Geometry Generator style that you apply to a point layer with the same CRS as a present line layer.

Any points are converted to polygons limited by the "network" of lines in your line layer. You could say that the style "fills" selected areas limited by the lines (roads).

To convert the generated polygons to actual geometry, you can use the "Geometry by expression" processing tool.

The style is only applied to the visible extent of the map canvas.