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ListCurrentEmacsBuffersAndSizesInBarChart.org

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Listing current Emacs buffers and showing their size in bar chart

Prerequisites

You will need csv-mode (M-x package-install csv-mode) and graph-cli for the bar chart generation. This is easy to install: pip install graph-cli. Also make sure to have followed the setup in the README: in particular (me-setup-molds) makes molds available.

Aim

We want to find out how the sizes of our buffers relate to each other… in a glimpse. It is boring to compare numbers, but a bar chart would be ideal.

Let’s do it

  1. invoke M-x and type me-mold

    This is the command that let you access the molds that can be useful in this context.

  2. type “Playground”

    This is a “jolly” mold: it is always available and it is a buffer where you can evaluate Elisp. It always tries to set a self variable according to the context.

  3. hit return

    A new buffer called “Playground” should open.

  4. Insert the following Elisp in the buffer: 
    (--map
 (list :buffer (buffer-name it) :size (buffer-size it))
 (buffer-list))

    This creates a plist with the buffers name and its size.

  5. move the cursor on the first open parenthesis
  6. invoke M-x and type me-mold
  7. type “EvalSexp” and hit return

    You should see a buffer “EvalSexp” with a plist containing all your open buffers and sizes.

  8. move at the beginning of the buffer (the useful shortcut is M-<)
  9. invoke M-x and type me-mold
  10. type “PlistToBarChart” and hit return

    “PlistToBarChart” is a composition of many molds: you will find many mold buffers open in your Emacs. That is by design (in case you wanted to inspect/modify the intermediate molds)

  11. You should see a bar chart with all your buffers sizes!

Mini discussion

Once you familiarize with the me-mold command, step (4) is the one that requires your brain. Indeed, me-mold is contextual, so it takes away most of the toll of deciding what to use. The code you need to write is minimal. By combining existing molds (and step (4)) you manage to reuse useful functionality for the problem you are facing, spending minimum time on integration of old molds. Indeed, in this realistic tutorial you used the following molds (I found useful to implement – you may find out others!):

  1. Playground
  2. EvalSexp
  3. PlistToBarChart

    which really is the composition of:

    1. ElispListToOrgTable
    2. FirstOrgTableToBarChart

      which really is the composition of:

      1. FirstOrgTable
      2. OrgTableToCSV
      3. CSVToBarChart

Basically you used 8 molds, which let you focus on the 3 lines of custom Lisp you needed to solve our problem. Isn’t that cool?

Again, if you were to prefer a different kind of chart, you just need to change a composition. See the tutorial about writing a mold for that.