From 7a5bc222fd916a7f12c418880899ddac9086b19b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tjark=20M=C3=BCller?= <t.mueller@iwm-tuebingen.de>
Date: Thu, 4 May 2023 13:28:58 +0200
Subject: [PATCH] documented/ solved svg rotation bug

---
 lib/flippable.html | 36 ++++++++++++++++++++++++------------
 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/lib/flippable.html b/lib/flippable.html
index add8b31..db361eb 100644
--- a/lib/flippable.html
+++ b/lib/flippable.html
@@ -17,19 +17,27 @@
                 <div class="flipFace back" style="visibility:hidden;"></div>
             </div>
                 <!-- Very tricky problem to scale svgs: see https://css-tricks.com/scale-svg/ -->
-            <svg class="flipButton backBtn" style="visibility:hidden;" viewBox="0 0 100 100" preserveAspectRatio="xMidYMid meet">
-                <g stroke-width="8" stroke="white">
-                    <circle  cx="50" cy="50" r="44" fill="gray" />
-                    <line x1="30" y1="30" x2="70" y2="70"  />
-                    <line x1="30" y1="70" x2="70" y2="30"  />
-                </g>
-            </svg>
+                <!-- SVG viewPort interferes with DOMMatrix calculations: see  
+                    https://stackoverflow.com/questions/70696387/how-to-get-transform-matrix-of-a-dom-element-->
+            <div class="flipButton backBtn" style="visibility:hidden;">
+                <svg viewBox="0 0 100 100" preserveAspectRatio="xMidYMid meet" style="width:inherit; height:inherit;">
+                    <g stroke-width="8" stroke="white">
+                        <circle  cx="50" cy="50" r="44" fill="gray" />
+                        <line x1="30" y1="30" x2="70" y2="70"  />
+                        <line x1="30" y1="70" x2="70" y2="30"  />
+                    </g>
+                </svg>
+            </div>
+            
 
-            <svg class="flipButton infoBtn" viewBox="0 0 100 100" preserveAspectRatio="xMidYMid meet">
-                <circle cx="50" cy="50" r="44" stroke="white" stroke-width="8" fill="gray" />
-                <circle cx="50" cy="32" r="7" fill="white" />
-                <line x1="50" y1="46" x2="50" y2="78" stroke="white" stroke-width="12" />
-            </svg>
+            <div class="flipButton infoBtn">
+                <svg  viewBox="0 0 100 100" preserveAspectRatio="xMidYMid meet"  style="width:inherit; height:inherit;">
+                    <circle cx="50" cy="50" r="44" stroke="white" stroke-width="8" fill="gray" />
+                    <circle cx="50" cy="32" r="7" fill="white" />
+                    <line x1="50" y1="46" x2="50" y2="78" stroke="white" stroke-width="12" />
+                </svg>
+            </div>
+            
         </div>
     </template>
 
@@ -46,6 +54,10 @@ via a HTML template that defines the placeholders for front and back views. The
 style file "css/flipeffect.css" holds reasonable default styles for this kind of
 templates.
 </p>
+<p>
+The SVG buttons have to be wrapped in an HTML DOM element which handles events. Otherwise, 
+the viewbox of the SVG will interfere with the coordinate transformation.
+</p>
 <pre><code>
     &lt;template id="flipTemplate"&gt;
         &lt;div class="flipWrapper"&gt;