added null pointer check and assert

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

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%% Name:        varhscrollhelper.tex
%% Purpose:     wxVarHScrollHelper Documentation
%% Author:      Bryan Petty
%% Modified by: 
%% Created:     2007-04-04
%% RCS-ID:      $Id$
%% Copyright:   (c) 2007 wxWidgets Team
%% License:     wxWindows Licence
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\section{\class{wxVarHScrollHelper}}\label{wxvarhscrollhelper}

This class provides functions wrapping the 
\helpref{wxVarScrollHelperBase}{wxvarscrollhelperbase} class, targeted for
horizontal-specific scrolling using \helpref{wxHScrolledWindow}{wxhscrolledwindow}.

Like wxVarScrollHelperBase, this class is mostly only useful to those classes
built into wxWidgets deriving from here, and this documentation is mostly
only provided for referencing those functions provided. You will likely want
to derive your window from wxHScrolledWindow rather than from here directly.

\wxheading{Derived from}

\helpref{wxVarScrollHelperBase}{wxvarscrollhelperbase}

\wxheading{Include files}

<wx/vscroll.h>

\wxheading{Library}

\helpref{wxCore}{librarieslist}

\wxheading{See also}

\helpref{wxHScrolledWindow}{wxhscrolledwindow},
\rtfsp\helpref{wxHVScrolledWindow}{wxhvscrolledwindow},
\rtfsp\helpref{wxVScrolledWindow}{wxvscrolledwindow}

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


\membersection{wxVarHScrollHelper::wxVarHScrollHelper}\label{wxvarhscrollhelperwxvarhscrollhelper}

\func{}{wxVarHScrollHelper}{\param{wxWindow* }{winToScroll}}

Constructor taking the target window to be scrolled by this helper class.
This will attach scroll event handlers to the target window to catch and
handle scroll events appropriately.


\membersection{wxVarHScrollHelper::EstimateTotalWidth}\label{wxvarhscrollhelperestimatetotalwidth}

\constfunc{virtual wxCoord}{EstimateTotalWidth}{\void}

This class forwards calls from
\helpref{wxVarScrollHelperBase::EstimateTotalSize}{wxvarscrollhelperbaseestimatetotalsize}
to this function so derived classes can override either just the height or
the width estimation, or just estimate both differently if desired in any
\helpref{wxHVScrolledWindow}{wxhvscrolledwindow} derived class.

Please note that this function will not be called if {\tt EstimateTotalSize()}
is overridden in your derived class.


\membersection{wxVarHScrollHelper::GetColumnCount}\label{wxvarhscrollhelpergetcolumncount}

\constfunc{size\_t}{GetColumnCount}{\void}

Returns the number of columns the target window contains.

\wxheading{See also}

\helpref{SetColumnCount()}{wxvarhscrollhelpersetcolumncount}


\membersection{wxVarHScrollHelper::GetVisibleColumnsBegin}\label{wxvarhscrollhelpergetvisiblecolumnsbegin}

\constfunc{size\_t}{GetVisibleColumnsBegin}{\void}

Returns the index of the first visible column based on the scroll position.


\membersection{wxVarHScrollHelper::GetVisibleColumnsEnd}\label{wxvarhscrollhelpergetvisiblecolumnsend}

\constfunc{size\_t}{GetVisibleColumnsEnd}{\void}

Returns the index of the last visible column based on the scroll position. This
includes the last column even if it is only partially visible.


\membersection{wxVarHScrollHelper::IsColumnVisible}\label{wxvarhscrollhelperiscolumnvisible}

\constfunc{bool}{IsColumnVisible}{\param{size\_t }{column}}

Returns {\tt true} if the given column is currently visible (even if only
partially visible) or {\tt false} otherwise.


\membersection{wxVarHScrollHelper::OnGetColumnWidth}\label{wxvarhscrollhelperongetcolumnwidth}

\constfunc{virtual wxCoord}{OnGetColumnWidth}{\param{size\_t }{column}}

This function must be overridden in the derived class, and should return the
width of the given column in pixels.


\membersection{wxVarHScrollHelper::OnGetColumnsWidthHint}\label{wxvarhscrollhelperongetcolumnswidthhint}

\constfunc{virtual void}{OnGetColumnsWidthHint}{\param{size\_t }{columnMin}, \param{size\_t }{columnMax}}

This function doesn't have to be overridden but it may be useful to do so if
calculating the columns' sizes is a relatively expensive operation as it gives
your code a chance to calculate several of them at once and cache the result
if necessary.

{\tt OnGetColumnsWidthHint()} is normally called just before
\helpref{OnGetColumnWidth()}{wxvarhscrollhelperongetcolumnwidth} but you
shouldn't rely on the latter being called for all columns in the interval
specified here. It is also possible that OnGetColumnWidth() will be called for
units outside of this interval, so this is really just a hint, not a promise.

Finally, note that columnMin is inclusive, while columnMax is exclusive.


\membersection{wxVarHScrollHelper::RefreshColumn}\label{wxvarhscrollhelperrefreshcolumn}

\func{virtual void}{RefreshColumn}{\param{size\_t }{column}}

Triggers a refresh for just the given column's area of the window if it's visible.


\membersection{wxVarHScrollHelper::RefreshColumns}\label{wxvarhscrollhelperrefreshcolumns}

\func{virtual void}{RefreshColumns}{\param{size\_t }{from}, \param{size\_t }{to}}

Triggers a refresh for the area between the specified range of columns given
(inclusively).


\membersection{wxVarHScrollHelper::ScrollColumnPages}\label{wxvarhscrollhelperscrollcolumnpages}

\func{virtual bool}{ScrollColumnPages}{\param{int }{pages}}

Scroll by the specified number of pages which may be positive (to scroll right)
or negative (to scroll left).


\membersection{wxVarHScrollHelper::ScrollColumns}\label{wxvarhscrollhelperscrollcolumns}

\func{virtual bool}{ScrollColumns}{\param{int }{columns}}

Scroll by the specified number of columns which may be positive (to scroll right)
or negative (to scroll left).

Returns {\tt true} if the window was scrolled, {\tt false} otherwise (for
example, if we're trying to scroll right but we are already showing the last
column).


\membersection{wxVarHScrollHelper::ScrollToColumn}\label{wxvarhscrollhelperscrolltocolumn}

\func{bool}{ScrollToColumn}{\param{size\_t }{column}}

Scroll to the specified column. It will become the first visible column in the window.

Returns {\tt true} if we scrolled the window, {\tt false} if nothing was done.


\membersection{wxVarHScrollHelper::SetColumnCount}\label{wxvarhscrollhelpersetcolumncount}

\func{void}{SetColumnCount}{\param{size\_t }{columnCount}}

Set the number of columns the window contains. The derived class must provide
the widths for all columns with indices up to the one given here in it's
\helpref{OnGetColumnWidth()}{wxvarhscrollhelperongetcolumnwidth} implementation.

\wxheading{See also}

\helpref{GetColumnCount()}{wxvarhscrollhelpergetcolumncount}