Wow, that is hella impressive! Kudos!

What about TMK layouts (from Hasu at GitHub), can those be at least imported? I know he makes some JSON output but it's probably not like your format?

Maybe you should provide more sources. When you say 'Extend' for instance, what are your mappings based on? Mine? Farkas'? Your own flavour? A few links in comments would be good.

I didn't see any dead keys for PKL in your examples. Can you support the more hairy variants there (Unicode that's not always implemented in fonts, for instance "slash"+⊆ triggering ⊈; the ⊆ being generated by "maths"+<)?

I too, have wished for such a format. I think that we may have to define it ourselves.

For my projects, I'm close to accepting the TMK keymap. It's a simple 16×16 matrix so it holds all possible scan codes, yet there are compiler macros that allow conversion of simpler keymaps to the full matrix. The way I've set mine up, they're fairly intuitive in relation to a real keyboard – but not perfect to look at still. All keys have names that are based on the usual scan code names, optionally abbreviated to 3–4 characters to fit in the map matrix.

Below is a KEYMAP_ALL (that's translated as a macro to AWide-ISO; that's handy!) so all sorts of special and Asian++ keys are there. There are simpler map formats without those, but here's the full monty.

#if ACTIVELAYOUT == 0
    /* Plain QWERTY
     *         ,---------------. ,---------------. ,---------------.
     *         |F13|F14|F15|F16| |F17|F18|F19|F20| |F21|F22|F23|F24|
     * ,---.   |---------------| |---------------| |---------------| ,-----------. ,---------------. ,-------.
     * |Esc|   |F1 |F2 |F3 |F4 | |F5 |F6 |F7 |F8 | |F9 |F10|F11|F12| |PrS|ScL|Pau| |VoD|VoU|Mut|Pwr| | Help  |
     * `---'   `---------------' `---------------' `---------------' `-----------' `---------------' `-------'
     * ,-----------------------------------------------------------. ,-----------. ,---------------. ,-------.
     * |  `|  1|  2|  3|  4|  5|  6|  7|  8|  9|  0|  -|  =|JPY|BSp| |Ins|Hom|PgU| |NLk|  /|  *|  -| |Stp|Agn|
     * |-----------------------------------------------------------| |-----------| |---------------| |-------|
     * | Tab |  Q|  W|  E|  R|  T|  Y|  U|  I|  O|  P|  [|  ]|  \  | |Del|End|PgD| |  7|  8|  9|  +| |Mnu|Und|
     * |-----------------------------------------------------------| `-----------' |---------------| |-------|
     * |*Caps*|  A|  S|  D|  F|  G|  H|  J|  K|  L|  ;|  :|  #|Ent |               |  4|  5|  6|KP,| |Sel|Cpy|
     * |-----------------------------------------------------------|     ,---.     |---------------| |-------|
     * | Sft|  <|  Z|  X|  C|  V|  B|  N|  M|  ,|  ,|  /| RO| Shft |     |Up |     |  1|  2|  3|KP=| |Exe|Pst|
     * |-----------------------------------------------------------| ,-----------. |---------------| |-------|
     * |Ctrl|Gui|Alt|MHEN|HNJ| Space |H/E|HENK|KANA|Alt|Gui|App|Ctl| |Lft|Dwn|Rgh| |  0    |  .|Ent| |Fnd|Cut|
     * `-----------------------------------------------------------' `-----------' `---------------' `-------'
     */
    [0] = KEYMAP_AWIDEISO(
              F13 ,F14 ,F15 ,F16 ,F17 ,F18 ,F19 ,F20 ,F21 ,F22 ,F23 ,F24 ,
    ESC ,      F1 , F2 , F3 , F4 , F5 , F6 , F7 , F8 , F9 ,F10 ,F11 ,F12 ,         PSCR,SLCK,PAUS,    VOLD,VOLU,MUTE,PWR ,    HELP,
    GRV ,  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9 ,  0 ,MINS,EQL ,JYEN,BSPC,    INS ,HOME,PGUP,    NLCK,PSLS,PAST,PMNS,    STOP,AGIN,
    FN0   ,  Q ,  W ,  E ,  R ,  T ,  Y ,  U ,  I ,  O ,  P ,LBRC,RBRC,   BSLS,    DEL ,END ,PGDN,     P7 , P8 , P9 ,PPLS,    MENU,UNDO,
    FN1    ,  A ,  S ,  D ,  F ,  G ,  H ,  J ,  K ,  L ,SCLN,QUOT,NUHS,  ENT ,                        P4 , P5 , P6 ,PCMM,    SLCT,COPY,
    LSFT ,NUBS,  Z ,  X ,  C ,  V ,  B ,  N ,  M ,COMM,DOT ,SLSH, RO ,    RSFT,          UP ,          P1 , P2 , P3 ,PEQL,    EXEC,PSTE,
    LCTL ,LGUI,FN6 ,MHEN,HANJ,    SPC     ,HAEN,HENK,KANA,FN7 ,RGUI,APP , RCTL,    LEFT,DOWN,RGHT,     P0      ,PDOT,PENT,    FIND,CUT 
    ),    /* <-- Layer 0: Default Layer */

It would be good to have some examples of usage of the program. I'm talking about the Windows executable, I could not make it to work.

Anyone know of a typing tutor that allows custom keyboard layouts? I am just learning to touch type and I would like to try a couple of the Colemak mods and/ or add my own changes as to which physical keys I want to press with which fingers.

Do you really need one though? With PKL you can have any help image showing your layout at the top or bottom of your screen, if you don't want to use a printed help image. And using Tarmak, there's so few keys to learn at a time that you may rely a lot less on help images altogether.

I've not used any Colemak-specific tutors showing the layout. Didn't miss it.

Glad you like it! I indeed designed the format to be flexible without being too verbose. It could be a bit less verbose, but I wanted to use an existing format (JSON). YAML support, which is a superset of JSON, could be added to remove most quotes around strings. But I don't think its really needed.

I am working on support for TMK, basic support should probably be ready in a few weeks.

Since I experienced some quirks in PKL, and PKL has some missing features, I have added support for exporting directly to AutoHotkey scripts. The implementation doesn't have help images, but it has some other features:
* No stuck modifiers
* Multiple extend layers: combinations like Shift+Extend, as well as multiple extend keys
* (Multiple) shifted, latched or locked modifiers on a key
* Chained dead keys, which enable a compose key
* It still supports nested dead keys, so 'slash'+⊆ triggers ⊈, with ⊆ generated by 'math'+<

You could indeed say that it is like PKL. I may port some improvements to PKL, although the source code doesn't look very flexible. Removing stuck modifiers, adding chained dead keys and adding multiple extend layers should be possible though.

As a start, I tried to compile the PKL source code, but it doesn't work :(. If I compile pkl.ahk and execute pkl.exe, I get the error "You must set the layout file in pkl.ini!". And if I directly run the script, I even get an error inside the script...

The problem is that I have put a valid pkl.ini file in the right place... If I remove it, PKL (correctly) says that pkl.ini is missing, which is a different error.

The problems really occur due to the compilation: if I replace my self-compiled pkl.exe by a precompiled one, everything works fine. I should have been more clear about that.

I would like to get vVv's code, but his link in this post redirects me to the homepage of filedropper :(. Do you still have it, or do we have to ask vVv? Also, there are nice tools to view the difference between files, so it should be doable to figure out what he's done.

So... Will you also share his code?