Lists the tiles a viewport shows: each visible page cut into a grid of tileSize pixel squares from its pixel
origin (the last row and column clipped to the page), at the viewport's zoom and the layout's rotation, page by page in order.
public int GetVisibleTiles(in Viewport viewport, int tileSize, Span<Tile> destination, double margin = 0)
The viewport.
The side of a tile in pixels.
Receives the tiles, as many as fit.
Pixels added on every side of the viewport, for render-ahead.
destination holds, call again with more room.