module/cpu: make ‘content’ particle a template

Before this patch, the cpu module instantiated a single particle (the
‘content’ particle), with one tag ("cpu") representing the total CPU
usage, and then one tag (cpuN) for each core.

This makes it cumbersome to configure, since you need to explicitly
reference each cpuN tag to get per-core usage.

This patch rewrites this, so that ‘content’ is now a template. It’s
instantiated once to represent the total CPU usage, and then once for
each core.

Each instance has a "cpu" tag, representing the CPU usage of that
core (or total usage). It also has an "id" tag. The ID is 0..n for
actual cores, and -1 for total usage.

This means you can do something like this in your config:

- cpu:
    content:
      map:
        conditions:
          id < 0: {string: {text: "Total: {cpu}%"}}
          id >= 0: {string: {text: "Core #{id}: {cpu}%"}}

Closes #207

doc/yambar-modules-cpu.5.scd

@@ -3,17 +3,24 @@ yambar-modules-cpu(5)
 # NAME
 cpu - This module provides the CPU usage
 
+# DESCRIPTION
+
+This module reports CPU usage, in percent. The _content_ particle is a
+template that is instantiated once for each core, and once for the
+total CPU usage.
+
 # TAGS
 
 [[ *Name*
 :[ *Type*
 :[ *Description*
+|  id
+:  int
+:  Core ID. 0..n represents individual cores, and -1 represents the
+   total usage
 |  cpu
 :  range
-:  Current usage of the whole CPU in percent
-|  cpu<0..X>
-:  range
-:  Current usage of CPU core X in percent
+:  Current usage of CPU core {id}, in percent
 
 # CONFIGURATION
 
@@ -24,19 +31,49 @@ cpu - This module provides the CPU usage
 |  interval
 :  int
 :  no
-:  Refresh interval of the CPU usage stats in ms (default=500). Cannot be less then 500 ms
+:  Refresh interval of the CPU usage stats in ms (default=500). Cannot
+   be less then 500 ms
 
 # EXAMPLES
 
+## Display total CPU usage as a number
 ```
 bar:
   left:
     - cpu:
         interval: 2500
         content:
-          string: {text: "{cpu1}%"}
+          map:
+            conditions:
+              id < 0:
+                - string: {text: , font: Font Awesome 6 Free:style=solid}
+                - string: {text: "{cpu}%"}
 ```
 
+## Display a vertical bar for each core
+```
+bar:
+  left:
+    - cpu:
+        interval: 2500
+        content:
+          map:
+            conditions:
+              id >= 0:
+                - ramp:
+                    tag: cpu
+                    items:
+                      - string: {text: ▁}
+                      - string: {text: ▂}
+                      - string: {text: ▃}
+                      - string: {text: ▄}
+                      - string: {text: ▅}
+                      - string: {text: ▆}
+                      - string: {text: ▇}
+                      - string: {text: █}
+```
+
+
 # SEE ALSO
 
 *yambar-modules*(5), *yambar-particles*(5), *yambar-tags*(5), *yambar-decorations*(5)