Bug 104897

Consider the following situation (after bug 103627 has landed): <div style="width: 400px"> <div style="overflow-x: scroll"> <div style="width: 800px"> This text should be autosized to 40px computed font size (16 * 800/320), since it's wider than the lowest common ancestor of its enclosing cluster and therefore becomes a cluster itself.<br> Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. </div> </div> </div> The innermost div is 800px wide so will get a large textAutosizingMultiplier. But only 400px of the div will ever be visible at once, so the core assumption - that the user is going to zoom such that the full 800px of the div is onscreen at once - is false! Instead the innermost div should be autosized as if it were 400px wide (i.e. assume the user will zoom such that as much as possible [400px] of the div is onscreen at once). In general, after computing the width of the lowest common ancestor of a cluster, this should be limited using the minimum of the widths of all overflow:scroll ancestors as an upper bound.