1 files changed, 33 insertions, 0 deletions
diff --git a/indra/llui/llscrollcontainer.cpp b/indra/llui/llscrollcontainer.cpp
index e36fd45bb4..ad2f58db69 100644
--- a/indra/llui/llscrollcontainer.cpp
+++ b/indra/llui/llscrollcontainer.cpp
@@ -75,6 +75,7 @@ LLScrollContainer::Params::Params()
     max_auto_scroll_rate("max_auto_scroll_rate", 1000),
     max_auto_scroll_zone("max_auto_scroll_zone", 16),
     reserve_scroll_corner("reserve_scroll_corner", false),
+    keep_scroll_pos("keep_scroll_pos", false),
     size("size", -1)
 {}
 
@@ -93,8 +94,12 @@ LLScrollContainer::LLScrollContainer(const LLScrollContainer::Params& p)
     mMaxAutoScrollRate(p.max_auto_scroll_rate),
     mMaxAutoScrollZone(p.max_auto_scroll_zone),
     mScrolledView(NULL),
+    mKeepScrollPos(p.keep_scroll_pos),
     mSize(p.size)
 {
+    mStoredDocPos[VERTICAL] = 0;
+    mStoredDocPos[HORIZONTAL] = 0;
+
     static LLUICachedControl<S32> scrollbar_size_control ("UIScrollbarSize", 0);
     S32 scrollbar_size = (mSize == -1 ? scrollbar_size_control : mSize);
 
@@ -605,6 +610,22 @@ void LLScrollContainer::updateScroll()
     calcVisibleSize( &visible_width, &visible_height, &show_h_scrollbar, &show_v_scrollbar );
 
     S32 border_width = getBorderWidth();
+
+    // Remember the position only while the scrollbar is genuinely showing scrollable
+    // content, so a transient empty pass (e.g. a list clearing before it repopulates)
+    // cannot overwrite it with 0.
+    if (mKeepScrollPos)
+    {
+        if (show_v_scrollbar && mScrollbar[VERTICAL]->getVisible())
+        {
+            mStoredDocPos[VERTICAL] = mScrollbar[VERTICAL]->getDocPos();
+        }
+        if (show_h_scrollbar && mScrollbar[HORIZONTAL]->getVisible())
+        {
+            mStoredDocPos[HORIZONTAL] = mScrollbar[HORIZONTAL]->getDocPos();
+        }
+    }
+
     if( show_v_scrollbar )
     {
         if( doc_rect.mTop < getRect().getHeight() - border_width )
@@ -673,6 +694,18 @@ void LLScrollContainer::updateScroll()
 
     mScrollbar[VERTICAL]->setDocSize( doc_height );
     mScrollbar[VERTICAL]->setPageSize( visible_height );
+
+    if (mKeepScrollPos)
+    {
+        if (show_v_scrollbar)
+        {
+            mScrollbar[VERTICAL]->setDocPos(mStoredDocPos[VERTICAL]);
+        }
+        if (show_h_scrollbar)
+        {
+            mScrollbar[HORIZONTAL]->setDocPos(mStoredDocPos[HORIZONTAL]);
+        }
+    }
 } // end updateScroll
 
 void LLScrollContainer::setBorderVisible(bool b)