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
2015-11-13 21:11:21 -06:00
2023-10-04 13:26:30 +00:00
2023-10-04 13:26:30 +00:00
2023-03-22 13:36:35 +00:00

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