Files
ionic-framework/core
Liam DeBeasi 3259da0de1 fix(header): collapsible large title main header does not flicker on load (#28277)
Issue number: resolves #27060

---------

<!-- Please do not submit updates to dependencies unless it fixes an
issue. -->

<!-- Please try to limit your pull request to one type (bugfix, feature,
etc). Submit multiple pull requests if needed. -->

## What is the current behavior?
<!-- Please describe the current behavior that you are modifying. -->

The main header is controlled by the header with `collapse="condense"`
set:
a04a11be35/core/src/components/header/header.tsx (L144)

The collapse header will hide the main header and then show it once the
user has scrolled enough. However, if the main header is rendered before
the collapse header is rendered, then the main header will be visible
for a brief moment before being hidden by the collapse header. This
gives the perception of flicker that is reported on the linked issue.

## What is the new behavior?
<!-- Please describe the behavior or changes that are being added by
this PR. -->

- The main header will be hidden on load if it loads before the collapse
header

The selector was written in a way such that once the collapse header
loads, this CSS no longer applies (since the collapse header will add
`.header-collapse-main` to the main header)

| `main` | branch |
| - | - |
| <video
src="https://github.com/ionic-team/ionic-framework/assets/2721089/3cb11a57-e084-435a-89c2-e1c2afba04b1"></video>
| <video
src="https://github.com/ionic-team/ionic-framework/assets/2721089/c5caeb5e-3b33-4598-986f-bf097c46251c"></video>
|

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

<!-- If this introduces a breaking change, please describe the impact
and migration path for existing applications below. -->


## Other information

<!-- Any other information that is important to this PR such as
screenshots of how the component looks before and after the change. -->

Note: `:has` browser compat is still fairly new. However, it is
available on both Chromium and WebKit browsers (and has been for at
least a year): https://caniuse.com/?search=%3Ahas

Given that this bug is a fairly minor UI glitch (as opposed to something
that would cause an app to crash or otherwise malfunction), I think this
is an acceptable tradeoff. As time goes on this will become less of a
concern as more users update their devices.

Dev build: `7.4.3-dev.11696365694.156f41d3`
2023-10-05 18:27:44 +00:00
..
2023-10-04 13:26:30 +00:00

@ionic/core

Ionic is an open source App Development Framework that makes it easy to build top quality Native and Progressive Web Apps with web technologies.

The Ionic Core package contains the Web Components that make up the reusable UI building blocks of Ionic Framework. These components are designed to be used in traditional frontend view libraries/frameworks (such as Stencil, React, Angular, or Vue), or on their own through traditional JavaScript in the browser.

Features

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Vanilla HTML

Easiest way to start using Ionic Core is by adding a script tag to the CDN:

<script type="module" src="https://cdn.jsdelivr.net/npm/@ionic/core/dist/ionic/ionic.esm.js"></script>
<script nomodule src="https://cdn.jsdelivr.net/npm/@ionic/core/dist/ionic/ionic.js"></script>
<link href="https://cdn.jsdelivr.net/npm/@ionic/core/css/ionic.bundle.css" rel="stylesheet">

Any Ionic component added to the webpage will automatically load. This includes writing the component tag directly in HTML, or using JavaScript such as document.createElement('ion-toggle').

Additionally, within this package is a dist/ionic.js file and accompanying dist/ionic/ directory. These are the same files which are used by the CDN, and they're available in this package so they can be apart of an app's local development.

Framework Bindings

The @ionic/core package can be used in simple HTML, or by vanilla JavaScript without any framework at all. Ionic also has packages that make it easier to integrate Ionic into a framework's traditional ecosystem and patterns. (However, at the lowest-level framework bindings are still just using Ionic Core and Web Components).

Custom Elements Build

In addition to the default, self lazy-loading components built by Stencil, this package also comes with each component exported as a stand-alone custom element within @ionic/core/components. Each component extends HTMLElement, and does not lazy-load itself. Instead, this package is useful for projects already using a bundler such as Webpack or Rollup. While all components are available to be imported, the custom elements build also ensures bundlers only import what's used, and tree-shakes any unused components.

Below is an example of importing ion-badge, and initializing Ionic so it is able to correctly load the "mode", such as Material Design or iOS. Additionally, the initialize({...}) function can receive the Ionic config.

import { defineCustomElement } from "@ionic/core/components/ion-badge.js";
import { initialize } from "@ionic/core/components";

// Initializes the Ionic config and `mode` behavior
initialize();

//  Defines the `ion-badge` web component
defineCustomElement();

Notice how we import from @ionic/core/components as opposed to @ionic/core. This helps bundlers pull in only the code that is needed.

The defineCustomElement function will automatically define the component as well as any child components that may be required.

For example, if you wanted to use ion-modal, you would do the following:

import { defineCustomElement } from "@ionic/core/components/ion-modal.js";
import { initialize } from "@ionic/core/components";

// Initializes the Ionic config and `mode` behavior
initialize();

//  Defines the `ion-modal` and child `ion-backdrop` web components.
defineCustomElement();

The defineCustomElement function will define ion-modal, but it will also define ion-backdrop, which is a component that ion-modal uses internally.

Using Overlay Controllers

When using an overlay controller, developers will need to define the overlay component before it can be used. Below is an example of using modalController:

import { defineCustomElement } from '@ionic/core/components/ion-modal.js';
import { initialize, modalController } from '@ionic/core/components';

initialize();
defineCustomElement();

const showModal = async () => {
  const modal = await modalController.create({ ... });
  
  ...
}

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License