AST_GRFSET

Register a graphics routine for use by a Plot

Description:

This routine can be used to select the underlying graphics routines to be used when the supplied Plot produces graphical output. If this routine is not called prior to producing graphical output, then the underlying graphics routines selected at link-time (using the ast_link command) will be used. To use alternative graphics routines, call this routine before the graphical output is created, specifying the graphics routines to be used. This will register the routine for future use, but the routine will not actually be used until the Grf attribute is given a non-zero value.

Invocation

CALL AST_GRFSET( THIS, NAME, FUN, STATUS )

Arguments

THIS = INTEGER (Given)
Pointer to the Plot.
NAME = CHARACTER $\ast$ ( $\ast$ ) (Given)
A name indicating the graphics routine to be replaced. Various graphics routines are used by the Plot class, and any combination of them may be supplied by calling this routine once for each routine to be replaced. If any of the graphics routines are not replaced in this way, the corresponding routines in the graphics interface selected at link-time (using the ast_link command) are used. The allowed function names are:
• Attr - Enquire or set a graphics attribute value

• BBuf - Start a new graphics buffering context

• Cap - Inquire a capability

• EBuf - End the current graphics buffering context

• Flush - Flush all pending graphics to the output device

• Line - Draw a polyline (i.e. a set of connected lines)

• Mark - Draw a set of markers

• Qch - Return the character height in world coordinates

• Scales - Get the axis scales

• Text - Draw a character string

• TxExt - Get the extent of a character string

The string is case insensitive. For details of the interface required for each, see the sections below.

FUN = INTEGER FUNCTION (Given)
The name of the routine to be used to provide the functionality indicated by parameter NAME (the name should also appear in a Fortran EXTERNAL statement in the routine which invokes AST_GRFSET).

Once a routine has been provided, the " null" routine AST_NULL can be supplied in a subsequent call to astGrfSet to reset the routine to the corresponding routine in the graphics interface selected at link-time. AST_NULL is defined in the AST_PAR include file.

STATUS = INTEGER (Given and Returned)
The global status.

Function Interfaces

All the functions listed below (except for " Cap" ) should return an integer value of 0 if an error occurs, and 1 otherwise. All x and y values refer to " graphics cordinates" as defined by the GRAPHBOX parameter of the AST_PLOT call which created the Plot.

The first argument (GRFCON) for each function is an AST KeyMap pointer that can be used by the called function to establish the context in which it is being called. The contents of the KeyMap are determined by the calling application, which should obtain a pointer to the KeyMap using the AST_GETGRFCONTEXT routine, and then store any necessary information in the KeyMap using the methods of the KeyMap class. Note, the functions listed below should never annul or delete the supplied KeyMap pointer.

Attr

The " Attr" function returns the current value of a specified graphics attribute, and optionally establishes a new value. The supplied value is converted to an integer value if necessary before use. It requires the following interface:

INTEGER FUNCTION ATTR( GRFCON, ATT, VAL, OLDVAL, PRIM )

• GRFCON = INTEGER (Given) - A KeyMap containing information passed from the calling application.

• ATT = INTEGER (Given) - An integer identifying the required attribute. The following symbolic values are defined in GRF_PAR: GRF__STYLE (Line style), GRF__WIDTH (Line width), GRF__SIZE (Character and marker size scale factor), GRF__FONT (Character font), GRF__COLOUR (Colour index).

• VAL = DOUBLE PRECISION (Given) - no value is stored.

• OLDVAL = DOUBLE PRECISION (Returned) - Returned holding the attribute value.

• PRIM = INTEGER (Given) - The sort of graphics primitive to be drawn with the new attribute. Identified by the following values defined in GRF_PAR: GRF__LINE, GRF__MARK, GRF__TEXT.

BBuf

The " BBuf" function should start a new graphics buffering context. A matching call to the function " EBuf" should be used to end the context. The nature of the buffering is determined by the underlying graphics system.

INTEGER FUNCTION BBUF( GRFCON )

• GRFCON = INTEGER (Given) - A KeyMap containing information passed from the calling application.

Cap

The " Cap" function is called to determine if the grf module has a given capability, as indicated by the " cap" argument:

INTEGER FUNCTION CAP( GRFCON, CAP, VALUE )

• GRFCON = INTEGER (Given) - A KeyMap containing information passed from the calling application.

• CAP = INTEGER (Given) The capability being inquired about. This will be one of the following constants defined in GRF_PAR:

GRF__SCALES: This function should return a non-zero value if the " Scales" function is implemented, and zero otherwise. The supplied VALUE argument should be ignored.

GRF__MJUST: This function should return a non-zero value if the " Text" and " TxExt" functions recognise " M" as a character in the justification string. If the first character of a justification string is " M" , then the text should be justified with the given reference point at the bottom of the bounding box. This is different to " B" justification, which requests that the reference point be put on the baseline of the text, since some characters hang down below the baseline. If the " Text" or " TxExt" function cannot differentiate between " M" and " B" , then this function should return zero, in which case " M" justification will never be requested by Plot. The supplied VALUE argument should be ignored.

GRF__ESC: This function should return a non-zero value if the " Text" and " TxExt" functions can recognise and interpret graphics escape sequences within the supplied string (see attribute Escape). Zero should be returned if escape sequences cannot be interpreted (in which case the Plot class will interpret them itself if needed). The supplied VALUE argument should be ignored only if escape sequences cannot be interpreted by " Text" and " TxExt" . Otherwise, VALUE indicates whether " Text" and " TxExt" should interpret escape sequences in subsequent calls. If VALUE is non-zero then escape sequences should be interpreted by " Text" and " TxExt" . Otherwise, they should be drawn as literal text.

• VALUE = INTEGER (Given) The use of this parameter depends on the value of CAP as described above.

• Returned Function Value: The value returned by the function depends on the value of CAP as described above. Zero should be returned if the supplied capability is not recognised.

EBuf

The " EBuf" function should end the current graphics buffering context. See the description of " BBuf" above for further details. It requires the following interface:

INTEGER FUNCTION EBUF( GRFCON )

• GRFCON = INTEGER (Given) - A KeyMap containing information passed from the calling application.

Flush

The " Flush" function ensures that the display device is up-to-date, by flushing any pending graphics to the output device. It requires the following interface:

INTEGER FUNCTION FLUSH( GRFCON )

• GRFCON = INTEGER (Given) - A KeyMap containing information passed from the calling application.

Line

The " Line" function displays lines joining the given positions and requires the following interface:

INTEGER FUNCTION LINE( GRFCON, N, X, Y )

• GRFCON = INTEGER (Given) - A KeyMap containing information passed from the calling application.

• N = INTEGER (Given) - The number of positions to be joined together.

• X( N ) = REAL (Given) - An array holding the " n" x values.

• Y( N ) = REAL (Given) - An array holding the " n" y values.

Mark

The " Mark" function displays markers at the given positions. It requires the following interface:

INTEGER FUNCTION MARK( GRFCON, N, X, Y, TYPE )

• GRFCON = INTEGER (Given) - A KeyMap containing information passed from the calling application.

• N = INTEGER (Given) - The number of positions to be marked.

• X( N ) = REAL (Given) - An array holding the " n" x values.

• Y( N ) = REAL (Given) - An array holding the " n" y values.

• TYPE = INTEGER (Given) - An integer which can be used to indicate the type of marker symbol required.

Qch

The " Qch" function returns the heights of characters drawn vertically and horizontally in graphics coordinates. It requires the following interface:

INTEGER FUNCTION QCH( GRFCON, CHV, CHH )

• GRFCON = INTEGER (Given) - A KeyMap containing information passed from the calling application.

• CHV = REAL (Returned) The height of characters drawn with a vertical baseline. This will be an increment in the X axis.

• CHH = REAL (Returned) The height of characters drawn with a horizontal baseline. This will be an increment in the Y axis.

Scales

The " Scales" function returns two values (one for each axis) which scale increments on the corresponding axis into a " normal" coordinate system in which: 1) the axes have equal scale in terms of (for instance) millimetres per unit distance, 2) X values increase from left to right, and 3) Y values increase from bottom to top. It requires the following interface:

INTEGER FUNCTION SCALES( GRFCON, ALPHA, BETA )

• GRFCON = INTEGER (Given) - A KeyMap containing information passed from the calling application.

• ALPHA = REAL (Returned) The scale for the X axis (i.e. Xnorm = alpha$\ast$Xworld).

• BETA = REAL (Returned) The scale for the Y axis (i.e. Ynorm = beta$\ast$Yworld).

Text

The " Text" function displays a character string at a given position using a specified justification and up-vector. It requires the following interface:

INTEGER FUNCTION TEXT( GRFCON, TEXT, X, Y, JUST, UPX, UPY )

• GRFCON = INTEGER (Given) - A KeyMap containing information passed from the calling application.

• TEXT = CHARACTER $\ast$ ( $\ast$ ) (Given) - The string to be displayed.

• X = REAL (Given) - The reference x coordinate.

• Y = REAL (Given) - The reference y coordinate.

• JUST = CHARACTER $\ast$ ( $\ast$ ) (Given ) - A string which specifies the location within the text string which is to be placed at the reference position given by x and y. The first character may be ’ T’ for " top" , ’ C’ for " centre" , or ’ B’ for " bottom" , and specifies the vertical location of the reference position. Note, " bottom" corresponds to the base-line of normal text. Some characters (eg " y" , " g" , " p" , etc) descend below the base-line. The second character may be ’ L’ for " left" , ’ C’ for " centre" , or ’ R’ for " right" , and specifies the horizontal location of the reference position. If the string has less than 2 characters then ’ C’ is used for the missing characters.

• UPX = REAL (Given) - The x component of the up-vector for the text. If necessary the supplied value should be negated to ensure that positive values always refer to displacements from left to right on the screen.

• UPX = REAL (Given) - The y component of the up-vector for the text. If necessary the supplied value should be negated to ensure that positive values always refer to displacements from bottom to top on the screen.

TxExt

The " TxExt" function returns the corners of a box which would enclose the supplied character string if it were displayed using the Text function described above. The returned box includes any leading or trailing spaces. It requires the following interface:

INTEGER FUNCTION TXEXT( GRFCON, TEXT, X, Y, JUST, UPX, UPY, XB, YB )

• GRFCON = INTEGER (Given) - A KeyMap containing information passed from the calling application.

• TEXT = CHARACTER $\ast$ ( $\ast$ ) (Given) - The string to be displayed.

• X = REAL (Given) - The reference x coordinate.

• Y = REAL (Given) - The reference y coordinate.

• JUST = CHARACTER $\ast$ ( $\ast$ ) (Given ) - A string which specifies the location within the text string which is to be placed at the reference position given by x and y. See " Text" above.

• UPX = REAL (Given) - The x component of the up-vector for the text. See " Text" above.

• UPX = REAL (Given) - The y component of the up-vector for the text. See " Text" above.

• XB( 4 ) = REAL (Returned) - Returned holding the x coordinate of each corner of the bounding box.

• YB( 4 ) = REAL (Returned) - Returned holding the y coordinate of each corner of the bounding box.