LibWeb: Fix "incorrect behavior on select()"

[An-n-ya]

This patch resolves the problem outlined in issue #1446. The problem is the cursor_position node could be substituted with any other existing node by the mousedown event. Previously, if this new node was not equal to m_text_node, the function would return prematurely without updating the selection.

With this fix, we ensure that the selection is properly updated in such cases, rather than simply exiting the function.

Also, in order to address the issue in #1339, the logic of document().set_cursor_position has been put behind to the logic of Selection.

Closes #1446

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[circl-lastname]

The Issue number is not needed in the commit name, instead you can put Closes #1446 inside the pull request description, which will also make GitHub automatically close the issue this fixes.

[gmta]

Paging @Gingeh !

[Gingeh]

Very good!
Could it be worth adding a test for this?

[An-n-ya]

Very good! Could it be worth adding a test for this?

Normally, we can use inputNode === document.activeElement to check if an input is focused, but in Ladybird, activeElement is still not right. So, I can only provide a very basic test like this:

<input type="text" id="input" value="foo" />
<input type="text" id="boo"/>
<script src="../include.js"></script>
<script>
    test(() => {
        // simulate issue #1446
        let input = document.getElementById("input");
        let boo = document.getElementById("input");
        input.select();
        boo.select();
        input.select();

        let sel = document.getSelection();
        if (sel.anchorNode) {
            println("PASS");
        }
    });
</script>

which doesn't correspond to issue in #1446 precisely, so I think it would be better to complete this test case once we have a more robust interface (e.g., document.activeElement).

[ronak69]

The test case in Issue-1446 works fine now but I also checked with setInterval(mySelect, 3000) and it does not select.

[shlyakpavel]

In light of recent changes, is this still relevant? If so, @An-n-ya, could you please rebase and resolve the conflicts?

[An-n-ya]

The function selection_was_changed is no longer needed, so this patch is irrelevant to original problem.