awtk/3rd/svgtiny

Libsvgtiny
==========
http://www.netsurf-browser.org/projects/libsvgtiny/

Libsvgtiny is a library for parsing SVG files for display.

The overall idea of the library is to take some SVG as input, and return a list
of paths and texts which can be rendered easily. The library does not do the
actual rendering.

All supported SVG objects, for example circles, lines, and gradient filled
shapes, are converted to flat-filled paths or a fragment of text, and all
coordinates are converted, transformed etc. to pixels.

Libsvgtiny is Licensed under the MIT License,
http://opensource.org/licenses/mit-license.php

Written by James Bursa <james@netsurf-browser.org>.

SVG support
-----------
Libsvgtiny is initially aiming to implement SVG Tiny, as defined in
http://www.w3.org/TR/SVGMobile/.

SVG Tiny elements supported: defs, g, svg, circle, line, path, polygon,
polyline, rect, text

SVG Tiny elements not yet supported: desc, metadata, title, use, a, switch,
ellipse, image, font, font-face, font-face-name, font-face-src, glyph, hkern,
missing-glyph, animate, animateColor, animateMotion, animateTransform, mpath,
set, foreignObject

Additional elements supported: linearGradient, stop

Text support is incomplete.

The style attribute is supported.

Building libsvgtiny
-------------------
You will require the following tools:

- a C compiler (some parts of C99 support are required)
- gperf

and the following libraries:

- libxml2

To compile libsvgtiny, use the command

  make

To install libsvgtiny into /usr/local, use

  make install

To cross-compile for RISC OS, use

  make TARGET=riscos
  make install TARGET=riscos

Testing libsvgtiny
------------------
The svgtiny_display script uses the library to render an SVG. It requires that
ImageMagick convert is installed.

Get an SVG file, for example
http://www.croczilla.com/svg/samples/tiger/tiger.svg

Then use svgtiny_display to parse and render it:

  ./svgtiny_display tiger.svg
  ./svgtiny_display tiger.svg 2

The optional 2nd argument is a scale.

Using libsvgtiny
----------------
The interface is in the header svgtiny.h

  #include <svgtiny.h>

First create a svgtiny_diagram using svgtiny_create():

  struct svgtiny_diagram *diagram;
  diagram = svgtiny_create();

This will return a pointer to a new diagram, or NULL if there was not enough
memory.

SVGs are parsed from memory using svgtiny_parse():

  svgtiny_code code;
  code = svgtiny_parse(diagram, buffer, size, url, 1000, 1000);

The arguments are the pointer returned by svgtiny_create(), a buffer containing
the SVG data, the size of the SVG in bytes, the url that the SVG came from, and
the target viewport width and height in pixels.

The function returns svgtiny_OK if there were no problems, and diagram is
updated. The diagram can then be rendered by looping through the array
diagram->shape[0..diagram->shape_count]:

  for (unsigned int i = 0; i != diagram->shape_count; i++) {

Path shapes have a non-NULL path pointer. The path is an array of floats of
length path_length. The array contains segment type codes followed by 0 to 3
pairs of coordinates (depending on the segment type):

- svgtiny_PATH_MOVE x y
- svgtiny_PATH_CLOSE
- svgtiny_PATH_LINE x y
- svgtiny_PATH_BEZIER x1 y1 x2 y2 x3 y3

A path always starts with a MOVE.

The fill and stroke attributes give the colors of the path, or
svgtiny_TRANSPARENT if the path is not filled or stroked. Colors are in 0xRRGGBB
format (except when compiled for RISC OS). The macros svgtiny_RED,
svgtiny_GREEN, and svgtiny_BLUE can be used to extract the components.

The width of the path is in stroke_width.

Text shapes have a NULL path pointer and a non-NULL text pointer. Text is in
UTF-8. The coordinates of the text are in text_x, text_y. Text colors and stroke
width are as for paths.

If memory runs out during parsing, svgtiny_parse() returns
svgtiny_OUT_OF_MEMORY, but the diagram is still valid up to the point when
memory was exhausted, and may safely be rendered.

If there is an error in the SVG (for example, an element is missing an attribute
required by the specification), svgtiny_SVG_ERROR is returned, but the diagram
is still valid up to the point of the error. The error is recorded in
diagram->error_message and the line that caused it in diagram->error_line.

svgtiny_LIBXML_ERROR indicates that parsing the XML failed. The returned diagram
will contain no shapes. svgtiny_NOT_SVG means that the XML did not contain a
top-level <svg> element.

To free memory used by a diagram, use svgtiny_free():

  svgtiny_free(diagram);

For an example, see svgtiny_test.c.