关于box-sizing:border-box与Contempo主题的兼容性问题问询

为什么box-sizing: border-box会导致Contempo主题的分享功能异常？ #

Hey there! Let's unpack exactly what happened here.

First, let's recap what box-sizing: border-box does: by default, browsers use content-box for this property, which means an element's declared width/height only applies to its content area—padding and border get added on top, making the element larger than you set. border-box changes that: it includes padding and border within the declared width/height, so the element's total size stays exactly what you specify.

Here's the problem with your setup: the Contempo theme's share functionality was built assuming the default content-box model. The theme's CSS defines sizes, spacing, and positioning for share buttons (and their interactive elements like popups) based on how content-box calculates element dimensions.

When you copied that grid example code, it likely included a global rule like:

* {
  box-sizing: border-box;
}

This forces every element on your site—including the theme's share components—to use border-box. Suddenly, the share buttons' padding and borders are being counted against their declared width/height instead of added to it. That throws off the theme's carefully calculated layout: buttons might overlap, their clickable areas might shift, or popup menus might render in the wrong position—all of which breaks the share functionality.

The good news is you already found the fix by isolating the problematic code! Going forward, if you want to use grid layouts without messing up your theme, avoid applying box-sizing: border-box globally. Instead, scope it only to your grid elements. For example:

.my-custom-grid-container,
.my-custom-grid-container * {
  box-sizing: border-box;
}

This way, only your grid content uses the border-box model, and the rest of your theme (including the share features) stays on the default layout it was designed for.

内容的提问来源于stack exchange，提问作者Farquhar