feat: Add parse_config.zmk_preamble

Defaults to the current behavior that `#define`s `KEYMAP_DRAWER`.

Fixes #103

CONFIGURATION.md

@@ -372,3 +372,12 @@ E.g. `{"combo_esc": {"align": "top", "offset": 0.5}}` would add these two fields
 _Type:_ `dict[str, dict]`
 
 _Default:_ `{}`
+
+#### `zmk_preamble`
+
+A string to prepend to ZMK keymaps before parsing that can be used to influence the parsed content.
+The default defines a `KEYMAP_DRAWER` symbol which can be used for checks with preprocessor directives.
+
+_Type:_ `str`
+
+_Default:_ `#define KEYMAP_DRAWER`

keymap_drawer/config.py

@@ -468,6 +468,9 @@ class ModifierFnMap(BaseModel):
     # e.g. {"combo_esc": {"align": "top", "offset": 0.5}}
     zmk_combos: dict[str, dict] = {}
 
+    # prepend this to ZMK keymaps before processing to customize parsing output
+    zmk_preamble: str = "#define KEYMAP_DRAWER"
+
 
 class Config(BaseSettings, env_prefix="KEYMAP_"):
     """All configuration settings used for this module."""

keymap_drawer/parse/dts.py

@@ -101,19 +101,17 @@ class DeviceTree:
     _compatible_re = re.compile(r'compatible = "(.*?)"')
     _custom_data_header = "__keymap_drawer_data__"
 
-    def __init__(
-        self, in_str: str, file_name: str | None = None, preprocess: bool = True, add_define: str | None = None
-    ):
+    def __init__(self, in_str: str, file_name: str | None = None, preprocess: bool = True, preamble: str | None = None):
         """
         Given an input DTS string `in_str` and `file_name` it is read from, parse it into an internap
         tree representation and track what "compatible" value each node has.
 
-        If `add_define` is set to a string, #define it for the preprocessor.
+        If `preamble` is set to a non-empty string, prepend it to the read buffer.
         """
         self.raw_buffer = in_str
         self.file_name = file_name
-        if add_define:
-            self.raw_buffer = f"#define {add_define}\n" + self.raw_buffer
+        if preamble:
+            self.raw_buffer = preamble + "\n" + self.raw_buffer
 
         prepped = self._preprocess(self.raw_buffer, file_name) if preprocess else in_str
 

keymap_drawer/parse/zmk.py

@@ -240,7 +240,7 @@ def _parse(self, in_str: str, file_name: str | None = None) -> tuple[dict, Keyma
         """
         Parse a ZMK keymap with its content and path and return the layout spec and KeymapData to be dumped to YAML.
         """
-        dts = DeviceTree(in_str, file_name, self.cfg.preprocess, add_define="KEYMAP_DRAWER")
+        dts = DeviceTree(in_str, file_name, self.cfg.preprocess, preamble=self.cfg.zmk_preamble)
 
         if self.cfg.preprocess and self.raw_binding_map:
             self._update_raw_binding_map(dts)