From e66f1d72de2311a4ad55f9af88eec08162ea349c Mon Sep 17 00:00:00 2001
From: thawk <thawk009@gmail.com>
Date: Wed, 19 Jan 2022 17:52:45 +0800
Subject: [PATCH] add data-rel-inherit

---
 js/impress.js          | 29 ++++++++++++++++++++++++++++-
 src/plugins/rel/rel.js | 32 +++++++++++++++++++++++++++++++-
 2 files changed, 59 insertions(+), 2 deletions(-)

diff --git a/js/impress.js b/js/impress.js
index b8a4095ea..573d7b0bf 100644
--- a/js/impress.js
+++ b/js/impress.js
@@ -4125,9 +4125,10 @@
             };
         }
 
+        var ref = prev;
         if ( data.relTo ) {
 
-            var ref = document.getElementById( data.relTo );
+            ref = document.getElementById( data.relTo );
             if ( ref ) {
 
                 // Test, if it is a previous step that already has some assigned position data
@@ -4164,6 +4165,7 @@
             }
         }
 
+
         // While ``data-rel-reset="relative"`` or just ``data-rel-reset``,
         // ``data-rel-x/y/z`` and ``data-rel-rotate-x/y/z`` will have default value of 0,
         // instead of inherit from previous slide.
@@ -4185,6 +4187,25 @@
             if ( data.relReset === "all" ) {
                 inheritRotation = false;
             }
+        } else if ( el.hasAttribute( "data-rel-inherit" ) ) {
+            var inheritFrom = null;
+            if ( data.relInherit ) {
+
+                // If data-rel-inherit has value, it's the referenced node
+                inheritFrom = document.getElementById( data.relInherit );
+            }
+
+            if ( ! inheritFrom ) {
+                inheritFrom = ref;
+            }
+
+            prev.relative.x = toNumberAdvanced( inheritFrom.getAttribute( "data-rel-x" ), 0 );
+            prev.relative.y = toNumberAdvanced( inheritFrom.getAttribute( "data-rel-y" ), 0 );
+            prev.relative.z = toNumberAdvanced( inheritFrom.getAttribute( "data-rel-z" ), 0 );
+            prev.relative.rotate.x = toNumberAdvanced( inheritFrom.getAttribute( "data-rel-rotate-x" ), 0 );
+            prev.relative.rotate.y = toNumberAdvanced( inheritFrom.getAttribute( "data-rel-rotate-y" ), 0 );
+            prev.relative.rotate.z = toNumberAdvanced( inheritFrom.getAttribute( "data-rel-rotate-z" ), 0 );
+            prev.relative.rotate.order = inheritFrom.getAttribute( "data-rel-rotate-order" ) ||  "xyz";
         }
 
         var step = {
@@ -4296,6 +4317,12 @@
             el.setAttribute( "data-rotate-z", step.rotate.z );
             el.setAttribute( "data-rotate-order", step.rotate.order );
             el.setAttribute( "data-rel-position", step.relative.position );
+            el.setAttribute( "data-rel-x", step.relative.x );
+            el.setAttribute( "data-rel-y", step.relative.y );
+            el.setAttribute( "data-rel-z", step.relative.z );
+            el.setAttribute( "data-rel-rotate-x", step.relative.rotate.x );
+            el.setAttribute( "data-rel-rotate-y", step.relative.rotate.y );
+            el.setAttribute( "data-rel-rotate-z", step.relative.rotate.z );
             prev = step;
         }
     };
diff --git a/src/plugins/rel/rel.js b/src/plugins/rel/rel.js
index a0e9fb481..6a87071e7 100644
--- a/src/plugins/rel/rel.js
+++ b/src/plugins/rel/rel.js
@@ -72,9 +72,10 @@
             };
         }
 
+        var ref = prev;
         if ( data.relTo ) {
 
-            var ref = document.getElementById( data.relTo );
+            ref = document.getElementById( data.relTo );
             if ( ref ) {
 
                 // Test, if it is a previous step that already has some assigned position data
@@ -132,6 +133,29 @@
             if ( data.relReset === "all" ) {
                 inheritRotation = false;
             }
+        } else if ( el.hasAttribute( "data-rel-inherit" ) ) {
+            var inheritFrom = null;
+            if ( data.relInherit ) {
+
+                // If data-rel-inherit has value, it's the referenced node
+                inheritFrom = document.getElementById( data.relInherit );
+            }
+
+            if ( !inheritFrom ) {
+                inheritFrom = ref;
+            }
+
+            prev.relative.x = toNumberAdvanced( inheritFrom.getAttribute( "data-rel-x" ), 0 );
+            prev.relative.y = toNumberAdvanced( inheritFrom.getAttribute( "data-rel-y" ), 0 );
+            prev.relative.z = toNumberAdvanced( inheritFrom.getAttribute( "data-rel-z" ), 0 );
+            prev.relative.rotate.x =
+                toNumberAdvanced( inheritFrom.getAttribute( "data-rel-rotate-x" ), 0 );
+            prev.relative.rotate.y =
+                toNumberAdvanced( inheritFrom.getAttribute( "data-rel-rotate-y" ), 0 );
+            prev.relative.rotate.z =
+                toNumberAdvanced( inheritFrom.getAttribute( "data-rel-rotate-z" ), 0 );
+            prev.relative.rotate.order =
+                inheritFrom.getAttribute( "data-rel-rotate-order" ) ||  "xyz";
         }
 
         var step = {
@@ -243,6 +267,12 @@
             el.setAttribute( "data-rotate-z", step.rotate.z );
             el.setAttribute( "data-rotate-order", step.rotate.order );
             el.setAttribute( "data-rel-position", step.relative.position );
+            el.setAttribute( "data-rel-x", step.relative.x );
+            el.setAttribute( "data-rel-y", step.relative.y );
+            el.setAttribute( "data-rel-z", step.relative.z );
+            el.setAttribute( "data-rel-rotate-x", step.relative.rotate.x );
+            el.setAttribute( "data-rel-rotate-y", step.relative.rotate.y );
+            el.setAttribute( "data-rel-rotate-z", step.relative.rotate.z );
             prev = step;
         }
     };