Revert 640c0566: TreeNode: Fixed nodes with ImGuiTreeNodeFlags_Leaf flag always returning true which was meaningless -> more flexible to keep allowing it by default so it setup an ID scope.

CHANGELOG.txt

@@ -68,7 +68,6 @@ Other Changes:
    Note that you may still get false positive (e.g. drag value and while holding return on the same value). (#820, #956, #1875)
  - Nav: Added support for PageUp/PageDown (explorer-style: first aim at bottom/top most item, when scroll a page worth of contents). (#787)
  - Nav: To keep the navigated item in view we also attempt to scroll the parent window as well as the current window. (#787)
- - TreeNode: Fixed nodes with ImGuiTreeNodeFlags_Leaf flag always returning true which was meaningless.
  - ColorEdit3, ColorEdit4, ColorButton: Added ImGuiColorEditFlags_NoDragDrop flag to disable ColorEditX as drag target and ColorButton as drag source. (#1826) 
  - BeginDragDropSource(): Offset tooltip position so it is off the mouse cursor, but also closer to it than regular tooltips, and not clamped by viewport. (#1739)
  - BeginDragDropTarget(): Added ImGuiDragDropFlags_AcceptNoPreviewTooltip flag to request hiding the drag source tooltip from the target site. (#143)

imgui.cpp

@@ -8323,7 +8323,7 @@ void ImGui::LogButtons()
 bool ImGui::TreeNodeBehaviorIsOpen(ImGuiID id, ImGuiTreeNodeFlags flags)
 {
     if (flags & ImGuiTreeNodeFlags_Leaf)
-        return false;
+        return true;
 
     // We only write to the tree storage if the user clicks (or explicitly use SetNextTreeNode*** functions)
     ImGuiContext& g = *GImGui;

imgui_demo.cpp

@@ -458,7 +458,7 @@ void ImGui::ShowDemoWindow(bool* p_open)
                     else
                     {
                         // Leaf: The only reason we have a TreeNode at all is to allow selection of the leaf. Otherwise we can use BulletText() or TreeAdvanceToLabelPos()+Text().
-                        node_flags |= ImGuiTreeNodeFlags_Leaf; // | ImGuiTreeNodeFlags_Bullet;
+                        node_flags |= ImGuiTreeNodeFlags_Leaf | ImGuiTreeNodeFlags_NoTreePushOnOpen; // ImGuiTreeNodeFlags_Bullet
                         ImGui::TreeNodeEx((void*)(intptr_t)i, node_flags, "Selectable Leaf %d", i);
                         if (ImGui::IsItemClicked())
                             node_clicked = i;