/////////////////////////////////////////////////////////////////////////////
// Name: dc.h
// Purpose: interface of wxDC
// Author: wxWidgets team
// Licence: wxWindows licence
/////////////////////////////////////////////////////////////////////////////
/**
Logical raster operations which can be used with wxDC::SetLogicalFunction
and some other wxDC functions (e.g. wxDC::Blit and wxDC::StretchBlit).
The description of the values below refer to how a generic @e src source pixel
and the corresponding @e dst destination pixel gets combined together to produce
the final pixel. E.g. @c wxCLEAR and @c wxSET completely ignore the source
and the destination pixel and always put zeroes or ones in the final surface.
*/
enum wxRasterOperationMode
{
wxCLEAR, //!< 0
wxXOR, //!< @e src XOR @e dst
wxINVERT, //!< NOT @e dst
wxOR_REVERSE, //!< @e src OR (NOT @e dst)
wxAND_REVERSE, //!< @e src AND (NOT @e dst)
wxCOPY, //!< @e src
wxAND, //!< @e src AND @e dst
wxAND_INVERT, //!< (NOT @e src) AND @e dst
wxNO_OP, //!< @e dst
wxNOR, //!< (NOT @e src) AND (NOT @e dst)
wxEQUIV, //!< (NOT @e src) XOR @e dst
wxSRC_INVERT, //!< (NOT @e src)
wxOR_INVERT, //!< (NOT @e src) OR @e dst
wxNAND, //!< (NOT @e src) OR (NOT @e dst)
wxOR, //!< @e src OR @e dst
wxSET //!< 1
};
/**
Flood styles used by wxDC::FloodFill.
*/
enum wxFloodFillStyle
{
/** The flooding occurs until a colour other than the given colour is encountered. */
wxFLOOD_SURFACE = 1,
/** The area to be flooded is bounded by the given colour. */
wxFLOOD_BORDER
};
/**
The mapping used to transform @e logical units to @e device units.
See wxDC::SetMapMode.
*/
enum wxMappingMode
{
/**
Each logical unit is 1 device pixel.
This is the default mapping mode for all wxDC-derived classes.
*/
wxMM_TEXT = 1,
/** Each logical unit is 1 millimeter. */
wxMM_METRIC,
/** Each logical unit is 1/10 of a millimeter. */
wxMM_LOMETRIC,
/**
Each logical unit is 1/20 of a @e "printer point", or 1/1440 of an inch
(also known as "twip"). Equivalent to about 17.64 micrometers.
*/
wxMM_TWIPS,
/**
Each logical unit is a @e "printer point" i.e.\ 1/72 of an inch.
Equivalent to about 353 micrometers.
*/
wxMM_POINTS
};
/**
Simple collection of various font metrics.
This object is returned by wxDC::GetFontMetrics().
@since 2.9.2
@library{wxcore}
@category{dc,gdi}
*/
struct wxFontMetrics
{
/// Constructor initializes all fields to 0.
wxFontMetrics();
int height, ///< Total character height.
ascent, ///< Part of the height above the baseline.
descent, ///< Part of the height below the baseline.
internalLeading, ///< Intra-line spacing.
externalLeading, ///< Inter-line spacing.
averageWidth; ///< Average font width, a.k.a. "x-width".
};
/**
@class wxDC
A wxDC is a @e "device context" onto which graphics and text can be drawn.
It is intended to represent different output devices and offers a common
abstract API for drawing on any of them.
wxWidgets offers an alternative drawing API based on the modern drawing
backends GDI+, CoreGraphics and Cairo. See wxGraphicsContext, wxGraphicsRenderer
and related classes. There is also a wxGCDC linking the APIs by offering
the wxDC API on top of a wxGraphicsContext.
wxDC is an abstract base class and cannot be created directly.
Use wxPaintDC, wxClientDC, wxWindowDC, wxScreenDC, wxMemoryDC or
wxPrinterDC. Notice that device contexts which are associated with windows
(i.e. wxClientDC, wxWindowDC and wxPaintDC) use the window font and colours
by default (starting with wxWidgets 2.9.0) but the other device context
classes use system-default values so you always must set the appropriate
fonts and colours before using them.
In addition to the versions of the methods documented below, there
are also versions which accept single wxPoint parameter instead
of the two wxCoord ones or wxPoint and wxSize instead of the four
wxCoord parameters.
Beginning with wxWidgets 2.9.0 the entire wxDC code has been
reorganized. All platform dependent code (actually all drawing code)
has been moved into backend classes which derive from a common
wxDCImpl class. The user-visible classes such as wxClientDC and
wxPaintDC merely forward all calls to the backend implementation.
@section dc_units Device and logical units
In the wxDC context there is a distinction between @e logical units and @e device units.
@b Device units are the units native to the particular device; e.g. for a screen,
a device unit is a @e pixel. For a printer, the device unit is defined by the
resolution of the printer (usually given in @c DPI: dot-per-inch).
All wxDC functions use instead @b logical units, unless where explicitly
stated. Logical units are arbitrary units mapped to device units using
the current mapping mode (see wxDC::SetMapMode).
This mechanism allows to reuse the same code which prints on e.g. a window
on the screen to print on e.g. a paper.
@section dc_alpha_support Support for Transparency / Alpha Channel
In general wxDC methods don't support alpha transparency and the alpha
component of wxColour is simply ignored and you need to use wxGraphicsContext
for full transparency support. There are, however, a few exceptions: first,
under OS X colours with alpha channel are supported in all the normal
wxDC-derived classes as they use wxGraphicsContext internally. Second,
under all platforms wxSVGFileDC also fully supports alpha channel. In both
of these cases the instances of wxPen or wxBrush that are built from
wxColour use the colour's alpha values when stroking or filling.
@section Support for Transformation Matrix
On some platforms (currently only under MSW) wxDC has support for applying
an arbitrary affine transformation matrix to its coordinate system. Call
CanUseTransformMatrix() to check if this support is available and then call
SetTransformMatrix() if it is. If the transformation matrix is not
supported, SetTransformMatrix() always simply returns false and doesn't do
anything.
@library{wxcore}
@category{dc,gdi}
@see @ref overview_dc, wxGraphicsContext, wxDCFontChanger, wxDCTextColourChanger,
wxDCPenChanger, wxDCBrushChanger, wxDCClipper
@todo Precise definition of default/initial state.
@todo Pixelwise definition of operations (e.g. last point of a line not
drawn).
*/
class wxDC : public wxObject
{
public:
/**
@name Coordinate conversion functions
*/
//@{
/**
Convert @e device X coordinate to logical coordinate, using the current
mapping mode, user scale factor, device origin and axis orientation.
*/
wxCoord DeviceToLogicalX(wxCoord x) const;
/**
Convert @e device X coordinate to relative logical coordinate, using the
current mapping mode and user scale factor but ignoring the
axis orientation. Use this for converting a width, for example.
*/
wxCoord DeviceToLogicalXRel(wxCoord x) const;
/**
Converts @e device Y coordinate to logical coordinate, using the current
mapping mode, user scale factor, device origin and axis orientation.
*/
wxCoord DeviceToLogicalY(wxCoord y) const;
/**
Convert @e device Y coordinate to relative logical coordinate, using the
current mapping mode and user scale factor but ignoring the
axis orientation. Use this for converting a height, for example.
*/
wxCoord DeviceToLogicalYRel(wxCoord y) const;
/**
Converts logical X coordinate to device coordinate, using the current
mapping mode, user scale factor, device origin and axis orientation.
*/
wxCoord LogicalToDeviceX(wxCoord x) const;
/**
Converts logical X coordinate to relative device coordinate, using the
current mapping mode and user scale factor but ignoring the
axis orientation. Use this for converting a width, for example.
*/
wxCoord LogicalToDeviceXRel(wxCoord x) const;
/**
Converts logical Y coordinate to device coordinate, using the current
mapping mode, user scale factor, device origin and axis orientation.
*/
wxCoord LogicalToDeviceY(wxCoord y) const;
/**
Converts logical Y coordinate to relative device coordinate, using the
current mapping mode and user scale factor but ignoring the
axis orientation. Use this for converting a height, for example.
*/
wxCoord LogicalToDeviceYRel(wxCoord y) const;
//@}
/**
@name Drawing functions
*/
//@{
/**
Clears the device context using the current background brush.
*/
void Clear();
/**
Draws an arc from the given start to the given end point.
@note DrawEllipticArc() has more clear semantics and it is recommended
to use it instead of this function.
The arc drawn is an arc of the circle centered at (@a xc, @a yc). Its
start point is (@a xStart, @a yStart) whereas its end point is the
point of intersection of the line passing by (@a xc, @a yc) and (@a
xEnd, @a yEnd) with the circle passing by (@a xStart, @a yStart).
The arc is drawn in a counter-clockwise direction between the start and
the end points.
The current pen is used for the outline and the current brush for
filling the shape. Notice that unless the brush is transparent, the
lines connecting the centre of the circle to the end points of the arc
are drawn as well.
*/
void DrawArc(wxCoord xStart, wxCoord yStart, wxCoord xEnd, wxCoord yEnd,
wxCoord xc, wxCoord yc);
/**
@overload
*/
void DrawArc(const wxPoint& ptStart, const wxPoint& ptEnd, const wxPoint& centre);
/**
Draw a bitmap on the device context at the specified point. If
@a 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 SetTextForeground(), SetTextBackground(), wxMemoryDC
*/
void DrawBitmap(const wxBitmap& bitmap, wxCoord x, wxCoord y,
bool useMask = false);
/**
@overload
*/
void DrawBitmap(const wxBitmap &bmp, const wxPoint& pt,
bool useMask = false);
/**
Draws a check mark inside the given rectangle.
*/
void DrawCheckMark(wxCoord x, wxCoord y, wxCoord width, wxCoord height);
/**
@overload
*/
void DrawCheckMark(const wxRect& rect);
/**
Draws a circle with the given centre and radius.
@see DrawEllipse()
*/
void DrawCircle(wxCoord x, wxCoord y, wxCoord radius);
/**
@overload
*/
void DrawCircle(const wxPoint& pt, wxCoord radius);
/**
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.
@see DrawCircle()
*/
void DrawEllipse(wxCoord x, wxCoord y, wxCoord width, wxCoord height);
/**
@overload
*/
void DrawEllipse(const wxPoint& pt, const wxSize& size);
/**
@overload
*/
void DrawEllipse(const wxRect& rect);
/**
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.
@a x and @a y specify the x and y coordinates of the upper-left corner
of the rectangle that contains the ellipse.
@a width and @a height specify the width and height of the rectangle
that contains the ellipse.
@a start and @a end specify the end points of the arc relative to
the three-o'clock position from the center of the rectangle. Angles are
specified in degrees with 0 degree angle corresponding to the positive
horizontal axis (3 o'clock) direction.
Independently of whether @a start is greater than or less than @a end,
the arc is drawn in the counter-clockwise direction. Also, if @a start
is equal to @e end, a complete ellipse is drawn.
Notice that unlike DrawArc(), this function does not draw the lines to
the arc ends, even when using non-transparent brush.
*/
void DrawEllipticArc(wxCoord x, wxCoord y, wxCoord width, wxCoord height,
double start, double end);
/**
@overload
*/
void DrawEllipticArc(const wxPoint& pt, const wxSize& sz,
double sa, double ea);
/**
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.
*/
void DrawIcon(const wxIcon& icon, wxCoord x, wxCoord y);
/**
@overload
*/
void DrawIcon(const wxIcon& icon, const wxPoint& pt);
/**
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.
*/
void DrawLabel(const wxString& text, const wxBitmap& bitmap,
const wxRect& rect,
int alignment = wxALIGN_LEFT | wxALIGN_TOP,
int indexAccel = -1, wxRect* rectBounding = NULL);
/**
@overload
*/
void DrawLabel(const wxString& text, const wxRect& rect,
int alignment = wxALIGN_LEFT | wxALIGN_TOP,
int indexAccel = -1);
/**
Draws a line from the first point to the second. The current pen is
used for drawing the line. Note that the point (@a x2, @a y2) is not
part of the line and is not drawn by this function (this is consistent
with the behaviour of many other toolkits).
*/
void DrawLine(wxCoord x1, wxCoord y1, wxCoord x2, wxCoord y2);
/**
@overload
*/
void DrawLine(const wxPoint& pt1, const wxPoint& pt2);
/**
Draws lines using an array of points of size @a n adding the optional
offset coordinate. The current pen is used for drawing the lines.
@beginWxPerlOnly
Not supported by wxPerl.
@endWxPerlOnly
*/
void DrawLines(int n, const wxPoint points[], wxCoord xoffset = 0,
wxCoord yoffset = 0);
/**
This method uses a list of wxPoints, adding the optional offset
coordinate. The programmer is responsible for deleting the list of
points.
@beginWxPerlOnly
The wxPerl version of this method accepts
as its first parameter a reference to an array
of wxPoint objects.
@endWxPerlOnly
*/
void DrawLines(const wxPointList* points,
wxCoord xoffset = 0, wxCoord yoffset = 0);
/**
Draws a point using the color of the current pen. Note that the other
properties of the pen are not used, such as width.
*/
void DrawPoint(wxCoord x, wxCoord y);
/**
@overload
*/
void DrawPoint(const wxPoint& pt);
/**
Draws a filled polygon using an array of points of size @a n, adding
the optional offset coordinate. The first and last points are
automatically closed.
The last argument specifies the fill rule: @b wxODDEVEN_RULE (the
default) or @b 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.
@beginWxPerlOnly
Not supported by wxPerl.
@endWxPerlOnly
*/
void DrawPolygon(int n, const wxPoint points[], wxCoord xoffset = 0,
wxCoord yoffset = 0,
wxPolygonFillMode fill_style = wxODDEVEN_RULE);
/**
This method draws a filled polygon using a list of wxPoints, adding the
optional offset coordinate. The first and last points are automatically
closed.
The last argument specifies the fill rule: @b wxODDEVEN_RULE (the
default) or @b 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.
@beginWxPerlOnly
The wxPerl version of this method accepts
as its first parameter a reference to an array
of wxPoint objects.
@endWxPerlOnly
*/
void DrawPolygon(const wxPointList* points,
wxCoord xoffset = 0, wxCoord yoffset = 0,
wxPolygonFillMode fill_style = wxODDEVEN_RULE);
/**
Draws two or more filled polygons using an array of @a 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 DrawPolygon() in a loop.
@a n specifies the number of polygons to draw, the array @e count of
size @a n specifies the number of points in each of the polygons in the
@a points array.
The last argument specifies the fill rule: @b wxODDEVEN_RULE (the
default) or @b 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 DrawPolyPolygon() must be closed. Unlike polygons created by
the DrawPolygon() member function, the polygons created by this
method are not closed automatically.
*/
void DrawPolyPolygon(int n, const int count[], const wxPoint points[],
wxCoord xoffset = 0, wxCoord yoffset = 0,
wxPolygonFillMode fill_style = wxODDEVEN_RULE);
/**
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.
*/
void DrawRectangle(wxCoord x, wxCoord y, wxCoord width, wxCoord height);
/**
@overload
*/
void DrawRectangle(const wxPoint& pt, const wxSize& sz);
/**
@overload
*/
void DrawRectangle(const wxRect& rect);
/**
Draws the text rotated by @a angle degrees
(positive angles are counterclockwise; the full angle is 360 degrees).
Notice that, as with DrawText(), the @a text can contain multiple lines
separated by the new line (@c '\\n') characters.
@note Under MSW only TrueType fonts can be drawn by this function. In
particular, a font different from @c wxNORMAL_FONT should be used
as the latter is not a TrueType font. @c wxSWISS_FONT is an
example of a font which is.
@see DrawText()
*/
void DrawRotatedText(const wxString& text, wxCoord x, wxCoord y,
double angle);
/**
@overload
*/
void DrawRotatedText(const wxString& text, const wxPoint& point,
double angle);
/**
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 @a radius is positive, the value is assumed to be the radius of the
rounded corner. If @a radius is negative, the absolute value is assumed
to be the @e 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.
*/
void DrawRoundedRectangle(wxCoord x, wxCoord y, wxCoord width,
wxCoord height, double radius);
/**
@overload
*/
void DrawRoundedRectangle(const wxPoint& pt, const wxSize& sz,
double radius);
/**
@overload
*/
void DrawRoundedRectangle(const wxRect& rect, double radius);
/**
Draws a spline between all given points using the current pen.
@beginWxPerlOnly
Not supported by wxPerl.
@endWxPerlOnly
*/
void DrawSpline(int n, const wxPoint points[]);
/**
@overload
@beginWxPerlOnly
The wxPerl version of this method accepts
as its first parameter a reference to an array
of wxPoint objects.
@endWxPerlOnly
*/
void DrawSpline(const wxPointList* points);
/**
@overload
@beginWxPerlOnly
Not supported by wxPerl.
@endWxPerlOnly
*/
void DrawSpline(wxCoord x1, wxCoord y1, wxCoord x2, wxCoord y2,
wxCoord x3, wxCoord y3);
/**
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 GetTextExtent() for how to get the dimensions of a text
string, which can be used to position the text more precisely and
DrawLabel() if you need to align the string differently.
Starting from wxWidgets 2.9.2 @a text parameter can be a multi-line
string, i.e. contain new line characters, and will be rendered
correctly.
@note The current @ref GetLogicalFunction() "logical function" is
ignored by this function.
*/
void DrawText(const wxString& text, wxCoord x, wxCoord y);
/**
@overload
*/
void DrawText(const wxString& text, const wxPoint& pt);
/**
Fill the area specified by rect with a radial gradient, starting from
@a initialColour at the centre of the circle and fading to
@a destColour on the circle outside.
The circle is placed at the centre of @a rect.
@note Currently this function is very slow, don't use it for real-time
drawing.
*/
void GradientFillConcentric(const wxRect& rect,
const wxColour& initialColour,
const wxColour& destColour);
/**
Fill the area specified by rect with a radial gradient, starting from
@a initialColour at the centre of the circle and fading to
@a destColour on the circle outside.
@a circleCenter are the relative coordinates of centre of the circle in
the specified @a rect.
@note Currently this function is very slow, don't use it for real-time
drawing.
*/
void GradientFillConcentric(const wxRect& rect,
const wxColour& initialColour,
const wxColour& destColour,
const wxPoint& circleCenter);
/**
Fill the area specified by @a rect with a linear gradient, starting
from @a initialColour and eventually fading to @e destColour.
The @a nDirection specifies the direction of the colour change, default is
to use @a initialColour on the left part of the rectangle and
@a destColour on the right one.
*/
void GradientFillLinear(const wxRect& rect, const wxColour& initialColour,
const wxColour& destColour,
wxDirection nDirection = wxRIGHT);
/**
Flood fills the device context starting from the given point, using
the current brush colour, and using a style:
- wxFLOOD_SURFACE: The flooding occurs until a colour other than the
given colour is encountered.
- wxFLOOD_BORDER: The area to be flooded is bounded by the given
colour.
Currently this method is not implemented in wxOSX and does nothing
there.
@return @false if the operation failed.
@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.
@note This method shouldn't be used with wxPaintDC under non-Windows
platforms as it uses GetPixel() internally and this may give
wrong results, notably in wxGTK. If you need to flood fill
wxPaintDC, create a temporary wxMemoryDC, flood fill it and then
blit it to, or draw as a bitmap on, wxPaintDC. See the example of
doing this in the drawing sample and wxBufferedPaintDC class.
*/
bool FloodFill(wxCoord x, wxCoord y, const wxColour& colour,
wxFloodFillStyle style = wxFLOOD_SURFACE);
/**
@overload
*/
bool FloodFill(const wxPoint& pt, const wxColour& col,
wxFloodFillStyle style = wxFLOOD_SURFACE);
/**
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.
*/
void CrossHair(wxCoord x, wxCoord y);
/**
@overload
*/
void CrossHair(const wxPoint& pt);
//@}
/**
@name Clipping region functions
*/
//@{
/**
Destroys the current clipping region so that none of the DC is clipped.
@see SetClippingRegion()
*/
void DestroyClippingRegion();
/**
Gets the rectangle surrounding the current clipping region.
*/
void GetClippingBox(wxCoord *x, wxCoord *y, wxCoord *width, wxCoord *height) const;
/**
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.
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.
Notice that you need to call DestroyClippingRegion() if you want to set
the clipping region exactly to the region specified.
Also note that if the clipping region is empty, any previously set
clipping region is destroyed, i.e. it is equivalent to calling
DestroyClippingRegion(), and not to clipping out all drawing on the DC
as might be expected.
@see DestroyClippingRegion(), wxRegion
*/
void SetClippingRegion(wxCoord x, wxCoord y, wxCoord width, wxCoord height);
/**
@overload
*/
void SetClippingRegion(const wxPoint& pt, const wxSize& sz);
/**
@overload
*/
void SetClippingRegion(const wxRect& rect);
/**
Sets the clipping region for this device context.
Unlike SetClippingRegion(), this function works with physical
coordinates and not with the logical ones.
*/
void SetDeviceClippingRegion(const wxRegion& region);
//@}
/**
@name Text/character extent functions
*/
//@{
/**
Gets the character height of the currently set font.
*/
wxCoord GetCharHeight() const;
/**
Gets the average character width of the currently set font.
*/
wxCoord GetCharWidth() const;
/**
Returns the various font characteristics.
This method allows to retrieve some of the font characteristics not
returned by GetTextExtent(), notably internal leading and average
character width.
Currently this method returns correct results only under wxMSW, in the
other ports the internal leading will always be 0 and the average
character width will be computed as the width of the character 'x'.
@since 2.9.2
*/
wxFontMetrics GetFontMetrics() const;
/**
Gets the dimensions of the string using the currently selected font.
@a string is the text string to measure, @e heightLine, if non @NULL,
is where to store the height of a single line.
The text extent is set in the given @a w and @a h pointers.
If the optional parameter @a font is specified and valid, then it is
used for the text extent calculation, otherwise the currently selected
font is used.
@note This function works with both single-line and multi-line strings.
@beginWxPerlOnly
In wxPerl this method is implemented as
GetMultiLineTextExtent(string, font = undef) returning a
3-element list (width, height, line_height)
@endWxPerlOnly
@see wxFont, SetFont(), GetPartialTextExtents(), GetTextExtent()
*/
void GetMultiLineTextExtent(const wxString& string, wxCoord* w,
wxCoord* h,
wxCoord* heightLine = NULL,
const wxFont* font = NULL) const;
/**
Gets the dimensions of the string using the currently selected font.
@a string is the text string to measure, @e heightLine, if non @NULL,
is where to store the height of a single line.
@return The text extent as a wxSize object.
@note This function works with both single-line and multi-line strings.
@beginWxPerlOnly
Not supported by wxPerl.
@endWxPerlOnly
@see wxFont, SetFont(), GetPartialTextExtents(), GetTextExtent()
*/
wxSize GetMultiLineTextExtent(const wxString& string) const;
/**
Fills the @a widths array with the widths from the beginning of @a text
to the corresponding character of @a text. The generic version simply
builds a running total of the widths of each character using
GetTextExtent(), 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.
@beginWxPerlOnly
In wxPerl this method only takes the @a text parameter and
returns the widths as a list of integers.
@endWxPerlOnly
@see GetMultiLineTextExtent(), GetTextExtent()
*/
bool GetPartialTextExtents(const wxString& text,
wxArrayInt& widths) const;
/**
Gets the dimensions of the string using the currently selected font.
@a string is the text string to measure, @a descent is the dimension
from the baseline of the font to the bottom of the descender, and
@a externalLeading is any extra vertical space added to the font by the
font designer (usually is zero).
The text extent is returned in @a w and @a h pointers or as a wxSize
object depending on which version of this function is used.
If the optional parameter @a font is specified and valid, then it is
used for the text extent calculation. Otherwise the currently selected
font is.
@note This function only works with single-line strings.
@beginWxPerlOnly
In wxPerl this method is implemented as GetTextExtent(string,
font = undef) returning a 4-element list (width, height,
descent, externalLeading)
@endWxPerlOnly
@see wxFont, SetFont(), GetPartialTextExtents(),
GetMultiLineTextExtent()
*/
void GetTextExtent(const wxString& string, wxCoord* w, wxCoord* h,
wxCoord* descent = NULL,
wxCoord* externalLeading = NULL,
const wxFont* font = NULL) const;
/**
@overload
@beginWxPerlOnly
Not supported by wxPerl.
@endWxPerlOnly
*/
wxSize GetTextExtent(const wxString& string) const;
//@}
/**
@name Text properties functions
*/
//@{
/**
Returns the current background mode: @c wxPENSTYLE_SOLID or @c wxPENSTYLE_TRANSPARENT.
@see SetBackgroundMode()
*/
int GetBackgroundMode() const;
/**
Gets the current font.
Notice that even although each device context object has some default font
after creation, this method would return a ::wxNullFont initially and only
after calling SetFont() a valid font is returned.
*/
const wxFont& GetFont() const;
/**
Gets the current layout direction of the device context. On platforms
where RTL layout is supported, the return value will either be
@c wxLayout_LeftToRight or @c wxLayout_RightToLeft. If RTL layout is
not supported, the return value will be @c wxLayout_Default.
@see SetLayoutDirection()
*/
wxLayoutDirection GetLayoutDirection() const;
/**
Gets the current text background colour.
@see SetTextBackground()
*/
const wxColour& GetTextBackground() const;
/**
Gets the current text foreground colour.
@see SetTextForeground()
*/
const wxColour& GetTextForeground() const;
/**
@a mode may be one of @c wxPENSTYLE_SOLID and @c wxPENSTYLE_TRANSPARENT.
This setting determines whether text will be drawn with a background
colour or not.
*/
void SetBackgroundMode(int mode);
/**
Sets the current font for the DC.
If the argument is ::wxNullFont (or another invalid font; see wxFont::IsOk),
the current font is selected out of the device context (leaving wxDC without
any valid font), allowing the current font to be destroyed safely.
@see wxFont
*/
void SetFont(const wxFont& font);
/**
Sets the current text background colour for the DC.
*/
void SetTextBackground(const wxColour& colour);
/**
Sets the current text foreground colour for the DC.
@see wxMemoryDC for the interpretation of colours when drawing into a
monochrome bitmap.
*/
void SetTextForeground(const wxColour& colour);
/**
Sets the current layout direction for the device context.
@param dir
May be either @c wxLayout_Default, @c wxLayout_LeftToRight or
@c wxLayout_RightToLeft.
@see GetLayoutDirection()
*/
void SetLayoutDirection(wxLayoutDirection dir);
//@}
/**
@name Bounding box functions
*/
//@{
/**
Adds the specified point to the bounding box which can be retrieved
with MinX(), MaxX() and MinY(), MaxY() functions.
@see ResetBoundingBox()
*/
void CalcBoundingBox(wxCoord x, wxCoord y);
/**
Gets the maximum horizontal extent used in drawing commands so far.
*/
wxCoord MaxX() const;
/**
Gets the maximum vertical extent used in drawing commands so far.
*/
wxCoord MaxY() const;
/**
Gets the minimum horizontal extent used in drawing commands so far.
*/
wxCoord MinX() const;
/**
Gets the minimum vertical extent used in drawing commands so far.
*/
wxCoord MinY() const;
/**
Resets the bounding box: after a call to this function, the bounding
box doesn't contain anything.
@see CalcBoundingBox()
*/
void ResetBoundingBox();
//@}
/**
@name Page and document start/end functions
*/
//@{
/**
Starts a document (only relevant when outputting to a printer).
@a message is a message to show while printing.
*/
bool StartDoc(const wxString& message);
/**
Starts a document page (only relevant when outputting to a printer).
*/
void StartPage();
/**
Ends a document (only relevant when outputting to a printer).
*/
void EndDoc();
/**
Ends a document page (only relevant when outputting to a printer).
*/
void EndPage();
//@}
/**
@name Bit-Block Transfer operations (blit)
*/
//@{
/**
Copy from a source DC to this DC.
With this method you can specify the destination coordinates and the
size of area to copy which will be the same for both the source and
target DCs. If you need to apply scaling while copying, use
StretchBlit().
Notice that source DC coordinates @a xsrc and @a ysrc are interpreted
using the current source DC coordinate system, i.e. the scale, origin
position and axis directions are taken into account when transforming
them to physical (pixel) coordinates.
@param xdest
Destination device context x position.
@param ydest
Destination device context y position.
@param width
Width of source area to be copied.
@param height
Height of source area to be copied.
@param source
Source device context.
@param xsrc
Source device context x position.
@param ysrc
Source device context y position.
@param logicalFunc
Logical function to use, see SetLogicalFunction().
@param 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:
- Creates a temporary bitmap and copies the destination area into
it.
- Copies the source area into the temporary bitmap using the
specified logical function.
- 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.
- 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.
- ORs the temporary bitmap with the destination area.
- Deletes the temporary bitmap.
This sequence of operations ensures that the source's transparent
area need not be black, and logical functions are supported.
@n @b Note: on Windows, blitting with masks can be speeded up
considerably by compiling wxWidgets with the wxUSE_DC_CACHEING option
enabled. You can also influence whether MaskBlt or the explicit
mask blitting code above is used, by using wxSystemOptions and
setting the @c no-maskblt option to 1.
@param xsrcMask
Source x position on the mask. If both xsrcMask and ysrcMask are
@c -1, xsrc and ysrc will be assumed for the mask source position.
Currently only implemented on Windows.
@param ysrcMask
Source y position on the mask. If both xsrcMask and ysrcMask are
@c -1, xsrc and ysrc will be assumed for the mask source position.
Currently only implemented on Windows.
@remarks There is partial support for Blit() in wxPostScriptDC, under X.
@see StretchBlit(), wxMemoryDC, wxBitmap, wxMask
*/
bool Blit(wxCoord xdest, wxCoord ydest, wxCoord width,
wxCoord height, wxDC* source, wxCoord xsrc, wxCoord ysrc,
wxRasterOperationMode logicalFunc = wxCOPY, bool useMask = false,
wxCoord xsrcMask = wxDefaultCoord, wxCoord ysrcMask = wxDefaultCoord);
/**
Copy from a source DC to this DC possibly changing the scale.
Unlike Blit(), this method allows to specify different source and
destination region sizes, meaning that it can stretch or shrink it
while copying. The same can be achieved by changing the scale of the
source or target DC but calling this method is simpler and can also be
more efficient if the platform provides a native implementation of it.
The meaning of its other parameters is the same as with Blit(), in
particular all source coordinates are interpreted using the source DC
coordinate system, i.e. are affected by its scale, origin translation
and axis direction.
@param xdest
Destination device context x position.
@param ydest
Destination device context y position.
@param dstWidth
Width of destination area.
@param dstHeight
Height of destination area.
@param source
Source device context.
@param xsrc
Source device context x position.
@param ysrc
Source device context y position.
@param srcWidth
Width of source area to be copied.
@param srcHeight
Height of source area to be copied.
@param logicalFunc
Logical function to use, see SetLogicalFunction().
@param 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:
- Creates a temporary bitmap and copies the destination area into
it.
- Copies the source area into the temporary bitmap using the
specified logical function.
- 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.
- 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.
- ORs the temporary bitmap with the destination area.
- Deletes the temporary bitmap.
This sequence of operations ensures that the source's transparent
area need not be black, and logical functions are supported.
@n @b Note: on Windows, blitting with masks can be speeded up
considerably by compiling wxWidgets with the wxUSE_DC_CACHEING option
enabled. You can also influence whether MaskBlt or the explicit
mask blitting code above is used, by using wxSystemOptions and
setting the @c no-maskblt option to 1.
@param xsrcMask
Source x position on the mask. If both xsrcMask and ysrcMask are
wxDefaultCoord, @a xsrc and @a ysrc will be assumed for the mask
source position. Currently only implemented on Windows.
@param ysrcMask
Source y position on the mask. If both xsrcMask and ysrcMask are
wxDefaultCoord, @a xsrc and @a ysrc will be assumed for the mask
source position. Currently only implemented on Windows.
There is partial support for Blit() in wxPostScriptDC, under X.
See wxMemoryDC for typical usage.
@since 2.9.0
@see Blit(), wxMemoryDC, wxBitmap, wxMask
*/
bool StretchBlit(wxCoord xdest, wxCoord ydest,
wxCoord dstWidth, wxCoord dstHeight,
wxDC* source, wxCoord xsrc, wxCoord ysrc,
wxCoord srcWidth, wxCoord srcHeight,
wxRasterOperationMode logicalFunc = wxCOPY,
bool useMask = false,
wxCoord xsrcMask = wxDefaultCoord,
wxCoord ysrcMask = wxDefaultCoord);
//@}
/**
@name Background/foreground brush and pen
*/
//@{
/**
Gets the brush used for painting the background.
@see wxDC::SetBackground()
*/
const wxBrush& GetBackground() const;
/**
Gets the current brush.
@see wxDC::SetBrush()
*/
const wxBrush& GetBrush() const;
/**
Gets the current pen.
@see SetPen()
*/
const wxPen& GetPen() const;
/**
Sets the current background brush for the DC.
*/
void SetBackground(const wxBrush& brush);
/**
Sets the current brush for the DC.
If the argument is ::wxNullBrush (or another invalid brush; see wxBrush::IsOk),
the current brush is selected out of the device context (leaving wxDC without
any valid brush), allowing the current brush to be destroyed safely.
@see wxBrush, wxMemoryDC (for the interpretation of colours when
drawing into a monochrome bitmap)
*/
void SetBrush(const wxBrush& brush);
/**
Sets the current pen for the DC.
If the argument is ::wxNullPen (or another invalid pen; see wxPen::IsOk),
the current pen is selected out of the device context (leaving wxDC without any
valid pen), allowing the current pen to be destroyed safely.
@see wxMemoryDC for the interpretation of colours when drawing into a
monochrome bitmap.
*/
void SetPen(const wxPen& pen);
//@}
/**
Copy attributes from another DC.
The copied attributes currently are:
- Font
- Text foreground and background colours
- Background brush
- Layout direction
@param dc
A valid (i.e. its IsOk() must return @true) source device context.
*/
void CopyAttributes(const wxDC& dc);
/**
Returns the depth (number of bits/pixel) of this DC.
@see wxDisplayDepth()
*/
int GetDepth() const;
/**
Returns the current device origin.
@see SetDeviceOrigin()
*/
wxPoint GetDeviceOrigin() const;
/**
Gets the current logical function.
@see SetLogicalFunction()
*/
wxRasterOperationMode GetLogicalFunction() const;
/**
Gets the current mapping mode for the device context.
@see SetMapMode()
*/
wxMappingMode GetMapMode() const;
/**
Gets in @a colour the colour at the specified location. Not available
for wxPostScriptDC or wxMetafileDC.
@note Setting a pixel can be done using DrawPoint().
@note This method shouldn't be used with wxPaintDC as accessing the DC
while drawing can result in unexpected results, notably in wxGTK.
*/
bool GetPixel(wxCoord x, wxCoord y, wxColour* colour) const;
/**
Returns the resolution of the device in pixels per inch.
*/
wxSize GetPPI() const;
/**
Gets the horizontal and vertical extent of this device context in @e device units.
It can be used to scale graphics to fit the page.
For example, if @e maxX and @e maxY 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:
@code
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));
@endcode
@beginWxPerlOnly
In wxPerl there are two methods instead of a single overloaded
method:
- GetSize(): returns a Wx::Size object.
- GetSizeWH(): returns a 2-element list (width, height).
@endWxPerlOnly
*/
void GetSize(wxCoord* width, wxCoord* height) const;
/**
@overload
*/
wxSize GetSize() const;
/**
Returns the horizontal and vertical resolution in millimetres.
*/
void GetSizeMM(wxCoord* width, wxCoord* height) const;
/**
@overload
*/
wxSize GetSizeMM() const;
/**
Gets the current user scale factor.
@beginWxPerlOnly
In wxPerl this method takes no arguments and return a two
element array (x, y).
@endWxPerlOnly
@see SetUserScale()
*/
void GetUserScale(double* x, double* y) const;
/**
Returns @true if the DC is ok to use.
*/
bool IsOk() const;
/**
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.
@param xLeftRight
True to set the x axis orientation to the natural left to right
orientation, @false to invert it.
@param yBottomUp
True to set the y axis orientation to the natural bottom up
orientation, @false to invert it.
*/
void SetAxisOrientation(bool xLeftRight, bool yBottomUp);
/**
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.
*/
void SetDeviceOrigin(wxCoord x, wxCoord y);
/**
Sets the current logical function for the device context.
It determines how a @e source pixel (from a pen or brush colour, or source
device context if using Blit()) combines with a @e destination pixel in
the current device context.
Text drawing is not affected by this function.
See ::wxRasterOperationMode enumeration values for more info.
The default is @c wxCOPY, which simply draws with the current colour.
The others combine the current colour and the background using a logical
operation. @c wxINVERT is commonly used for drawing rubber bands or moving
outlines, since drawing twice reverts to the original colour.
*/
void SetLogicalFunction(wxRasterOperationMode function);
/**
The mapping mode of the device context defines the unit of measurement
used to convert @e logical units to @e 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 user scale (see
SetUserScale()) 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.
*/
void SetMapMode(wxMappingMode mode);
/**
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 wxPalette
*/
void SetPalette(const wxPalette& palette);
/**
Sets the user scaling factor, useful for applications which require
'zooming'.
*/
void SetUserScale(double xScale, double yScale);
/**
@name Transformation matrix
See the notes about the availability of these functions in the class
documentation.
*/
//@{
/**
Check if the use of transformation matrix is supported by the current
system.
Currently this function always returns @false for non-MSW platforms.
@since 2.9.2
*/
bool CanUseTransformMatrix() const;
/**
Set the transformation matrix.
If transformation matrix is supported on the current system, the
specified @a matrix will be used to transform between wxDC and physical
coordinates. Otherwise the function returns @false and doesn't change
the coordinate mapping.
@since 2.9.2
*/
bool SetTransformMatrix(const wxAffineMatrix2D& matrix);
/**
Return the transformation matrix used by this device context.
By default the transformation matrix is the identity matrix.
@since 2.9.2
*/
wxAffineMatrix2D GetTransformMatrix() const;
/**
Revert the transformation matrix to identity matrix.
@since 2.9.2
*/
void ResetTransformMatrix();
//@}
/**
@name query capabilities
*/
//@{
/**
Does the DC support drawing bitmaps?
*/
bool CanDrawBitmap() const;
/**
Does the DC support calculating the size required to draw text?
*/
bool CanGetTextExtent() const;
//@}
/**
Returns a value that can be used as a handle to the native drawing
context, if this wxDC has something that could be thought of in that
way. (Not all of them do.)
For example, on Windows the return value is an HDC, on OS X it is a
CGContextRef and on wxGTK it will be a GdkDrawable. If the DC is a
wxGCDC then the return value will be the value returned from
wxGraphicsContext::GetNativeContext. A value of NULL is returned if
the DC does not have anything that fits the handle concept.
@since 2.9.5
*/
void* GetHandle() const;
/**
If supported by the platform and the type of DC, fetch the contents of the DC, or a subset of it, as a bitmap.
*/
wxBitmap GetAsBitmap(const wxRect *subrect = NULL) const;
/**
Set the scale to use for translating wxDC coordinates to the physical
pixels.
The effect of calling this function is similar to that of calling
SetUserScale().
*/
void SetLogicalScale(double x, double y);
/**
Return the scale set by the last call to SetLogicalScale().
*/
void GetLogicalScale(double *x, double *y) const;
/**
Change the offset used for translating wxDC coordinates.
@see SetLogicalOrigin(), SetDeviceOrigin()
*/
void SetLogicalOrigin(wxCoord x, wxCoord y);
//@{
/**
Return the coordinates of the logical point (0, 0).
@see SetLogicalOrigin()
*/
void GetLogicalOrigin(wxCoord *x, wxCoord *y) const;
wxPoint GetLogicalOrigin() const;
//@}
};
/**
@class wxDCClipper
wxDCClipper is a helper class for setting a clipping region on a wxDC
during its lifetime.
An object of wxDCClipper class is typically created on the stack so that it
is automatically destroyed when the object goes out of scope. A typical
usage example:
@code
void MyFunction(wxDC& dc)
{
wxDCClipper clip(dc, rect);
// ... drawing functions here are affected by clipping rect ...
}
void OtherFunction()
{
wxDC dc;
MyFunction(dc);
// ... drawing functions here are not affected by clipping rect ...
}
@endcode
@note Unlike other similar classes such as wxDCFontChanger, wxDCClipper
currently doesn't restore the previously active clipping region when it
is destroyed but simply resets clipping on the associated wxDC. This
may be changed in the future wxWidgets versions but has to be taken
into account explicitly in the current one.
@library{wxcore}
@category{gdi}
@see wxDC::SetClippingRegion(), wxDCFontChanger, wxDCTextColourChanger, wxDCPenChanger,
wxDCBrushChanger
*/
class wxDCClipper
{
public:
//@{
/**
Sets the clipping region to the specified region/coordinates.
The clipping region is automatically unset when this object is destroyed.
*/
wxDCClipper(wxDC& dc, const wxRegion& region);
wxDCClipper(wxDC& dc, const wxRect& rect);
wxDCClipper(wxDC& dc, wxCoord x, wxCoord y, wxCoord w, wxCoord h);
//@}
/**
Destroys the clipping region associated with the DC passed to the ctor.
*/
~wxDCClipper();
};
/**
@class wxDCBrushChanger
wxDCBrushChanger is a small helper class for setting a brush on a wxDC
and unsetting it automatically in the destructor, restoring the previous one.
@library{wxcore}
@category{gdi}
@see wxDC::SetBrush(), wxDCFontChanger, wxDCTextColourChanger, wxDCPenChanger,
wxDCClipper
*/
class wxDCBrushChanger
{
public:
/**
Sets @a brush on the given @a dc, storing the old one.
@param dc
The DC where the brush must be temporary set.
@param brush
The brush to set.
*/
wxDCBrushChanger(wxDC& dc, const wxBrush& brush);
/**
Restores the brush originally selected in the DC passed to the ctor.
*/
~wxDCBrushChanger();
};
/**
@class wxDCPenChanger
wxDCPenChanger is a small helper class for setting a pen on a wxDC
and unsetting it automatically in the destructor, restoring the previous one.
@library{wxcore}
@category{gdi}
@see wxDC::SetPen(), wxDCFontChanger, wxDCTextColourChanger, wxDCBrushChanger,
wxDCClipper
*/
class wxDCPenChanger
{
public:
/**
Sets @a pen on the given @a dc, storing the old one.
@param dc
The DC where the pen must be temporary set.
@param pen
The pen to set.
*/
wxDCPenChanger(wxDC& dc, const wxPen& pen);
/**
Restores the pen originally selected in the DC passed to the ctor.
*/
~wxDCPenChanger();
};
/**
@class wxDCTextColourChanger
wxDCTextColourChanger is a small helper class for setting a foreground
text colour on a wxDC and unsetting it automatically in the destructor,
restoring the previous one.
@library{wxcore}
@category{gdi}
@see wxDC::SetTextForeground(), wxDCFontChanger, wxDCPenChanger, wxDCBrushChanger,
wxDCClipper
*/
class wxDCTextColourChanger
{
public:
/**
Trivial constructor not changing anything.
This constructor is useful if you don't know beforehand if the colour
needs to be changed or not. It simply creates the object which won't do
anything in its destructor unless Set() is called -- in which case it
would reset the previous colour.
*/
wxDCTextColourChanger(wxDC& dc);
/**
Sets @a col on the given @a dc, storing the old one.
@param dc
The DC where the colour must be temporary set.
@param col
The colour to set.
*/
wxDCTextColourChanger(wxDC& dc, const wxColour& col);
/**
Set the colour to use.
This method is meant to be called once only and only on the objects
created with the constructor overload not taking wxColour argument and
has the same effect as the other constructor, i.e. sets the colour to
the given @a col and ensures that the old value is restored when this
object is destroyed.
*/
void Set(const wxColour& col);
/**
Restores the colour originally selected in the DC passed to the ctor.
*/
~wxDCTextColourChanger();
};
/**
@class wxDCFontChanger
wxDCFontChanger is a small helper class for setting a font on a wxDC and
unsetting it automatically in the destructor, restoring the previous one.
@since 2.9.0
@library{wxcore}
@category{gdi}
@see wxDC::SetFont(), wxDCTextColourChanger, wxDCPenChanger, wxDCBrushChanger,
wxDCClipper
*/
class wxDCFontChanger
{
public:
/**
Trivial constructor not changing anything.
This constructor is useful if you don't know beforehand if the font
needs to be changed or not. It simply creates the object which won't do
anything in its destructor unless Set() is called -- in which case it
would reset the previous font.
@since 2.9.1
*/
wxDCFontChanger(wxDC& dc);
/**
Sets @a font on the given @a dc, storing the old one.
@param dc
The DC where the font must be temporary set.
@param font
The font to set.
*/
wxDCFontChanger(wxDC& dc, const wxFont& font);
/**
Set the font to use.
This method is meant to be called once only and only on the objects
created with the constructor overload not taking wxColour argument and
has the same effect as the other constructor, i.e. sets the font to
the given @a font and ensures that the old value is restored when this
object is destroyed.
*/
void Set(const wxFont& font);
/**
Restores the font originally selected in the DC passed to the ctor.
*/
~wxDCFontChanger();
};