[librsvg] defs: Do the right thing for duplicate ids

[Benjamin Otte <otte src gnome org>]

commit 775178c2d7480895ce1b2bb86477a45e48bd22e4
Author: Benjamin Otte <otte redhat com>
Date:   Tue Oct 20 18:11:46 2015 +0200

    defs: Do the right thing for duplicate ids
    
    When an id (illegally) exists twice in an SVG file, all renderers keep
    the definition that appears first.
    Do the same in rsvg.

 rsvg-defs.c                                  |    3 +++
 tests/fixtures/reftests/duplicate-id-ref.png |  Bin 0 -> 155 bytes
 tests/fixtures/reftests/duplicate-id.svg     |    7 +++++++
 3 files changed, 10 insertions(+), 0 deletions(-)
---
diff --git a/rsvg-defs.c b/rsvg-defs.c
index 280f87f..d2c6a06 100644
--- a/rsvg-defs.c
+++ b/rsvg-defs.c
@@ -135,6 +135,9 @@ rsvg_defs_set (RsvgDefs * defs, const char *name, RsvgNode * val)
 void
 rsvg_defs_register_name (RsvgDefs * defs, const char *name, RsvgNode * val)
 {
+    if (g_hash_table_lookup (defs->hash, name))
+        return;
+
     g_hash_table_insert (defs->hash, g_strdup (name), val);
 }
 
diff --git a/tests/fixtures/reftests/duplicate-id-ref.png b/tests/fixtures/reftests/duplicate-id-ref.png
new file mode 100644
index 0000000..162a658
Binary files /dev/null and b/tests/fixtures/reftests/duplicate-id-ref.png differ
diff --git a/tests/fixtures/reftests/duplicate-id.svg b/tests/fixtures/reftests/duplicate-id.svg
new file mode 100644
index 0000000..c05f341
--- /dev/null
+++ b/tests/fixtures/reftests/duplicate-id.svg
@@ -0,0 +1,7 @@
+<svg xmlns="http://www.w3.org/2000/svg"; xmlns:xlink="http://www.w3.org/1999/xlink"; width="10" height="10">
+  <defs>
+    <rect fill="chartreuse" id="a" width="10" height="10" />
+    <rect fill="tomato" id="a" width="10" height="10" />
+  </defs>
+  <use xlink:href="#a"/>
+</svg>