bug#27078: 25.2; wrong or ugly display of SVG image

[ynyaaa]

(1) If an SVG image includes another SVG image and magnifies it,
    the displayed image looks like a magnified raster image.

(2) Numbers '0.xxx' in SVG parameters may be written as '.xxx'.
    Using such descriptions may cause wrong display.

(3) Spaces between numbers in SVG parameters may be omitted
    if distinguishable.
    For example '.1 .9' may be written as '.1.9'.
    Using such descriptions may cause wrong display.

I obtained librsvg-2.40.1-2-w32-bin.zip
from http://sourceforge.net/projects/ezwinports/files/.

appearance-*.png in attached tgz file are what are displayed in
emacs buffers viewing sample-*.svg by C-x C-f.

emacs.svg is copied from
emacs-25.2/share/icons/hicolor/scalable/apps/emacs.svg

sample-icon-internal.svg: including contents of emacs.svg internally
sample-icon-external.svg: including emacs.svg as an external image
    sample-icon-internal.svg looks fine.
    sample-icon-external.svg looks like a magnified raster image.

sample-triangle-path.svg: a blue triangle in a red square
sample-triangle-polygon.svg: a yellow triangle in a red square
    sample-triangle-path.svg uses <path> tag for the triangle.
      <path d="M 0.1 0.9 0.9 0.9 0.5 0.1" fill="blue"/>
    sample-triangle-polygon.svg uses <polygon> tag for the triangle.
      <polygon points="0.1 0.9 0.9 0.9 0.5 0.1" fill="yellow"/>
    The first(bottom left) vertex coordinates are '0.1 0.9'.
    The second(bottom right) vertex coordinates are '0.9 0.9'.
    The third(top) vertex coordinates are '0.5 0.1'.
    Expected images are shown.

sample-triangle-path-omit-zero.svg
sample-triangle-polygon-omit-zero.svg
    The bottom left vertex coordinates are '.1 .9'.
    An expected image is shown for <polygon> tag.
    An unexpected image is shown for <path> tag.
    The vertex goes to '0 0'.

sample-triangle-path-omit-zero-and-space.svg
sample-triangle-polygon-omit-zero-and-space.svg
    The bottom left vertex coordinates are '.1.9'.
    Unexpected images are shown.
    The vertex goes to '0 9' for <path> tag.
    The coordinates are interpreted as one number '.1'
    for <polygon> tag.

sample-triangle-path-exp-omit-zero.svg
sample-triangle-polygon-exp-omit-zero.svg
    The bottom left vertex coordinates are '1e-1 .9'.
    An expected image is shown for <polygon> tag.
    An unexpected image is shown for <path> tag.
    The vertex goes to '0.1 0'.

sample-triangle-path-exp-omit-zero-and-space.svg
sample-triangle-polygon-exp-omit-zero-and-space.svg
    The bottom left vertex coordinates are '1e-1.9'.
    Unexpected images are shown.
    The coordinates are interpreted as one number '0'
    for <path> tag.
    The coordinates are interpreted as one number '0.1'
    for <polygon> tag.

test-svg.tgz
Description: Binary data

In GNU Emacs 25.2.1 (i686-w64-mingw32)
 of 2017-04-25 built on LAPHROAIG
Windowing system distributor 'Microsoft Corp.', version 6.0.6002
Configured using:
 'configure --host=i686-w64-mingw32 --without-dbus
 --without-compress-install 'CFLAGS=-static -O2 -g3''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY ACL GNUTLS LIBXML2 ZLIB
TOOLKIT_SCROLL_BARS

Important settings:
  value of $LANG: JPN
  locale-coding-system: cp932

Major mode: Tar

Minor modes in effect:
  shell-dirtrack-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message format-spec rfc822 mml mml-sec
password-cache epg epg-config gnus-util mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils tar-mode jka-compr
wdired shell pcomplete comint ansi-color ring cl-extra help-fns diff
image-file novice thingatpt misearch multi-isearch dired-aux help-mode
cl-loaddefs pcase cl-lib nxml-uchnm rng-xsd xsd-regexp rng-cmpct
rng-nxml rng-valid rng-loc rng-uri rng-parse nxml-parse rng-match rng-dt
rng-util rng-pttrn nxml-ns nxml-mode nxml-outln nxml-rap nxml-util
nxml-glyph nxml-enc xmltok image-mode easymenu dired time-date mule-util
japan-util tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel dos-w32 ls-lisp disp-table w32-win w32-vars
term/common-win tool-bar dnd fontset image regexp-opt fringe
tabulated-list newcomment elisp-mode lisp-mode prog-mode register page
menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock font-lock
syntax facemenu font-core frame cl-generic cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms
cp51932 hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese charscript case-table epa-hook jka-cmpr-hook help
simple abbrev minibuffer cl-preloaded nadvice loaddefs button faces
cus-face macroexp files text-properties overlay sha1 md5 base64 format
env code-pages mule custom widget hashtable-print-readable backquote
w32notify w32 multi-tty make-network-process emacs)

Memory information:
((conses 8 127224 9880)
 (symbols 32 22914 0)
 (miscs 32 163 494)
 (strings 16 24608 5443)
 (string-bytes 1 686299)
 (vectors 8 16677)
 (vector-slots 4 575327 7948)
 (floats 8 191 245)
 (intervals 28 2794 821)
 (buffers 520 32))