TreeTable: PassThrough (PT) Applies Only to Root — Internal DOM Structure Not Supported (v20.3)

[bageerathan-pandian]

Hi Team,
I'm facing a limitation with PrimeNG TreeTable PT (PassThrough) support.
Currently, PT works only on the root element, but all internal DOM nodes ignore PT attributes, making it impossible to style TreeTable locally without using global CSS or ::ng-deep.
This contradicts PrimeNG’s PT design goal of component‑scoped customization.

Problem Summary
The following TreeTable internal elements do not receive any PT classes/attributes:

Frozen / Unfrozen containers
Scrollable header / body

elements (scrollable/frozen views) Rows, cells, togglers Structural tags: , , ,

This severely limits customization, especially when migrating away from deprecated ::ng-deep. What Works Only the root PT key: HTML What Cannot Be Styled Using PT These DOM nodes never receive PT classes: HTML Reproduction PT Configuration export const CertificateSiteTreeTablePT = { root: { class: "certificate-site-table-wrapper" }, table: { class: "my-table" }, // ❌ Not applied thead: { class: "my-thead" }, // ❌ Not applied tbody: { class: "my-tbody" }, // ❌ Not applied row: { class: "my-row" }, // ❌ Not applied cell: { class: "my-cell" }, // ❌ Not applied}; Component Usage <p-treeTable [pt]="CertificateSiteTreeTablePT"> Inspecting DOM Only root PT applied No PT classes on internal elements What We Tried Approach 1 — Direct PT keys Only root works. Others are ignored silently. Approach 2 — Dynamic PT with callback TypeScripttable: ({ parent }) => ({ class: parent.instance.frozen ? "my-frozen" : "my-unfrozen"}); Callback executes, but no classes appear in DOM. Approach 3 — Local component SCSS Not applied → TreeTable DOM is outside Angular encapsulation. Approach 4 — CSS variables TreeTable does not expose variables for scroll containers, layout, toggler, frozen view behavior. Approach 5 — Directives (DT) DT does not expose internal structure either. Approach 6 — Passing styleClass from child to shared component Not working Need suggestion on this. Stackbliz: https://stackblitz.com/edit/stackblitz-starters-ftaeujz1?file=src%2Fapp%2Fcustom-treetable%2Fcustom-treetable.html