added null pointer check and assert

[wxWidgets.git] / docs / latex / wx / htcell.tex

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%% Name:        htcell.tex
%% Purpose:     wxHtmlCell documentation
%% Author:      wxWidgets Team
%% Modified by:
%% Created:     21/Mar/99 22:45:23
%% RCS-ID:      $Id$
%% Copyright:   (c) wxWidgets Team
%% License:     wxWindows license
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\section{\class{wxHtmlCell}}\label{wxhtmlcell}

Internal data structure. It represents fragments of parsed HTML
page, the so-called {\bf cell} - a word, picture, table, horizontal line and so on.
It is used by \helpref{wxHtmlWindow}{wxhtmlwindow} and 
\helpref{wxHtmlWinParser}{wxhtmlwinparser} to represent HTML page in memory.

You can divide cells into two groups : {\it visible} cells with non-zero width and
height and {\it helper} cells (usually with zero width and height) that
perform special actions such as color or font change.

\wxheading{Derived from}

\helpref{wxObject}{wxobject}

\wxheading{Include files}

<wx/html/htmlcell.h>

\wxheading{Library}

\helpref{wxHtml}{librarieslist}

\wxheading{See Also}

\helpref{Cells Overview}{cells},
\helpref{wxHtmlContainerCell}{wxhtmlcontainercell}

\latexignore{\rtfignore{\wxheading{Members}}}

\membersection{wxHtmlCell::wxHtmlCell}\label{wxhtmlcellwxhtmlcell}

\func{}{wxHtmlCell}{\void}

Constructor.

\membersection{wxHtmlCell::AdjustPagebreak}\label{wxhtmlcelladjustpagebreak}

\func{virtual bool}{AdjustPagebreak}{\param{int * }{pagebreak}}

This method is used to adjust pagebreak position. The parameter is
variable that contains y-coordinate of page break (= horizontal line that
should not be crossed by words, images etc.). If this cell cannot be divided
into two pieces (each one on another page) then it moves the pagebreak
few pixels up.

Returns true if pagebreak was modified, false otherwise

Usage: 
\begin{verbatim}
while (container->AdjustPagebreak(&p)) {}
\end{verbatim}

\membersection{wxHtmlCell::Draw}\label{wxhtmlcelldraw}

\func{virtual void}{Draw}{\param{wxDC\& }{dc}, \param{int }{x}, \param{int }{y}, \param{int }{view\_y1}, \param{int }{view\_y2}}

Renders the cell.

\wxheading{Parameters}

\docparam{dc}{Device context to which the cell is to be drawn}

\docparam{x,y}{Coordinates of parent's upper left corner (origin). You must
add this to m\_PosX,m\_PosY when passing coordinates to dc's methods
Example : {\tt dc -> DrawText("hello", x + m\_PosX, y + m\_PosY)}}

\docparam{view\_y1}{y-coord of the first line visible in window. This is
used to optimize rendering speed}

\docparam{view\_y2}{y-coord of the last line visible in window. This is
used to optimize rendering speed}

\membersection{wxHtmlCell::DrawInvisible}\label{wxhtmlcelldrawinvisible}

\func{virtual void}{DrawInvisible}{\param{wxDC\& }{dc}, \param{int }{x}, \param{int }{y}}

This method is called instead of \helpref{Draw}{wxhtmlcelldraw} when the
cell is certainly out of the screen (and thus invisible). This is not
nonsense - some tags (like \helpref{wxHtmlColourCell}{wxhtmlcolourcell}
or font setter) must be drawn even if they are invisible!

\wxheading{Parameters}

\docparam{dc}{Device context to which the cell is to be drawn}

\docparam{x,y}{Coordinates of parent's upper left corner. You must
add this to m\_PosX,m\_PosY when passing coordinates to dc's methods
Example : {\tt dc -> DrawText("hello", x + m\_PosX, y + m\_PosY)}}

\membersection{wxHtmlCell::Find}\label{wxhtmlcellfind}

\func{virtual const wxHtmlCell*}{Find}{\param{int }{condition}, \param{const void* }{param}}

Returns pointer to itself if this cell matches condition (or if any of the cells
following in the list matches), NULL otherwise.
(In other words if you call top-level container's Find it will
return pointer to the first cell that matches the condition)

It is recommended way how to obtain pointer to particular cell or
to cell of some type (e.g. wxHtmlAnchorCell reacts on
wxHTML\_COND\_ISANCHOR condition)

\wxheading{Parameters}

\docparam{condition}{Unique integer identifier of condition}

\docparam{param}{Optional parameters}

\wxheading{Defined conditions}

\begin{twocollist}\itemsep=0pt
\twocolitem{{\bf wxHTML\_COND\_ISANCHOR}}{Finds particular anchor. 
{\it param} is pointer to wxString with name of the anchor.}
\twocolitem{{\bf wxHTML\_COND\_USER}}{User-defined conditions start
from this number.}
\end{twocollist}

\membersection{wxHtmlCell::GetDescent}\label{wxhtmlcellgetdescent}

\constfunc{int}{GetDescent}{\void}

Returns descent value of the cell (m\_Descent member). 
\helponly{See explanation:

\image{}{descent.bmp}
}

\membersection{wxHtmlCell::GetFirstChild}\label{wxhtmlcellgetfirstchild}

\func{wxHtmlCell*}{GetFirstChild}{\void}

Returns pointer to the first cell in the list.
You can then use child's \helpref{GetNext}{wxhtmlcellgetnext}
method to obtain pointer to the next cell in list.

{\bf Note:} This shouldn't be used by the end user. If you need some way of
finding particular cell in the list, try \helpref{Find}{wxhtmlcellfind} method
instead.

\membersection{wxHtmlCell::GetHeight}\label{wxhtmlcellgetheight}

\constfunc{int}{GetHeight}{\void}

Returns height of the cell (m\_Height member).

\membersection{wxHtmlCell::GetId}\label{wxhtmlcellgetid}

\constfunc{virtual wxString}{GetId}{\void}

Returns unique cell identifier if there is any, empty string otherwise.

\membersection{wxHtmlCell::GetLink}\label{wxhtmlcellgetlink}

\constfunc{virtual wxHtmlLinkInfo*}{GetLink}{\param{int }{x = 0}, \param{int }{y = 0}}

Returns hypertext link if associated with this cell or NULL otherwise.
See \helpref{wxHtmlLinkInfo}{wxhtmllinkinfo}.
(Note: this makes sense only for visible tags).

\wxheading{Parameters}

\docparam{x,y}{Coordinates of position where the user pressed mouse button.
These coordinates are used e.g. by COLORMAP. Values are relative to the
upper left corner of THIS cell (i.e. from 0 to m\_Width or m\_Height)}

\membersection{wxHtmlCell::GetMouseCursor}\label{wxhtmlcellgetmousecursor}

\func{virtual wxCursor}{GetMouseCursor}{\param{wxHtmlWindowInterface* }{window}}

Returns cursor to show when mouse pointer is over the cell.

\wxheading{Parameters}

\docparam{window}{interface to the parent HTML window}

\newsince{2.7.0} (before \tt{GetCursor} method served a similar purpose, which is now deprecated).


\membersection{wxHtmlCell::GetNext}\label{wxhtmlcellgetnext}

\constfunc{wxHtmlCell*}{GetNext}{\void}

Returns pointer to the next cell in list (see htmlcell.h if you're
interested in details).

\membersection{wxHtmlCell::GetParent}\label{wxhtmlcellgetparent}

\constfunc{wxHtmlContainerCell*}{GetParent}{\void}

Returns pointer to parent container.

\membersection{wxHtmlCell::GetPosX}\label{wxhtmlcellgetposx}

\constfunc{int}{GetPosX}{\void}

Returns X position within parent (the value is relative to parent's
upper left corner). The returned value is meaningful only if
parent's \helpref{Layout}{wxhtmlcelllayout} was called before!

\membersection{wxHtmlCell::GetPosY}\label{wxhtmlcellgetposy}

\constfunc{int}{GetPosY}{\void}

Returns Y position within parent (the value is relative to parent's
upper left corner). The returned value is meaningful only if
parent's \helpref{Layout}{wxhtmlcelllayout} was called before!

\membersection{wxHtmlCell::GetWidth}\label{wxhtmlcellgetwidth}

\constfunc{int}{GetWidth}{\void}

Returns width of the cell (m\_Width member).

\membersection{wxHtmlCell::Layout}\label{wxhtmlcelllayout}

\func{virtual void}{Layout}{\param{int }{w}}

This method performs two actions:

\begin{enumerate}\itemsep=0pt
\item adjusts the cell's width according to the fact that maximal possible width is {\it w}.
(this has sense when working with horizontal lines, tables etc.)
\item prepares layout (=fill-in m\_PosX, m\_PosY (and sometimes m\_Height) members)
based on actual width {\it w}
\end{enumerate}

It must be called before displaying cells structure because
m\_PosX and m\_PosY are undefined (or invalid)
before calling Layout.

\membersection{wxHtmlCell::ProcessMouseClick}\label{wxhtmlcellprocessmouseclick}

\func{virtual bool}{ProcessMouseClick}{\param{wxHtmlWindowInterface* }{window}, \param{const wxPoint\& }{pos}, \param{const wxMouseEvent\& }{event}}

This function is simple event handler. Each time the user clicks mouse button
over a cell within \helpref{wxHtmlWindow}{wxhtmlwindow} this method of that
cell is called. Default behavior is to call
\helpref{wxHtmlWindow::LoadPage}{wxhtmlwindowloadpage}.

\wxheading{Note}

If you need more "advanced" event handling
you should use wxHtmlBinderCell instead.

\wxheading{Parameters}

\docparam{window}{interface to the parent HTML window}

\docparam{pos}{coordinates of mouse click (this is relative to cell's origin}

\docparam{event}{mouse event that triggered the call}

\wxheading{Return value}

\true if a link was clicked, \false otherwise.

\newsince{2.7.0} (before \tt{OnMouseClick} method served a similar purpose).


\membersection{wxHtmlCell::SetId}\label{wxhtmlcellsetid}

\func{void}{SetId}{\param{const wxString\& }{id}}

Sets unique cell identifier. Default value is no identifier, i.e. empty string.

\membersection{wxHtmlCell::SetLink}\label{wxhtmlcellsetlink}

\func{void}{SetLink}{\param{const wxHtmlLinkInfo\& }{link}}

Sets the hypertext link associated with this cell. (Default value
is \helpref{wxHtmlLinkInfo}{wxhtmllinkinfo}("", "") (no link))

\membersection{wxHtmlCell::SetNext}\label{wxhtmlcellsetnext}

\func{void}{SetNext}{\param{wxHtmlCell }{*cell}}

Sets the next cell in the list. This shouldn't be called by user - it is
to be used only by \helpref{wxHtmlContainerCell::InsertCell}{wxhtmlcontainercellinsertcell}.

\membersection{wxHtmlCell::SetParent}\label{wxhtmlcellsetparent}

\func{void}{SetParent}{\param{wxHtmlContainerCell }{*p}}

Sets parent container of this cell. This is called from
\helpref{wxHtmlContainerCell::InsertCell}{wxhtmlcontainercellinsertcell}.

\membersection{wxHtmlCell::SetPos}\label{wxhtmlcellsetpos}

\func{void}{SetPos}{\param{int }{x}, \param{int }{y}}

Sets the cell's position within parent container.