以下是widthratio标签官网中的内容:
""" For creating bar charts and such, this tag calculates the ratio of a given value to a maximum value, and then applies that ratio to a constant. For example:: <img src='bar.gif' height='10' width='{% widthratio this_value max_value 100 %}' /> Above, if ``this_value`` is 175 and ``max_value`` is 200, the image in the above example will be 88 pixels wide (because 175/200 = .875; .875 * 100 = 87.5 which is rounded up to 88). """
简单的说,
{% widthratio this_value max_value 100 %}
的意思就是 this_value / max_value * 100
这样一来,widthratio 就可以用来显示图表,比例时用的,一个数字占了多少百分比等。
有了这些知识,Openstack Horizon中的这段代码就很容易明白了:
文件名:horizon/templates/horizon/common/_limit_summary.html
{% widthratio usage.limits.totalInstancesUsed usage.limits.maxTotalInstances 100 %}
这句代码的意思就是,计算当前创建的vm的vm总量的百分比。