/usr/share/doc/libwmf0.2-7/tutipa.html

<html>
<head>
<title>libwmf-0.2.0 Tutorial 2: The IPA</title>
</head>
<body link="#CC0000" alink="#FF3300" vlink="#330099" text="#000000" bgcolor="#ffffff"
      background="caolan/pics/weave.jpg">
<h1>libwmf-0.2.0 Tutorial 2: The IPA</h1>

<h2>Contents</h2>

<ul>
<li><a href="#intro">Introduction</a>
<li><a href="#types">Types</a>
<li><a href="#ipafnref"><b>IPA</b> Function Reference</a>
<li><a href="#ipafns">IPA Functions</a>
<li><a href="#bitmap">Bitmap Functions</a>
<li><a href="#fns">Other Functions</a>
<li><a href="#guide">Guidelines</a>
<li><a href="#compile">Compiling - The Distribution</a>
</ul>

<a name="intro"><h2>Introduction</h2></a>

<p>
This is a combination of tutorial and reference guide for writing new device
layers for <tt>libwmf</tt>.
</p>
<p>
Since no two graphics interfaces are identical, the task of the <b>IPA</b>
(the interface between the interpreter and the device layer) is to simplify the
task of translating the metafile drawing commands. (It cannot be denied that
there is still considerable room for improvement.)
</p>
<p>
When writing a new device layer you will need to include the following headers:
</p>
<font color=blue>
<pre>
#include &#60;libwmf/ipa.h&#62;
#include &#60;libwmf/defs.h&#62;
</pre>
</font>
<p>
The former includes the <b>API</b> declarations as well as the <b>IPA</b>
declarations, while the latter defines metafile constants.
</p>

<a name="types"><h2>Types</h2></a>

  <a href="#RGB">wmfRGB</a>
| <a href="#BMP">wmfBMP</a>
| <a href="#Brush">wmfBrush</a>
| <a href="#Pen">wmfPen</a>
| <a href="#Font">wmfFont</a>
| <a href="#DC">wmfDC</a>
| <a href="#Flood">wmfFlood_t</a>
| <a href="#DrawPixel">wmfDrawPixel_t</a>
| <a href="#DrawArc">wmfDrawArc_t</a>
| <a href="#DrawLine">wmfDrawLine_t</a>
| <a href="#PolyLine">wmfPolyLine_t</a>
| <a href="#DrawRect">wmfDrawRectangle_t</a>
| <a href="#PolyRect">wmfPolyRectangle_t</a>
| <a href="#BMPRead">wmfBMP_Read_t</a>
| <a href="#BMPDraw">wmfBMP_Draw_t</a>
| <a href="#ROPDraw">wmfROP_Draw_t</a>
| <a href="#DrawText">wmfDrawText_t</a>
| <a href="#UserData">wmfUserData_t</a>
| <a href="#CharDrawer">wmfCharDrawer</a>

<ul>
<li><a name="RGB"><b>wmfRGB</b></a>
<font color=blue>
<pre>
typedef struct _wmfRGB wmfRGB;

struct _wmfRGB
{	unsigned char r;
	unsigned char g;
	unsigned char b;
};
</pre>
</font>
<p>
<tt>wmfRGB</tt> describes a color, with <tt>r = g = b = 255</tt> corresponding
to <i>white</i> and <tt>r = g = b = 0</tt> corresponding to <i>black</i>.
</p>

<li><a name="BMP"><b>wmfBMP</b></a>
<font color=blue>
<pre>
typedef struct _wmfBMP wmfBMP;

struct _wmfBMP
{	U16 width;
	U16 height;

	void* data;
};
</pre>
</font>
<p>
Container for a bitmap, of dimensions <tt>width</tt> and <tt>height</tt>.
If non-zero, <tt>data</tt> is a pointer to an internal representation of the
bitmap. The interpreter does not reference <tt>data</tt> and will not attempt
to draw a bitmap if <tt>data</tt> is zero; however, a bitmap brush pattern
may be set even though <tt>data</tt> is zero. (<tt>data=0</tt> indicates
either that the device layer has no support for bitmaps or that the bitmap
is corrupt or unreadable.)
</p>

<li><a name="Brush"><b>wmfBrush</b></a>
<font color=blue>
<pre>
typedef struct _wmfBrush wmfBrush;

struct _wmfBrush
{	U16 lbStyle;
	U16 lbHatch;

	wmfRGB lbColor;
	wmfBMP bmp;
};
</pre>
</font>
<p>
<tt>wmfBrush</tt> is one element of the current drawing context.
<tt>lbStyle</tt> is one of the following:
</p>
<font color=blue>
<pre>
/* Brush Styles */
#define BS_SOLID            0
#define BS_NULL             1
#define BS_HOLLOW     BS_NULL
#define BS_HATCHED          2
#define BS_PATTERN          3
#define BS_INDEXED          4
#define BS_DIBPATTERN       5
#define BS_DIBPATTERNPT     6
#define BS_PATTERN8X8       7
#define BS_DIBPATTERN8X8    8
</pre>
</font>
<p>
where <tt>BS_NULL</tt> indicates that no brush is set. If
<tt>lbStyle=BS_HATCHED</tt> then the brush has the pattern, specified by
<tt>lbHatch</tt> which is one of:
</p>
<font color=blue>
<pre>
/* Hatch Styles */
#define HS_HORIZONTAL       0       /* ----- */
#define HS_VERTICAL         1       /* ||||| */
#define HS_FDIAGONAL        2       /* \\\\\ */
#define HS_BDIAGONAL        3       /* ///// */
#define HS_CROSS            4       /* +++++ */
#define HS_DIAGCROSS        5       /* xxxxx */
</pre>
</font>
<p>
If <tt>lbStyle=BS_HATCHED</tt> or <tt>lbStyle=BS_SOLID</tt> then the foreground
color of the brush is <tt>lbColor</tt>. Otherwise, if the brush is a bitmap,
ensure that <tt>bmp.data</tt> is non-zero.
</p>
<p>
The following macros should be used to retrieve the above info.:
</p>
<font color=blue>
<pre>
#include <libwmf/macro.h>

/* WMF_BRUSH_STYLE(wmfBrush* B) -> (U16) brush style
 * WMF_BRUSH_HATCH(wmfBrush* B) -> (U16) brush hatch style
 * 
 * WMF_BRUSH_COLOR(wmfBrush* B) -> (wmfRGB*) brush color
 * 
 * WMF_BRUSH_BITMAP(wmfBrush* B) -> (wmfBMP*) brush bitmap
 */
#define WMF_BRUSH_STYLE(B)  ((B)->lbStyle)
#define WMF_BRUSH_HATCH(B)  ((B)->lbHatch)

#define WMF_BRUSH_COLOR(B)  (&((B)->lbColor))

#define WMF_BRUSH_BITMAP(B) (&((B)->bmp))
</pre>
</font>

<li><a name="Pen"><b>wmfPen</b></a>
<font color=blue>
<pre>
typedef struct _wmfPen wmfPen;

struct _wmfPen
{	U16 lopnStyle;

	double width;
	double height;

	wmfRGB lopnColor;
};
</pre>
</font>
<p>
<tt>wmfPen</tt> is one element of the current drawing context. The nib has
dimensions <tt>width</tt> and <tt>height</tt> and color <tt>lopnColor</tt>.
<tt>lopnStyle</tt> contains style information on the line itself, on the ends,
on the joins, and on the type:
</p>
<font color=blue>
<pre>
#define PS_STYLE_MASK       0x0000000F
#define PS_ENDCAP_MASK      0x00000F00
#define PS_JOIN_MASK        0x0000F000
#define PS_TYPE_MASK        0x000F0000
</pre>
</font>
<p>
<tt>lopnStyle & PS_STYLE_MASK</tt> is one of:
</p>
<font color=blue>
<pre>
#define PS_SOLID            0
#define PS_DASH             1       /* -------  */
#define PS_DOT              2       /* .......  */
#define PS_DASHDOT          3       /* _._._._  */
#define PS_DASHDOTDOT       4       /* _.._.._  */
#define PS_NULL             5
#define PS_INSIDEFRAME      6
#define PS_USERSTYLE        7
#define PS_ALTERNATE        8
</pre>
</font>
<p>
where PS_NULL indicates that no pen has been set.
<tt>lopnStyle & PS_ENDCAP_MASK</tt> is one of:
</p>
<font color=blue>
<pre>
#define PS_ENDCAP_ROUND     0x00000000
#define PS_ENDCAP_SQUARE    0x00000100
#define PS_ENDCAP_FLAT      0x00000200
</pre>
</font>
<p>
and <tt>lopnStyle & PS_JOIN_MASK</tt> is one of:
</p>
<font color=blue>
<pre>
#define PS_JOIN_ROUND       0x00000000
#define PS_JOIN_BEVEL       0x00001000
#define PS_JOIN_MITER       0x00002000
</pre>
</font>
<p>
Finally, <tt>lopnStyle & PS_TYPE_MASK</tt> is one of:
</p>
<font color=blue>
<pre>
#define PS_COSMETIC         0x00000000
#define PS_GEOMETRIC        0x00010000
</pre>
</font>
<p>
The following macros should be used to retrieve the above info.:
</p>
<font color=blue>
<pre>
#include <libwmf/macro.h>

/* WMF_PEN_STYLE(wmfPen* P)  -> (U16) pen style
 * WMF_PEN_ENDCAP(wmfPen* P) -> (U16) endcap style
 * WMF_PEN_JOIN(wmfPen* P)   -> (U16) join style
 * WMF_PEN_TYPE(wmfPen* P)   -> (U16) `type' of pen (??)
 * 
 * WMF_PEN_WIDTH(wmfPen* P)  -> (double) pen `width'  (thickness w.r.t. x-axis)
 * WMF_PEN_HEIGHT(wmfPen* P) -> (double) pen `height' (thickness w.r.t. y-axis)
 * 
 * WMF_PEN_COLOR(wmfPen* P) -> (wmfRGB*) pen color
 */
#define WMF_PEN_STYLE(P)  ((P)->lopnStyle & PS_STYLE_MASK)
#define WMF_PEN_ENDCAP(P) ((P)->lopnStyle & PS_ENDCAP_MASK)
#define WMF_PEN_JOIN(P)   ((P)->lopnStyle & PS_JOIN_MASK)
#define WMF_PEN_TYPE(P)   ((P)->lopnStyle & PS_TYPE_MASK)

#define WMF_PEN_WIDTH(P)  ((P)->width)
#define WMF_PEN_HEIGHT(P) ((P)->height)

#define WMF_PEN_COLOR(P)  (&((P)->lopnColor))
</pre>
</font>

<li><a name="Font"><b>wmfFont</b></a>
<font color=blue>
<pre>
typedef struct _wmfFont wmfFont;

struct _wmfFont
{	U16 lfHeight;
	U16 lfWidth;

	S16 lfEscapement;
	S16 lfOrientation;

	U16 lfWeight;

	U8 lfItalic;
	U8 lfUnderline;
	U8 lfStrikeOut;
	U8 lfCharSet;
	U8 lfOutPrecision;
	U8 lfClipPrecision;
	U8 lfQuality;
	U8 lfPitchAndFamily;

	char* lfFaceName;

	char* ps_name;

	FT_Face ft_face;
};
</pre>
</font>
<p>
<tt>wmfFont</tt> is one element of the current drawing context. Of all of this,
the most important elements are <tt>ps_name</tt> (the postscript font name) and
<tt>ft_face</tt>, the freetype (2) font face for which <b>bold</b> and
<i>italics</i> have already been determined.
</p>
<p>
The following macros should be used to retrieve the above info.:
</p>
<font color=blue>
<pre>
#include <libwmf/macro.h>

/* WMF_TEXT_ANGLE(wmfFont* F) -> (double) text angle in radians
 * 
 * WMF_TEXT_UNDERLINE(wmfFont* F) -> (U8) ?? whether to underline (?? how thick)
 * WMF_TEXT_STRIKEOUT(wmfFont* F) -> (U8) ?? whether to strikeout (?? how thick)
 * 
 * WMF_FONT_NAME(wmfFont* F)   -> (char*) font name supplied by metafile
 * WMF_FONT_PSNAME(wmfFont* F) -> (char*) font name to use in postscript output
 * WMF_FONT_FTFACE(wmfFont* F) -> (FT_Face) freetype(2) font face
 */
#define WMF_TEXT_ANGLE(F)     ((((double) (F)->lfEscapement) / 10) * M_PI / 180)

#define WMF_TEXT_UNDERLINE(F) ((F)->lfUnderline)
#define WMF_TEXT_STRIKEOUT(F) ((F)->lfStrikeOut)

#define WMF_FONT_NAME(F)   ((F)->lfFaceName)
#define WMF_FONT_PSNAME(F) ((F)->ps_name)
#define WMF_FONT_FTFACE(F) ((F)->ft_face)
</pre>
</font>

<li><a name="DC"><b>wmfDC</b></a>
<font color=blue>
<pre>
typedef struct _wmfDC wmfDC;

struct _wmfDC
{	void* userdata;

	wmfBrush* brush;
	wmfPen* pen;
	wmfFont* font;

	int key;     /* Is this used ?? */

	wmfDC* next; /* Is this used ?? */

	wmfRGB textcolor;
	wmfRGB bgcolor;

	U16 textalign;
	U16 bgmode;
	U16 polyfillmode;
	U16 charextra;
	U16 breakextra;

	U16 ROPmode;

	struct
	{	S32 Ox;
		S32 Oy;
		S32 width;
		S32 height;
	} Window;

	double pixel_width; /* Display pixel dimensions (inches) */
	double pixel_height;

	U16 map_mode;

	void* clip;
};
</pre>
</font>
<p>
<i>Still very much a work in progress, especially with regard to the drawing
context <tt>wmfDC</tt>; there is much in this structure that is (or should
be) irrelevant to the <b>IPA</b>.</i>
</p>
<p>
See <b>wmfBrush</b>, <b>wmfPen</b> and <b>wmfFont</b>. <tt>textcolor</tt> is
the color to draw text, <tt>bgcolor</tt> is the background color (generally, as
well as with text) unless <tt>bgmode=TRANSPARENT</tt>, in which case there is
no background. <tt>bgmode</tt> is one of:
</p>
<font color=blue>
<pre>
#define TRANSPARENT         1
#define OPAQUE              2
#define BKMODE_LAST         2
</pre>
</font>
<p>
The following macros should be used to retrieve the above info.:
</p>
<font color=blue>
<pre>
#include <libwmf/macro.h>

/* WMF_DC_BRUSH(wmfDC* C) -> (wmfBrush*) current brush
 * WMF_DC_PEN(wmfDC* C)   -> (wmfPen*)   current pen
 * WMF_DC_FONT(wmfDC* C)  -> (wmfFont*)  current font
 * 
 * WMF_DC_TEXTCOLOR(wmfDC* C)  -> (wmfRGB*) text color
 * WMF_DC_BACKGROUND(wmfDC* C) -> (wmfRGB*) background color
 * 
 * WMF_DC_OPAQUE(wmfDC* C) -> (U16) whether to fill opaque (non-zero if true)
 * 
 * WMF_DC_POLYFILL(wmfDC* C) -> (U16) how to fill polygons
 * 
 * WMF_DC_ROP(wmfDC* C) -> (U16) ROP mode
 */
#define WMF_DC_BRUSH(C)      ((C)->brush)
#define WMF_DC_PEN(C)        ((C)->pen)
#define WMF_DC_FONT(C)       ((C)->font)

#define WMF_DC_TEXTCOLOR(C)  (&((C)->textcolor))
#define WMF_DC_BACKGROUND(C) (&((C)->bgcolor))

#define WMF_DC_OPAQUE(C)     ((C)->bgmode - 1)

#define WMF_DC_POLYFILL(C)   ((C)->polyfillmode)

#define WMF_DC_ROP(C)        ((C)->ROPmode)
</pre>
</font>

<li><a name="Flood"><b>wmfFlood_t</b></a>
<font color=blue>
<pre>
typedef struct _wmfFlood_t wmfFlood_t;

struct _wmfFlood_t
{	wmfDC* dc;

	wmfD_Coord pt;
	wmfRGB color;

	U16 type;

	double pixel_width;
	double pixel_height;
};
</pre>
</font>
<p>
Flood-fill region with color <tt>color</tt>, starting at point <tt>pt</tt>.
Since this is almost certainly not a vector operation, the pixel width and
height are given (and are probably best ignored...). <tt>type</tt> is one
of:
</p>
<font color=blue>
<pre>
#define  FLOODFILLBORDER    0
#define  FLOODFILLSURFACE   1
</pre>
</font>

<li><a name="DrawPixel"><b>wmfDrawPixel_t</b></a>
<font color=blue>
<pre>
typedef struct _wmfDrawPixel_t wmfDrawPixel_t;

struct _wmfDrawPixel_t
{	wmfDC* dc;

	wmfD_Coord pt;
	wmfRGB color;

	double pixel_width;
	double pixel_height;
};
</pre>
</font>
<p>
Set pixel at point <tt>pt</tt> to color <tt>color</tt>. The pixel width and
height are given.
</p>

<li><a name="DrawArc"><b>wmfDrawArc_t</b></a>
<font color=blue>
<pre>
typedef struct _wmfDrawArc_t wmfDrawArc_t;

struct _wmfDrawArc_t
{	wmfDC* dc;

	wmfD_Coord TL;
	wmfD_Coord BR;

	wmfD_Coord start; /* draw_ellipse: (ignored) */
	wmfD_Coord end;
};
</pre>
</font>
<p>
Draw a complete or partial ellipse. <tt>TL</tt> and <tt>BR</tt> are the
coordinates of the top left and bottom right of the ellipse's bounding box
respectively. If incomplete, then <tt>start</tt> and <tt>end</tt> give the
start and end coordinates of the arc.
</p>

<li><a name="DrawLine"><b>wmfDrawLine_t</b></a>
<font color=blue>
<pre>
typedef struct _wmfDrawLine_t wmfDrawLine_t;

struct _wmfDrawLine_t
{	wmfDC* dc;

	wmfD_Coord from;
	wmfD_Coord to;
};
</pre>
</font>
<p>
Draw line from point <tt>from</tt> to point <tt>to</tt>.
</p>

<li><a name="PolyLine"><b>wmfPolyLine_t</b></a>
<font color=blue>
<pre>
typedef struct _wmfPolyLine_t wmfPolyLine_t;

struct _wmfPolyLine_t
{	wmfDC* dc;

	wmfD_Coord* pt;

	U16 count;
};
</pre>
</font>
<p>
An array (of length <tt>count</tt>) of points <tt>pt[]</tt>. This may be used
to describe polygons as well as line sequences.
</p>

<li><a name="DrawRect"><b>wmfDrawRectangle_t</b></a>
<font color=blue>
<pre>
typedef struct _wmfDrawRectangle_t wmfDrawRectangle_t;

struct _wmfDrawRectangle_t
{	wmfDC* dc;

	wmfD_Coord TL;
	wmfD_Coord BR;

	float width; /* draw_rectangle: axes of corner ellipses; zero if un-rounded */
	float height;
};
</pre>
</font>
<p>
A rectangle, possibly with rounded corners - in which case <tt>width</tt> and
<tt>height</tt> give the elliptic axes of the rectangle's corners.
</p>

<li><a name="PolyRect"><b>wmfPolyRectangle_t</b></a>
<font color=blue>
<pre>
typedef struct _wmfPolyRectangle_t wmfPolyRectangle_t;

struct _wmfPolyRectangle_t
{	wmfDC* dc;

	wmfD_Coord* TL; /* region_frame & region_paint: TL[count],BR[count] give the */
	wmfD_Coord* BR; /* final `extents'... */

	unsigned int count;

	float width;  /* region_frame: border thickness; zero otherwise */
	float height;
};
</pre>
</font>
<p>
Used by region and clip calls, <tt>wmfPolyRectangle_t</tt> is used to describe
multiple rectangles, whose top left and bottom right corners are given by the
<tt>TL</tt> and <tt>BR</tt> arrays respectively. These arrays are of length
<tt>count</tt> in the case of clip calls, and of length <tt>count</tt> + 1 in
the case of the region calls, the extra element containing the overall bounding
box (the region extents). In the case of <tt>region_frame</tt>, <tt>width</tt>
and <tt>height</tt> give the thickness of the frame.
</p>

<li><a name="BMPRead"><b>wmfBMP_Read_t</b></a>
<font color=blue>
<pre>
typedef struct _wmfBMP_Read_t wmfBMP_Read_t;

struct _wmfBMP_Read_t          /* Two means available for accessing BMP image:        */
{	long offset;           /* (1) position in source file of start of BMP;        *
                                * use API->bbuf.seek to set pos(ition), etc.          */
	long length;           /* (2) buffer of length length containing image of BMP */
	unsigned char* buffer;

	U16 width;  /* WMF player may preset these values; zero otherwise. */
	U16 height; /* Use caution - may be buggy... ?? [TODO]             */

	wmfBMP bmp;
};
</pre>
</font>
<p>
There are two ways to read a bitmap presented by <tt>libwmf</tt>: the first is
to read it directly from the input stream using the internal stream functions:
<font color=blue>
<pre>
/* Macro-wrappers for stream functions:
 * (int)  WMF_READ ((wmfAPI*) API)                 - returns unsigned char cast to int, or EOF
 * (int)  WMF_SEEK ((wmfAPI*) API,(long) position) - returns (-1) on error, else 0
 * (long) WMF_TELL ((wmfAPI*) API)                 - returns (-1) on error, else current position
 */
</pre>
</font>
where the bitmap starts at offset <tt>offset</tt>; the second (which is
preferred) is to use the buffer <tt>buffer</tt> of length <tt>length</tt>.
</p>
<p>
To complicate matters, the bitmap's data may be truncated so that the bitmap's
header is incorrect - <tt>width</tt> and <tt>height</tt> give the <i>real</i>
dimensions of the bitmap.
</p>
<p>
The bitmap's width and height should be entered into <tt>bmp</tt> (see
<a href="#BMP">wmfBMP</a> above) as well as a pointer to the bitmap data (which
can be in any format you choose; the library does not need to know).
</p>

<li><a name="BMPDraw"><b>wmfBMP_Draw_t</b></a>
<font color=blue>
<pre>
typedef struct _wmfBMP_Draw_t wmfBMP_Draw_t;

struct _wmfBMP_Draw_t
{	wmfDC* dc;

	wmfD_Coord pt;
	wmfBMP bmp;

	U32 type;

	struct
	{	U16 x;
		U16 y;
		U16 w;
		U16 h;
	} crop;

	double pixel_width;
	double pixel_height;
};
</pre>
</font>
<p>
In contrast to earlier versions, <tt>libwmf</tt> no longer makes any attempt to
crop or scale the bitmap. Instead the crop data are presented to the device
layer to use as it sees fit, and the pixel width and height as well. The bitmap
referenced by <tt>bmp</tt> (see <a href="#BMP">wmfBMP</a> above) is to be drawn
at point <tt>pt</tt>.
</p>
<p>
<i><b>TODO:</b> info on <tt>type</tt></i>
</p>

<li><a name="ROPDraw"><b>wmfROP_Draw_t</b></a>
<font color=blue>
<pre>
typedef struct _wmfROP_Draw_t wmfROP_Draw_t;

struct _wmfROP_Draw_t
{	wmfDC* dc;

	wmfD_Coord TL;
	wmfD_Coord BR;

	U32 ROP;

	double pixel_width;
	double pixel_height;
};
</pre>
</font>
<p>
<i><b>TODO:</b></i>
</p>

<li><a name="DrawText"><b>wmfDrawText_t</b></a>
<font color=blue>
<pre>
typedef struct _wmfDrawText_t wmfDrawText_t;

struct _wmfDrawText_t
{	wmfDC* dc;

	wmfD_Coord pt;

	wmfD_Coord TL; /* Clip zone */
	wmfD_Coord BR;

	struct /* An estimated surround zone */
	{	wmfD_Coord TL;
		wmfD_Coord TR;
		wmfD_Coord BL;
		wmfD_Coord BR;
	} bbox;

	char* str;

	U16 flags;

	double font_height;
	double font_ratio;  /* width to height ratio */
};
</pre>
</font>
<p>
Fonts and text are <i>triiicky</i>! Fortunately <tt>libwmf</tt> tries to do
most of the work. As such text justification is taken care of by the
interpreter, and fonts (<b>bold</b>, <i>italic</i>, etc.) are selected
elsewhere. The emphasis with <tt>wmfDrawText_t</tt> is therefore the rendering
of text.
</p>
<p>
The text can be assumed to be left-justified, starting at point <tt>pt</tt>.
<tt>TL</tt> and <tt>BR</tt> are the corners of a clip rectangle. <tt>bbox</tt>
gives four corners of rectangle - an <i>estimate</i> of the background zone.
<tt>str</tt> is the text to draw; <tt>font_height</tt> is the height of the
font and <tt>font_ratio</tt> is how much to stretch the font width-wise. The
values for <tt>flags</tt> are:
</p>
<font color=blue>
<pre>
#define ETO_OPAQUE          0x0002
#define ETO_CLIPPED         0x0004
#define ETO_GLYPH_INDEX     0x0010
#define ETO_RTLREADING      0x0080
</pre>
</font>

<li><a name="UserData"><b>wmfUserData_t</b></a>
<font color=blue>
<pre>
typedef struct _wmfUserData_t wmfUserData_t;

struct _wmfUserData_t	/* TODO: Need to be careful with usage here; not all these are set by the player! */
{	wmfDC* dc;          /* dc is guaranteed */

	void* data;         /* data also, except for init */
};
</pre>
</font>
<p>
Redundant; may be removed at some point...
</p>

<li><a name="CharDrawer"><b>wmfCharDrawer</b></a>
<font color=blue>
<pre>
typedef void (*wmfCharDrawer) (wmfAPI*,wmfDrawText_t*);
</pre>
</font>
</ul>

<a name="ipafnref"><h2>IPA Function Reference</h2></a>

<p>
Let us assume that you are writing a device layer called <i>mydev</i>, then the
first requirement is an initialization function:
</p>
<font color=blue>
<pre>
#include &#60;libwmf/ipa.h&#62;
#include &#60;libwmf/defs.h&#62;
#include &#60;libwmf/<i>mydev</i>.h&#62;

void wmf_<i>mydev</i>_function (wmfAPI* API)
{	wmfFunctionReference* FR = (wmfFunctionReference*) API->function_reference;

	/* */
</pre>
</font>
The function reference has the following definition:
<font color=blue>
<pre>
typedef struct _wmfFunctionReference wmfFunctionReference;

struct _wmfFunctionReference
{	void (*device_open) (wmfAPI*);
	void (*device_close) (wmfAPI*);
	void (*device_begin) (wmfAPI*);
	void (*device_end) (wmfAPI*);

	void (*flood_interior) (wmfAPI*,wmfFlood_t*);
	void (*flood_exterior) (wmfAPI*,wmfFlood_t*);

	void (*draw_pixel) (wmfAPI*,wmfDrawPixel_t*);
	void (*draw_pie) (wmfAPI*,wmfDrawArc_t*);
	void (*draw_chord) (wmfAPI*,wmfDrawArc_t*);
	void (*draw_arc) (wmfAPI*,wmfDrawArc_t*);
	void (*draw_ellipse) (wmfAPI*,wmfDrawArc_t*);
	void (*draw_line) (wmfAPI*,wmfDrawLine_t*);
	void (*poly_line) (wmfAPI*,wmfPolyLine_t*);
	void (*draw_polygon) (wmfAPI*,wmfPolyLine_t*);
	void (*draw_rectangle) (wmfAPI*,wmfDrawRectangle_t*);

	void (*rop_draw) (wmfAPI*,wmfROP_Draw_t*);
	void (*bmp_draw) (wmfAPI*,wmfBMP_Draw_t*);
	void (*bmp_read) (wmfAPI*,wmfBMP_Read_t*);
	void (*bmp_free) (wmfAPI*,wmfBMP*);

	void (*draw_text) (wmfAPI*,wmfDrawText_t*);

	void (*udata_init) (wmfAPI*,wmfUserData_t*);
	void (*udata_copy) (wmfAPI*,wmfUserData_t*);
	void (*udata_set) (wmfAPI*,wmfUserData_t*);
	void (*udata_free) (wmfAPI*,wmfUserData_t*);

	void (*region_frame) (wmfAPI*,wmfPolyRectangle_t*);
	void (*region_paint) (wmfAPI*,wmfPolyRectangle_t*);
	void (*region_clip) (wmfAPI*,wmfPolyRectangle_t*);
};
</pre>
</font>
<p>
The initialization function has two purposes, the first being to establish the
links that create the <b>IPA</b> by pointing the function reference variables
to your own drawing functions:
</p>
<font color=blue>
<pre>
#include &#60;libwmf/ipa.h&#62;
#include &#60;libwmf/defs.h&#62;
#include &#60;libwmf/<i>mydev</i>.h&#62;

void wmf_<i>mydev</i>_function (wmfAPI* API)
{	wmfFunctionReference* FR = (wmfFunctionReference*) API-&#62;function_reference;

	FR-&#62;device_open  = wmf_<i>mydev</i>_device_open;
	FR-&#62;device_close = wmf_<i>mydev</i>_device_close;
	FR-&#62;device_begin = wmf_<i>mydev</i>_device_begin;
	FR-&#62;device_end   = wmf_<i>mydev</i>_device_end;
	/* etc. */

	/* */
}

void wmf_<i>mydev</i>_device_open (wmfAPI* API)
{	/* */
}

/* etc. */
</pre>
</font>
<p>
The second purpose of the initialization function is to allocate the device's
data structure, set the device parameters to default values if necessary, and
then to attach the data to the <tt>API->device_data</tt> hook.
</p>
<font color=blue>
<pre>
/* */

typedef struct _wmf_<i>mydev</i>_t wmf_<i>mydev</i>_t;

struct _wmf_<i>mydev</i>_t
{	/* */

	unsigned long flags;
}

void wmf_<i>mydev</i>_function (wmfAPI* API)
{	wmfFunctionReference* FR = (wmfFunctionReference*) API-&#62;function_reference;

	wmf_<i>mydev</i>_t* ddata = 0;

	FR-&#62;device_open  = wmf_<i>mydev</i>_device_open;
	/* etc. */

	API-&#62;device_data = wmf_malloc (API,sizeof (wmf_<i>mydev</i>_t));

	if (API->err != wmf_E_None) return; /* insufficient memory? */

	ddata = (wmf_<i>mydev</i>_t*) API-&#62;device_data;

	/* */

	ddata->flags = 0;
}

/* */
</pre>
</font>

<a name="ipafns"><h2>IPA Functions</h2></a>

<p>
The <b>IPA</b> functions are called by <tt>wmf_play ()</tt>, the only exception
being <tt>device_close</tt> which is called by <tt>wmf_api_destroy ()</tt> -
and then only if <tt>device_open</tt> has been called by <tt>wmf_play ()</tt>.
</p>
<p>
<tt>device_open</tt> is called the first time (and <i>only</i> the first time)
<tt>wmf_play ()</tt> is called, and is the very first <b>IPA</b> function to be
called, just as <tt>device_close</tt> will be the very last.
</p>
<p>
At the beginning of each <i>play</i> cycle (i.e., each call to
<tt>wmf_play ()</tt>) <tt>device_begin</tt> is called (after
<tt>device_open</tt> if it is the first cycle), and at the end of each cycle
<tt>device_end</tt> is called. The metafile graphics use other <b>IPA</b>
functions.
</p>
<p>
<tt>device_open</tt>, <tt>device_begin</tt>, <tt>device_end</tt> and
<tt>device_close</tt> <i>should</i> be written so that <tt>wmf_play ()</tt> can
be called repeatedly.
</p>
<p>
The names of the functions are not important. The generic names are used below:
</p>

  <a href="#devopen">device_open</a>
| <a href="#devclose">device_close</a>
| <a href="#devbegin">device_begin</a>
| <a href="#devend">device_end</a>
| <a href="#floodint">flood_interior</a>
| <a href="#floodext">flood_exterior</a>
| <a href="#dpixel">draw_pixel</a>
| <a href="#dpie">draw_pie</a>
| <a href="#dchord">draw_chord</a>
| <a href="#darc">draw_arc</a>
| <a href="#dellipse">draw_ellipse</a>
| <a href="#dline">draw_line</a>
| <a href="#pline">poly_line</a>
| <a href="#dpoly">draw_polygon</a>
| <a href="#drect">draw_rectangle</a>
| <a href="#ropdraw">rop_draw</a>
| <a href="#bmpdraw">bmp_draw</a>
| <a href="#bmpread">bmp_read</a>
| <a href="#bmpfree">bmp_free</a>
| <a href="#dtext">draw_text</a>
| <a href="#uinit">udata_init</a>
| <a href="#ucopy">udata_copy</a>
| <a href="#uset">udata_set</a>
| <a href="#ufree">udata_free</a>
| <a href="#rframe">region_frame</a>
| <a href="#rpaint">region_paint</a>
| <a href="#rclip">region_clip</a>

<ul>
<li><a name="devopen"><b>device_open</b></a>
<font color=blue>
<pre>
void device_open (wmfAPI*);
</pre>
</font>
<p>
<tt>device_open</tt> is the very first <b>IPA</b> function to be called. It is
called only once, the first time <tt>wmf_play ()</tt> is called.
</p>

<li><a name="devclose"><b>device_close</b></a>
<font color=blue>
<pre>
void device_close (wmfAPI*);
</pre>
</font>
<p>
<tt>device_close</tt> is the very last <b>IPA</b> function to be called. It is
called by <tt>wmf_api_destroy ()</tt>, and only if <tt>device_open</tt> has
been called earlier.
</p>

<li><a name="devbegin"><b>device_begin</b></a>
<font color=blue>
<pre>
void device_begin (wmfAPI*);
</pre>
</font>
<p>
<tt>device_begin</tt> is the first <b>IPA</b> function called from
<tt>wmf_play ()</tt> (with the exception of <tt>device_open</tt> the first time
<tt>wmf_play ()</tt> is called).
</p>

<li><a name="devend"><b>device_end</b></a>
<font color=blue>
<pre>
void device_end (wmfAPI*);
</pre>
</font>
<p>
<tt>device_end</tt> is the last <b>IPA</b> function called from
<tt>wmf_play ()</tt>.
</p>

<li><a name="floodint"><b>flood_interior</b></a>
<font color=blue>
<pre>
void flood_interior (wmfAPI*,<a href="#Flood">wmfFlood_t</a>*);
</pre>
</font>

<li><a name="floodext"><b>flood_exterior</b></a>
<font color=blue>
<pre>
void flood_exterior (wmfAPI*,<a href="#Flood">wmfFlood_t</a>*);
</pre>
</font>

<li><a name="dpixel"><b>draw_pixel</b></a>
<font color=blue>
<pre>
void draw_pixel (wmfAPI*,<a href="#DrawPixel">wmfDrawPixel_t</a>*);
</pre>
</font>

<li><a name="dpie"><b>draw_pie</b></a>
<font color=blue>
<pre>
void draw_pie (wmfAPI*,<a href="#DrawArc">wmfDrawArc_t</a>*);
</pre>
</font>

<li><a name="dchord"><b>draw_chord</b></a>
<font color=blue>
<pre>
void draw_chord (wmfAPI*,<a href="#DrawArc">wmfDrawArc_t</a>*);
</pre>
</font>

<li><a name="darc"><b>draw_arc</b></a>
<font color=blue>
<pre>
void draw_arc (wmfAPI*,<a href="#DrawArc">wmfDrawArc_t</a>*);
</pre>
</font>

<li><a name="dellipse"><b>draw_ellipse</b></a>
<font color=blue>
<pre>
void draw_ellipse (wmfAPI*,<a href="#DrawArc">wmfDrawArc_t</a>*);
</pre>
</font>

<li><a name="dline"><b>draw_line</b></a>
<font color=blue>
<pre>
void draw_line (wmfAPI*,<a href="#DrawLine">wmfDrawLine_t</a>*);
</pre>
</font>

<li><a name="pline"><b>poly_line</b></a>
<font color=blue>
<pre>
void poly_line (wmfAPI*,<a href="#PolyLine">wmfPolyLine_t</a>*);
</pre>
</font>

<li><a name="dpoly"><b>draw_polygon</b></a>
<font color=blue>
<pre>
void draw_polygon (wmfAPI*,<a href="#PolyLine">wmfPolyLine_t</a>*);
</pre>
</font>

<li><a name="drect"><b>draw_rectangle</b></a>
<font color=blue>
<pre>
void draw_rectangle (wmfAPI*,<a href="#DrawRect">wmfDrawRectangle_t</a>*);
</pre>
</font>

<li><a name="ropdraw"><b>rop_draw</b></a>
<font color=blue>
<pre>
void rop_draw (wmfAPI*,<a href="#ROPDraw">wmfROP_Draw_t</a>*);
</pre>
</font>
<p>
<i><b>TODO:</b></i>
</p>

<li><a name="bmpdraw"><b>bmp_draw</b></a>
<font color=blue>
<pre>
void bmp_draw (wmfAPI*,<a href="#BMPDraw">wmfBMP_Draw_t</a>*);
</pre>
</font>
<p>
<b>Note:</b> Unless you're feeling masochistic and want to write, or re-write,
your own suite of functions for the reading, writing and general manipulation
of bitmaps, you should defer this to <tt>libwmf</tt>'s built-in support which
is adapted from <tt>ImageMagick</tt>'s excellent BMP coder.
</p>
<p>
See section on bitmaps below.
</p>

<li><a name="bmpread"><b>bmp_read</b></a>
<font color=blue>
<pre>
void bmp_read (wmfAPI*,<a href="#BMPRead">wmfBMP_Read_t</a>*);
</pre>
</font>
<p>
<b>Note:</b> Unless you're feeling masochistic and want to write, or re-write,
your own suite of functions for the reading, writing and general manipulation
of bitmaps, you should defer this to <tt>libwmf</tt>'s built-in support which
is adapted from <tt>ImageMagick</tt>'s excellent BMP coder.
</p>
<font color=blue>
<pre>
void bmp_read (wmfAPI* API,<a href="#BMPRead">wmfBMP_Read_t</a>* bmp_read)
{	wmf_ipa_bmp_read (API,bmp_read);
}
</pre>
</font>

<li><a name="bmpfree"><b>bmp_free</b></a>
<font color=blue>
<pre>
void bmp_free (wmfAPI*,<a href="#BMP">wmfBMP</a>*);
</pre>
</font>
<p>
<b>Note:</b> Unless you're feeling masochistic and want to write, or re-write,
your own suite of functions for the reading, writing and general manipulation
of bitmaps, you should defer this to <tt>libwmf</tt>'s built-in support which
is adapted from <tt>ImageMagick</tt>'s excellent BMP coder.
</p>
<font color=blue>
<pre>
void bmp_free (wmfAPI* API,<a href="#BMP">wmfBMP</a>* bmp)
{	wmf_ipa_bmp_free (API,bmp);
}
</pre>
</font>

<li><a name="dtext"><b>draw_text</b></a>
<font color=blue>
<pre>
void draw_text (wmfAPI*,<a href="#DrawText">wmfDrawText_t</a>*);
</pre>
</font>
<p>
If desired, strings can be decomposed into individual chars using
<tt>wmf_ipa_draw_text ()</tt>. Best to see source for the various device layers
in <tt>libwmf</tt>.
</p>

<li><a name="uinit"><b>udata_init</b></a>
<font color=blue>
<pre>
void udata_init (wmfAPI*,<a href="#UserData">wmfUserData_t</a>*);
</pre>
</font>
<p>
Redundant; may be removed at some point...
</p>

<li><a name="ucopy"><b>udata_copy</b></a>
<font color=blue>
<pre>
void udata_copy (wmfAPI*,<a href="#UserData">wmfUserData_t</a>*);
</pre>
</font>
<p>
Redundant; may be removed at some point...
</p>

<li><a name="uset"><b>udata_set</b></a>
<font color=blue>
<pre>
void udata_set (wmfAPI*,<a href="#UserData">wmfUserData_t</a>*);
</pre>
</font>
<p>
Redundant; may be removed at some point...
</p>

<li><a name="ufree"><b>udata_free</b></a>
<font color=blue>
<pre>
void udata_free (wmfAPI*,<a href="#UserData">wmfUserData_t</a>*);
</pre>
</font>
<p>
Redundant; may be removed at some point...
</p>

<li><a name="rframe"><b>region_frame</b></a>
<font color=blue>
<pre>
void region_frame (wmfAPI*,<a href="#PolyRect">wmfPolyRectangle_t</a>*);
</pre>
</font>

<li><a name="rpaint"><b>region_paint</b></a>
<font color=blue>
<pre>
void region_paint (wmfAPI*,<a href="#PolyRect">wmfPolyRectangle_t</a>*);
</pre>
</font>

<li><a name="rclip"><b>region_clip</b></a>
<font color=blue>
<pre>
void region_clip (wmfAPI*,<a href="#PolyRect">wmfPolyRectangle_t</a>*);
</pre>
</font>
<p>
If the number of clip rectangles is zero, the current clip region should be
unset.
</p>
</ul>

<a name="bitmap"><h2>Bitmap Functions</h2></a>

<a name="fns"><h2>Other Functions</h2></a>

<a name="guide"><h2>Guidelines</h2></a>

<a name="compile"><h2>Compiling - The Distribution</h2></a>

<p>
The section applies only if you are working on the <tt>libwmf</tt> sources.
</p>
<p>
The build system uses <b>automake</b> and <b>autoconf</b>. If any changes are
made to any of the various <tt>Makefile.am</tt> files, or to
<tt>configure.in</tt> or <tt>libwmf.m4</tt>, then the build system will need to
be updated. Change to the top source directory (containing
<tt>configure.in</tt> and <tt>libwmf.m4</tt>) and:
</p>
<font color=blue>
<pre>
# aclocal
# automake
# autoheader
# autoconf
# date > stamp-h.in
</pre>
</font>
<p>
When adding a new device layer, <tt>include/libwmf/Makefile.am</tt> and
<tt>src/ipa/Makefile.am</tt> will need to be modifiled. Source files
(<tt>src/ipa/new.c</tt>) and installing header files
(<tt>include/libwmf/new.h</tt>) do not need to be added to the distribution,
but other headers (<tt>src/ipa/new.h</tt> &amp; <tt>src/ipa/new/*.h</tt>) will.
</p>

<hr>

<address>
Copyright 2001 wvWare/libwmf <a href="http://www.wvware.com/">http://www.wvware.com/</a>
</address>

</body>
</html>
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