## Issue
4797: Markdown preview breaks when using a lbry link in angle brackets
This is similar to the Embed case in commit dbcd677e.
## Change
Replaced it with a dummy link that looks like what the final outcome would be, but would not be clickable.
Again, similar to the embed case, unless there is a way to pass the store over, I don't have an alternative that makes sense: Adding a dummy router or replacing it as a regular <a> will just make React spew security errors.
Not being able to click it is not ideal as we (as a user) can't verify our links, but it's better than the current case of not rendering anything at all.
## Issue
4644: Markdown Preview breaks when <iframe> is present
Error: "Invariant violation: could not find 'store' ..."
## Change
Until we figure out a way to pass the store to the SimpleMDE preview formatter, just replace the embed with a stub region.
## Issue
In the `Autoplay` case, if the `WaitUntilOnPage` has already opened the gates previously, the next video's Related will be loaded regardless of scroll position.
## Changes
Add a `lastUpdateDate` prop to `WaitUntilOnPage` to allow the parent to reset the gating state.
I don't really like the `lastUpdateDate` prop since it's purpose is not intuitive. Is there a standard way to do a "one-time trigger" from the parent?
There are cases where `WaitUntilOnPage` will incorrectly render, such as at the beginning if the upper components hasn't expanded to full size, so `WaitUntilOnPage` would be briefly visible.
Added a 300ms debounce to fix this, which would also improve scrolling performance a bit by doing less. Hopefully 300ms is enough for the upper components to inflate to full size.
Implementation:
- The code is placed in <VideoJs> instead of <VideoViewer> as we need to control the video itself. It's more self-contained here, rather than trying to pass refs around between parent and child.
- useState cannot be used as it will cause a re-render when the hint it clicked and dismissed. The DOM is used to hide the button.
