Virtual slides ignore initialSlide in the beginning

[websirnik]

This is a (multiple allowed):

• bug

• enhancement

• feature-discussion (RFC)

• Swiper Version: 4.3.5

• Platform/Target and Browser Versions: CHROME

• Live Link or JSFiddle/Codepen or website with isssue: https://jsfiddle.net/bqv2137n/11/

What you did

When using initialSlide setting together with virtual, there is extra computing happening. Despite the value of initialSlide, Swiper currently always calls renderSlide with 0&1 indexes before rendering initialSlide slide. This is costly, when my createSlide() function is heavy.

var mySwiper = new Swiper('.swiper-container', {
    initialSlide: 4,
    virtual: {
        slides: ['Slide 1', 'Slide 2', 'Slide 3', 'Slide 4', 'Slide 5', 'Slide 6'],
        renderSlide: function(slide, index){
            console.log(slide);
            return createSlide(slide);
        }
    }
});

Expected Behavior

Console Output:

Slide 4
Slide 5
Slide 6

Actual Behavior

Console Output:

Slide 0
Slide 1
Slide 4
Slide 5
Slide 6

[nolimits4web]

Fixed by #2756