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Then the waveforms that are saved as .do files are displayed without their results
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Those .do files are only used to configure the waveform panel.
You can save results by exporting or printing.
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it a hassle to re-simulate my project each and every time
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Maybe you work in a virtual machine or a sandbox environnement (look at firewall(ex. COMODO) and antivirus (ex. AVAST)).
Maybe it is a problem of permissions.
Could you precise your PC configuration : Windows Version, Modelsim version, Quartus Version, "administrator" or "restricted user", work in a network (your home and/or directory is on network)... ?
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Mine got opened (sometimes) outside of it: as text file. Not a major issue but annoying as I don't to have too many windows on the desktop.
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Look at Modelsim preferences. And maybe reinstall.