.\" This is a wxWidgets manpage page generated from the XML docs .TH wxDC 3wx 2005-02-15 "wxWidgets" "wxWidgets class documentation" .SH NAME wxDC \- The device context base class .SH DESCRIPTION A wxDC is a 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. Derived types of wxDC have documentation for specific features only, so refer to this section for most device context information. Please note that in addition to the versions of the methods documented here, there are also versions which accept single wxPoint parameter instead of two wxCoord ones or wxPoint and wxSize instead of four of them. .SH "PARENTS" wxObject .SH "INCLUDE FILES" wx/dc.h .SH MEMBERS .SS wxDC () Constructor. .SS ~wxDC () Destructor. .SS void BeginDrawing () Allows optimization of drawing code under MS Windows. Enclose drawing primitives between BeginDrawing and EndDrawing calls. Drawing to a wxDialog panel device context outside of a system-generated OnPaint event requires this pair of calls to enclose drawing code. This is because a Windows dialog box does not have a retained device context associated with it, and selections such as pen and brush settings would be lost if the device context were obtained and released for each drawing operation. .SS bool Blit (wxCoord xdestwxCoord ydestwxCoord widthwxCoord heightwxDC* sourcewxCoord xsrcwxCoord ysrcint logicalFunc = wxCOPYbool useMask = falsewxCoord xsrcMask = -1wxCoord ysrcMask = -1) .SS static bool CacheEnabled () .SS void CalcBoundingBox (wxCoord xwxCoord y) Adds the specified point to the bounding box which can be retrieved with MinX , MaxX and MinY , MaxY functions. .SS void Clear () Clears the device context using the current background brush. \begin{comment} .SS static void ClearCache () .SS virtual void ComputeScaleAndOrigin () 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. .SS void CrossHair (wxCoord xwxCoord 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. .SS void DestroyClippingRegion () Destroys the current clipping region so that none of the DC is clipped. See also wxDC::SetClippingRegion . .SS wxCoord DeviceToLogicalX (wxCoord x) Convert device X coordinate to logical coordinate, using the current mapping mode. .SS wxCoord DeviceToLogicalXRel (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. .SS wxCoord DeviceToLogicalY (wxCoord y) Converts device Y coordinate to logical coordinate, using the current mapping mode. .SS wxCoord DeviceToLogicalYRel (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. .SS void DrawArc (wxCoord x1wxCoord y1wxCoord x2wxCoord y2wxCoord xcwxCoord yc) Draws an arc of a circle, centred on ( xc, yc ), with starting point ( x1, y1 ) and ending at ( 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. .SS void DrawBitmap (const wxBitmap& bitmapwxCoord xwxCoord ybool transparent) Draw a bitmap on the device context at the specified point. If 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 SetTextForeground , SetTextBackground and wxMemoryDC . .SS void DrawCheckMark (wxCoord xwxCoord ywxCoord widthwxCoord height) .SS void DrawCheckMark (const wxRect &rect) Draws a check mark inside the given rectangle. .SS void DrawCircle (wxCoord xwxCoord ywxCoord radius) .SS void DrawCircle (const wxPoint& ptwxCoord radius) Draws a circle with the given centre and radius. .SS void DrawEllipse (wxCoord xwxCoord ywxCoord widthwxCoord height) .SS void DrawEllipse (const wxPoint& ptconst wxSize& size) .SS void DrawEllipse (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. .SS void DrawEllipticArc (wxCoord xwxCoord ywxCoord widthwxCoord heightdouble startdouble 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. x and y specify the x and y coordinates of the upper-left corner of the rectangle that contains the ellipse. width and height specify the width and height of the rectangle that contains the ellipse. start and 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 start is equal to end , a complete ellipse will be drawn. .SS void DrawIcon (const wxIcon& iconwxCoord xwxCoord 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. .SS virtual void DrawLabel (const wxString& textconst wxBitmap& imageconst wxRect& rectint alignment = wxALIGN_LEFTint indexAccel = -1wxRect *rectBounding = NULL) .SS void DrawLabel (const wxString& textconst wxRect& rectint alignment = wxALIGN_LEFTint 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. .SS void DrawLine (wxCoord x1wxCoord y1wxCoord x2wxCoord 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 not part of the line and is not drawn by this function (this is consistent with the behaviour of many other toolkits). .SS void DrawLines (int nwxPoint points[]wxCoord xoffset = 0wxCoord yoffset = 0) .SS void DrawLines (wxList *pointswxCoord xoffset = 0wxCoord yoffset = 0) Draws lines using an array of points of size 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. .SS void DrawPolygon (int nwxPoint points[]wxCoord xoffset = 0wxCoord yoffset = 0int fill_style = wxODDEVEN_RULE) .SS void DrawPolygon (wxList *pointswxCoord xoffset = 0wxCoord yoffset = 0int fill_style = wxODDEVEN_RULE) Draws a filled polygon using an array of points of size n , or list of pointers to points, adding the optional offset coordinate. The last argument specifies the fill rule: wxODDEVEN_RULE (the default) or 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. .SS void DrawPolyPolygon (int nint count[]wxPoint points[]wxCoord xoffset = 0wxCoord yoffset = 0int fill_style = wxODDEVEN_RULE) Draws two or more filled polygons using an array of 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. n specifies the number of polygons to draw, the array count of size n specifies the number of points in each of the polygons in the points array. The last argument specifies the fill rule: wxODDEVEN_RULE (the default) or 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 DrawPolyPolygon are not closed automatically. .SS void DrawPoint (wxCoord xwxCoord 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.. .SS void DrawRectangle (wxCoord xwxCoord ywxCoord widthwxCoord 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. .SS void DrawRotatedText (const wxString& textwxCoord xwxCoord ydouble angle) Draws the text rotated by angle degrees. NB: Under Win9x only TrueType fonts can be drawn by this function. In particular, a font different from wxNORMAL_FONT should be used as the latter is not a TrueType font. wxSWISS_FONT is an example of a font which is. .SS void DrawRoundedRectangle (wxCoord xwxCoord ywxCoord widthwxCoord heightdouble 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 radius is positive, the value is assumed to be the radius of the rounded corner. If radius is negative, the absolute value is assumed to be the 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. .SS void DrawSpline (int nwxPoint points[]) Draws a spline between all given control points, using the current pen. .SS void DrawSpline (wxList *points) Draws a spline between all given control points, using the current pen. Doesn't delete the wxList and contents. .SS void DrawSpline (wxCoord x1wxCoord y1wxCoord x2wxCoord y2wxCoord x3wxCoord y3) Draws a three-point spline using the current pen. .SS void DrawText (const wxString& textwxCoord xwxCoord 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 wxDC::GetTextExtent for how to get the dimensions of a text string, which can be used to position the text more precisely. NB: under wxGTK the current logical function 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} .SS static void EnableCache (bool enableCache) .SS void EndDoc () Ends a document (only relevant when outputting to a printer). .SS void EndDrawing () Allows optimization of drawing code under MS Windows. Enclose drawing primitives between BeginDrawing and EndDrawing calls. .SS void EndPage () Ends a document page (only relevant when outputting to a printer). .SS bool FloodFill (wxCoord xwxCoord yconst wxColour& colourint style = wxFLOOD_SURFACE) 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. Returns 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. .SS const wxBrush& GetBackground () Gets the brush used for painting the background (see wxDC::SetBackground ). .SS int GetBackgroundMode () Returns the current background mode: wxSOLID or wxTRANSPARENT . .SS const wxBrush& GetBrush () Gets the current brush (see wxDC::SetBrush ). .SS wxCoord GetCharHeight () Gets the character height of the currently set font. .SS wxCoord GetCharWidth () Gets the average character width of the currently set font. .SS void GetClippingBox (wxCoord *xwxCoord *ywxCoord *widthwxCoord *height) Gets the rectangle surrounding the current clipping region. .SS const wxFont& GetFont () Gets the current font (see wxDC::SetFont ). .SS int GetLogicalFunction () Gets the current logical function (see wxDC::SetLogicalFunction ). .SS int GetMapMode () Gets the mapping mode for the device context (see wxDC::SetMapMode ). .SS bool GetPartialTextExtents (const wxString& textwxArrayInt& widths) Fills the widths array with the widths from the beginning of text to the corresponding character of 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. .SS const wxPen& GetPen () Gets the current pen (see wxDC::SetPen ). .SS bool GetPixel (wxCoord xwxCoord ywxColour *colour) Gets in colour the colour at the specified location. Not available for wxPostScriptDC or wxMetafileDC. Note that setting a pixel can be done using DrawPoint . .SS wxSize GetPPI () Returns the resolution of the device in pixels per inch. .SS void GetSize (wxCoord *widthwxCoord *height) .SS wxSize GetSize () This gets the horizontal and vertical resolution in device units. It can be used to scale graphics to fit the page. For example, if maxX and 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: 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)); .SS void GetSizeMM (wxCoord *widthwxCoord *height) .SS wxSize GetSizeMM () Returns the horizontal and vertical resolution in millimetres. .SS const wxColour& GetTextBackground () Gets the current text background colour (see wxDC::SetTextBackground ). .SS void GetTextExtent (const wxString& stringwxCoord *wwxCoord *hwxCoord *descent = NULLwxCoord *externalLeading = NULLwxFont *font = NULL) Gets the dimensions of the string using the currently selected font. string is the text string to measure, w and h are the total width and height respectively, descent is the dimension from the baseline of the font to the bottom of the descender, and externalLeading is any extra vertical space added to the font by the font designer (usually is zero). The optional parameter font specifies an alternative to the currently selected font: but note that this does not yet work under Windows, so you need to set a font for the device context first. See also wxFont , wxDC::SetFont . .SS const wxColour& GetTextForeground () Gets the current text foreground colour (see wxDC::SetTextForeground ). .SS void GetUserScale (double *xdouble *y) Gets the current user scale factor (set by SetUserScale ). .SS wxCoord LogicalToDeviceX (wxCoord x) Converts logical X coordinate to device coordinate, using the current mapping mode. .SS wxCoord LogicalToDeviceXRel (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. .SS wxCoord LogicalToDeviceY (wxCoord y) Converts logical Y coordinate to device coordinate, using the current mapping mode. .SS wxCoord LogicalToDeviceYRel (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. .SS wxCoord MaxX () Gets the maximum horizontal extent used in drawing commands so far. .SS wxCoord MaxY () Gets the maximum vertical extent used in drawing commands so far. .SS wxCoord MinX () Gets the minimum horizontal extent used in drawing commands so far. .SS wxCoord MinY () Gets the minimum vertical extent used in drawing commands so far. .SS bool Ok () Returns true if the DC is ok to use. .SS void ResetBoundingBox () Resets the bounding box: after a call to this function, the bounding box doesn't contain anything. .SS void SetAxisOrientation (bool xLeftRightbool 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. .SS void SetBackground (const wxBrush& brush) Sets the current background brush for the DC. .SS void SetBackgroundMode (int mode) mode may be one of wxSOLID and wxTRANSPARENT. This setting determines whether text will be drawn with a background colour or not. .SS void SetBrush (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 wxBrush . See also wxMemoryDC for the interpretation of colours when drawing into a monochrome bitmap. .SS void SetClippingRegion (wxCoord xwxCoord ywxCoord widthwxCoord height) .SS void SetClippingRegion (const wxPoint& ptconst wxSize& sz) .SS void SetClippingRegion (const wxRect& rect) .SS void SetClippingRegion (const wxRegion& region) .SS void SetDeviceOrigin (wxCoord xwxCoord 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. .SS void SetFont (const wxFont& font) Sets the current font for the DC. It must be a valid font, in particular you should not pass wxNullFont to this method. See also wxFont . .SS void SetLogicalFunction (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 wxDC::Blit ) 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: 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 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. .SS void SetMapMode (int int) The 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 user scale (see wxDC::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. The mapping mode can be one of the following: wxMM_TWIPS Each logical unit is 1/20 of a point, or 1/1440 of an inch. wxMM_POINTS Each logical unit is a point, or 1/72 of an inch. wxMM_METRIC Each logical unit is 1 mm. wxMM_LOMETRIC Each logical unit is 1/10 of a mm. wxMM_TEXT Each logical unit is 1 pixel. .SS void SetPalette (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 wxPalette for further details. .SS void SetPen (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 wxMemoryDC for the interpretation of colours when drawing into a monochrome bitmap. .SS void SetTextBackground (const wxColour& colour) Sets the current text background colour for the DC. .SS void SetTextForeground (const wxColour& colour) Sets the current text foreground colour for the DC. See also wxMemoryDC for the interpretation of colours when drawing into a monochrome bitmap. .SS void SetUserScale (double xScaledouble yScale) Sets the user scaling factor, useful for applications which require `zooming'. .SS bool StartDoc (const wxString& message) Starts a document (only relevant when outputting to a printer). Message is a message to show while printing. .SS bool StartPage () Starts a document page (only relevant when outputting to a printer). .SH "SEE ALSO" wxObject Overview .SH "AUTHORS" Documentation content by Julian Smart, Robert Roebling, Vadim Zeitlin, Robin Dunn, et al Conversion to manpage format by Arnout Engelen (http://bzzt.net), bugreports welcome.