Overlay problem with <lightning-combobox> node dropdowns that live on a slds modal hosted by an LWC.
Trailblazer Community

Overlay problem with <lightning-combobox> node dropdowns that live on a slds modal hosted by an LWC.

Web Container , Lightning , Summer 22

Last updated 17 days ago ·Reference W-11638940 ·Reported By 3 users

In Review

Summary
When using a vanilla SLDS blueprint to create a modal, we can see an overlay problem with <lightning-combobox> dropdowns that live on a slds modal hosted by an LWC.

When using an Aura component and LWC Combobox modal, the Lightning Combobox dropdowns are appearing behind the parent modal.

Note: This will be supported once `LightningModal` goes out, but we can support this in the interim.

Repro
Steps To Reproduce:

Login into your own org of choice or activate a Scratch Org.

Create a generic modal with a <lightning-combobox> dropdown.

Lightning dropdown:
<lightning-combobox name="stage" label="Stage" value={defaultStage} options={options} onchange={handleStageChange} required key={field.Name__c}></lightning-combobox>

Options: {'Prospect', 'Qualified', 'Technical Validation, 'Business Validation', 'Closed', 'Launched'}

Aura component:
<aura:component implements="flexipage:availableForAllPageTypes,lightning:isUrlAddressable,lightning:actionOverride,force:hasRecordId" description="Opportunity Quick Create Shell Aura component"><c:parentContainer/></aura:component>

LWC Parent Module:
<template><section role="dialog" tabindex="-1" aria-labelledby="modal-heading-01" aria-modal="true" aria-describedby="modal-content-id-1" class="slds-modal slds-fade-in-open uiModal"><div class="slds-modal__container"><div class="slds-is-relative"><header class="slds-modal__header"><div class="slds-text-heading--large slds-text-align_left"><b>TEST GENERIC PARENT</b></div></header><div class="slds-modal__content generic-modal-content" id="modal-content-id-1"><c-child-container></c-child-container></div><footer class="slds-modal__footer"><lightning-button variant="Neutral" label="Cancel"></lightning-button><lightning-button class="slds-m-left_small" variant="brand" label="Next"></lightning-button></footer></div></div></section></template>

LWC Child Module:
<template><lightning-record-edit-form class="slds-m-top_medium" density="comfy" object-api-name="Opportunity"><div class="slds-m-around_small slds-is-relative"><lightning-input-field field-name="Name"></lightning-input-field><lightning-input-field field-name="AccountId" ></lightning-input-field><lightning-input-field field-name="StageName"></lightning-input-field><lightning-input-field field-name="CloseDate"></lightning-input-field><lightning-input-field field-name="Name"></lightning-input-field><lightning-input-field field-name="AccountId" ></lightning-input-field><lightning-input-field field-name="StageName"></lightning-input-field><lightning-input-field field-name="CloseDate"></lightning-input-field><lightning-input-field field-name="StageName"></lightning-input-field><lightning-input-field field-name="StageName"></lightning-input-field></div></lightning-record-edit-form></template>

Parent CSS:
.slds-modal__content{max-height: 20rem;overflow-y: scroll;}


1. From Setup, open the Opportunity object and select Buttons, Links, and Actions.
2. Edit the NEW button and change the Lightning Experience Override to your component.
3. Go to the Opportunity list view and click NEW in the upper right corner.
4. In the modal, expand the dropdowns.
5. Notice that the <lightning-combobox> dropdown does not overlay the parent container.

Workaround
================================

This is working as documented, by default lightning-combox will open the dropdown box at bottom of the field. If you need the dropdown to open where there is available space then you need to add attribute:

dropdownAlignment=”auto”

https://developer.salesforce.com/docs/component-library/bundle/lightning:combobox/specification

If the workaround found in bug W-11616816 (https://trailblazer.salesforce.com/issues_view?id=a1p4V000001cUv8QAE) is applied, the lightning:combobox will now overlay the parent container. Once the bug is fixed, this workaround will no longer be necessary.

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Is it Fixed?

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