nix-build-view using ncurses

31 may 2014


nix-build-view is a graphical frontend for nix-build, to visualize parallel execution of downloads and builds, taking place when doing nixos-rebuild for example.

i’ve been working on nix-build-view a lot and this is the first preview of my work. if you like/dislike my work please let me know using email to you can find my work at [1].

looking back

this project was born on FOSDEM14 when i was talking to niksnut and iElectric and was motivated by the quality of Gentoo tools in regards to usability.

originally i did not want to use ncurses because of its C-nature i despise. but after hacking several prototypes i concluded it can’t just be done NOT using ncurses since NIX is running on linux, mac os x and other posix systems and they might have different terminals.

anyway, an interesting finding was that a terminal is like viewing a richt text document with a given resolution to render to. however, it is very limited and one cannot navigate the cursor in the document like one would expect of a DOM-tree nowadays. it is more like a 1980…

one thing that hurts is how string and color processing is done both in a normal terminal and using ncurses. both do NOT have a notion of colored text, this has to be composed by the application developers. this was the primary reason i created AdvancedString and AdvancedStringContainer [2]. i’ve also added a list of unit tests for AdvancedString, see [3].

current state

the current implementation of nix-build-view/ is a RFC (not in the classical sense though). if you think i’ve been missing something please let me know.

nix-shell -p cmake -p clang -p ncurses
git clone
cd nix-build-view//nix-build-view
mkdir build
cd build
cmake ..

currently i’m emulating nix-build but the next thing is to connect nix-build-view to nix-build either by integrating nix-build-view into nix-build or by using some form of message passing. i’m not sure yet how to go on.

there are known issues and i’ve listed a lot of them in the code itself using the keyword ‘FIXME’.


the good news is that nix-build-view is nearly done and that i will integrate nix-build-view into nixos soon.

some open points at this time are:

  • reduce the amount of update() calls from FetchWidgetManager/BuildWidgetManager
  • make rendering more effiction by adding caching
  • fixing all FIXMEs in the code
  • integrate nix-build-view into nix-build or attach it using message passing


my goal was to have a tool equal to htop in quality. i’m sure nix-build-view will be very helpful and many NixOS devs already had great interest in nix-build-view.

i’ll keep you posted about usability updates in NixOS of which i think we need to address!

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