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X-CAD Database format ===================== The following document describes the X-CAD database format as used in the. xdr files created by X-CAD versions 1.3 and 1.4 and X-SKETCH. The file consists of a header followed by two or more blocks describing each entity or object held in the database. The block descriptions that follow use the C language structure type to define each element belonging to a block. The space considerations for each element type are: byte One 8 bit byte. short Two byte integer. long Four byte integer. float Four byte floating point number. double Eight byte floating point number. File Header =========== The file header consists of 5 data elements describing the type, revision and size of the. xdr file. struct HEADER { long ID; short REV; long ENTS; long MEMREQ; short FLAGS; } ID This is the file identifier - a 4 byte code that must be equal to the string "ACDR". REV The drawing file revision number. ENTS The number of entity blocks that follow this header block. MEMREQ The total amount of data ( as a number of bytes ) in this file excluding the header block. FLAGS Bit encoded flags: Bit 0 on = This drawing file contains no graphics information ( there are no GIBLOCKs or GBBLOCKS in this file ). Bit 1 on = This drawing file contains a password. If this bit is set, then the header block is followed by 8 bytes containing a coded password. ( Currently unused ). Entity Blocks ============= Following the file header are two or more entity blocks. Each block contains the total description for an entity. Entity blocks are formatted as follows: INDEX [] denotes optional HIBLOCK (s) denotes block may be repeated EHBLOCK EDBLOCK(s) [ GIBLOCK(s) ] [ GBBLOCK(s) ] Entity Index ============ The entity index is a 2 byte unsigned integer containg the unique index number of this entity. The index number is used as a reference throughout an X-CAD drawing file and database. Entity index numbers are allocated according to the following criteria: Index 1 The drawing entity. Index 2 The SHEET viewport. Index 3-33 Auxiliary viewports. Index 34-512 Attribute entities. Index 513-1024 Reserved. Index 1025-65535 Drawing entities. Entity HIBLOCK ============== The entity HIBLOCK is a data structure containing the basic information about this entity. An HIBLOCK always follows the entity index. struct HIBLOCK { struct EHBLOCK *EHBLOCK; short FLAGS1; short FLAGS2; struct GIBLOCK *GRAPHICS; } EHBLOCK Used as a pointer to an EHBLOCK structure when the .xdr file is loaded, but has no meaning within the .xdr file. FLAGS1 Bit encoded word: 0-4 Entity type 5 Transient bit used by redraw routines 6 On if entity is visible 7 On if entity identified by IDENTS 8-15 Entity layer FLAGS2 Bit encoded word: 0-4 Viewport number ( +2 = index number of viewport entity ) 5-8 Entity depth 9 Non-delete flag 10 On if entity is tagged by IDENTS 11 On if entity is highlighted 12 On if entity is currently displayed 13-14 Transient bits used by symbols 15 Transient bit used for family tracing GRAPHICS Used internally as a pointer to the first GIBLOCK for this entity. If GRAPHICS is non-zero, then a GIBLOCK will follow on after the last EDBLOCK. If GRAPHICS is zero then there are no GIBLOCKs present. This element should be ignore if bit 0 is set in the FLAGS element of the file header. Entity EHBLOCK ============== The entity EHBLOCK is a data structure containing additional information about each entity. An EHBLOCK always follows the HIBLOCK. struct EHBLOCK { struct EDBLOCK *FIRST; short FLAGS; short AWORD1; short AWORD2; short AWORD3; } FIRST Used internally as a pointer to the first EDBLOCK that follows this EHBLOCK. If FIRST is non-zero, then one or more EDBLOCKs follow. If FIRST is zero, there are no EDBLOCKs present. FLAGS Unused. AWORD1/2/3 Three 2 byte words available internally to any application. Entity EDBLOCK ============== An entity EDBLOCK is a structure containing a block of data or a set of parameters relevent to the entity. Each entity can contain one or more EDBLOCKs that make up the database description of the entity. struct EDBLOCK { struct EDBLOCK *NEXT; unsigned char *BLOCKID; unsigned char *SUBID; long LENGTH; } DATA NEXT Used internally as a pointer to the next EDBLOCK. If NEXT is non-zero then another EDBLOCK follows on from this one. If NEXT is zero then there are no more EDBLOCKs present. BLOCKID The data block identifier used to determine the type of data found after the EDBLOCK. SUBID The data block sub-identifier. LENGTH The length of the data block in bytes ( always an even number ). DATA The actual data. The format of this is dependent on the BLOCKID and SUBID. Entity GIBLOCK ============== The entity GIBLOCK data structure contains information about the display list data associated with this entity. GIBLOCKs are only present if the GRAPHICS element is non-zero in the entity HIBLOCK, and only then if bit 0 in the FLAGS element of the file header is not set. struct GIBLOCK { struct GIBLOCK *NEXT; unsigned char *LAYOFF; unsigned char *DEPOFF; struct GBBLOCK *FIRST; } NEXT Used internally as a pointer to the next GIBLOCK. If NEXT is non-zero, then another GIBLOCK follows on after any GBBLOCKs associated with this GIBLOCK. If NEXT is zero there are no more GIBLOCKs present. LAYOFF Contains a layer offset to apply to all display list data associated with this GIBLOCK. ie the actual layer is ( entity layer + LAYOFF ) mod 256 . DEPOFF Contains a depth offset to apply to all display list data associated with this GIBLOCK. ie the actual depth is ( entity depth + DEPOFF ) mod 8 . FIRST Used internally as a pointer to the first GBBLOCK associated with this GIBLOCK. Any GBBLOCKs associated with a GIBLOCK follow before the next GIBLOCK in the list. If FIRST is non- zero a GBBLOCK follows. If FIRST is zero, there are no GBBLOCKs associated with this GIBLOCK. Entity GBBLOCK ============== The entity GBBLOCK contains display list data associated with the last GIBLOCK. Display list data is in the form of a vector list describing what is actually shown on the screen. struct GBBLOCK { struct GBBLOCK *NEXT; unsigned char TYPE; unsigned char FLAGS; long SIZE; } DATA NEXT Used internally as a pointer to the next GBBLOCK in this list. If NEXT is non-zero another GBBLOCK follows this one. If GBBLOCK is zero there are no more GBBLOCKs in this list. TYPE The display list data block type. =1 Stroke vector list =2 Filled polygon vector list =3 Filled line vector list =4 Non-scaled symbol coordinate list FLAGS Unused. SIZE The size of the display list data block in bytes. DATA The display list data block. The contents of this data block are dependent on the TYPE element. ( See section on GBBLOCK data ). Entity Types ============ Entity types are represented by a number between 0 and 31 encoded in the FLAGS1 element of the HIBLOCK. The entity types current used by X-CAD are as follows: 0 Drawing parameters entity 1 Viewport entity 2 Attribute entity 3 String entity 4 Arc entity 5 Ellipse entity 6 Construction point entity 7 Polygon entity 8 Line entity 9 Spline entity 10 Cross-hatch polygon entity 11 Text entity 12 Text-node entity 13 Dimension entity 14 Symbol entity 15 Terminal entity 16 Netline entity 17-31 Not allocated EDBLOCKS Associated with entity types ===================================== Each entity type must have one or more EDBLOCKs associated with it. The following list shows which EDBLOCK types must be present to correctly define the entity in the X-CAD drawing database. Entity type: 0 Drawing parameters entity BLOCKID 2 Drawing parameters data. Entity type: 1 Viewport entity BLOCKID 1 Viewport parameters. Entity type: 2 Attribute entity BLOCKID 12 Text string - contains attribute name. BLOCKID 13 Child member list - lists all entities with this attribute. Entity type: 3 String entity BLOCKID 3 Coordinate list. Entity type: 4 Arc entity BLOCKID 3 Coordinate list - describes arc origin. BLOCKID 5 Arc parameters. Entity type: 5 Ellipse entity BLOCKID 3 Coordinate list - describes ellipse origin. BLOCKID 6 Ellipse parameters. Entity type: 6 Construction point entity BLOCKID 3 Coordinate list. Entity type: 7 Polygon entity BLOCKID 3 Coordinate list - each boundary within the polygon entity is described with a separate type 3 EDBLOCK. Entity type: 8 Line entity BLOCKID 3 Coordinate list. Entity type: 9 Spline entity BLOCKID 3 Coordinate list - describes spline control points. Entity type: 10 Cross-hatch polygon entity BLOCKID 3 Coordinate list - each boundary within the polygon entity is described with a separate type 3 EDBLOCK. BLOCKID 8 Xhatch parameters. Entity type: 11 Text entity BLOCKID 3 Coordinate list - represents origin of text. BLOCKID 11 Text parameters. BLOCKID 12 Text string. Entity type: 12 Text-node entity BLOCKID 3 Coordinate list - represents origin of text-node. BLOCKID 11 Text parameters. BLOCKID 13 Child member list - lists index of related text entity. Entity type: 13 Dimension entity BLOCKID 11 Text parameters. BLOCKID 17 Dimension parameters. BLOCKID 19 Dimension details. Entity type: 14 Symbol entity BLOCKID 3 Coordinate list - represents symbol origin. BLOCKID 12 Text string - symbol name. BLOCKID 16 Symbol parameters. Entity type: 15 Terminal entity. BLOCKID 3 Coordinate list - represents origin of terminal. BLOCKID 21 Terminal type. Entity type: 16 Netline entity. BLOCKID 3 Coordinate list. BLOCKID 1 Viewport Parameters ============================= Each viewport entity in a drawing must have associated with it a Viewport parameters data structure. struct ACViewPort { char NAME[22]; double WIDTH; double HEIGHT; short UNITS; double XORG; double YORG; double SCL; short XOFF; short YOFF; short XMAX; short YMAX; short CXMIN; short CYMIN; short CXMAX; short CYMAX; short VISIBLE; double SHXOFF; double SHYOFF; }; NAME The viewport name as a null terminated character string. The name can have a maximum of 20 characters. WIDTH The width of the viewport in viewport units. HEIGHT The height of the viewport in viewport units. UNITS The viewport units: 0 = Millimetres 1 = Centimetres 2 = Metres 3 = Kilometres 4 = Inches 5 = Feet 6 = Miles XORG X origin of the viewport in viewport units relative to the bottom left corner of the viewport. YORG Y origin of the viewport in viewport units relative to the bottom left corner of the viewport. SCL Scale to apply to viewport coordinates to transform to display coordinate system. ( See section on coordinate systems ). XOFF X offset of viewport in display coordinate system. YOFF Y offset of viewport in display coordinate system. XMAX Width of viewport in display coordinate system. YMAX Height of viewport in display coordinate system. CXMIN Current minimum x clip for viewport in viewport coordinate system. This value is relative to the viewport origin (0,0) at the top left corner of the viewport. CYMIN Current minimum y clip for this viewport. CXMAX Current maximum x clip for this viewport. CYMAX Current maximum y clip for this viewport. VISIBLE Viewport open/close flag. 1 = open, 0 = closed. SHXOFF X coordinate of the viewport origin ( bottom left corner ) in the sheet viewport ( viewport 0 ) coordinates. SHYOFF Y coordinate of the viewport origin in sheet viewport coordinates. BLOCKID 2 Drawing Parameter Data ================================ Each X-CAD drawing has a drawing parameters entity. Associated with the drawing parameters entity is a number of drawing parameters data blocks. The SUBID of each type 2 BLOCKID defines the type of data found. A SUBID of 1 defines a layer name data structure: struct LayerName { char NAME[16]; short LAYER; }; NAME The layer name. A maximum 14 character null terminated text string. LAYER The actual layer number associated with the layer name. A SUBID of 2 defines a layer list data structure: struct LayerList { char NAME[16]; short LAYLIST[16]; }; NAME The layer name. A maximum 14 character null terminated text string. LAYLIST A visibility mask for all 255 layers associated with this named layer list. Word 1 defines visibility for layers 0-15, word 2 for layers 16-32 etc. Each bit on within the word specifies that layer is visible. A SUBID of 4 defines the current layer colour assignments for the drawing. The data that follows is 256 bytes each of which use the first 7 bits to define the assigned layer colour. The first byte corresponds to layer 0, the second byte to layer 1 etc. A SUBID of 5 defines an image data structure associated with this drawing: struct ZoomImage { char NAME[10]; short XMIN; short YMIN; short XMAX; short YMAX; }; NAME The image name. A maximum 8 character null terminated text string. XMIN Minimum x clip of window in display coordinate system for sheet viewport. YMIN Minimum y clip of window. XMAX Maximum x clip of window. YMAX Maximum y clip of window. A SUBID of 6 defines the colours currectly selected for this drawing. 9 two byte integers follow this EDBLOCK. The first 8 words define each of the 8 visible colours, the last word defines the colour of the cursor. Each word defines a colour as a combination of 3 nibbles describing the RGB components of the colour: Bits 0-3 blue Bits 4-7 green Bits 8-11 red A SUBID of 7 defines the currently selected symbol directory for this drawing. The data that follows is a null terminated character string containing the directory name. A SUBID of 8 defines the currently selected patternfill datafile for this drawing. The data that follows is a null terminated character string containing the patternfill datafile name. A SUBID of 9 defines the currently selected softfont datafile for this drawing. The data that follows is a null terminated character string containing the softfont datafile name. BLOCKID 3 Coordinate List ========================= Most entity types within an X-CAD drawing have a type 3 BLOCKID. The data following this type of EDBLOCK is aways one or sets of xy coordinates. Each set of xy coordinate points is represented by 2 doubles. The coordinate points are always relative to the entities viewport. Most type 3 BLOCKIDs have a SUBID of 0 denoting no special meaning. The meaning of other SUBIDs are as follows. A SUBID of 2 occurs on polygon and cross-hatch polygon entities. This type of entity can have one or more type 3 BLOCKIDs, one for each boundary of the polygon. A SUBID of 2 defines the outer or first boundary. A SUBID of 3 defines any inner or subsequent boundaries. A SUBID of 4 occurs only on spline entities. This means that the spline is closed, ie it runs smoothly through the first and last control points. BLOCKID 4 Font Parameters ========================= A type 4 BLOCKID can occur on most entities as it defines the appearance or font of the entity. The type of data structure used to define the font is dependent on the SUBID of the EDBLOCK. A SUBID of 1 defines a hardfont data structure: struct HardFont { char THICK; char STYLE; }; THICK Line thickness as a value between 1-5. STYLE Line style as a value between 0-15. If this SUBID is found on a type 4 BLOCKID associated with a viewport entity, it defines the default hardfont for the text parameters associated with this viewport. A SUBID of 2 defines a named softfont data structure: struct NamedSoftFont { char NAME[16]; float SCALE; }; NAME The softfont name. A maximum 15 character null terminated character string containing the softfont name. SCALE Scale to apply to the font width etc. A SUBID of 3 defines a local softfont data structure: struct SoftFont { char TYPE; char UNITS; char NAME[16]; char FLAGS; char COLOUR; char PATNAME[12]; short HARDSTYLE; float WIDTH; short DASH_DOT; float SP[16]; }; TYPE Bit flag containing information about font type: Bit 0 On indicates local font ( used internally ). 1 On indicates named font ( used internally ). 2 On indicates fixed scale font, units stored in UNITS. 3 On indicates patterfilled font. UNITS The units type of the viewport used to define the font. Units values are as in the Viewport Parameters data structure. NAME The name of the font if TYPE bit 1 is set. ( Used internally ). FLAGS Bit flag containing additional information about font. Bit 0 On indicates font has a width. 1 On indicates font width is left justified. 2 On indicates font width is right justified. 3 On indicates width font is open-ended. 4 On indicates width font has extended ends. 5 On indicates width font is filled. 6 On indicates width font is filled with an absolute colour. 7 On indicates width font has an outline in the layer assigned colour. COLOUR Fill colour if FLAGS bit 6 is set. PATNAME Patternfill name if TYPE bit 3 is set. WIDTH Width of the font in UNITS if TYPE bit 1 is set else viewport units. DASH_DOT The number of dash/space values in SP. SP A list of dash/space pairs for the font in UNITS if TYPE bit 1 is set else viewport units. A SUBID of 4 indicates a polygon fill data structure. This SUBID only occurs on polygon entities. struct PolyFont { char TYPE; char DUM; char FLAGS; char COLOUR; char PATNAME; }; TYPE Bit flag containing information about font type: Bit 3 On indicates patterfilled font. 4 On indicates background of single colour patternfilled polygon is rendered in layer assigned colour. 5 On indicates shadow polygon. DUM Not used. FLAGS Bit flag containing additional information about font. Bit 1 On indicates patternfilled polygon has transparent background. 2 On indicates single colour patternfilled polygon is used as a mask. 3 On indicates colour filled polygon is halftoned. 5 On indicates polygon is filled. 6 On indicates polygon is filled with an absolute colour. 7 On indicates polygon has an outline in the layer assigned colour. COLOUR Fill colour if FLAGS bit 6 is set. PATNAME Patternfill name if TYPE bit 3 is set. A SUBID of 11 defines hardfont data in the same way as SUBID 1. This SUBID only occurs on viewport entities. It defines the hardfont used for the default dimension parameters for this viewport. BLOCKID 5 Arc Parameters ======================== A type 5 EDBLOCK is followed by an arc parameters data structure: struct ArcParameters { double RADIUS; double AGO; double AEND; }; RADIUS The arc radius in viewport units. AGO The arc start angle in radians. AEND The arc end angle in radians. BLOCKID 6 Ellipse Parameters ============================ A type 6 EDBLOCK is followed by an ellipse parameters data structure: struct ElpParameters { double MAJOR; double MINOR; double INCL; double AGO; double AEND; }; MAJOR The ellipse major radius in viewport units. MINOR The ellipse minor radius in viewport units. INCL The ellipse inclination angle in radians. AGO The arc start angle in radians. AEND The arc end angle in radians. BLOCKID 8 Xhatch Parameters =========================== A type 8 EDBLOCK is followed by an xhatch parameters data structure: struct XhParameters { double SPACING; double ANGLE; }; SPACING Parallel distance of lines used for cross-hatch. ANGLE Angle of cross-hatch in radians. BLOCKID 11 Text Parameters ========================== A type 11 EDBLOCK is followed by a text parameters data structure: struct TextParams { char FONT[10]; float HEIGHT; float WIDTH; float ANGLE; float CSPACE; float SLANT; char JUST; char FLAGS; float LNSP; }; FONT The text font name. A maximum 8 charater null terminated text string. HEIGHT The height of the text in viewport units. WIDTH The width of the text in viewport units. The height and width used are for the tile size of the letter. The width does not include the space between letters, this is defined by the CSPACE variable. ANGLE The angle of the text in radians. CSPACE The text character spacing as a proportion of the width. ie, if CSPACE is 1.3, the space between each letter is .3 times the letter width. SLANT The slant of the text in radians. JUST Text justification flag: -1 = left justified 0 = centre justified 1 = right justified FLAGS Bit encoded flag: Bit 0 On indicates uniform spacing 0 Off indicates proportional spacing 1 On indicates filled text LNSP Text line spacing as a proportion of the text height. If this EDBLOCK is associated with a viewport entity, it defines the default text parameters associated with the viewport. EDBLOCK 12 Text String ====================== A type 12 EDBLOCK is always followed by a null terminated character string. This is generally used as some sort of label, ie. a symbol name or string associated with a text entity. EDBLOCK 13 Child Member List ============================ A type 13 EDBLOCK is followed by one or more 2 byte integers each of which are the index number of an entity. The entities in this list are all child members in the relationship for which this entity is the parent. Each of the child members should have a parent member list containing the index of this entity. The SUBIDs used with a type 13 EDBLOCK define the kind of relationship involved. The child member entities in a type 13 EDBLOCK with a specific SUBID must also contain a parent member list ( type 15 EDBLOCK ) with the same SUBID. A SUBID of 0 is found on an attribute entity. The child member list contains the indexes of all entities sharing this attribute. This SUBID is the exception to the rule in that the child entities do not have a type 15 BLOCKID with a SUBID of 0 containing the index of the parent attribute entity. Instead a type 22 BLOCKID is used to relate the child member back to its parent. A SUBID of 1 is found on a text-node or netline entity. This block should only contain a single member which is the text entity related to the text- node or netline. A SUBID of 2 is found on an exploded symbol entity. The child member list contains the indexes of all entities related to the symbol origin except for any text-node, symbol or terminal entities. A SUBID of 3 is found on a symbol entity. The child member list contains the indexes for any text-node, symbol or terminal entities related to the symbol. A SUBID of 6 is found on a symbol entity. The child member list contains the indexes for any construction point entities related to the symbol. A SUBID of 10 is found on a viewport entity. The child member list contains the indexes for any entities ( usually dimensions ) the are related to the viewport. A SUBID of 11 is found on a terminal entity. The child member list contains the indexes of all netline entities whose origin point is this terminal. A SUBID of 12 is found on a terminal entity. The child member list contains the indexes of all netline entities whose end point is this terminal. A SUBID of 100 is a general relationship with no specific meaning. This is usually set up using the RELATE ENTITY command. BLOCKID 14 Equal Member List ============================ A type 14 EDBLOCK is followed by one or more 2 byte integers each of which are the index number of an entity. The entities in this list are all equal members in the relationship for which this entity is a member. Each of the equal members should also have an equal member list containing the index of this entity. The only SUBID used on a type 14 EDBLOCK is 100 meaning general relationship. BLOCKID 15 Parent Member List ============================= A type 15 EDBLOCK is the exact inverse of a type 13 EDBLOCK. The block is followed by one or more 2 byte integers each of which are the index number of an entity. The entities in this list are all parent members in the relationship for which this entity is a child. The SUBIDs found are the same as described under the type 13 EDBLOCK. BLOCKID 16 Symbol Parameters ============================ A type 16 EDBLOCK is followed by a symbol parameters data structure: struct SymParams { double XSCL; double YSCL; double ANGLE; short FLAGS; }; XSCL The x scale to apply to the symbol. YSCL The y scale to apply to the symbol. ANGLE The symbol angle in radians. FLAGS Bit encoded word containing additional information about the symbol. Bit 0 On indicates the symbol is mirrored about its x axis. Bit 2 On indicates no units conversion should take place. Bit 3 On indicates symbol text should not be rotated. Bit 4 On indicates symbol text should not be scaled. Bit 5 On indicates symbol text should not be mirrored. Bit 6 On indicates use relative layer. Bit 7 On indicates use relative depth. Bit 15 On indicates an exploded symbol. BLOCKID 17 Dimension Parameters =============================== A type 17 EDBLOCK is followed by a dimension parameters data structure: struct DimParams { long FLAGS; float GAP; float EXT; float ALENGTH; float ARATIO; double SCALE; short FRAC; char PREC; char UNITS; float TOL[2]; }; FLAGS Bit encoded word containing additional information about dimension. Bit 0 On indicates suppress first dimension leader line. Bit 1 On indicates suppress second dimension leader line. Bit 2 On indicates use filled arrowhead. Bit 3 On indicates use open arrowhead ( > ). Bit 4 On indicates use dash arrowhead ( / ). Bit 5 On indicates that dimension text should be aligned to the witness line. Bit 6 On indicates that dimension text should be horizontally aligned. Bit 7 On indicates that the witness line should be broken to accomodate the dimension text. Bit 8 On indicates that the dimension is associative. Bit 9 On indicates that the dimension has prefix text. Bit 10 On indicates that the dimension has suffix text. Bit 11 On indicates that leading zeros should be suppressed when formatting dimension value text. Bit 12 On indicates that the dimension value should be in the units type under UNITS. Bit 13 On indicates no arrowhead should be used. Bit 14 On indicates that decimal notation should be used for imperial units. Bit 15 On indicates that trailing zeros should be suppressed when formatting the dimension value text. Bit 16 On indicates that fractions should be used for imperial units. Bit 17 On indicates that the fraction denominator should be fixed for imperial units. Bit 18 On indicates that the dimension value text should include a tolerance for +/-. Bit 19 On indicates that the dimension value text should include a separate tolerance for + and -. Bit 20 On indicates that the dimension value text should include a tolerance for + only. Bit 21 On indicates that the dimension value text should include a tolerance for - only. Bit 22 On indicates that the dimension text should consist of 2 values, one for the absolute + value, one for the absolute - value. Bit 23 On indicates use dot arrowhead. GAP The size of the gap between the dimensioned object and the start of the leader line in viewport units. EXT The length of the extension of the leader line beyond the dimension witness line in viewport units. ALENGTH The length of the arrowhead in viewport units. ARATIO The width of the arrowhead as a proportion of its length. SCALE Scale factor to apply to dimension values. FRAC Fractional denominator for imperial units. PREC Number of places of precision for dimension value text. UNITS Alternative units type to use if FLAGS bit 12 is set. The units type value is the same as used in the viewport parameters data structure. TOL Two tolerance values to use if FLAGS bits 18 to 22 are set. If this EDBLOCK is associated with a viewport entity, it defines the default dimension parameters associated with the viewport. Note, dimension parameter data structures that occur on X-CAD V1.3 drawings do not have the TOL element. The LENGTH value in the EDBLOCK should be checked to verify this. BLOCKID 18 Viewport Scale ========================= A type 18 EDBLOCK only appears in viewport entities. It is followed by a single double value specifing the viewport scale. ie, if the viewport was defined with a scale of 1 to 100, the value following the EDBLOCK would be 100.0. BLOCKID 19 Dimension Details ============================ A type 19 EDBLOCK is followed by a dimension details data structure containing additional information about the dimension. struct DimDetails { char TYPE; char FLAGS; double LOCS[10]; double RADIUS; char VPNUM; char NUM; }; TYPE The dimension type: 0 = horizontal 1 = vertical 2 = linear 3 = point 4 = angular 5 = diametric 6 = radial FLAGS Bit encoded word containing additional information about the dimension. Bit 0 On indicates that a fixed text string ( found in a type 11 EDBLOCK on the same entity ) is to be used in place of the dimension value. 1 On indicates that the dimension value should be calculated for the viewport VPNUM. 2 On indicates that the position of the text is specific and contained in LOCS. If this bit is not set, the position of the text is calculated automatically. LOCS A set of up to 5 coordinates used to define the position of the dimension. The coordinates correspond to those used the enter the dimension using DRAW DIMENSION. RADIUS The radius of the selected arc if the dimension type is radial or diametric. VPNUM Viewport number of viewport used to calculate dimension values if FLAGS bit 1 is on. NUM Number of coordinate pairs in LOCS. BLOCKID 20 Hide List ==================== A type 20 EDBLOCK is followed by one or more pairs of xy coordinate points. Each pair of xy points represent 2 points on a line, string or netline entity. These pairs of points on the entity represent off and on drawing positions when the entity is displayed thus generating hidden segments. The coordinate points in the type 20 EDBLOCK are always sorted with respect to the type 3 coordinate list associated with the same entity. BLOCKID 21 Terminal Type ======================== A type 20 EDBLOCK only occurs on a terminal entity. It is followed by a single 2 byte integer whose value specifies the number of connections that can be made to this terminal. The value should be -1 or 1-4. If it is -1 then this terminal allows any number of connections. BLOCKID 22 Attribute Value ========================== A type 22 BLOCKID can occur on any entity. It contains the parent index of the attribute entity plus any attribute value used by this entity. The EDBLOCK is followed by a 2 byte integer containing the index number of the parent attribute entity, followed by an optional set of data items. The type of data item is dependent on the SUBID of this EDBLOCK. A SUBID of 1 indicates that this is a NULL value attribute. Therefore there are no data items following the parent index. A SUBID of 2 indicates that this is an INTEGER value attribute. The parent index will be followed by one or more 4 byte integer values associated with the attribute. The number of values can be calculated from the LENGTH element in the EDBLOCK. A SUBID of 3 indicates that this is a REAL value attribute. The parent index will be followed by one or more 8 byte real values associated with the attribute. The number of values can be calculated from the LENGTH element in the EDBLOCK. A SUBID of 4 indicates that this is a TEXT value attribute. The parent index will be followed by a null terminated character string. Coordinate Systems ================== X-CAD drawings use a number of coordinate systems internally to represent the drawing database and the graphics display list. All coordinate systems used are based on the original definition of the sheet viewport ( viewport 0 ). The initial starting point is a sheet viewport of a given height and width. No other viewports can be defined outside of this area and no graphics can be created or moved outside of this area. The sheet viewport defines the maximum usable drawing area. The viewport coordinate system is based on the units and origin of a viewport. For the sheet viewport, the origin is always in the bottom left corner of the screen. The positive x axis runs to the right of the origin while the positive y axis runs above the origin. Other viewports defined within the sheet viewport have the own local origin and units. Any coordinate values found in an EDBLOCK associated with an entity are always relative to the viewport in which the entity resides. To map a coordinate from a secondary viewport to the sheet viewport, the following transformation must be made. coor_2 = ( ( coor_1 + viewport_origin ) * units_sf ) + vp_sheet_origin Where: viewport_origin This is the local origin of the secondary viewport. The local origin can be found in the XORG and YORG elements of its viewport parameters data structure. units_sf This is the scale factor to apply to the coordinate point to map the point from its local units type and scale to the sheet viewport units type. vp_sheet_origin This is the point in the sheet viewport of the bottom left corner of the secondary viewport. This point can be found in the SHXOFF and SHYOFF elements of the secondary viewports viewport parameters data structure. The size and height/width proportions are used to define the display coordinate system. The display coordinate system is used internally by X-CAD for drawing purposes and for the construction of the graphics display list. The longer of the height or width of the sheet viewport is used to set the height or width of the display coordinate system to 32767 arbitary units. The second dimension is then calculated as the proportion of the longest length. ie, a sheet viewport with a width of 22 inches and a height of 17 inches will set a maximum display coordinate area of 32767 units wide by 25319 units high. These values can be found in the XMAX and YMAX elements of the sheet viewport parameters structure. The orientation of the display coordinate system has the y axis reversed, ie the 0,0 origin point of the display coordinate system is always at the top left corner of the viewport. Secondary viewports also use a display coordinate system local to their own viewports. The scale of the display coordinate system is always set by the sheet viewport, but the origin is always the top left corner of the secondary viewport. ie, it is offset from the display coordinate system of the sheet viewport by the values XOFF and YOFF found in the secondary viewport parameters data structure. To map a coordinate from its viewport coordinate system to its display coordinate system, the following transformation must be made. dx = ( viewport_x + viewport_origin ) * viewport_scale dy = viewport_ymax - ( viewport_y + viewport_origin ) * viewport_scale Where: viewport_origin This is the local origin of the secondary viewport. The local origin can be found in the XORG and YORG elements of its viewport parameters data structure. viewport_scale This is the scale factor to apply to the coordinate point to map it from its viewport to its display coordinate system. This value can be found in the SCL element of the viewport parameters data structure. viewport_ymax This is the height of the viewport in the display coordinate system used to reverse the y axis of the viewport coordinate. This value can be found in the YMAX element of the viewport parameters data structure. To map a coordinate from its viewport coordinate system to the sheet viewports display coordinate system, the viewport display origin ( XOFF and YOFF ) must be added. X-CAD Display List ================== The display list associated with an X-CAD drawing file contains the data used when a redraw or zoom is performed on the screen. These functions do not access the entity coordinate data via EDBLOCKS as this would require a large amount of calculation and slow the redraw times. Instead, the GBBLOCKs associated with an entity contain lists of vectors in a third coordinate system - the display list coordinate system. This is exactly the same as the display coordinate system except that the origin is offset in the x and y by -16384 units. ie, the point 0,0 in the display coordinate system is the point 16384,16384 in the display list coordinate system. Although the X-CAD database contains objects such as arcs, ellipses and splines, the graphics display list holds these objects as a series of short straight vectors simplifing the clipping and transformation process. The most efficient way to access any graphics data from an X-CAD drawing file is to use the display list data held in GBBLOCKS. To map a coordinate from the display list coordinate system to real world or sheet viewport coordinates, the following transformation is used. real_x = ( dx - 16384 + view_doff ) / view_scl real_y = ( view_ymax - ( dy - 16384 + view_doff ) ) / view_scl Where: view_doff This is the display offset of the viewport. The offset can be found in the XOFF and YOFF elements of the viewport parameters data structure. view_scl This is the scale factor to apply to the coordinate point to map it from the display coordinate system to the sheet viewport coordinate system. This value can be found in the SCL element of the viewport parameters data structure for the sheet viewport. view_ymax This is the height of the sheet viewport in the display coordinate system used to reverse the y axis of the viewport coordinate. This value can be found in the YMAX element of the viewport parameters data structure for the sheet viewport. GBBLOCK Data ============ The display list data found after a GBBLOCK consists of a series of 2 byte integers formatted as follows: [ style data ] [ extents data ] [ vector block count ] [ vector blocks ] The contents of each of these blocks are dependent on the display list type found in the TYPE element of the GBBLOCK data structure. Style Data ---------- TYPE 1 2 3 4 word 1 [line style] [fill style ] [fill style ] [symbol type] word 2 [ ] [ ] word 3 [ ] [ ] word 4 [patternfill] [patternfill] word 5 [name ] [name ] word 6 [ ] [ ] word 7 [ ] [ ] [line style] This word contains a copy of the hardfont line style used to render the vector list: Bit 0-7 Hardware line style. Bit 8-15 Line draw thickness. [fill style] A bit encoded word defining the fill type for a polygon. Bit 0-3 Fill colour if bit 4 is set. Bit 1 Only applicable for pattern fills of a single colour and if bit 4 is not set. This bit on indicates the patternfill will be used as a mask. Bit 4 If this bit is set, then the colour used to fill the polygon is set in bits 0-3. If this bit is not set, the colour assigned to the layer of the entity is used. Bit 5 If this bit is set on, the polygon will be rendered with an outline in the colour assigned to the layer of the entity. Bit 6 If this bit is on, the polygon if filled with a pattern as opposed to a solid colour. If the bit is set off, then words 2-7 are not present. Bit 7 Only applicable for pattern fills of a single colour. This bit on indicates the background colour of the patternfill will be the colour assigned to the layer of the entity. Bit 8 Use a half-tone mask for solid colour fills. Bit 9 Use a mask to create a shadow fill polygon. [patternfill] These 6 words are only present if bit 6 is set in the fill- [name ] style word. The 6 words contain the null terminated pattern fill name. [symbol type] Contains the id of the bit pattern used to display a non- scalable symbol such as a text-node, construction-point or terminal. Extents Data ------------ TYPE 1 2 3 4 word 1 [xmin] [xmin] [xmin] no data word 2 [ymin] [ymin] [ymin] word 3 [xmax] [xmax] [xmax] word 4 [ymax] [ymax] [ymax] word 5 [width scale] [xmin] etc. These 4 words represent the bounding extents of all of the vector data described for this display list block. The extents values are in dsplay list coordinates. If word 1 is equal to hex ffff, words 2-4 are not present. [width scale] Contains the width of the filled vector sequence in display values. This word is used to determine if only a vector sequnce and not a polygon is worth drawing. Vector Block Count ------------------ TYPE 1 2 3 4 word 1 [block count] [block count] [block count] no data [block count] This word contains the number of vector blocks that follow. In the case of a TYPE 4 ( Non-scaled sysmbols ), only one vector block follows. Vector Blocks ------------- TYPE 1 2 3 4 word 1 [block extent] [block extent] [block extent] [coor count] word 2 [num vectors] [num vectors] [num vectors] [first x] word 3 [first x] [first x] [first x] [first y] word 4 [first y] [first y] [first y] [block extent] The is the diagonal length of the bounding box containing the following vector list. This value is used to determine if only a single pixel is required to render this vector list at the current zoom scale. [coor count] The number of xy coordinate pairs in display list coordinates that follows. [num vectors] The number of vectors represented by xy coordinate pairs in display list coordinates that follows. ie, there will be [num vectors]+1 coordinate pairs. [first x] First coordinate x value in display list coordinates. [first y] First coordinate y value in display list coordinates. APPENDIX A Example C routine ============================= The example program shown below is a simple display routine used to draw an X-CAD .xdr file in a window set up on the Workbench screen. The program examines the display list data within GBBLOCKs and maps these coordinates to a standard non-interlaced high res window. The program will run on an NTSC or PAL machine. ---------------------------------------------------------------------------- main.c ---------------------------------------------------------------------------- /* G.Osis 6-October-88 Example routine to read an X-CAD .xdr file and display the graphics to a workbench window. */ #include "include.h" #include "include/libraries/dos.h" #include "include/intuition/intuition.h" #define NOGRAPHICS 0x0001 #define PASSWORD 0x0002 #define ACDR 0x41434452 #define SWIDTH 640 /* change these to suit other formats */ #define SHEIGHT 400 struct IntuitionBase *IntuitionBase; struct GfxBase *GfxBase; struct ACViewPort views[32]; struct Header head; struct HeaderIndex hi; struct EntityHeader eh; struct EntityData ed; struct GraphicsInfo gi; struct GraphicsBlock gb; /* structures for area draws */ short tmem2[1280]; struct TmpRas t; struct AreaInfo a; /* display window definition */ struct NewWindow nw = { 0,0,0,0,0xff,0xff,VANILLAKEY,SMART_REFRESH|ACTIVATE,0,0,0,0,0,0,0,0,0, WBENCHSCREEN }; main( argc , argv ) long argc; char *argv[]; { long fh,ents_read,graphics,tmem1,rassize; short index,vpnum,close,code,*display_list; double ratio,scale_fac,rtemp; struct Window *w; struct IntuiMessage *mess; struct RastPort *r; /* open the libraries */ if ( (IntuitionBase=(struct IntuitionBase *)OpenLibrary( "intuition.library",0)) == 0 ) { printf(" Failed to open intuition.library\n"); Exit(0); } if ( (GfxBase=(struct GfxBase *)OpenLibrary("graphics.library",0)) == 0 ) { printf(" Failed to open graphics.library\n"); Exit(0); } /* check a drawing name was entered on the command line */ if ( argc != 2 ) { printf("\n Command format is: XDR my_drawing.xdr\n"); Exit(0); } /* open the file */ if ( !(fh=Open(argv[1],MODE_OLDFILE)) ) { printf("\n Cannot open %s due to error %d\n",argv[1],IoErr()); Exit(0); } /* read in and check the header */ Read(fh,&head,sizeof(struct Header)); if ( head.ID != ACDR ) { Close(fh); printf("\n %s is not an X-CAD drawing file\n",argv[1]); Exit(0); } if ( head.flags & NOGRAPHICS ) { Close(fh); printf("\n Drawing was saved with the NOGRAPHICS option\n"); Exit(0); } /* skip password if needs be */ if ( head.flags & PASSWORD ) Seek(fh,8,0); /* load all of the viewport data */ for(ents_read=0;ents_read<head.ents;ents_read++) { Read(fh,&index,2); if ( index > 33 ) break; Seek(fh,HIBLOCK+EHBLOCK,0); do { Read(fh,&ed,EDBLOCK); if ( ed.blockID == 1 ) Read(fh,&views[index-2],ed.length); else Seek(fh,ed.length,0); } while( ed.next ); } /* any more entities ? */ if ( ents_read == head.ents ) { Close(fh); printf("\n Drawing contains no graphics entities\n"); Exit(0); } Seek(fh,-2,0); /* set up display window based on sheet viewport proportions */ ratio=(double)SHEIGHT/(double)SWIDTH; if ( (rtemp=views[0].height/views[0].width) < ratio ) { scale_fac=(double)SWIDTH/(double)views[0].xmax; nw.Width=SWIDTH; nw.Height=(short)((double)SWIDTH*rtemp)>>1; } else { scale_fac=(double)SHEIGHT/(double)views[0].ymax; nw.Height=SHEIGHT>>1; nw.Width=(short)((double)SHEIGHT/rtemp); } rassize=RASSIZE(nw.Width,nw.Height); if ( !(tmem1=AllocMem(rassize,MEMF_CHIP|MEMF_CLEAR)) ) { Close(fh); printf("\n Cannot allocate enough TmpRas memory %d\n",rassize); Exit(0); } /* open the window */ if ( !(w=(struct Window *)OpenWindow(&nw)) ) { Close(fh); FreeMem(tmem1,rassize); printf("\n Cannot open display window %d %d\n", nw.Width,nw.Height); Exit(0); } r=w->RPort; SetAPen(r,3); /* add area for polygon draws */ w->RPort->TmpRas=(struct TmpRas *)InitTmpRas(&t,tmem1,rassize); InitArea(&a,tmem2,512); w->RPort->AreaInfo=&a; /* start loop to read all entities */ for( ;ents_read<head.ents;ents_read++) { /* save graphics and viewport data from HIBLOCK and skip past all the database stuff */ Read(fh,&index,2); Read(fh,&hi,HIBLOCK); graphics=hi.graphics; vpnum=hi.flags2&0x001f; Read(fh,&eh,EHBLOCK); if ( eh.first ) do { Read(fh,&ed,EDBLOCK); Seek(fh,ed.length,0); } while( ed.next ); /* any graphics display data to retrieve ? */ if ( graphics ) { do { Read(fh,&gi,GIBLOCK); do { Read(fh,&gb,GBBLOCK); if ( !(display_list=(short *)AllocMem(gb.size,0)) ) Seek(fh,gb.size,0); else { Read(fh,display_list,gb.size); render(display_list,gb.type,&views[vpnum],r,scale_fac); FreeMem(display_list,gb.size); } } while( gb.next ); } while( gi.next ); } } FreeMem(tmem1,rassize); /* display complete, close file */ Close(fh); /* wait for return to be pressed then close down */ SetAPen(r,2); SetBPen(r,1); Move(r,10,12); Text(r," Press return to end ",21); close=1; do { Wait(1<<w->UserPort->mp_SigBit); while( mess=(struct IntuiMessage *)GetMsg(w->UserPort) ) { code=mess->Code; ReplyMsg(mess); if ( code == 0x000d ) { close=0; break; } } } while( close ); CloseWindow(w); Exit(0); } /* Render the display list. */ #define HARD_VEC_LIST 1 #define COLOUR_FILL_POLY 2 #define COLOUR_FILL_VEC 3 render( display_list , type , view , r , scale_fac ) short *display_list; short type; struct ACViewPort *view; struct RastPort *r; double scale_fac; { register short vblocks,i,j,*vl; register unsigned short *p=display_list; short vec[2],num_vecs,pd; /* switch on type */ switch( type ) { /* vector list */ case HARD_VEC_LIST: p++; if ( *p == 0xffff ) p++; else p+=4; vblocks=*p++; for(i=0;i<vblocks;i++) { p++; for(num_vecs=(*p)+1,vl=p+1,j=0;j<num_vecs;j++,vl+=2) { map_display_to_screen(vl,vec,view,scale_fac); if ( !j ) Move(r,vec[0],vec[1]); else Draw(r,vec[0],vec[1]); } p+=(*p<<1)+3; } break; /* polygon data */ case COLOUR_FILL_POLY: case COLOUR_FILL_VEC: if ( *p & 0x0040 ) p+=11; else p+=5; if ( gb.type == COLOUR_FILL_VEC ) p++; vblocks=*p++; for(i=0,pd=0;i<vblocks;i++) { p++; for(num_vecs=(*p)+1,vl=p+1,j=0;j<num_vecs;j++,vl+=2) { map_display_to_screen(vl,vec,view,scale_fac); if ( !j ) AreaMove(r,vec[0],vec[1]); else AreaDraw(r,vec[0],vec[1]); } if ( ++pd == 32 ) { AreaEnd(r); pd=0; } p+=(*p<<1)+3; } if ( pd ) AreaEnd(r); break; } } /* Map display list coordinates to screen coordinates. */ map_display_to_screen( vl , vec , view , scale_fac ) unsigned short *vl; short *vec; struct ACViewPort *view; double scale_fac; { register short rx,ry; rx=*vl-16384+view->xoff; ry=*(vl+1)-16384+view->yoff; *vec=(short)((double)rx*scale_fac); *(vec+1)=(short)((double)ry*scale_fac)>>1; } --------------------------------------------------------------------------- include.h --------------------------------------------------------------------------- #include "INCLUDE:exec/types.h" #include "INCLUDE:exec/memory.h" struct Header { long ID; short rev; long ents; long memreq; short flags; }; struct HeaderIndex { long head; short flags1; short flags2; long graphics; }; struct EntityHeader { long first; short flags; short aword1; short aword2; short aword3; }; struct EntityData { long next; unsigned char blockID; unsigned char subID; long length; }; struct GraphicsInfo { long next; unsigned char layoff; unsigned char depoff; long gblock; }; struct GraphicsBlock { long next; char type; char flags; long size; }; #define HIBLOCK sizeof(struct HeaderIndex) #define EHBLOCK sizeof(struct EntityHeader) #define EDBLOCK sizeof(struct EntityData) #define GIBLOCK sizeof(struct GraphicsInfo) #define GBBLOCK sizeof(struct GraphicsBlock) struct ACViewPort { char name[22]; double width; double height; short units; double xorg; double yorg; double scl; short xoff; short yoff; short xmax; short ymax; short cxmin; short cymin; short cxmax; short cymax; short visible; double shxoff; double shyoff; };