Issue Summary

Texts in powerpoint thumbnail is not rendered correctly depending on Java version. Characters are overlaid each other.
As far as I confirmed,

• AdoptOpenJDK jdk8u202-b08 (which is a bundled one in most version of Confluence) can render correctly
• Oracle JRE jre-8u241-linux-x64 can render correctly
• AdoptOpenJDK jdk8u242-b08 is affected
• AdoptOpenJDK jdk-11.0.6+10 is affected
• AdoptOpenJDK jdk-11.0.5+10 is affected (it's bundled with 7.4.0)

Steps to Reproduce

1. Prepare Linux OS and install some fonts to enable server side rendering
   I've tested with Ubuntu

   sudo apt-get update
   sudo apt-get install -y fontconfig
   apt-get install -y fonts-dejavu
   

1. Install Confluence from tar.gz and configure it to use AdoptOpenJDK jdk8u242-b08
2. Open the editor, and drag and drop sample.pptx on your browser.

Expected Results

sample.pptx is rendered correctly.

Actual Results

The text is squashed.

Workaround

Use jdk8u202-b08 as Supported Platforms suggests.

Some AdoptOpenJDK versions have bugs that impact Confluence. We recommend version jdk8u202 (see CONFSERVER-58784).

Or, if you are already using Java 11, upgrade to version 11.0.7.

Note: Confluence LTS version 7.4.3 and later is bundled with AdoptOpenJDK version 11.0.7+10, which is unaffected by this bug. However, if Confluence is running using an older JDK version which is affected, the bug will still be experienced.