Doing math and formatting on machine variables before displaying on a widget

[kaydeeH]

Hi all,

I've been beating my head against this for a while, so it's time to reach out again. I feel like this has been asked in one form or another multiple times but I haven't found an answer that works in this specific case.

Context: this is MPF 0.57.3.dev2 with MC (not Godot).

Simply put, I'm trying to add a widget (to an already on-screen slide) that shows the master volume level. Because this can happen in either the attract loop or during the game and because it relates to the service buttons, I have this in my service mode for now (open to other suggestions there). I can get it to show the machine variable "master_volume" but it's a float and I want to format it as a percentage, and I cannot get it to do that. Here's what does work:

widgets:
  # volume up or down
  volume_display:

    - type: text
      x: center
      y: bottom+29%
      anchor_x: middle
      anchor_y: middle
      z: 10003
      color: black
      text: "Volume: (machine|master_volume)"
      expire: 2s

widget_player:
  # volume
  machine_var_master_volume:
    volume_display:
      action: add

When that runs, it shows on the slide just fine and expires after 2s as it should, but it says Volume: 0.35, for example (master_volume is a float from 0 to 1 that moves in 0.05 increments). How do I rework this to show Volume: 35%? I have been through just about everything I can think of. I'm sure it's something simple using a string formatter or something, but I've tried about everything I can find and nothing has worked. It either stops pulling the variable and formats the whole string as literal text, or MPF throws various errors.

I was originally trying to dynamically format the width of a rectangle as a sort of volume meter, scaled from 0 to a max width based on the master_volume machine variable, but that was an even tougher fight and I gave up and tried the simple text approach, as above.

Any help in either direction would be much appreciated!

Thanks,

Kaydee

[Dan - aka BorgDog]

according to the docs https://missionpinball.org/latest/config/instructions/text_templates/  any python formatting should work, and the link on that page to python docs shows the % symbol should do what you want, by using as {variable:format_string}

I have not tried it, but something like this is what I would try first.   text: "Volume: (machine|master_volume:%)"

[kaydeeH]

Thanks for the attempt! I wish I could say it worked. When I tried that, it just took the whole string as a literal and prints everything in the quotation marks exactly as written.

[Dan - aka BorgDog]

yeah, getting those format strings in the correct way seems to always be an adventure every time I do it.  here is an example that works on my machine that may lead to a solution. quotes and brackets and parentheses oh my!

text: "{(players[0].score):0>2,d}"

[Brad Myers]

https://chatgpt.com/s/t_6912e7030ef481919552d8d7d58d5da7

Hi all,

You’re super close — the trick is that formatting only kicks in when the placeholder is inside {}. Wrap your (machine|master_volume) token in braces and use Python’s percent format specifier:

# widget definition

widgets:

  volume_display:

    - type: text

      x: center

      y: bottom+29%

      anchor_x: middle

      anchor_y: middle

      z: 10003

      color: black

      text: "Volume: {(machine|master_volume):.0%}" # 0.35 -> "35%"

      expire: 2s

# show it whenever the machine var changes

widget_player:

  machine_var_master_volume:

    volume_display:

      action: add

:.0% multiplies by 100, appends %, and shows 0 decimals (e.g., 0.35 → 35%).

Use :.1% if you want one decimal place (e.g., 35.0%).

This is straight from MPF’s Text Templates behavior: variables go in {}, and the part after the colon is standard Python’s format mini-language. 

And yes, (machine|my_var) is the right token form for slide/text content; MPF documents that syntax specifically for slide widgets. 

(Optional) If you want a skinny “volume bar”

MPF’s rectangle width: is in pixels, so a quick pattern is to create a fixed-height rectangle and animate its width on machine_var_master_volume using the event’s (value):

# put a bar on the slide (start at width 0)

slides:

  service_overlay:

    widgets:

      - type: rectangle

        key: volume_bar

        x: left+5%

        y: bottom+25%

        anchor_x: left

        anchor_y: middle

        height: 14

        width: 0

        corner_radius: 3

        color: "00FF00"

# increase width whenever master_volume changes

widgets:

  volume_bar:

    - type: rectangle

      animations:

        machine_var_master_volume:

          - property: width

            value: (value) # see note below

Then scale it to your desired max width by feeding the event a pixel value (e.g., post a companion event or compute a machine var to pixels). The animation/how-to shows using value: (value) directly from the event; rectangle width itself is documented as pixel-based. 

But if all you needed was “35%” instead of “0.35”, the first snippet with:

text: "Volume: {(machine|master_volume):.0%}"

is the minimal, reliable fix. ✅

Hope that helps! —Kaydee helpers on MPF 😊

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[kaydeeH]

@Brad: Your format string produces this result: Volume: {0.15:.0%} So that's closer, it's at least showing the float volume now instead of treating it like a literal string, but the formatting instruction is shown as a literal string. In this case, my text: entry looks identical to yours.

@Dan: Your format string produces this result: Volume: {0.15>2,D} So it's about the same as Brad's. The float shows here as well, but it's still ignoring the formatting and displaying it as a literal string. In this case, I'm using the following: text: "Volume: {(machine|master_volume):0>2,d}"

I also tried removing the "Volume: " part to see if that was tripping it up, but it produced identical results, just without the "Volume: " text in front of it. I then also tried removing the quotation marks entirely, but then the game won't start due to a yaml validation error.

"yeah, getting those format strings in the correct way seems to always be an adventure every time I do it" - Truer words have never been spoken!