TreeNode: comments on ImGuiTreeNodeFlags_Leaf. (#4833)

imgui.h

@@ -1306,7 +1306,7 @@ enum ImGuiTreeNodeFlags_
     ImGuiTreeNodeFlags_DefaultOpen          = 1 << 5,   // Default node to be open
     ImGuiTreeNodeFlags_OpenOnDoubleClick    = 1 << 6,   // Open on double-click instead of simple click (default for multi-select unless any _OpenOnXXX behavior is set explicitly). Both behaviors may be combined.
     ImGuiTreeNodeFlags_OpenOnArrow          = 1 << 7,   // Open when clicking on the arrow part (default for multi-select unless any _OpenOnXXX behavior is set explicitly). Both behaviors may be combined.
-    ImGuiTreeNodeFlags_Leaf                 = 1 << 8,   // No collapsing, no arrow (use as a convenience for leaf nodes).
+    ImGuiTreeNodeFlags_Leaf                 = 1 << 8,   // No collapsing, no arrow (use as a convenience for leaf nodes). Note: will always open a tree/id scope and return true. If you never use that scope, add ImGuiTreeNodeFlags_NoTreePushOnOpen.
     ImGuiTreeNodeFlags_Bullet               = 1 << 9,   // Display a bullet instead of arrow. IMPORTANT: node can still be marked open/close if you don't set the _Leaf flag!
     ImGuiTreeNodeFlags_FramePadding         = 1 << 10,  // Use FramePadding (even for an unframed text node) to vertically align text baseline to regular widget height. Equivalent to calling AlignTextToFramePadding() before the node.
     ImGuiTreeNodeFlags_SpanAvailWidth       = 1 << 11,  // Extend hit box to the right-most edge, even if not framed. This is not the default in order to allow adding other items on the same line without using AllowOverlap mode.

imgui_widgets.cpp

@@ -6744,6 +6744,7 @@ void ImGui::TreeNodeSetOpen(ImGuiID storage_id, bool is_open)
 
 bool ImGui::TreeNodeUpdateNextOpen(ImGuiID storage_id, ImGuiTreeNodeFlags flags)
 {
+    // Leaf node always open a new tree/id scope. If you never use it, add ImGuiTreeNodeFlags_NoTreePushOnOpen.
     if (flags & ImGuiTreeNodeFlags_Leaf)
         return true;