read_page returns nothing under an element that has zero size #47

read_page drops an element's whole subtree when that element itself measures 0×0, even though its children are visible and interactive.

Repro

<!doctype html><title>repro</title>
<button style="position:absolute;left:100px;top:100px;width:200px;height:80px"
        onclick="window.clicks=(window.clicks||0)+1">click</button>

read_page on this page returns only the title:

# repro

The button is missing. computer can still click it at (200, 140), and find "click" should hit the same walker.

Cause

walk() in extension/content/ax-tree.js returns before visiting children when isVisible() is false (line 143), and isVisible() requires the element's own getBoundingClientRect() to be non-zero (line 19). Here <body> has zero height, because its only child is absolutely positioned, so the walk stops at the root.

The same pruning would hide:

• everything inside a display: contents wrapper, which has no box of its own (common in component frameworks and web components);
• children of any zero-height container whose content overflows it, such as fixed or absolutely positioned app shells.

Suggested direction

Only prune a subtree for reasons that really hide descendants: display: none, hidden, aria-hidden="true", and visibility: hidden (where children can override it). Treat a zero-size box as "don't list this element" rather than "don't descend". find uses the same walker and has the same gap (get_page_text reads innerText and is unaffected). Add a test page covering a zero-height body, display: contents, and an overflowing zero-height container.

Found while testing in Chrome for Testing 155 (headless). Running read_page with and without other CDP clients attached gave the same result, so this isn't related to debugger sharing.