This leads me to ask again my last question : should I replace all my icons in Sombre.theme with multi-sized icns files in order to display properly at both sizes ?
I'm answering to myself here. I did a test with common_Folder.png in Sombre.theme, created a icns containing multiple sizes and it works. 64x64 size default folder is less blury in GWorkspace.
Will there be a performance hit if I replace all icons ? Bertrand
