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141 lines
6.2 KiB
Plaintext
141 lines
6.2 KiB
Plaintext
BGIFONT.INC v1.0 beta
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Written in pure assembler by Ivushkin Andrey aka Willow
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At present Menuet operation system has poor means to draw charaters. Its
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distro contains 2 raster fonts (CHAR.MT & CHAR2.MT files). The kernel supports
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them internally. That is Jarek Pelczar who makes certain efforts to develop
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scalable TTF-like fonts but huge Menuet C Library does not become widespread
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inside our assembly-written OS. Bulgarian MenuetOS team also tries to include
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third scalable font into the kernel, though, as far as I know, its characters
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are still under design and are incomplete. Therefore Bulgarian developing is
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not valuable for ordinary users. It is obvious that scalable fonts will help
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to develop such products as browsers and word processors where character
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formatting is of great importance.
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Let me introduce for public domain an include file BGIFONT.INC to process
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vector fonts (*.CHR) worked out by famous Borland Corporation to use in Turbo
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Pascal, Turbo C and Borland C++ compilers under MS-DOS. Sorry, I still fail to
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add BGI font support into kernel - deeper knowledge on memory allocation and
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system calls needed. I hope that Menuet system programmers will be glad to help
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me. Module compiling within kernel is supposed using constant BGI_LEVEL equ
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KERNEL. By means of conditional compiling it will be possible to use the module
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at both kernel and application levels. Following is concerned using the include
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file while programming an application.
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BGI fonts may reside in any folder on HD or RD. They are searched using value
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of constant BGI_PATH. If constant BGI_WINDOW_CLIP is equal to 1, module routines
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perform window bounds check to avoid artifacts while drawing. Use this if you
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aren't sure that strings are fit in window. All BGIFONT.INC routines are
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declared as macros, that is they are used without "call". To load 11 fonts into
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application's memory a contiguous free space up to 120 kb is needed. When
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loading, font data relocation is performed to save memory. Let us see a chart:
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| Font | | BGIrec | | Font | | BGIrec | | Font | | BGIrec |
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| counter | | structure| | data | | structure| | data | | structure| ...
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| (1 byte)| | | | | |
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| ------------->------ -------------->----- ----------
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- referenced by [BGIfont_Ptr]
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BGIrec structure fields have following meaning:
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+00 dword .FontName font name (4 characters)
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+04 byte .CharsCount amount of font characters
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+05 byte .FirstChar code of the first character present
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+06 byte .UpperMargin high bound of characters
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+07 byte .LowerMargin low bound of characters
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+08 dword .Widths offset to width array
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+12 dword .FirstData offset to vector table
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+16 dword .EOF pointer to the following BGIrec
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+20 dword .font_data here font data begin
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Font loading and verification are carried out by BGIfont_Prepare procedure.
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BGIfont_Prepare
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in: EDX - font name (4 characters) to be loaded. It must to be the same as
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the font filename (without extension)
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EDI - address to where font have to be loaded. Used only for the
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first time. Then you may find this value in [BGIfont_Ptr]
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out: EAX=0, if an error occured, otherwise EAX is identifier (ID) of the
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loaded font. Later it is possible to get font ID with BGIfont_GetID
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function.
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For the simultaneous loading of few fonts you may use BGIfont_Init routine.
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BGIfont_Init
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in: ESI - pointer to array of font names (for example db 'TRIPSIMPEURO')
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ECX is amount of fonts to load
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EDI - see BGIfont_Prepare
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out: nothing.
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To load 10 standard fonts the module defines an array BGIfont_names (see in
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BGITEST for usage demonstration).
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For compatibility and subsequent kernel introduction, the module offers 2
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routines for drawing vector characters. One of them uses registers (like sysfunc
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4), another uses a structure.
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BGIfont_Outtext
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in: EAX - "pivot point" of a string [x] shl 16+[y]
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ECX - text color and font size 0xXYRRGGBB,
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where X - vector font ID(4..F),
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Y - size of caracters divided by 4, e.g. 0x1 - 1/4 of
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ordinary size, 0xC - triple size.
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EDX - pointer to the string
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ESI - string length + formatting flags (see below). BGI_ITALIC and
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BGI_NODRAW flags are ignored.
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out: EAX - coords at the end of the string drawn [x] shl 16+[y].
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As you can see, BGIfont_Outtext is similar to the 4th system function,
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but provides an extended management of drawing symbols.
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The most complete use of vector fonts is provided by BGIfont_Freetext routine.
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Parameters are passed in a BGIfree structure.
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BGIfree structure fields have following meaning:
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+00 dword font name (4 characters)
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+04 dword "pivot point" of a string [x] shl 16+[y]
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+08 dword turn angle (clockwise, 0 is horizontal)
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+12 dword X scale (floating point value!)
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+16 dword Y scale (floating point value!)
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+20 dword pointer to the string
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+24 dword string length WITHOUT formatting flags
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+28 dword text color 0x00RRGGBB
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+32 dword formatting flags
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The module defines following formatting flags:
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BGI_NODRAW - do not draw
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BGI_ITALIC - italic
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BGI_BOLD - bold
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BGI_HALEFT - left alignment
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BGI_HARIGHT - right alignment
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BGI_HACENTER - center alignment
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BGI_VABOTTOM - bottom alignment
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BGI_VATOP - top alignment
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BGI_VACENTER - middle vertical alignment
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Combination of flags can be performed by addition or the OR operation.
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BGIfont_Freetext
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in: EBX - pointer to BGIfree structure
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out: EAX coords at the end of the string drawn [x] shl 16+[y].
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BGIfont_GetID routine returns font ID by its name.
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BGIfont_GetID
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in: EDX - font name (4 characters)
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out: EAX - ID of the font
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EDI - pointer on font's BGIrec structure.
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Using functions of BGIFONT.INC module is demonstrated by BGITEST app.
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Todo list:
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1. An insidious bug sometimes shows up while loading multiple fonts (as in
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BGITEST), that corrupts some characters. It disappears when font loading
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order is changed... :-(
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2. To correct a hardly reproduceable bug when moving along the font list.
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3. To perfect drawing of bold fonts.
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4. To add number drawing routines.
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