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Without enough space, one may face data corruption, which is really a terrible thing that can possibly happen for someones important data. In order to avoid falling into such a situation, it is good idea to give warning to the users in advance.

Code Pointers for generating warning for low disk space

To implement such a feature in LibreOffice, first place to look is this file sfx2/source/doc/sfxbasemodel.cxx.

The method to query the free space method should be added to the sal/osl folder in LibreOffice core source code. To add OS specific code, one may use unx and w32 folders inside it.

Please note that LibreOffice needs to know the disk space on different devices, so passing a vector containing path and free disk space is a good suggestion here.

You should know that guessing the required disk space to save the file is not easy. So, the idea is to have several megabytes free to avoid facing problems. That is in cases the file is not actually very huge. It is possible to add that limit as an option, placed in Tools > Options. These days, even 100-200 megabyte is not that much when comparing it to the very fast disk consumption by different applications like browsers and other similar huge software that people use regularly.

Another nice feature to implement is a handler that runs with low priority every several seconds and checks the available temporary space. That will help avoiding problems with saving images in that specifc temp directory.

Testing the Warning for Low Disk Space

One needs to create a test environment to actually test the patch in action. Using a small RAM drive, it is possible to do that. These commands are useful to create a 20 MB partition for testing:

mkdir /tmp/small
sudo /bin/mount -t tmpfs -o size=20m,mode=0700,uid=$USER,gid=$GROUP /dev/shm /tmp/small

After invoking the above instructions and filling the disk space, you can invoke LibreOffice with the below command to use temp drive. As a result, you will get the below error message:

But, no warning message is shown when you have some small disk space which is < 1 MB.

$ instdir/program/soffice -env:SAL_USE_VCLPLUGIN=gen -env:UserInstallation=file:///tmp/small /tmp/small/1.pptx

While having < 1 MB disk space, you will get this warning in the terminal, but not when the space is between 1 and 2 MBs.

warn:configmgr:57868:58063:configmgr/source/components.cxx:190: error writing modifications com.sun.star.uno.RuntimeException message: "cannot write to file:///tmp/small/user/nnePqE at ~/Projects/libreoffice/core/configmgr/source/writemodfile.cxx:109"

Please note that both the profile and the opened file were inside /tmp/small.

Final Words

The above issue is tdf#60909. If you like it, just follow the Bugzilla link to see more information.

To implement this feature, first you have to build LibreOffice from the sources. If you have not done that yet, please refer to this guide first:

Getting Started (Video Tutorial)