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Require hook_dom in node_map components #62

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fc085b9
Initial plan
Copilot Jan 22, 2026
26517d5
Add debug assertion enforcing hook_dom in node_map and simplify reord…
Copilot Jan 22, 2026
0c1d989
Improve error message and add null safety check for non-DEBUG builds
Copilot Jan 22, 2026
b916bd8
Remove redundant child.dom checks since hook_dom is now required
Copilot Jan 22, 2026
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3 changes: 3 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -121,6 +121,9 @@ The component you pass to `node_map` gets mounted for each item of the array you
> [!IMPORTANT]
> Allowed array items are numbers, strings and objects. If you pass objects, they must have an unique `id` property. There must not be two items of the same value or id.

> [!IMPORTANT]
> Components used with `node_map` must use `hook_dom` to define their root element. This is required for efficient reordering of list items.

### DOM components

The leaves of your component tree are mostly made out of native dom elements. To use such a component, use `node_dom` instead of `node`. The signature is the same, except for the first argument being a descriptor, similar to css selectors: `tagName[attr1=value][attr2][...]`
Expand Down
83 changes: 13 additions & 70 deletions src/lui.js
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Expand Up @@ -976,21 +976,21 @@ const instance_render = (dom_parent, dom_first) => {
dom_first
);

child.dom &&
dom_parent.insertBefore(
child.dom_first = child.dom,
dom_first
);
DEBUG &&
!child.dom &&
error('node_map item components must call hook_dom() to define their root DOM element');

dom_parent.insertBefore(
child.dom_first = child.dom,
dom_first
);
}
else {
// TODO this algorithm still sucks
const dom_last = instance_dom_last_get(child);
if (
dom_last &&
dom_last.nextSibling !== dom_first
child.dom.nextSibling !== dom_first
) {
VERBOSE && log('instance_reinsert ' + key);
instance_reinsert(child, dom_parent, dom_first);
VERBOSE && log('item reinsert ' + key);
dom_parent.insertBefore(child.dom, dom_first);
}

if (
Expand Down Expand Up @@ -1023,11 +1023,8 @@ const instance_render = (dom_parent, dom_first) => {
}
}

(
childs[child.parent_index = items_index] = child
).dom_first && (
dom_first = child.dom_first
);
childs[child.parent_index = items_index] = child;
dom_first = child.dom_first;
}

instance.dom_first =
Expand Down Expand Up @@ -1181,60 +1178,6 @@ const list_data_index = (list_data, items_map, items_order) => {
return items_objects;
}

/**
gets last node of an instance (only an ugly workaround!)
@param {TYPE_INSTANCE} instance
@return {?HTMLElement}
*/
const instance_dom_last_get = instance => {
if (instance.dom) return instance.dom;
let instance_childs;
let i = (
(instance_childs = instance.childs)
? instance_childs.length
: 0
);
let itm, itm_dom;
while (i > 0) {
if (
(
itm_dom = instance_childs[--i]
) &&
(
itm = instance_dom_last_get(itm_dom)
)
) return itm;
}
return null_;
};

/**
reinsert all dom nodes of an instance
@param {TYPE_INSTANCE} instance
@param {HTMLElement} dom_parent
@param {?HTMLElement} dom_first
@return {?HTMLElement}
*/
const instance_reinsert = (instance, dom_parent, dom_first) => {
if (instance.dom) {
return /** @type {HTMLElement} */ (dom_parent.insertBefore(instance.dom, dom_first));
}
if (instance.dom_first) {
let childs_index = instance.childs.length;
do {
instance.childs[--childs_index] && (
dom_first = instance_reinsert(
instance.childs[childs_index],
dom_parent,
dom_first
)
);
}
while (childs_index > 0);
}
return dom_first;
}

/**
return instance for slots
@param {TYPE_SLOTS} slots
Expand Down