitmap}{wxbitmapdataobjectsetbitmap} later
or override \helpref{WriteData}{wxbitmapdataobjectwritedata} and
\helpref{GetSize}{wxbitmapdataobjectgetsize} for providing data on-demand.
\func{}{wxBitmapDataObject}{\param{const wxBitmap\& }{bitmap}}
Constructor, passing a bitmap.
\membersection{wxBitmapDataObject::GetSize}\label{wxbitmapdataobjectgetsize}
\constfunc{virtual size\_t}{GetSize}{\void}
Returns the data size. By default, returns the size of the bitmap data
set in the constructor or using \helpref{SetBitmap}{wxbitmapdataobjectsetbitmap}.
This can be overridden to provide size data on-demand. Note that you'd
have to call the inherited GetSize method as this is the only way
to get to know the transfer size of the bitmap in a platform dependent
way - a bitmap has different size under GTK and Windows. In practice,
this would look like this:
\begin{verbatim}
size_t MyBitmapDataObject::GetSize()
{
// Get bitmap from global container. This container
// should be able to "produce" data in all formats
// offered by the application but store it only in
// one format to reduce memory consumption.
wxBitmap my_bitmap = my_global_container->GetBitmap();
// temporarily set bitmap
SetBitmap( my_bitmap );
size_t ret = wxBitmapDataObject::GetSize();
// unset bitmap again
SetBitmap( wxNullBitmap );
retrun ret;
}
\end{verbatim}
TODO: Offer a nicer way to do this. Maybe by providing a platform
dependent function in this class like
\begin{verbatim}
size_t GetBitmapSize( const wxBitmap &bitmap )
\end{verbatim}
\membersection{wxBitmapDataObject::GetBitmap}\label{wxbitmapdataobjectgettext}
\constfunc{virtual wxBitmap}{GetBitmap}{\void}
Returns the bitmap associated with the data object. You may wish to override
this method when offering data on-demand, but this is not required by
wxWindows' internals. Use this method to get data in bitmap form from
the \helpref{wxClipboard}{wxclipboard}.
\membersection{wxBitmapDataObject::SetBitmap}\label{wxbitmapdataobjectsetbitmap}
\func{virtual void}{SetBitmap}{\param{const wxBitmap\& }{bitmap}}
Sets the bitmap associated with the data object. This method is called
internally when retrieving data from the \helpref{wxClipboard}{wxclipboard}
and may be used to paste data to the clipboard directly (instead of
on-demand).
\membersection{wxBitmapDataObject::WriteData}\label{wxbitmapdataobjectwritedata}
\constfunc{virtual void}{WriteData}{\param{void}{*dest} }
Write the data owned by this class to {\it dest}. By default, this
calls \helpref{WriteBitmap}{wxbitmapdataobjectwritebitmap} with the bitmap
set in the constructor or using \helpref{SetBitmap}{wxbitmapdataobjectsetbitmap}.
This can be overridden to provide bitmap data on-demand; in this case
\helpref{WriteBitmap}{wxbitmapdataobjectwritebitmap} must be called from
within th overriding WriteData() method.
\membersection{wxBitmapDataObject::WriteBitmap}\label{wxbitmapdataobjectwritebitmap}
\constfunc{void}{WriteBitmap}{\param{const wxBitmap\& }{bitmap}\param{void}{*dest} }
Writes the the bitmap {\it bitmap} to {\it dest}. This method must be called
from \helpref{WriteData}{wxbitmapdataobjectwritedata}.