lazyPreloadPrevNext starts before the first slide is loaded

[chatziko]

Check that this is really a bug

• I confirm

Reproduction link

https://codesandbox.io/p/sandbox/swiper-lazy-load-images-forked-73s2c5?file=%2Findex.html%3A150%2C22&layout=%257B%2522sidebarPanel%2522%253A%2522EXPLORER%2522%252C%2522rootPanelGroup%2522%253A%257B%2522direction%2522%253A%2522vertical%2522%252C%2522contentType%2522%253A%2522UNKNOWN%2522%252C%2522type%2522%253A%2522PANEL_GROUP%2522%252C%2522id%2522%253A%2522ROOT_LAYOUT%2522%252C%2522panels%2522%253A%255B%257B%2522type%2522%253A%2522PANEL_GROUP%2522%252C%2522contentType%2522%253A%2522EDITOR%2522%252C%2522direction%2522%253A%2522horizontal%2522%252C%2522id%2522%253A%2522EDITOR%2522%252C%2522panels%2522%253A%255B%257B%2522type%2522%253A%2522PANEL%2522%252C%2522contentType%2522%253A%2522EDITOR%2522%252C%2522id%2522%253A%2522clt0idcqt002m2868hutsx7gb%2522%257D%255D%257D%252C%257B%2522type%2522%253A%2522PANEL_GROUP%2522%252C%2522contentType%2522%253A%2522DEVTOOLS%2522%252C%2522direction%2522%253A%2522horizontal%2522%252C%2522id%2522%253A%2522DEVTOOLS%2522%252C%2522panels%2522%253A%255B%257B%2522type%2522%253A%2522PANEL%2522%252C%2522contentType%2522%253A%2522DEVTOOLS%2522%252C%2522id%2522%253A%2522clt0idcqt002n2868esz0jd8j%2522%257D%255D%252C%2522sizes%2522%253A%255B100%255D%257D%255D%252C%2522sizes%2522%253A%255B50%252C50%255D%257D%252C%2522tabbedPanels%2522%253A%257B%2522clt0idcqt002m2868hutsx7gb%2522%253A%257B%2522id%2522%253A%2522clt0idcqt002m2868hutsx7gb%2522%252C%2522tabs%2522%253A%255B%255D%257D%252C%2522clt0idcqt002n2868esz0jd8j%2522%253A%257B%2522tabs%2522%253A%255B%257B%2522id%2522%253A%2522clt0i5mqo00052868i5ay33k0%2522%252C%2522mode%2522%253A%2522permanent%2522%252C%2522type%2522%253A%2522UNASSIGNED_PORT%2522%252C%2522port%2522%253A0%252C%2522path%2522%253A%2522%252F%2522%257D%255D%252C%2522id%2522%253A%2522clt0idcqt002n2868esz0jd8j%2522%252C%2522activeTabId%2522%253A%2522clt0i5mqo00052868i5ay33k0%2522%257D%257D%252C%2522showDevtools%2522%253Atrue%252C%2522showShells%2522%253Afalse%252C%2522showSidebar%2522%253Afalse%252C%2522sidebarPanelSize%2522%253A15%257D

Bug description

With lazyPreloadPrevNext: 1 we expect to preload slide N+1 when N is loaded. However, this is not true for N=1. Then second slide is loaded immediately, even when the first is delayed.

Expected Behavior

In the codesandbox demo nature-1.jpg is not loaded on page load since it's not visibe. nature-2.jpg is expected to be pre-loaded only after nature-1.jpg is actually loaded.

Actual Behavior

nature-2.jpg is loaded on page load, before nature-1.jpg, which is only loaded later when the page scrolls.

Swiper version

v11.0.6

Platform/Target and Browser Versions

Firefox 22.0.1 on Linux

Validations

• Follow our Code of Conduct
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.
• Make sure this is a Swiper issue and not a framework-specific issue

Would you like to open a PR for this bug?

• I'm willing to open a PR