linespace option seems add "space" only below the line

[kailiu42]

Describe the bug
I use neovide on macOS and set linespace=8 to make it looks good to my eyes. However, it seems neovide add that 8 all below the line, while I expect it to actually add 4 above and 4 below. In other word, I expect neovide place the line vertically in the middle of the extra spaces I add.

To Reproduce
Steps to reproduce the behavior:

1. set linespace to some large value that is easy to distinguish.
2. Look at the cursor, you will see the extra space is below the line, nothing above the line.

Expected behavior
Expect to have 0.5linespace above the line and 0.5linespace below the line.

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: macOS 13.3.1
• Neovide Version 0.10.4
• Neovim Version 0.9.0

Please run neovide --log and paste the contents of the .log file created in the current directory here:
It's 2.4MB big, please let me know if you really need it.