The R Project SVN R

/* New device driver structure

 * NOTES:

 * 1. All locations and dimensions are in device coordinates.

 * 2. I found this comment in the doc for dev_Open -- looks nasty

 *    Any known instances of such a thing happening?  Should be

 *    replaced by a function to query the device for preferred gpars

 *    settings? (to be called when the device is initialised)

         *

         * NOTE that it is perfectly acceptable for this	

         * function to set generic graphics parameters too	

         * (i.e., override the generic parameter settings	

         * which GInit sets up) all at the author's own risk	

         * of course :)						

	 *

 * 3. Do we really need dev_StrWidth as well as dev_MetricInfo?

 *    I can see the difference between the two -- its just a 

 *    question of whether dev_MetricInfo should just return

 *    what dev_StrWidth would give if font metric information is

 *    not available.  I guess having both allows the developer

 *    to decide when to ask for which sort of value, and to decide

 *    what to do when font metric information is not available.

 *    And why not a dev_StrHeight?

 * 4. Should "ipr", "asp", and "cra" be in the device description?

 *    If not, then where?

 *    I guess they don't need to be if no device makes use of them.

 *    On the other hand, they would need to be replaced by a device

 *    call that R base graphics could use to get enough information

 *    to figure them out.  (e.g., some sort of dpi() function to

 *    complement the size() function.)

 */

typedef struct {

    /* The first element is a boolean indicating whether this is 

     * a new device driver (always 1) -- the old device driver structure

     * has had a similar element added (which will always be 0)

     *

     * This needs to be removed once the old DevDesc structure has been

     * removed from the system.

     */

    int newDevStruct; 

    /********************************************************

     * Device physical characteristics

     ********************************************************/

    double left;	        /* left raster coordinate */

    double right;	        /* right raster coordinate */

    double bottom;	        /* bottom raster coordinate */

    double top;		        /* top raster coordinate */

    /* R only has the notion of a rectangular clipping region

     */

    double clipLeft;

    double clipRight;

    double clipBottom;

    double clipTop;

    /* I hate these next three -- they seem like a real fudge

     * BUT I'm not sure what to replace them with so they stay for now.

     */

    double xCharOffset;	        /* x character addressing offset */

    double yCharOffset;	        /* y character addressing offset */

    double yLineBias;	        /* 1/2 interline space as frac of line hght */

    double ipr[2];	        /* Inches per raster; [0]=x, [1]=y */

    double asp;		        /* Pixel aspect ratio = ipr[1]/ipr[0] */

    /* I hate this guy too -- seems to assume that a device can only

     * have one font size during its lifetime

     * BUT removing/replacing it would take quite a lot of work

     * to design and insert a good replacement so it stays for now.

     */

    double cra[2];	        /* Character size in rasters; [0]=x, [1]=y */

    double gamma;	        /* Device Gamma Correction */

    /********************************************************

     * Device capabilities

     ********************************************************/

    Rboolean canResizePlot;	/* can the graphics surface be resized */

    Rboolean canChangeFont;	/* device has multiple fonts */

    Rboolean canRotateText;	/* text can be rotated */

    Rboolean canResizeText;	/* text can be resized */

    Rboolean canClip;		/* Hardware clipping */

    Rboolean canChangeGamma;    /* can the gamma factor be modified */

    int canHAdj;	        /* Can do at least some horiz adjust of text

    /********************************************************

     * Device initial settings

     ********************************************************/

    /* These are things that the device must set up when it is created.

     * The graphics system can modify them and track current values,

     * but some devices want to know what the original setting was.

     */

    double startps;             

    int startcol;

    int startfill;

    int startlty;

    int startfont;

    double startgamma;

    /********************************************************

     * Device specific information

     ********************************************************/

    void *deviceSpecific;	/* pointer to device specific parameters */

    /********************************************************

     * Device display list

     ********************************************************/

    /* I think it would feel nicer if this stuff was part of the 

     * graphics engine (GEDevDesc), but this is another thing that

     * needs more time to implement a change properly.

     */

    Rboolean displayListOn;     /* toggle for display list status */

    SEXP displayList;           /* display list */

    SEXP savedSnapshot;         /* The last value of the display list

				 * just prior to when the display list

				 * was last initialised

				 */

    /********************************************************

     * Device procedures.

     ********************************************************/

    /*

     * ---------------------------------------

     * GENERAL COMMENT ON GRAPHICS PARAMETERS:

     * ---------------------------------------

     * Graphical parameters are now passed in a graphics context

     * structure (R_GE_gcontext*) rather than individually.

     * Each device action should extract the parameters it needs

     * and ignore the others.  Thought should be given to which 

     * parameters are relevant in each case -- the graphics engine

     * does not REQUIRE that each parameter is honoured, but if

     * a parameter is NOT honoured, it might be a good idea to

     * issue a warning when a parameter is not honoured (or at

     * the very least document which parameters are not honoured

     * in the user-level documentation for the device).  [An example

     * of a parameter that may not be honoured by many devices is

     * transparency.]

     */

    /*

     * device_Activate is called when a device becomes the	

     * active device.  For example, it can be used to change the

     * title of a window to indicate the active status of	

     * the device to the user.  Not all device types will	

     * do anything.			

     * The only parameter is a device driver structure.

     * An example is ...

     *

     * static void   X11_Activate(NewDevDesc *dd);

     *

     */

    void (*activate)();

    /*

     * device_Circle should have the side-effect that a	

     * circle is drawn, centred at the given location, with 

     * the given radius.  The border of the circle should be

     * drawn in the given "col", and the circle should be	

     * filled with the given "fill" colour.		

     * If "col" is NA_INTEGER then no border should be drawn

     * If "fill" is NA_INTEGER then the circle should not 

     * be filled.

     * An example is ...

     *

     * static void X11_Circle(double x, double y, double r,

     *                        R_GE_gcontext *gc,

     *                        NewDevDesc *dd);

     *

     * R_GE_gcontext parameters that should be honoured (if possible):

     *   col, fill, gamma, lty, lwd

     */

    void (*circle)();

    /*

     * device_Clip is given the left, right, bottom, and	

     * top of a rectangle (in DEVICE coordinates).	

     * It should have the side-effect that subsequent output	

     * is clipped to the given rectangle.

     * NOTE that R's graphics engine already clips to the 

     * extent of the device.

     * NOTE also that this will probably only be called if

     * the flag canClip is true.

     * An example is ...

     *

     * static void X11_Clip(double x0, double x1, double y0, double y1, 

     *                      NewDevDesc *dd)

     */

    void (*clip)();

    /*

     * device_Close is called when the device is killed.

     * This function is responsible for destroying any	

     * device-specific resources that were created in	

     * device_Open and for FREEing the device-specific	

     * parameters structure.	

     * An example is ...

     *

     * static void X11_Close(NewDevDesc *dd)

     *

     */

    void (*close)();

    /*

     * device_Deactivate is called when a device becomes	

     * inactive.  

     * This allows the device to undo anything it did in 

     * dev_Activate.

     * Not all device types will do anything.

     * An example is ...

     *

     * static void X11_Deactivate(NewDevDesc *dd)

     *

     */

    void (*deactivate)();

    void (*dot)();

    /*

     * I don't know what this is for and i can't find it	

     * being used anywhere, but i'm loath to kill it in	

     * case i'm missing something important			

     * An example is ...

     *

     * static void X11_Hold(NewDevDesc *dd)

     *

     */

    void (*hold)();

    /*

     * device_Locator should return the location of the next

     * mouse click (in DEVICE coordinates)	

     * Not all devices will do anything (e.g., postscript)	

     * An example is ...

     *

     * static Rboolean X11_Locator(double *x, double *y, NewDevDesc *dd)

     *

     */

    Rboolean (*locator)();

    /*

     * device_Line should have the side-effect that a single

     * line is drawn (from x1,y1 to x2,y2)			

     * An example is ...

     *

     * static void X11_Line(double x1, double y1, double x2, double y2,

     *                      R_GE_gcontext *gc,

     *                      NewDevDesc *dd);

     *

     * R_GE_gcontext parameters that should be honoured (if possible):

     *   col, gamma, lty, lwd

     */

    void (*line)();

    /*

     * device_MetricInfo should return height, depth, and	

     * width information for the given character in DEVICE	

     * units.

     * This is used for formatting mathematical expressions	

     * and for exact centering of text (see GText)		

     * If the device cannot provide metric information then 

     * it MUST return 0.0 for ascent, descent, and width.

     * An example is ...

     *

     * static void X11_MetricInfo(int c,

     *                            R_GE_gcontext *gc,

     *                            double* ascent, double* descent,

     *                            double* width, NewDevDesc *dd);

     *

     * R_GE_gcontext parameters that should be honoured (if possible):

     *   font, cex, ps

     */

    void (*metricInfo)();

    /*

     * device_Mode is called whenever the graphics engine	

     * starts drawing (mode=1) or stops drawing (mode=0)	

     * The device is not required to do anything		

     * An example is ...

     *

     * static void X11_Mode(int mode, NewDevDesc *dd);

     *

     */

    void (*mode)();

    /*

     * device_NewPage is called whenever a new plot requires

     * a new page.	

     * A new page might mean just clearing the	

     * device (e.g., X11) or moving to a new page	

     * (e.g., postscript)					

     * An example is ...

     *

     *

     * static void X11_NewPage(R_GE_gcontext *gc,

     *                         NewDevDesc *dd);

     *

     */

    void (*newPage)();

    /*

     * device_Open is not usually called directly by the	

     * graphics engine;  it is usually only called from	

     * the device-driver entry point.			

     * This function should set up all of the device-	

     * specific resources for a new device			

     * This function is given a newly-allocated NewDevDesc structure 

     * and it must FREE the structure if anything goes seriously wrong.

     * NOTE that different devices will accept different parameter

     * lists, corresponding to different device-specific preferences.

     * An example is ...

     *

     * Rboolean X11_Open(NewDevDesc *dd, char *dsp, double w, double h, 

     *                   double gamma_fac, X_COLORTYPE colormodel, 

     *                   int maxcube, int canvascolor);

     *

     */

    Rboolean (*open)();

    /*

     * device_Polygon should have the side-effect that a	

     * polygon is drawn using the given x and y values	

     * the polygon border should be drawn in the "col"	

     * colour and filled with the "fill" colour.

     * If "col" is NA_INTEGER don't draw the border		

     * If "fill" is NA_INTEGER don't fill the polygon		

     * An example is ...

     *

     * static void X11_Polygon(int n, double *x, double *y, 

     *                         R_GE_gcontext *gc,

     *                         NewDevDesc *dd);

     *

     * R_GE_gcontext parameters that should be honoured (if possible):

     *   col, fill, gamma, lty, lwd

     */

    void (*polygon)();

    /*

     * device_Polyline should have the side-effect that a	

     * series of line segments are drawn using the given x	

     * and y values.

     * An example is ...

     *

     * static void X11_Polyline(int n, double *x, double *y, 

     *                          R_GE_gcontext *gc,

     *                          NewDevDesc *dd);

     *

     * R_GE_gcontext parameters that should be honoured (if possible):

     *   col, gamma, lty, lwd

     */

    void (*polyline)();

    /*

     * device_Rect should have the side-effect that a	

     * rectangle is drawn with the given locations for its	

     * opposite corners.  The border of the rectangle	

     * should be in the given "col" colour and the rectangle	

     * should be filled with the given "fill" colour.

     * If "col" is NA_INTEGER then no border should be drawn 

     * If "fill" is NA_INTEGER then the rectangle should not	

     * be filled.						

     * An example is ...

     *

     * static void X11_Rect(double x0, double y0, double x1, double y1,

     *                      R_GE_gcontext *gc,

     *                      NewDevDesc *dd);

     *

     */

    void (*rect)();

    /*

     * device_Size is called whenever the device is	

     * resized.  

     * The function returns (left, right, bottom, and top) for the	

     * new device size.					

     * This is not usually called directly by the graphics	

     * engine because the detection of device resizes	

     * (e.g., a window resize) are usually detected by	

     * device-specific code.

     * An example is ...

     *

     * static void X11_Size(double *left, double *right,

     *                      double *bottom, double *top,

     *                      NewDevDesc *dd);

     *

     * R_GE_gcontext parameters that should be honoured (if possible):

     *   col, fill, gamma, lty, lwd

     */

    void (*size)();

    /*

     * device_StrWidth should return the width of the given 

     * string in DEVICE units.				

     * An example is ...

     *

     * static double X11_StrWidth(char *str, 

     *                            R_GE_gcontext *gc,

     *                            NewDevDesc *dd)

     *

     * R_GE_gcontext parameters that should be honoured (if possible):

     *   font, cex, ps

     */

    double (*strWidth)();

    /*

     * device_Text should have the side-effect that the	

     * given text is drawn at the given location.

     * The text should be rotated according to rot (degrees)

     * An example is ...

     *

     * static void X11_Text(double x, double y, char *str, 

     *                      double rot, double hadj, 

     *                      R_GE_gcontext *gc,

     * 	                    NewDevDesc *dd);

     *

     * R_GE_gcontext parameters that should be honoured (if possible):

     *   font, cex, ps, col, gamma

     */

    void (*text)();

} NewDevDesc;

	/********************************************************/

	/* the device-driver entry point is given a device	*/

	/* description structure that it must set up.  this	*/

	/* involves several important jobs ...			*/

	/* (1) it must ALLOCATE a new device-specific parameters*/

	/* structure and FREE that structure if anything goes	*/

	/* wrong (i.e., it won't report a successful setup to	*/

	/* the graphics engine (the graphics engine is NOT	*/

	/* responsible for allocating or freeing device-specific*/

	/* resources or parameters)				*/

	/* (2) it must initialise the device-specific resources */

	/* and parameters (mostly done by calling device_Open)	*/

	/* (3) it must initialise the generic graphical		*/

	/* parameters that are not initialised by GInit (because*/

	/* only the device knows what values they should have)	*/

	/* see Graphics.h for the official list of these	*/

	/* (4) it may reset generic graphics parameters that	*/

	/* have already been initialised by GInit (although you	*/

	/* should know what you are doing if you do this)	*/

	/* (5) it must attach the device-specific parameters	*/

	/* structure to the device description structure	*/

	/* e.g., dd->deviceSpecfic = (void *) xd;		*/

	/* (6) it must FREE the overall device description if	*/

	/* it wants to bail out to the top-level		*/

	/* the graphics engine is responsible for allocating	*/

	/* the device description and freeing it in most cases	*/

	/* but if the device driver freaks out it needs to do	*/

	/* the clean-up itself					*/

	/********************************************************/