svg: add a new function to specify the SVG document unit

Add a cairo_svg_surface_set_document_unit() function to allow users to
set a unit for the width and height values of the root <svg> element.

In particular this allows to draw in pixels and still have the expected
result when generating SVG output.

Add also the correspondent getter function.

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=90166
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/src/cairo-svg.h b/src/cairo-svg.h
index 592c645f6..95434dcf6 100644
--- a/src/cairo-svg.h
+++ b/src/cairo-svg.h
@@ -53,6 +53,46 @@ typedef enum _cairo_svg_version {
     CAIRO_SVG_VERSION_1_2
 } cairo_svg_version_t;
 
+/**
+ * cairo_svg_version_t:
+ *
+ * @CAIRO_SVG_UNIT_USER: User unit, a value in the current coordinate system.
+ *   If used in the root element for the initial coordinate systems it
+ *   corresponds to pixels. (Since 1.16)
+ * @CAIRO_SVG_UNIT_EM: The size of the element's font. (Since 1.16)
+ * @CAIRO_SVG_UNIT_EX: The x-height of the element’s font. (Since 1.16)
+ * @CAIRO_SVG_UNIT_PX: Pixels (1px = 1/96th of 1in). (Since 1.16)
+ * @CAIRO_SVG_UNIT_IN: Inches (1in = 2.54cm = 96px). (Since 1.16)
+ * @CAIRO_SVG_UNIT_CM: Centimeters (1cm = 96px/2.54). (Since 1.16)
+ * @CAIRO_SVG_UNIT_MM: Millimeters (1mm = 1/10th of 1cm). (Since 1.16)
+ * @CAIRO_SVG_UNIT_PT: Points (1pt = 1/72th of 1in). (Since 1.16)
+ * @CAIRO_SVG_UNIT_PC: Picas (1pc = 1/6th of 1in). (Since 1.16)
+ * @CAIRO_SVG_UNIT_PERCENT: Percent, a value that is some fraction of another
+ *   reference value. (Since 1.16)
+ *
+ * #cairo_svg_unit_t is used to describe the units valid for coordinates and
+ * lengths in the SVG specification.
+ *
+ * See also:
+ * https://www.w3.org/TR/SVG/coords.html#Units
+ * https://www.w3.org/TR/SVG/types.html#DataTypeLength
+ * https://www.w3.org/TR/css-values-3/#lengths
+ *
+ * Since: 1.16
+ **/
+typedef enum _cairo_svg_unit {
+    CAIRO_SVG_UNIT_USER = 0,
+    CAIRO_SVG_UNIT_EM,
+    CAIRO_SVG_UNIT_EX,
+    CAIRO_SVG_UNIT_PX,
+    CAIRO_SVG_UNIT_IN,
+    CAIRO_SVG_UNIT_CM,
+    CAIRO_SVG_UNIT_MM,
+    CAIRO_SVG_UNIT_PT,
+    CAIRO_SVG_UNIT_PC,
+    CAIRO_SVG_UNIT_PERCENT
+} cairo_svg_unit_t;
+
 cairo_public cairo_surface_t *
 cairo_svg_surface_create (const char   *filename,
 			  double	width_in_points,
@@ -75,6 +115,13 @@ cairo_svg_get_versions (cairo_svg_version_t const	**versions,
 cairo_public const char *
 cairo_svg_version_to_string (cairo_svg_version_t version);
 
+cairo_public void
+cairo_svg_surface_set_document_unit (cairo_surface_t	*surface,
+				     cairo_svg_unit_t	 unit);
+
+cairo_public cairo_svg_unit_t
+cairo_svg_surface_get_document_unit (cairo_surface_t	*surface);
+
 CAIRO_END_DECLS
 
 #else  /* CAIRO_HAS_SVG_SURFACE */