Question: am trying to focus the scroll based on the selected add class,when clicking on the previous and next button the scroll need to focus it. how can i make it possible please check my fiddle 
<https://jsfiddle.net/kannankds/bcszkqLu/>

```
<ul class="kds">
<li>tile dtls1</li>
<li>tile dtls2</li>
<li>tile dtls3</li>
</ul>
<input type="button" value="previous" class="previous">
<input type="button" value="next" class="next">

```

Answer: 
I had fixed this problem.The core of this problem is that we recompile some content in libpng,maybe it exits in other ios framework.Then it makes a conflict.Opncv 3.1 has 3rdparty in it's code.What you should do is find the lines 117-121 in libpng's pngpriv.h.Then just follow [Iphone - device - linker error](https://stackoverflow.com/questions/19089014/iphone-device-linker-error).
It appears that this commit fixes the issue, while still keeping NEON support for iOS devices:

<https://github.com/opencv/opencv/commit/262a52f3063c50fbb1236e2cba2bd3c68f9979bb>

Essentially, the clause that appends `-DENABLE_NEON=ON` to the `cmake` line was only applying to architectures beginning with `"armv"` (note the "v"); the above commit changes `opencv/platforms/ios/build_framework.py` to allow the cmake command to work with `"arm64"` as well.

Before:

```
    if arch.startswith("armv"):
        cmakecmd.append("-DENABLE_NEON=ON")

```

After:

```
    if arch.startswith("armv") or arch.startswith("arm64"):
        cmakecmd.append("-DENABLE_NEON=ON")

```

---

Diagnostic process, since it might be useful:

Found this by starting a `script build.log` before invoking `python ../opencv/platforms/ios/build_framework.py ios` and digging through output; `arm_init.c` was not built for `arm64` (which is where `png_init_filter_functions_neon` was defined) but was for `armv7` and `armv7s`. From there, looking through `3rdparty/libpng/CMakeLists.txt` pointed at `ENABLE_NEON` not being set.