SVG 变换旋转 90、180 或 270 度不适用于 Safari iOS 10 中的圆圈

Question

我想通过设置stroke-dasharray 和改变stroke-dashoffset 来使用SVG 圆形元素创建一个圆环图。 SVG 元素需要旋转 270（或 -90）度，以便图表“条形图”从顶部开始。代码如下：

http://jsfiddle.net/q3wb6gkq/

使用transform="rotate(270, 80, 80)"中的第一个数字指定旋转角度。

问题是：在 iOS 10 上的 Safari 中查看时，未应用此旋转。实际上，设置 90、180 或 270 度旋转都没有效果。也不会应用相同的角度但为负（例如 -90）。

这是 iOS 10.0.1 上 Safari 中上述小提琴的截图：

在 iOS 9.3.5 上的 Safari 中也是如此：

作为一种解决方法，我发现使用类似 270.1 度的值可以解决问题，但是我想知道为什么 270 不工作以及是否有更好的处理方法。

Answer 1

我在 iOS 10.1 和 Safari 10.0.1 上经历过这种痛苦。该错误肯定是由任何rotate 值触发的，该值计算为可被 90 度整除的值。

但它变得更奇怪了：错误的存在受当前缩放级别的影响。

查看我整理的这个演示/系列最小测试用例（jsFiddle 版本here）。最好运行 sn -p 然后展开到整页：

svg {
  height: 80px;
  width: 80px;
}

circle {
  fill: none;
  stroke-dasharray: 150;
  stroke-width: 4px;
  stroke: #6fdb6f;
  transform-origin: center center;
}

.degrot {
  transform: rotate(-90deg);
}

.degrot-offset {
  transform: rotate(-90.1deg);
}

.degrot-offset-more {
  transform: rotate(-92deg);
}

.turnrot {
  transform: rotate(-0.25turn);
}

.turnrot-offset {
  transform: rotate(-0.251turn);
}


svg[viewBox] circle {
  stroke-dasharray: 300;
  stroke-width: 8px;
}

svg[viewBox].scaledown circle {
  stroke-dasharray: 300;
  stroke-width: 8px;
}

svg[viewBox].noscale circle {
  stroke-dasharray: 150;
  stroke-width: 4px;
}

svg[viewBox].scaleup circle {
  stroke-dasharray: 75;
  stroke-width: 2px;
}

.wc {
  will-change: transform;
}


/* Demo prettification */

p:last-child {
  margin-bottom: 0;
}

td {
  padding: 10px;
}

tr td:first-of-type {
  width: 80px;
  min-height: 80px;
}

tr + tr td {
  border-top: 1px solid #dcdcdc;
}

<table>
  <tr><td colspan="2">In Safari 10.0.1 and iOS 10.1, strange behavior can be observed on SVG shapes with <code>rotate</code> values not divisible by 90 degrees, when <code>transform-origin: center center;</code></td></tr>
  <tr>
    <td>

      <svg xmlns="http://www.w3.org/2000/svg">
        <circle class="degrot" r="35" cy="40" cx="40" />
      </svg>

    </td>
    <td>
      <code>transform: rotate(-90deg);</code>
      <p>The stroke improperly begins <a href="https://www.w3.org/TR/SVG11/shapes.html#CircleElement">at 3:00</a>, as if the <code>transform</code> rule hadn't been applied.</p>
    </td>
  </tr>

  <tr>
    <td>

      <svg xmlns="http://www.w3.org/2000/svg">
        <circle class="degrot-offset" r="35" cy="40" cx="40" />
      </svg>

    </td>
    <td>
      <code>transform: rotate(-90.1deg);</code>
      <p>The stroke begins at (twelve seconds before) 12:00, as expected.</p>
    </td>
  </tr>

  <tr>
    <td>

      <svg xmlns="http://www.w3.org/2000/svg">
        <circle class="turnrot" r="35" cy="40" cx="40" />
      </svg>

    </td>
    <td>
      <code>transform: rotate(-0.25turn);</code>
      <p>The same bug applies to any <code>rotate</code> value which computes to a multiple of 90 degrees.</p>
    </td>
  </tr>

  <tr>
    <td>

      <svg xmlns="http://www.w3.org/2000/svg">
        <circle class="turnrot-offset" r="35" cy="40" cx="40" />
      </svg>

    </td>
    <td>
      <code>transform: rotate(-0.251turn);</code>
      <p>43 seconds before noon.</p>
    </td>
  </tr>


  <tr><td colspan="2">But when the SVG element specifies a <code>viewBox</code> which is being scaled down, things can get weird:</td></tr>
  
  <tr>
    <td>

      <svg viewBox="0 0 160 160" xmlns="http://www.w3.org/2000/svg">
        <circle class="degrot" r="70" cy="80" cx="80" />
      </svg>

    </td>
    <td>
      <code>transform: rotate(-90deg);</code>
      <p>So far, so the same.</p>
    </td>
  </tr>

  <tr>
    <td>

      <svg viewBox="0 0 160 160" xmlns="http://www.w3.org/2000/svg">
        <circle class="degrot-offset" r="70" cy="80" cx="80" />
      </svg>

    </td>
    <td>
      <code>transform: rotate(-90.1deg);</code>
      <p>But now, offsetting by a little bit doesn't work, <em>unless</em> you zoom in the page in past a certain zoom threshold (either via pinching, or <code>View > Zoom</code> and/or keyboard shortcut). Try it; it's unsetting!</p>
      <p>This is probably because of some rounding of that the zooming engine performs, because...</p>
    </td>
  </tr>

  <tr>
    <td>

      <svg viewBox="0 0 160 160" class="scaledown" xmlns="http://www.w3.org/2000/svg">
        <circle class="degrot-offset-more" r="70" cy="80" cx="80" />
      </svg>

    </td>
    <td>
      <code>transform: rotate(-92deg);</code>
      <p>offsetting by a larger amount restores expected behavior.</p>
    </td>
  </tr>

  <tr><td colspan="2">If the SVG element is not being scaled <em>down</em>, behavior identical to the first section resumes. Zooming has no effect:</td></tr>
  
  <tr>
    <td>
      
      <svg viewBox="0 0 80 80" class="noscale" xmlns="http://www.w3.org/2000/svg">
        <circle class="degrot" r="35" cy="40" cx="40" />
      </svg>

      <svg viewBox="0 0 40 40" class="scaleup" xmlns="http://www.w3.org/2000/svg">
        <circle class="degrot" r="17.5" cy="20" cx="20" />
      </svg>

    </td>
    <td>
      <code>transform: rotate(-90deg);</code>
      <p>
      Top: No scaling (viewBox dimensions match parent element's)<br><br>
      Bottom: Scaling up (viewBox dimensions half of parent element's)
      </p>
    </td>
  </tr>

  <tr>
    <td>
      
      <svg viewBox="0 0 80 80" class="noscale" xmlns="http://www.w3.org/2000/svg">
        <circle class="degrot-offset" r="35" cy="40" cx="40" />
      </svg>

      <svg viewBox="0 0 40 40" class="scaleup" xmlns="http://www.w3.org/2000/svg">
        <circle class="degrot-offset" r="17.5" cy="20" cx="20" />
      </svg>

    </td>
    <td>
      <code>transform: rotate(-90.1deg);</code>
      <p>
        Top: No scaling (viewBox dimensions match parent element's)<br><br>
        Bottom: Scaling up (viewBox dimensions half of parent element's)
      </p>
    </td>
  </tr>

  <tr><td colspan="2">But there is one exception:</td></tr>

  <tr>
    <td>
      
      <svg class="degrot wc" xmlns="http://www.w3.org/2000/svg">
        <circle r="35" cy="40" cx="40" />
      </svg>

    </td>
    <td>
      <p>On the parent <code>svg</code> element:</p>
      <code>transform: rotate(-90deg);<br>will-change: transform;</code>
      <p>Iff the the the rotation is applied to a <em>parent</em> of the SVG shape (including the SVG element itself) along with the rule <code>will-change: transform</code>, all rotation values work as expected.</p>
    </td>
  </tr>

  <tr><td colspan="2">All these behaviors have been observed in Safari 10.0.1 and iOS 10.1. They appear to be fixed as of iOS 10.2 Beta 2.</td></tr>
</table>

正如演示中所述，它似乎已在 iOS 10.2 中得到修复，至少在我刚刚下载的公测版中是这样。据推测，Safari 修复程序也将在适当的时候到达。

iOS 10.1

iOS 10.2（公测 2）

Answer 2

确实，将旋转变换设置为 90.1 度可以解决问题...

我测试了很多东西，在这里报告：https://codepen.io/KevinNTH/pen/ZBgKdG

<!-- workaround ios -->
<svg class="wka-ios">
  <g transform="rotate(-90.1 30 30)">
    <circle cx="25" cy="25" r="15"/>
  </g>
</svg>

Answer 3

这也发生在我身上，我决定使用几乎不能被 90 度整除的旋转来临时解决这个问题。