The union COLOR_ENTRY contains the colour table entry. In future, colour spaces other than RGB may be available:
typedef union
{
COLOR_RGB rgb;
COLOR_CMYK cmyk;
} COLOR_ENTRY;
typedef struct
{
uint16 reserved; /* Set to 0 or the index of the entry */
uint16 red; /* Red: 0<->65535 */
uint16 green; /* Green: 0<->65535 */
uint16 blue; /* Blue: 0<->65535 */
} COLOR_RGB;
If the colour data in a program is present in a sensible format (e.g. 8 bits per channel) already, one can save oneself a transformation with multiplication and division. The Shift and OR functions of the processor perform this faster and more elegantly. eleganter.
Example: The colour value is described by the byte variables r, g, b. The correct conversion to the 16-bit format of the COLOR_RGB structure proceeds as follows:
COLOR_RGB color; color.reserved = 0; color.red = r; color.red |= (color.red << 8); color.green = g; color.green |= (color.green << 8); color.blue = b; color.blue |= (color.blue << 8);
The structure element reserved should be set to 0 or (for building up a colour table) contain the index of the entry. In each case, however, the upper 8 bits of reserved must be set to 0, as they may be used by the colour routines for some flags.
typedef struct /* Colour table */
{
int32 magic; /* 'ctab' */
int32 length;
int32 format; /* Format (0) */
int32 reserved; /* Reserved, set to 0 */
int32 map_id; /* Colour table ID */
int32 color_space; /* Colour space (at present only
CSPACE_RGB) */
int32 flags; /* VDI-internal flags, set to 0 */
int32 no_colors; /* Number of colour entries */
int32 reserved1; /* Reserved, must be 0 */
int32 reserved2; /* Reserved, must be 0 */
int32 reserved3; /* Reserved, must be 0 */
int32 reserved4; /* Reserved, must be 0 */
COLOR_ENTRY colors[];
} COLOR_TAB;
The data type fix31 corresponds to the type LONG, and is required in connection with vector fonts where one calculates positions and steps in 1/65536. Here the width of a pixel corresponds to the value 65536. The upper 16 bits represent the whole number part and the lower 16 bits the decimal part of the number.
Examples:
| Hex | Dec | |
| $00010000 | 65536 | 1.0 pixels |
| $0001c000 | 114688 | 1.75 pixels |
| $fffec000 | -81920 | -1.25 pixels |
| $fffe4000 | -114688 | -1.75 pixels |
Important: The decimal part may never be cut off!
If you add advance widths (returned by vqt_advance) and you would like to determine the discrete coordinate for cursor placement, you should use the following code:
int16_t fix31_to_pixel( fix31 a )
{
int16_t b;
b = (int16_t) (( a + 32768L ) >> 16 ); /* Round !! */
return( b ); /* Return pixel value */
}
See also: GDOS NVDI SpeedoGDOS
The following structure describes the file-header for a bitmap font in the Digital Research standard format. In this format the font is organised as a wide, monochrome raster image; the width of the raster is the sum of all character widths, the raster height corres- ponds to the height of a single character. From this follows: The left edge of a character does not necessarily have to fall on a byte boundary; only the end of each raster line is filled with NULL- bits so that the next line falls on a WORD boundary again.
typedef struct font_hdr
{
int16_t font_id; /* Font number */
int16_t point; /* Size in points */
int8_t name[32]; /* Name of the font */
uint16_t first_ade; /* First character in font */
uint16_t last_ade; /* Last character in font */
uint16_t top; /* Distance: Top line <-> Baseline */
uint16_t ascent; /* Distance: Ascent line <-> Baseline */
uint16_t half; /* Distance: Half line <-> Baseline */
uint16_t descent; /* Distance: Descent line<-> Baseline */
uint16_t bottom; /* Distance: Bottom line <-> Baseline */
uint16_t max_char_width; /* Largest character width */
uint16_t max_cell_width; /* Largest character cell width */
uint16_t left_offset; /* Left offset for italic (skewed) */
uint16_t right_offset; /* Right offset for italic (skewed) */
uint16_t thicken; /* Thickening factor for bold */
uint16_t ul_size; /* Width of underline */
uint16_t lighten; /* Mask for light (0x5555) */
uint16_t skew; /* Mask for italic (0x5555) */
uint16_t flags; /* Various flags:
Set for system font
Bit 1: Set if horizontal offset
table is in use
Bit 2: Set if Motorola format
Bit 3: Set if non-proportional */
uint8_t *hor_table; /* Pointer to horizontal offset table */
uint16_t *off_table; /* Pointer to character offset table */
uint16_t *dat_table; /* Pointer to font image */
uint16_t form_width; /* Width of the font image */
uint16_t form_height; /* Height of the font image */
font_hdr *next_font; /* Pointer to next font header */
} FONT_HDR;
Note: As GEM was originally developed on the PC, all data is normally in the Intel format, so that on computers with Motorola processors we have to swap the upper and lower bytes of all words. Warning: To be able to interrogate the Motorola/Intel flag (bit 2 of the component flags), one must actually know already in which format the font is present. The solution to this problem: Start from the assumption that bit 10 of the flag will never be used and test whether bit 2 of the 67th byte of the header is set (because then the font is present in the Motorola format).
The character offset table contains entries of 16-bit values that hold the horizontal pixel offsets for each character within the font raster. So for the index one must use the character's ASCII code minus the ASCII code of the first character in the font (component first_ade). The width of a character results from the difference to the offset value of the next higher character; so that this formula works for the last character as well, the table always has one more entry than the number of characters available.
The horizontal offset table contains positive or negative offset values that are added to the X-poisition before the output of a character; however, this is supported only for a few fonts.
Last but not least one should point out that a normal application should never have to deal with this format; this infomation is of importance only for developers of font editors or GDOS versions.
See also:
GDOS NVDI SpeedoGDOS Vector fonts vst_alignment
vst_load_fonts vst_unload_fonts vqt_fontheader
typedef struct _gcbitmap /* Published bitmap description (structure */
/* with version header) */
{
LONG magic; /* Structure identifier 'cbtm' */
LONG length; /* Structure length */
LONG format; /* Structure format (0) */
LONG reserved; /* Reserved (0) */
BYTE *addr; /* Address of bitmap */
LONG width; /* Width of a line in bytes */
LONG bits; /* Bit-depth */
ULONG px_format; /* Pixel format */
LONG xmin; /* Minimum discrete X-coordinate of bitmap */
LONG ymin; /* Minimum discrete Y-coordinate of bitmap */
LONG xmax; /* Maximum discrete X-coordinate of bitmap + 1 */
LONG ymax; /* Maximum discrete Y-coordinate of bitmap + 1 */
CTAB_REF ctab; /* Reference to colour table, or 0L */
ITAB_REF itab; /* Reference to inverse colour table, or 0L */
LONG reserved0; /* Reserved, must be 0 */
LONG reserved1; /* Reserved, must be 0 */
} GCBITMAP;
See also: NVDI v_open_bm vr_transfer_bits
The Memory Form Definition Block is a data structure that is used by the VDI to describe destination and source memory blocks for raster operations.
C-declaration:
typedef struct mfdb
{
VOID *fd_addr; /* Pointer to the start of the
memory block, e.g. the
screen memory base address */
WORD fd_w; /* Width in pixels */
WORD fd_h; /* Height in pixels */
WORD fd_wdwidth; /* Width of a line in words */
WORD fd_stand; /* 0 = Device-specific format */
/* 1 = Standard format */
WORD fd_nplanes; /* Number of planes */
WORD fd_r1, fd_r2, fd_r3; /* Reserved, must be 0 */
} MFDB;
Note: If the component fd_addr contains a 0, the rest of the MFDB does not have to be filled out. The raster operations vrt_cpyfm and vro_cpyfm then automatically refer to the screen (or, in the case of a printer driver to the printer bitmap). The reserved words fd_r1, fd_r2 and fd_r3 should be set to 0 to cater for future extensions!
See also: Raster formats Raster functions
typedef struct /* Point for 16-bit coordinates */
{
int16 x;
int16 y;
} POINT16;
typedef struct /* Point for 32-bit coordinates */
{
int32 x;
int32 y;
} POINT32;
pxyarray is used in VDI to depict various graphical objects based on several coordinate pairs (x,y). Examples for the use of a pxyarray are for the depiction of rectangles:
| pxyarray[0] | X-coordinate of the top left corner point |
| pxyarray[1] | Y-coordinate of the top left corner point |
| pxyarray[2] | X-coordinate of the bottom right corner point |
| pxyarray[3] | Y-coordinate of the bottom right corner point |
Or generally, for n point-pairs:
| pxyarray[0] | X-coordinate of the first point-pair |
| pxyarray[1] | Y-coordinate of the first point-pair |
| pxyarray[2] | X-coordinate of the second point-pair |
| pxyarray[3] | Y-coordinate of the second point-pair |
| : | |
| : | |
| : | |
| pxyarray[2*n - 2] | X-coordinate of the n-th point-pair |
| pxyarray[2*n - 1] | Y-coordinate of the n-th point-pair |
See also: About the VDI VDI bindings
typedef struct /* Rectangle for 16-bit coordinates */
{
int16 x1;
int16 y1;
int16 x2;
int16 y2;
} RECT16;
typedef struct /* Rectangle for 32-bit coordinates */
{
int32 x1;
int32 y1;
int32 x2;
int32 y2;
} RECT32;
typedef struct
{
int32_t size; /* Length of the structure; initialize
this entry before calling vqt_xfntinfo */
int16_t format; /* Font format, e.g. 4 for TrueType */
int16_t id; /* Font ID, e.g. 6059 */
int16_t index; /* Index */
int8_t font_name[50]; /* Font name, e.g. "Century 725 Italic BT" */
int8_t family_name[50]; /* Font family name, e.g. "Century725 BT" */
int8_t style_name[50]; /* Font style name, e.g. "Italic" */
int8_t file_name1[200]; /* Name and path of the first font file, */
/* e.g. "C:\FONTS\TT1059M_.TTF" */
int8_t file_name2[200]; /* Name of the 2nd font file */
int8_t file_name3[200]; /* Name of the 3rd font file */
int16_t pt_cnt; /* Number of available point sizes */
/* (vst_point), e.g. 10 */
int16_t pt_sizes[64]; /* Available point sizes, e.g. { 8, 9, 10, */
/* 11, 12, 14, 18, 24, 36, 48 } */
} XFNT_INFO;
Note: So that the information can be entered in the structure, the size of the structure must be entered into the component size.
The following apply for the component format:
| 1 | = | Bitmap font |
| 2 | = | Speedo font |
| 4 | = | TrueType font |
| 8 | = | Type-1 font |
All character strings are NULL-terminated strings in C format. Structure elements that are not demanded have no defined contents.
See also: GEM NVDI vqt_xfntinfo