htop meters are in wrong order

[rvl]

Issue description

I tried out programs.htop with the example configuration:

{ config, ... }: {
  programs.htop = {
    enable = true;
    settings = {
       color_scheme = 6;
       cpu_count_from_one = 0;
       delay = 15;
       fields = with config.lib.htop.fields; [
         PID
         USER
         PRIORITY
         NICE
         M_SIZE
         M_RESIDENT
         M_SHARE
         STATE
         PERCENT_CPU
         PERCENT_MEM
         TIME
         COMM
       ];
       highlight_base_name = 1;
       highlight_megabytes = 1;
       highlight_threads = 1;
     } // (with config.lib.htop; leftMeters {
       AllCPUs2 = modes.Bar;
       Memory = modes.Bar;
       Swap = modes.Bar;
       Zram = modes.Text;
     }) // (with config.lib.htop; rightMeters {
       Tasks = modes.Text;
       LoadAverage = modes.Text;
       Uptime = modes.Text;
       Systemd = modes.Text;
     });
  };
}

Expected Result

Meters in right-hand column are in order as defined in configuration: Tasks, LoadAverage, Uptime, Systemd.

Actual Result

Meters in right-hand column are in alphabetical order: LoadAverage, Systemd, Tasks, Uptime.

  0[|||                    6.5%]    4[||                     5.3%] Load average: 1.01 3.71 4.26
  1[|||||||||             27.7%]    5[||                     4.8%] Systemd: N/A (?/? failed) (?/? jobs)
  2[||||                   7.1%]    6[||                     6.0%] Tasks: 179, 1064 thr, 168 kthr; 1 running
  3[|||||                 13.6%]    7[|||                    6.5%] Uptime: 5 days, 21:45:29
Mem[||||||||||||||||||||||||||||||||||||||||||||||||||15.4G/31.1G]
Swp[||                                                 812M/32.0G]
zrm:0K used:0K uncompressed:0K

Info

It is very useful to be able to customize the order of meters.

This bug probably occurs because nix attrsets are unordered, and #1844 changes the meters lists to be attrsets.

Also

Also I don't know why the systemd meter doesn't work. Do I need to configure something else for that?

Maintainer CC

cc: @bjpbakker

Technical details

Using home-manager rev 9049302.

Thanks

Thank you for the programs.htop module - it's cool.

[berbiche]

Yeah, this is an unfortunate restriction of the Nix language.

Attribute sets are stored in a lexicographical order and not insertion order so it's not possible to order keys.

I think the functions leftMeters and rightMeters should accept a list of attributes to maintain the order:

home-manager/modules/programs/htop.nix

Lines 13 to 18 in cb227dc

	formatMeters = side: meters: {
	"${side}_meters" = mapAttrsToList (x: _: x) meters;
	"${side}_meter_modes" = mapAttrsToList (_: y: y) meters;
	};
	leftMeters = formatMeters "left";
	rightMeters = formatMeters "right";

[rvl]

Something like this might work (and allow for backwards compatibility):

programs.htop.settings = otherStuff // (with config.lib.htop; metersSettings {
  left = [
    (bar "AllCPUs2")
    "Memory"
    (bar "Swap")
  ];[
  right = [
    (text "Tasks")
    (graph "LoadAverage")
    (led "Clock")
   ];
};

# implementation would have something like this
let
  text = meter: { kind = meter; mode = modes.Text };
  # etc.

  metersSettings = { left ? [], right ? [] }:
    formatMeterList "left" left //
    formatMeterList "right" right;

  # similar to formatMeters
  formatMeterList = side: meters: {
    "${side}_meters" = builtins.map
      (m: if builtins.isAttrs m then m.kind else m)
       modes;
    "${side}_meter_modes" = builtins.map
      (m: if (builtins.isAttrs m) then (if (m.mode or null) == null then meters.${m.kind} else m.mode) else meters.${m})
       modes;
  };
in
  ...

But actually, it may be better to just use nixos options for configuring this.

[bjpbakker]

Hm yes, that's a good point. Thanks for bringing it up.

A single settings key still is preferable IMO. Splitting the settings in various nixos options (like before) is too limiting. But the input type should probably be a list of pairs rather than an attrset, like you suggest above.

I will provide a fix for this.

[bjpbakker]

@rvl I opened #2065 to address this. I'll backport to 21.05 when merged.

Also I like your suggestion of having 1 function to pass both the left and right meters lists to. I'll add that a bit later after I've done some cleanup of the deprecated things on master.

Thanks again for bringing this up :)