(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.