TreeNode, Tables: fixed ImGuiTreeNodeFlags_DrawLinesXXX feature when TreePop() is called in table: in no column or at top of row. (#2920)

docs/CHANGELOG.txt

@@ -55,8 +55,8 @@ Other changes:
 - Windows: loosened code to allow hovering of resize grips, borders, and table
   borders while hovering a sibling child window, so that the code in master matches
   one in docking (they accidentally diverged). (#8554)
-- TreeNode: added flags to draw tree hierarchy outlines linking parent
-  and tree nodes: (#2920)
+- TreeNode: added experimental flags to draw tree hierarchy outlines linking
+  parent and tree nodes: (#2920)
   - ImGuiTreeNodeFlags_DrawLinesNone: No lines drawn (default value in style.TreeLinesFlags).
   - ImGuiTreeNodeFlags_DrawLinesFull: Horizontal lines to child nodes. Vertical line drawn down to TreePop() position: cover full contents.
   - ImGuiTreeNodeFlags_DrawLinesToNodes: Horizontal lines to child nodes. Vertical line drawn down to bottom-most child node.
@@ -69,6 +69,11 @@ Other changes:
       nodes in unusual ways, using indent to create tree-looking structures, etc.)
       and the feature may not accurately represent them in every cases.
     - The feature adds a little cost as extra data needs to be stored.
+      (ImGuiTreeNodeFlags_DrawLinesToNodes is slower than ImGuiTreeNodeFlags_DrawLinesFull
+      which may be meaningful on very large trees, as it needs to record bottom-most
+      Y position even for clipped nodes).
+    - The feature is unlikely to ever work properly when using a coarse clipper
+      such as ImGuiListClipper.
 - TreeNode: fixed incorrect clipping of arrow/bullet when using ImGuiTreeNodeFlags_SpanAllColumns.
 - Nav: fixed assertion when holding gamepad FaceLeft/West button to open
   CTRL+Tab windowing + pressing a keyboard key. (#8525)