Ref counting overview.

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

\section{\class{wxDC}}\label{wxdc}

A wxDC is a {\it device context} onto which graphics and text can be drawn.
It is intended to represent a number of output devices in a generic way,
so a window can have a device context associated with it, and a printer also has a device context.
In this way, the same piece of code may write to a number of different devices,
if the device context is used as a parameter.

Notice that wxDC is an abstract base class and can't be created directly,
please use \helpref{wxPaintDC}{wxpaintdc}, \helpref{wxClientDC}{wxclientdc}, 
\helpref{wxWindowDC}{wxwindowdc}, \helpref{wxScreenDC}{wxscreendc}, 
\helpref{wxMemoryDC}{wxmemorydc} or \helpref{wxPrinterDC}{wxprinterdc}.

% VZ: we should really document them instead of this lame excuse, but I don't
%     have time for it now, when it is done please remove this
Please note that in addition to the versions of the methods documented here,
there are also versions which accept single {\tt wxPoint} parameter instead of
two {\tt wxCoord} ones or {\tt wxPoint} and {\tt wxSize} instead of four of
them.

\wxheading{Support for Transparency / Alpha Channel}

On Mac OS X when using Core Graphics (wx\_MAC\_USE\_CORE\_GRAPHICS set to 1) 
colors with alpha are supported, so instances  {\tt wxPen} or  {\tt wxBrush} that are built from  {\tt wxColour} use
the color's alpha values when stroking or filling.

\wxheading{Derived from}

\helpref{wxObject}{wxobject}

\wxheading{Include files}

<wx/dc.h>

\wxheading{See also}

\helpref{Overview}{dcoverview}

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


\membersection{wxDC::Blit}\label{wxdcblit}

\func{bool}{Blit}{\param{wxCoord}{ xdest}, \param{wxCoord}{ ydest}, \param{wxCoord}{ width}, \param{wxCoord}{ height},
  \param{wxDC* }{source}, \param{wxCoord}{ xsrc}, \param{wxCoord}{ ysrc}, \param{int}{ logicalFunc = wxCOPY},
  \param{bool }{useMask = false}, \param{wxCoord}{ xsrcMask = -1}, \param{wxCoord}{ ysrcMask = -1}}

Copy from a source DC to this DC, specifying the destination
coordinates, size of area to copy, source DC, source coordinates,
logical function, whether to use a bitmap mask, and mask source position.

\wxheading{Parameters}

\docparam{xdest}{Destination device context x position.}

\docparam{ydest}{Destination device context y position.}

\docparam{width}{Width of source area to be copied.}

\docparam{height}{Height of source area to be copied.}

\docparam{source}{Source device context.}

\docparam{xsrc}{Source device context x position.}

\docparam{ysrc}{Source device context y position.}

\docparam{logicalFunc}{Logical function to use: see \helpref{wxDC::SetLogicalFunction}{wxdcsetlogicalfunction}.}

\docparam{useMask}{If true, Blit does a transparent blit using the mask that is associated with the bitmap
selected into the source device context. The Windows implementation does the following if MaskBlt cannot be used:

\begin{enumerate}
\item Creates a temporary bitmap and copies the destination area into it.
\item Copies the source area into the temporary bitmap using the specified logical function.
\item Sets the masked area in the temporary bitmap to BLACK by ANDing the
mask bitmap with the temp bitmap with the foreground colour set to WHITE
and the bg colour set to BLACK.
\item Sets the unmasked area in the destination area to BLACK by ANDing the
mask bitmap with the destination area with the foreground colour set to BLACK
and the background colour set to WHITE.
\item ORs the temporary bitmap with the destination area.
\item Deletes the temporary bitmap.
\end{enumerate}

This sequence of operations ensures that the source's transparent area need not be black,
and logical functions are supported.

{\bf Note:} on Windows, blitting with masks can be speeded up considerably by compiling
wxWidgets with the wxUSE\_DC\_CACHE option enabled. You can also influence whether MaskBlt
or the explicit mask blitting code above is used, by using \helpref{wxSystemOptions}{wxsystemoptions} and
setting the {\bf no-maskblt} option to 1.

}

\docparam{xsrcMask}{Source x position on the mask. If both xsrcMask and ysrcMask are -1, xsrc and ysrc
will be assumed for the mask source position. Currently only implemented on Windows.}

\docparam{ysrcMask}{Source y position on the mask. If both xsrcMask and ysrcMask are -1, xsrc and ysrc
will be assumed for the mask source position. Currently only implemented on Windows.}


\wxheading{Remarks}

There is partial support for Blit in wxPostScriptDC, under X.

See \helpref{wxMemoryDC}{wxmemorydc} for typical usage.

\wxheading{See also}

\helpref{wxMemoryDC}{wxmemorydc}, \helpref{wxBitmap}{wxbitmap}, \helpref{wxMask}{wxmask}

\begin{comment}

\membersection{wxDC::CacheEnabled}\label{wxdccacheenabled}

\func{static bool}{CacheEnabled}{\void}

On supported platforms (currently only Windows), returns true
if the DC cache is enabled. The DC cache
can speed up the \helpref{Blit}{wxdcblit} operation when
drawing a large number of masked bitmaps.

If using the cache functions in your code, please test for the
wxUSE\_DC\_CACHEING preprocessor symbol for portability.

\wxheading{See also}

\helpref{wxDC::EnableCache}{wxdcenablecache}, \helpref{wxDC::ClearCache}
\end{comment}


\membersection{wxDC::CalcBoundingBox}\label{wxdccalcboundingbox}

\func{void}{CalcBoundingBox}{\param{wxCoord }{x}, \param{wxCoord }{y}}

Adds the specified point to the bounding box which can be retrieved with 
\helpref{MinX}{wxdcminx}, \helpref{MaxX}{wxdcmaxx} and 
\helpref{MinY}{wxdcminy}, \helpref{MaxY}{wxdcmaxy} functions.

\wxheading{See also}

\helpref{ResetBoundingBox}{wxdcresetboundingbox}


\membersection{wxDC::Clear}\label{wxdcclear}

\func{void}{Clear}{\void}

Clears the device context using the current background brush.

\begin{comment}

\membersection{wxDC::ClearCache}\label{wxdcclearcache}

\func{static void}{ClearCache}{\void}

On supported platforms (currently only Windows), clears
the contents of the DC cache (one bitmap and two Windows device contexts). The DC cache
can speed up the \helpref{Blit}{wxdcblit} operation when
drawing a large number of masked bitmaps. You should
call ClearCache at the end of length DC operations if you wish to only use
the cache transiently; you should also call it as your application exits.

If using the cache functions in your code, please test for the
wxUSE\_DC\_CACHEING preprocessor symbol for portability.

\wxheading{See also}

\helpref{wxDC::EnableCache}{wxdcenablecache}, \helpref{wxDC::CacheEnabled}
\end{comment}


\membersection{wxDC::ComputeScaleAndOrigin}\label{wxdccomputescaleandorigin}

\func{virtual void}{ComputeScaleAndOrigin}{\void}

Performs all necessary computations for given platform and context type
after each change of scale and origin parameters. Usually called automatically 
internally after such changes.


\membersection{wxDC::CrossHair}\label{wxdccrosshair}

\func{void}{CrossHair}{\param{wxCoord}{ x}, \param{wxCoord}{ y}}

Displays a cross hair using the current pen. This is a vertical
and horizontal line the height and width of the window, centred
on the given point.


\membersection{wxDC::DestroyClippingRegion}\label{wxdcdestroyclippingregion}

\func{void}{DestroyClippingRegion}{\void}

Destroys the current clipping region so that none of the DC is clipped.
See also \helpref{wxDC::SetClippingRegion}{wxdcsetclippingregion}.


\membersection{wxDC::DeviceToLogicalX}\label{wxdcdevicetologicalx}

\func{wxCoord}{DeviceToLogicalX}{\param{wxCoord}{ x}}

Convert device X coordinate to logical coordinate, using the current
mapping mode.


\membersection{wxDC::DeviceToLogicalXRel}\label{wxdcdevicetologicalxrel}

\func{wxCoord}{DeviceToLogicalXRel}{\param{wxCoord}{ x}}

Convert device X coordinate to relative logical coordinate, using the current
mapping mode but ignoring the x axis orientation.
Use this function for converting a width, for example.


\membersection{wxDC::DeviceToLogicalY}\label{wxdcdevicetologicaly}

\func{wxCoord}{DeviceToLogicalY}{\param{wxCoord}{ y}}

Converts device Y coordinate to logical coordinate, using the current
mapping mode.


\membersection{wxDC::DeviceToLogicalYRel}\label{wxdcdevicetologicalyrel}

\func{wxCoord}{DeviceToLogicalYRel}{\param{wxCoord}{ y}}

Convert device Y coordinate to relative logical coordinate, using the current
mapping mode but ignoring the y axis orientation.
Use this function for converting a height, for example.


\membersection{wxDC::DrawArc}\label{wxdcdrawarc}

\func{void}{DrawArc}{\param{wxCoord}{ x1}, \param{wxCoord}{ y1}, \param{wxCoord}{ x2}, \param{wxCoord}{ y2}, \param{wxCoord}{ xc}, \param{wxCoord}{ yc}}

Draws an arc of a circle, centred on ({\it xc, yc}), with starting point ({\it x1, y1})
and ending at ({\it x2, y2}).   The current pen is used for the outline
and the current brush for filling the shape.

The arc is drawn in an anticlockwise direction from the start point to the end point.


\membersection{wxDC::DrawBitmap}\label{wxdcdrawbitmap}

\func{void}{DrawBitmap}{\param{const wxBitmap\&}{ bitmap}, \param{wxCoord}{ x}, \param{wxCoord}{ y}, \param{bool}{ transparent}}

Draw a bitmap on the device context at the specified point. If {\it transparent} is true and the bitmap has
a transparency mask, the bitmap will be drawn transparently.

When drawing a mono-bitmap, the current text foreground colour will be used to draw the foreground
of the bitmap (all bits set to 1), and the current text background colour to draw the background
(all bits set to 0). See also \helpref{SetTextForeground}{wxdcsettextforeground}, 
\helpref{SetTextBackground}{wxdcsettextbackground} and \helpref{wxMemoryDC}{wxmemorydc}.


\membersection{wxDC::DrawCheckMark}\label{wxdcdrawcheckmark}

\func{void}{DrawCheckMark}{\param{wxCoord}{ x}, \param{wxCoord}{ y}, \param{wxCoord}{ width}, \param{wxCoord}{ height}}

\func{void}{DrawCheckMark}{\param{const wxRect \&}{rect}}

Draws a check mark inside the given rectangle.


\membersection{wxDC::DrawCircle}\label{wxdcdrawcircle}

\func{void}{DrawCircle}{\param{wxCoord}{ x}, \param{wxCoord}{ y}, \param{wxCoord}{ radius}}

\func{void}{DrawCircle}{\param{const wxPoint\&}{ pt}, \param{wxCoord}{ radius}}

Draws a circle with the given centre and radius.

\wxheading{See also}

\helpref{DrawEllipse}{wxdcdrawellipse}


\membersection{wxDC::DrawEllipse}\label{wxdcdrawellipse}

\func{void}{DrawEllipse}{\param{wxCoord}{ x}, \param{wxCoord}{ y}, \param{wxCoord}{ width}, \param{wxCoord}{ height}}

\func{void}{DrawEllipse}{\param{const wxPoint\&}{ pt}, \param{const wxSize\&}{ size}}

\func{void}{DrawEllipse}{\param{const wxRect\&}{ rect}}

Draws an ellipse contained in the rectangle specified either with the given top
left corner and the given size or directly. The current pen is used for the
outline and the current brush for filling the shape.

\wxheading{See also}

\helpref{DrawCircle}{wxdcdrawcircle}


\membersection{wxDC::DrawEllipticArc}\label{wxdcdrawellipticarc}

\func{void}{DrawEllipticArc}{\param{wxCoord}{ x}, \param{wxCoord}{ y}, \param{wxCoord}{ width}, \param{wxCoord}{ height},
 \param{double}{ start}, \param{double}{ end}}

Draws an arc of an ellipse. The current pen is used for drawing the arc and
the current brush is used for drawing the pie.

{\it x} and {\it y} specify the x and y coordinates of the upper-left corner of the rectangle that contains
the ellipse.

{\it width} and {\it height} specify the width and height of the rectangle that contains
the ellipse.

{\it start} and {\it end} specify the start and end of the arc relative to the three-o'clock
position from the center of the rectangle. Angles are specified
in degrees (360 is a complete circle). Positive values mean
counter-clockwise motion. If {\it start} is equal to {\it end}, a
complete ellipse will be drawn.


\membersection{wxDC::DrawIcon}\label{wxdcdrawicon}

\func{void}{DrawIcon}{\param{const wxIcon\&}{ icon}, \param{wxCoord}{ x}, \param{wxCoord}{ y}}

Draw an icon on the display (does nothing if the device context is PostScript).
This can be the simplest way of drawing bitmaps on a window.


\membersection{wxDC::DrawLabel}\label{wxdcdrawlabel}

\func{virtual void}{DrawLabel}{\param{const wxString\&}{ text},
                               \param{const wxBitmap\&}{ image},
                               \param{const wxRect\&}{ rect},
                               \param{int}{ alignment = wxALIGN\_LEFT | wxALIGN\_TOP},
                               \param{int}{ indexAccel = -1},
                               \param{wxRect *}{rectBounding = NULL}}

\func{void}{DrawLabel}{\param{const wxString\&}{ text}, \param{const wxRect\&}{ rect},
                       \param{int}{ alignment = wxALIGN\_LEFT | wxALIGN\_TOP},
                       \param{int}{ indexAccel = -1}}

Draw optional bitmap and the text into the given rectangle and aligns it as specified
by alignment parameter; it also will emphasize the character with the given index if
it is != -1 and return the bounding rectangle if required.


\membersection{wxDC::DrawLine}\label{wxdcdrawline}

\func{void}{DrawLine}{\param{wxCoord}{ x1}, \param{wxCoord}{ y1}, \param{wxCoord}{ x2}, \param{wxCoord}{ y2}}

Draws a line from the first point to the second. The current pen is used
for drawing the line. Note that the point $(x2, y2)$ is {\emph not} part of the
line and is not drawn by this function (this is consistent with the behaviour
of many other toolkits).


\membersection{wxDC::DrawLines}\label{wxdcdrawlines}

\func{void}{DrawLines}{\param{int}{ n}, \param{wxPoint}{ points[]}, \param{wxCoord}{ xoffset = 0}, \param{wxCoord}{ yoffset = 0}}

\func{void}{DrawLines}{\param{wxList *}{points}, \param{wxCoord}{ xoffset = 0}, \param{wxCoord}{ yoffset = 0}}

Draws lines using an array of {\it points} of size {\it n}, or list of
pointers to points, adding the optional offset coordinate. The current
pen is used for drawing the lines.  The programmer is responsible for
deleting the list of points.

\pythonnote{The wxPython version of this method accepts a Python list
of wxPoint objects.}

\perlnote{The wxPerl version of this method accepts 
  as its first parameter a reference to an array
  of wxPoint objects.}


\membersection{wxDC::DrawPolygon}\label{wxdcdrawpolygon}

\func{void}{DrawPolygon}{\param{int}{ n}, \param{wxPoint}{ points[]}, \param{wxCoord}{ xoffset = 0}, \param{wxCoord}{ yoffset = 0},\\
  \param{int }{fill\_style = wxODDEVEN\_RULE}}

\func{void}{DrawPolygon}{\param{wxList *}{points}, \param{wxCoord}{ xoffset = 0}, \param{wxCoord}{ yoffset = 0},\\
  \param{int }{fill\_style = wxODDEVEN\_RULE}}

Draws a filled polygon using an array of {\it points} of size {\it n},
or list of pointers to points, adding the optional offset coordinate.

The last argument specifies the fill rule: {\bf wxODDEVEN\_RULE} (the
default) or {\bf wxWINDING\_RULE}.

The current pen is used for drawing the outline, and the current brush
for filling the shape.  Using a transparent brush suppresses filling.
The programmer is responsible for deleting the list of points.

Note that wxWidgets automatically closes the first and last points.

\pythonnote{The wxPython version of this method accepts a Python list
of wxPoint objects.}

\perlnote{The wxPerl version of this method accepts 
  as its first parameter a reference to an array
  of wxPoint objects.}


\membersection{wxDC::DrawPolyPolygon}\label{wxdcdrawpolypolygon}

\func{void}{DrawPolyPolygon}{\param{int}{ n}, \param{int}{ count[]}, \param{wxPoint}{ points[]}, \param{wxCoord}{ xoffset = 0}, \param{wxCoord}{ yoffset = 0},\\
  \param{int }{fill\_style = wxODDEVEN\_RULE}}

Draws two or more filled polygons using an array of {\it points}, adding the
optional offset coordinates.

Notice that for the platforms providing a native implementation
of this function (Windows and PostScript-based wxDC currently), this is more
efficient than using \helpref{DrawPolygon}{wxdcdrawpolygon} in a loop.

{\it n} specifies the number of polygons to draw, the array {\it count} of size 
{\it n} specifies the number of points in each of the polygons in the 
{\it points} array.

The last argument specifies the fill rule: {\bf wxODDEVEN\_RULE} (the default)
or {\bf wxWINDING\_RULE}.

The current pen is used for drawing the outline, and the current brush for
filling the shape.  Using a transparent brush suppresses filling.

The polygons maybe disjoint or overlapping. Each polygon specified in a call to
{\bf DrawPolyPolygon} must be closed. Unlike polygons created by the
\helpref{DrawPolygon}{wxdcdrawpolygon} member function, the polygons created by
{\bf DrawPolyPolygon} are not closed automatically.

\pythonnote{Not implemented yet}

\perlnote{Not implemented yet}


\membersection{wxDC::DrawPoint}\label{wxdcdrawpoint}

\func{void}{DrawPoint}{\param{wxCoord}{ x}, \param{wxCoord}{ y}}

Draws a point using the color of the current pen. Note that the other properties of the pen are not used, such as width etc..


\membersection{wxDC::DrawRectangle}\label{wxdcdrawrectangle}

\func{void}{DrawRectangle}{\param{wxCoord}{ x}, \param{wxCoord}{ y}, \param{wxCoord}{ width}, \param{wxCoord}{ height}}

Draws a rectangle with the given top left corner, and with the given
size.  The current pen is used for the outline and the current brush
for filling the shape.


\membersection{wxDC::DrawRotatedText}\label{wxdcdrawrotatedtext}

\func{void}{DrawRotatedText}{\param{const wxString\& }{text}, \param{wxCoord}{ x}, \param{wxCoord}{ y}, \param{double}{ angle}}

Draws the text rotated by {\it angle} degrees.

{\bf NB:} Under Win9x only TrueType fonts can be drawn by this function. In
particular, a font different from {\tt wxNORMAL\_FONT} should be used as the
latter is not a TrueType font. {\tt wxSWISS\_FONT} is an example of a font
which is.

\wxheading{See also}

\helpref{DrawText}{wxdcdrawtext}


\membersection{wxDC::DrawRoundedRectangle}\label{wxdcdrawroundedrectangle}

\func{void}{DrawRoundedRectangle}{\param{wxCoord}{ x}, \param{wxCoord}{ y}, \param{wxCoord}{ width}, \param{wxCoord}{ height}, \param{double}{ radius}}

Draws a rectangle with the given top left corner, and with the given
size.  The corners are quarter-circles using the given radius. The
current pen is used for the outline and the current brush for filling
the shape.

If {\it radius} is positive, the value is assumed to be the
radius of the rounded corner. If {\it radius} is negative,
the absolute value is assumed to be the {\it proportion} of the smallest
dimension of the rectangle. This means that the corner can be
a sensible size relative to the size of the rectangle, and also avoids
the strange effects X produces when the corners are too big for
the rectangle.


\membersection{wxDC::DrawSpline}\label{wxdcdrawspline}

\func{void}{DrawSpline}{\param{int }{n}, \param{wxPoint }{points[]}}

Draws a spline between all given control points, using the current
pen.

\func{void}{DrawSpline}{\param{wxList *}{points}}

Draws a spline between all given control points, using the current
pen.  Doesn't delete the wxList and contents.

\func{void}{DrawSpline}{\param{wxCoord}{ x1}, \param{wxCoord}{ y1}, \param{wxCoord}{ x2}, \param{wxCoord}{ y2}, \param{wxCoord}{ x3}, \param{wxCoord}{ y3}}

Draws a three-point spline using the current pen.

\pythonnote{The wxPython version of this method accepts a Python list
of wxPoint objects.}

\perlnote{The wxPerl version of this method accepts a reference to an array
  of wxPoint objects.}


\membersection{wxDC::DrawText}\label{wxdcdrawtext}

\func{void}{DrawText}{\param{const wxString\& }{text}, \param{wxCoord}{ x}, \param{wxCoord}{ y}}

Draws a text string at the specified point, using the current text font,
and the current text foreground and background colours.

The coordinates refer to the top-left corner of the rectangle bounding
the string. See \helpref{wxDC::GetTextExtent}{wxdcgettextextent} for how
to get the dimensions of a text string, which can be used to position the
text more precisely.

{\bf NB:} under wxGTK the current 
\helpref{logical function}{wxdcgetlogicalfunction} is used by this function
but it is ignored by wxMSW. Thus, you should avoid using logical functions
with this function in portable programs.

\begin{comment}

\membersection{wxDC::EnableCache}\label{wxdcenablecache}

\func{static void}{EnableCache}{\param{bool}{ enableCache}}

On supported platforms (currently only Windows), enables the DC cache
which can speed up the \helpref{Blit}{wxdcblit} operation when
drawing a large number of masked bitmaps.

If using the cache functions in your code, please test for the
wxUSE\_DC\_CACHEING preprocessor symbol for portability.

\wxheading{See also}

\helpref{wxDC::CacheEnabled}{wxdccacheenabled}, \helpref{wxDC::ClearCache}
\end{comment}


\membersection{wxDC::EndDoc}\label{wxdcenddoc}

\func{void}{EndDoc}{\void}

Ends a document (only relevant when outputting to a printer).


\membersection{wxDC::EndPage}\label{wxdcendpage}

\func{void}{EndPage}{\void}

Ends a document page (only relevant when outputting to a printer).


\membersection{wxDC::FloodFill}\label{wxdcfloodfill}

\func{bool}{FloodFill}{\param{wxCoord}{ x}, \param{wxCoord}{ y}, \param{const wxColour\&}{ colour}, \param{int}{ style=wxFLOOD\_SURFACE}}

Flood fills the device context starting from the given point, using
the {\it current brush colour}, and using a style:

\begin{itemize}\itemsep=0pt
\item wxFLOOD\_SURFACE: the flooding occurs until a colour other than the given colour is encountered.
\item wxFLOOD\_BORDER: the area to be flooded is bounded by the given colour.
\end{itemize}

Returns false if the operation failed.

{\it Note:} The present implementation for non-Windows platforms may fail to find
colour borders if the pixels do not match the colour exactly. However the
function will still return true.


\membersection{wxDC::GetBackground}\label{wxdcgetbackground}

\constfunc{const wxBrush\&}{GetBackground}{\void}

Gets the brush used for painting the background (see \helpref{wxDC::SetBackground}{wxdcsetbackground}).


\membersection{wxDC::GetBackgroundMode}\label{wxdcgetbackgroundmode}

\constfunc{int}{GetBackgroundMode}{\void}

Returns the current background mode: {\tt wxSOLID} or {\tt wxTRANSPARENT}.

\wxheading{See also}

\helpref{SetBackgroundMode}{wxdcsetbackgroundmode}


\membersection{wxDC::GetBrush}\label{wxdcgetbrush}

\constfunc{const wxBrush\&}{GetBrush}{\void}

Gets the current brush (see \helpref{wxDC::SetBrush}{wxdcsetbrush}).


\membersection{wxDC::GetCharHeight}\label{wxdcgetcharheight}

\func{wxCoord}{GetCharHeight}{\void}

Gets the character height of the currently set font.


\membersection{wxDC::GetCharWidth}\label{wxdcgetcharwidth}

\func{wxCoord}{GetCharWidth}{\void}

Gets the average character width of the currently set font.


\membersection{wxDC::GetClippingBox}\label{wxdcgetclippingbox}

\func{void}{GetClippingBox}{\param{wxCoord}{ *x}, \param{wxCoord}{ *y}, \param{wxCoord}{ *width}, \param{wxCoord}{ *height}}

Gets the rectangle surrounding the current clipping region.

\pythonnote{No arguments are required and the four values defining the
rectangle are returned as a tuple.}

\perlnote{This method takes no arguments and returns a four element list
{\tt ( x, y, width, height )}}


\membersection{wxDC::GetFont}\label{wxdcgetfont}

\constfunc{const wxFont\&}{GetFont}{\void}

Gets the current font. Notice that even although each device context object has
some default font after creation, this method would return a \texttt{wxNullFont} 
initially and only after calling \helpref{wxDC::SetFont}{wxdcsetfont} a valid
font is returned.


\membersection{wxDC::GetLayoutDirection}\label{wxdcgetlayoutdirection}

\constfunc{wxLayoutDirection}{GetLayoutDirection}{\void}

Gets the current layout direction of the device context. On platforms where RTL layout
is supported, the return value will either be \texttt{wxLayout\_LeftToRight} or 
\texttt{wxLayout\_RightToLeft}. If RTL layout is not supported, the return value will 
be \texttt{wxLayout\_Default}.

\wxheading{See also}

\helpref{SetLayoutDirection}{wxdcsetlayoutdirection}


\membersection{wxDC::GetLogicalFunction}\label{wxdcgetlogicalfunction}

\func{int}{GetLogicalFunction}{\void}

Gets the current logical function (see \helpref{wxDC::SetLogicalFunction}{wxdcsetlogicalfunction}).


\membersection{wxDC::GetMapMode}\label{wxdcgetmapmode}

\func{int}{GetMapMode}{\void}

Gets the {\it mapping mode} for the device context (see \helpref{wxDC::SetMapMode}{wxdcsetmapmode}).


\membersection{wxDC::GetPartialTextExtents}\label{wxdcgetpartialtextextents}

\constfunc{bool}{GetPartialTextExtents}{\param{const wxString\&  }{text}, 
\param{wxArrayInt\& }{widths}}

Fills the {\it widths} array with the widths from the beginning of 
{\it text} to the corresponding character of {\it text}.  The generic
version simply builds a running total of the widths of each character
using \helpref{GetTextExtent}{wxdcgettextextent}, however if the
various platforms have a native API function that is faster or more
accurate than the generic implementation then it should be used
instead. 

\pythonnote{This method only takes the {\it text} parameter and
  returns a Python list of integers.}


\membersection{wxDC::GetPen}\label{wxdcgetpen}

\constfunc{const wxPen\&}{GetPen}{\void}

Gets the current pen (see \helpref{wxDC::SetPen}{wxdcsetpen}).


\membersection{wxDC::GetPixel}\label{wxdcgetpixel}

\func{bool}{GetPixel}{\param{wxCoord}{ x}, \param{wxCoord}{ y}, \param{wxColour *}{colour}}

Gets in {\it colour} the colour at the specified location.
Not available for wxPostScriptDC or wxMetafileDC.

Note that setting a pixel can be done using \helpref{DrawPoint}{wxdcdrawpoint}.

\pythonnote{For wxPython the wxColour value is returned and is not
required as a parameter.}

\perlnote{This method only takes the parameters {\tt x} and {\tt y} and returns
a Wx::Colour value}

\membersection{wxDC::GetPPI}\label{wxdcgetppi}

\constfunc{wxSize}{GetPPI}{\void}

Returns the resolution of the device in pixels per inch.

\membersection{wxDC::GetSize}\label{wxdcgetsize}

\constfunc{void}{GetSize}{\param{wxCoord *}{width}, \param{wxCoord *}{height}}

\constfunc{wxSize}{GetSize}{\void}

This gets the horizontal and vertical resolution in device units. It can be used to scale graphics to fit the page.
For example, if {\it maxX} and {\it maxY}\rtfsp
represent the maximum horizontal and vertical `pixel' values used in your
application, the following code will scale the graphic to fit on the
printer page:

\begin{verbatim}
  wxCoord w, h;
  dc.GetSize(&w, &h);
  double scaleX=(double)(maxX/w);
  double scaleY=(double)(maxY/h);
  dc.SetUserScale(min(scaleX,scaleY),min(scaleX,scaleY));
\end{verbatim}

\pythonnote{In place of a single overloaded method name, wxPython
implements the following methods:\par
\indented{2cm}{\begin{twocollist}
\twocolitem{{\bf GetSize()}}{Returns a wxSize}
\twocolitem{{\bf GetSizeTuple()}}{Returns a 2-tuple (width, height)}
\end{twocollist}}
}

\perlnote{In place of a single overloaded method, wxPerl uses:\par
\indented{2cm}{\begin{twocollist}
\twocolitem{{\bf GetSize()}}{Returns a Wx::Size}
\twocolitem{{\bf GetSizeWH()}}{Returns a 2-element list
  {\tt ( width, height )}}
\end{twocollist}
}}

\membersection{wxDC::GetSizeMM}\label{wxdcgetsizemm}

\constfunc{void}{GetSizeMM}{\param{wxCoord *}{width}, \param{wxCoord *}{height}}

\constfunc{wxSize}{GetSizeMM}{\void}

Returns the horizontal and vertical resolution in millimetres.

\membersection{wxDC::GetTextBackground}\label{wxdcgettextbackground}

\constfunc{const wxColour\&}{GetTextBackground}{\void}

Gets the current text background colour (see \helpref{wxDC::SetTextBackground}{wxdcsettextbackground}).


\membersection{wxDC::GetTextExtent}\label{wxdcgettextextent}

\func{void}{GetTextExtent}{\param{const wxString\& }{string}, \param{wxCoord *}{w}, \param{wxCoord *}{h},\\
  \param{wxCoord *}{descent = NULL}, \param{wxCoord *}{externalLeading = NULL}, \param{wxFont *}{font = NULL}}

Gets the dimensions of the string using the currently selected font.
\rtfsp{\it string} is the text string to measure, {\it w} and {\it h} are
the total width and height respectively, {\it descent} is the
dimension from the baseline of the font to the bottom of the
descender, and {\it externalLeading} is any extra vertical space added
to the font by the font designer (usually is zero).

If the optional parameter {\it font} is specified and valid, then it is used
for the text extent calculation. Otherwise the currently selected font is.

See also \helpref{wxFont}{wxfont}, \helpref{wxDC::SetFont}{wxdcsetfont}.

\pythonnote{The following methods are implemented in wxPython:\par
\indented{2cm}{\begin{twocollist}
\twocolitem{{\bf GetTextExtent(string)}}{Returns a 2-tuple, (width, height)}
\twocolitem{{\bf GetFullTextExtent(string, font=NULL)}}{Returns a
4-tuple, (width, height, descent, externalLeading) }
\end{twocollist}}
}

\perlnote{In wxPerl this method is implemented as 
  {\bf GetTextExtent( string, font = undef )} returning a four element
  array {\tt ( width, height, descent, externalLeading )}
}


\membersection{wxDC::GetTextForeground}\label{wxdcgettextforeground}

\constfunc{const wxColour\&}{GetTextForeground}{\void}

Gets the current text foreground colour (see \helpref{wxDC::SetTextForeground}{wxdcsettextforeground}).


\membersection{wxDC::GetUserScale}\label{wxdcgetuserscale}

\func{void}{GetUserScale}{\param{double}{ *x}, \param{double}{ *y}}

Gets the current user scale factor (set by \helpref{SetUserScale}{wxdcsetuserscale}).

\perlnote{In wxPerl this method takes no arguments and return a two element
 array {\tt ( x, y )}}


\membersection{wxDC::GradientFillConcentric}\label{wxdcgradientfillconcentric}

\func{void}{GradientFillConcentric}{\param{const wxRect\&}{ rect}, \param{const wxColour\&}{ initialColour}, \param{const wxColour\&}{ destColour}}

\func{void}{GradientFillConcentric}{\param{const wxRect\&}{ rect}, \param{const wxColour\&}{ initialColour}, \param{const wxColour\&}{ destColour}, \param{const wxPoint\& }{circleCenter}}

Fill the area specified by rect with a radial gradient, starting from 
\arg{initialColour} at the centre of the circle and fading to \arg{destColour} 
on the circle outside.

\arg{circleCenter} are the relative coordinates of centre of the circle in
the specified \arg{rect}. If not specified, the cercle is placed at the
centre of rect.

\textbf{Note: } Currently this function is very slow, don't use it for
real-time drawing.


\membersection{wxDC::GradientFillLinear}\label{wxdcgradientfilllinear}

\func{void}{GradientFillLinear}{\param{const wxRect\&}{ rect}, \param{const wxColour\&}{ initialColour}, \param{const wxColour\&}{ destColour}, \param{wxDirection}{ nDirection = wxEAST}}

Fill the area specified by \arg{rect} with a linear gradient, starting from 
\arg{initialColour} and eventually fading to \arg{destColour}. The 
\arg{nDirection} specifies the direction of the colour change, default is to
use \arg{initialColour} on the left part of the rectangle and 
\arg{destColour} on the right one.


\membersection{wxDC::LogicalToDeviceX}\label{wxdclogicaltodevicex}

\func{wxCoord}{LogicalToDeviceX}{\param{wxCoord}{ x}}

Converts logical X coordinate to device coordinate, using the current
mapping mode.


\membersection{wxDC::LogicalToDeviceXRel}\label{wxdclogicaltodevicexrel}

\func{wxCoord}{LogicalToDeviceXRel}{\param{wxCoord}{ x}}

Converts logical X coordinate to relative device coordinate, using the current
mapping mode but ignoring the x axis orientation.
Use this for converting a width, for example.


\membersection{wxDC::LogicalToDeviceY}\label{wxdclogicaltodevicey}

\func{wxCoord}{LogicalToDeviceY}{\param{wxCoord}{ y}}

Converts logical Y coordinate to device coordinate, using the current
mapping mode.


\membersection{wxDC::LogicalToDeviceYRel}\label{wxdclogicaltodeviceyrel}

\func{wxCoord}{LogicalToDeviceYRel}{\param{wxCoord}{ y}}

Converts logical Y coordinate to relative device coordinate, using the current
mapping mode but ignoring the y axis orientation.
Use this for converting a height, for example.


\membersection{wxDC::MaxX}\label{wxdcmaxx}

\func{wxCoord}{MaxX}{\void}

Gets the maximum horizontal extent used in drawing commands so far.


\membersection{wxDC::MaxY}\label{wxdcmaxy}

\func{wxCoord}{MaxY}{\void}

Gets the maximum vertical extent used in drawing commands so far.


\membersection{wxDC::MinX}\label{wxdcminx}

\func{wxCoord}{MinX}{\void}

Gets the minimum horizontal extent used in drawing commands so far.


\membersection{wxDC::MinY}\label{wxdcminy}

\func{wxCoord}{MinY}{\void}

Gets the minimum vertical extent used in drawing commands so far.


\membersection{wxDC::IsOk}\label{wxdcisok}

\func{bool}{Ok}{\void}

Returns true if the DC is ok to use.


\membersection{wxDC::ResetBoundingBox}\label{wxdcresetboundingbox}

\func{void}{ResetBoundingBox}{\void}

Resets the bounding box: after a call to this function, the bounding box
doesn't contain anything.

\wxheading{See also}

\helpref{CalcBoundingBox}{wxdccalcboundingbox}


\membersection{wxDC::SetAxisOrientation}\label{wxdcsetaxisorientation}

\func{void}{SetAxisOrientation}{\param{bool}{ xLeftRight},
                                \param{bool}{ yBottomUp}}

Sets the x and y axis orientation (i.e., the direction from lowest to
highest values on the axis). The default orientation is 
x axis from left to right and y axis from top down.

\wxheading{Parameters}

\docparam{xLeftRight}{True to set the x axis orientation to the natural
left to right orientation, false to invert it.}

\docparam{yBottomUp}{True to set the y axis orientation to the natural
bottom up orientation, false to invert it.}


\membersection{wxDC::SetBackground}\label{wxdcsetbackground}

\func{void}{SetBackground}{\param{const wxBrush\& }{brush}}

Sets the current background brush for the DC.


\membersection{wxDC::SetBackgroundMode}\label{wxdcsetbackgroundmode}

\func{void}{SetBackgroundMode}{\param{int}{ mode}}

{\it mode} may be one of wxSOLID and wxTRANSPARENT. This setting determines
whether text will be drawn with a background colour or not.


\membersection{wxDC::SetBrush}\label{wxdcsetbrush}

\func{void}{SetBrush}{\param{const wxBrush\& }{brush}}

Sets the current brush for the DC.

If the argument is wxNullBrush, the current brush is selected out of the device
context, and the original brush restored, allowing the current brush to
be destroyed safely.

See also \helpref{wxBrush}{wxbrush}.

See also \helpref{wxMemoryDC}{wxmemorydc} for the interpretation of colours
when drawing into a monochrome bitmap.

 
\membersection{wxDC::SetClippingRegion}\label{wxdcsetclippingregion}

\func{void}{SetClippingRegion}{\param{wxCoord}{ x}, \param{wxCoord}{ y}, \param{wxCoord}{ width}, \param{wxCoord}{ height}}

\func{void}{SetClippingRegion}{\param{const wxPoint\& }{pt}, \param{const wxSize\& }{sz}}

\func{void}{SetClippingRegion}{\param{const wxRect\&}{ rect}}

\func{void}{SetClippingRegion}{\param{const wxRegion\&}{ region}}

Sets the clipping region for this device context to the intersection of the
given region described by the parameters of this method and the previously set
clipping region. You should call 
\helpref{DestroyClippingRegion}{wxdcdestroyclippingregion} if you want to set
the clipping region exactly to the region specified.

The clipping region is an area to which drawing is restricted. Possible uses
for the clipping region are for clipping text or for speeding up window redraws
when only a known area of the screen is damaged.

\wxheading{See also}

\helpref{wxDC::DestroyClippingRegion}{wxdcdestroyclippingregion}, \helpref{wxRegion}{wxregion}


\membersection{wxDC::SetDeviceOrigin}\label{wxdcsetdeviceorigin}

\func{void}{SetDeviceOrigin}{\param{wxCoord}{ x}, \param{wxCoord}{ y}}

Sets the device origin (i.e., the origin in pixels after scaling has been
applied).

This function may be useful in Windows printing
operations for placing a graphic on a page.


\membersection{wxDC::SetFont}\label{wxdcsetfont}

\func{void}{SetFont}{\param{const wxFont\& }{font}}

Sets the current font for the DC. It must be a valid font, in particular you
should not pass {\tt wxNullFont} to this method.

See also \helpref{wxFont}{wxfont}.


\membersection{wxDC::SetLayoutDirection}\label{wxdcsetlayoutdirection}

\func{void}{SetLayoutDirection}{\param{wxLayoutDirection}{ dir}}

Sets the current layout direction for the device context. \arg{dir} may be either
\texttt{wxLayout\_Default}, \texttt{wxLayout\_LeftToRight} or \texttt{wxLayout\_RightToLeft}.

\wxheading{See also}

\helpref{GetLayoutDirection}{wxdcgetlayoutdirection}


\membersection{wxDC::SetLogicalFunction}\label{wxdcsetlogicalfunction}

\func{void}{SetLogicalFunction}{\param{int}{ function}}

Sets the current logical function for the device context.  This determines how
a source pixel (from a pen or brush colour, or source device context if
using \helpref{wxDC::Blit}{wxdcblit}) combines with a destination pixel in the
current device context.

The possible values
and their meaning in terms of source and destination pixel values are
as follows:

\begin{verbatim}
wxAND                 src AND dst
wxAND_INVERT          (NOT src) AND dst
wxAND_REVERSE         src AND (NOT dst)
wxCLEAR               0
wxCOPY                src
wxEQUIV               (NOT src) XOR dst
wxINVERT              NOT dst
wxNAND                (NOT src) OR (NOT dst)
wxNOR                 (NOT src) AND (NOT dst)
wxNO_OP               dst
wxOR                  src OR dst
wxOR_INVERT           (NOT src) OR dst
wxOR_REVERSE          src OR (NOT dst)
wxSET                 1
wxSRC_INVERT          NOT src
wxXOR                 src XOR dst
\end{verbatim}

The default is wxCOPY, which simply draws with the current colour.
The others combine the current colour and the background using a
logical operation.  wxINVERT is commonly used for drawing rubber bands or
moving outlines, since drawing twice reverts to the original colour.


\membersection{wxDC::SetMapMode}\label{wxdcsetmapmode}

\func{void}{SetMapMode}{\param{int}{ int}}

The {\it mapping mode} of the device context defines the unit of
measurement used to convert logical units to device units. Note that
in X, text drawing isn't handled consistently with the mapping mode; a
font is always specified in point size. However, setting the {\it
user scale} (see \helpref{wxDC::SetUserScale}{wxdcsetuserscale}) scales the text appropriately. In
Windows, scalable TrueType fonts are always used; in X, results depend
on availability of fonts, but usually a reasonable match is found.

The coordinate origin is always at the top left of the screen/printer.

Drawing to a Windows printer device context uses the current mapping mode,
but mapping mode is currently ignored for PostScript output.

The mapping mode can be one of the following:

\begin{twocollist}\itemsep=0pt
\twocolitem{wxMM\_TWIPS}{Each logical unit is 1/20 of a point, or 1/1440 of
  an inch.}
\twocolitem{wxMM\_POINTS}{Each logical unit is a point, or 1/72 of an inch.}
\twocolitem{wxMM\_METRIC}{Each logical unit is 1 mm.}
\twocolitem{wxMM\_LOMETRIC}{Each logical unit is 1/10 of a mm.}
\twocolitem{wxMM\_TEXT}{Each logical unit is 1 pixel.}
\end{twocollist}


\membersection{wxDC::SetPalette}\label{wxdcsetpalette}

\func{void}{SetPalette}{\param{const wxPalette\& }{palette}}

If this is a window DC or memory DC, assigns the given palette to the window
or bitmap associated with the DC. If the argument is wxNullPalette, the current
palette is selected out of the device context, and the original palette
restored.

See \helpref{wxPalette}{wxpalette} for further details. 


\membersection{wxDC::SetPen}\label{wxdcsetpen}

\func{void}{SetPen}{\param{const wxPen\& }{pen}}

Sets the current pen for the DC.

If the argument is wxNullPen, the current pen is selected out of the device
context, and the original pen restored.

See also \helpref{wxMemoryDC}{wxmemorydc} for the interpretation of colours
when drawing into a monochrome bitmap.


\membersection{wxDC::SetTextBackground}\label{wxdcsettextbackground}

\func{void}{SetTextBackground}{\param{const wxColour\& }{colour}}

Sets the current text background colour for the DC.


\membersection{wxDC::SetTextForeground}\label{wxdcsettextforeground}

\func{void}{SetTextForeground}{\param{const wxColour\& }{colour}}

Sets the current text foreground colour for the DC.

See also \helpref{wxMemoryDC}{wxmemorydc} for the interpretation of colours
when drawing into a monochrome bitmap.


\membersection{wxDC::SetUserScale}\label{wxdcsetuserscale}

\func{void}{SetUserScale}{\param{double}{ xScale}, \param{double}{ yScale}}

Sets the user scaling factor, useful for applications which require
`zooming'.


\membersection{wxDC::StartDoc}\label{wxdcstartdoc}

\func{bool}{StartDoc}{\param{const wxString\& }{message}}

Starts a document (only relevant when outputting to a printer).
Message is a message to show while printing.


\membersection{wxDC::StartPage}\label{wxdcstartpage}

\func{bool}{StartPage}{\void}

Starts a document page (only relevant when outputting to a printer).