Draw cell triangle mark: ctx.fillStyle caused bug ?

[sunnipaul]

I am implementing a "comment cell" function, when there is a comment text for a cell there will be a solid orange triangle at the top right corner of the cell. When clicking the cell, the comment text will be displayed.
I implemented it in drawCell function in core package. I think it's the right place for it. (I've ever tried implement in a GridCellKind.Custom way, however it's hard for NumberCell, TextCell etc. )

How ever it seems after it causes the text displayed in yellow in cells in the same column below the row.

Can anyone help me work it out?

    const r = getCellRenderer(cell);
    if (r !== undefined) {
        if (lastPrep?.renderer !== r) {
            lastPrep?.deprep?.(args);
            lastPrep = undefined;
        }
        const partialPrepResult = r.drawPrep?.(args, lastPrep);
        if (drawCellCallback !== undefined && !isInnerOnlyCell(args.cell)) {
            drawCellCallback(args as DrawArgs<GridCell>, () => r.draw(args, cell));
        } else {
            r.draw(args, cell);
        }
        if (cell.memoMark === true){   // here is where I draw triangle in the cell.
            setTimeout(()=>{
                ctx.save();
                ctx.fillStyle = 'orange';
                ctx.beginPath();
                ctx.moveTo(x + w - 8, y);
                ctx.lineTo(x + w, y);
                ctx.lineTo(x + w, y + 8);
                ctx.lineTo(x + w - 8, y);
                ctx.fill();
                ctx.restore();
                console.log(`memoMark`);
            }, 0);
        }
        result =

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