• Please commit to the dev branch

改进 PDF 导出时的分页策略
Improved PDF export paging strategy

尽量避免在如下内容中分页:
Try to avoid pagination in the following:

• 音频块内 | Inside the audio block
• 图表块内 | Inside the graph block
• 标题块内 | Inside the heading block
• IFrame 块内 | Inside the IFrame block
• 公式块内 | Inside the math block
• 段落块内 | Inside the paragraph block
• 分割线内 | Inside the thematic break block
• 视频块内 | Inside the video block
• 挂件块内 | Inside the widget block
• 表格块行内 | Inside the table row
• 图片内 | Inside the image

已使用默认主题在用户指南中 排版元素 文档进行测试
Tested on the Formatting elements document in the User Guide using the default theme.