Add global_index property for creating unique line numbers

README.md

@@ -116,12 +116,16 @@ For example every element accepts the value of `index`. You would encode that in
 
 - `document_start` and `document_end` accept the following:
   - `filename` file name of the file being saved
+  - `global_index` the global index starting from 0
+  - `global_index1` the global index starting from 1
 
 - `layer_start`, `layer_end` and `layer_join` accept the following:
   - `x` the last_x position before this layer, this is 0 for the first layer
   - `y` the last_y position before this layer, this is 0 for the first layer
   - `ix` the last integer x location before this layer, this is 0 for the first layer.
   - `iy` the last integer y location before this layer, this is 0 for the first layer.
+  - `global_index` the global index starting from 0
+  - `global_index1` the global index starting from 1
   - `index` same as `layer_index`
   - `index1` same as `layer_index1`
   - `layer_index` the current layer index starting from 0
@@ -134,6 +138,8 @@ For example every element accepts the value of `index`. You would encode that in
   - `y` the last_y position before this line, this is 0 for the first line of the first layer
   - `ix` the last integer x location before this layer, this is 0 for the first layer.
   - `iy` the last integer y location before this layer, this is 0 for the first layer.
+  - `global_index` the global index starting from 0
+  - `global_index1` the global index starting from 1
   - `index` same as `lines_index`
   - `index1` same as `lines_index1`
   - `lines_index` the current line index within this layer starting from 0
@@ -157,6 +163,8 @@ For example every element accepts the value of `index`. You would encode that in
   * `iy` absolute position y in integer number. eg `{iy:d}`
   * `idx` relative position x in integer number. eg `{idx:d}`
   * `idy` relative position y in integer number. eg `{idy:d}`
+  * `global_index` the global index starting from 0
+  * `global_index1` the global index starting from 1
   * `index` same as `segment_index`
   * `index1` same as `segment_index1`
   * `segment_index` the current segment within this line starting from 0
@@ -216,6 +224,50 @@ Alternatively, default values for string-based variable may be provided using th
 $ vpype [...] gwrite -p summary --default vp_color undefined output.txt
 ```
 
+Another example: Some CNC controllers require gcode with unique line numbers (`N10`, `N20` etc.).
+This can be accomplished by using the `global_index` (or `global_index1`) property.
+In below example it is used to create 4 digit line numbers with leading zeroes.
+By adding the trailing zero we create a step size of 10, which leaves space for inserting any additional lines.
+
+```toml
+[gwrite.line_numbers]
+document_start = """
+N{global_index1:03d}0 (document_start)
+N{global_index1:03d}1 (document_start, inserted line by the config)
+"""
+layer_join = "N{global_index1:03d}0 (layer_join)\n"
+segment_first = "N{global_index1:03d}0 (segment_first)\n"
+segment = "N{global_index1:03d}0 (segment)\n"
+segment_last = "N{global_index1:03d}0 (segment_last)\n"
+document_end = "N{global_index1:03d}0 (document_end)\n"
+```
+Example output:
+
+```
+N0010 (document_start)
+N0011 (document_start, inserted line by the config)
+N0020 (segment_first)
+N0030 (segment)
+N0040 (segment)
+N0050 (segment)
+N0060 (segment_last)
+N0080 (segment_first)
+N0090 (segment)
+N0100 (segment)
+N0110 (segment)
+N0120 (segment_last)
+N0140 (segment_first)
+N0150 (segment_last)
+N0170 (layer_join)
+N0170 (segment_first)
+N0180 (segment)
+N0190 (segment)
+N0200 (segment)
+N0210 (segment_last)
+N0230 (segment_first)
+N0240 (segment_last)
+N0260 (document_end)
+```
 
 ### Information Control
 - `info`: prints text to the console after file is written to inform the user of said information

vpype_gcode/gwrite.py

@@ -86,6 +86,7 @@ def gwrite(
     output most known non-gcode ascii text files.
     """
     gwrite_config = vp.config_manager.config["gwrite"]
+    global_index = 0 # for creating a global line index across layers
 
     # If no profile was provided, try to use a default
     if not profile:
@@ -172,12 +173,18 @@ def write_template(template: str | None, **context_vars: typing.Any):
 
     # process file
     filename = output.name
-    write_template(document_start, filename=filename)
+    write_template(
+        document_start,
+        filename=filename,
+        global_index=global_index,
+        global_index1=global_index + 1,
+    )
 
     last_x = 0
     last_y = 0
     xx = 0
     yy = 0
+    global_index += 1
     lastlayer_index = len(document.layers.values()) - 1
 
     for layer_index, (layer_id, layer) in enumerate(sorted(document.layers.items())):
@@ -195,6 +202,8 @@ def write_template(template: str | None, **context_vars: typing.Any):
             layer_index1=layer_index + 1,
             layer_id=layer_id,
             filename=filename,
+            global_index=global_index,
+            global_index1=global_index + 1,
         )
         lastlines_index = len(layer) - 1
         for lines_index, line in enumerate(layer):
@@ -212,6 +221,8 @@ def write_template(template: str | None, **context_vars: typing.Any):
                 layer_index1=layer_index + 1,
                 layer_id=layer_id,
                 filename=filename,
+                global_index=global_index,
+                global_index1=global_index + 1,
             )
 
             segment_last_index = len(line) - 1
@@ -255,11 +266,15 @@ def write_template(template: str | None, **context_vars: typing.Any):
                     layer_index1=layer_index + 1,
                     layer_id=layer_id,
                     filename=filename,
+                    global_index=global_index,
+                    global_index1=global_index + 1,
                 )
 
                 last_x = x
                 last_y = y
 
+                global_index += 1
+
             write_template(
                 line_end,
                 x=last_x,
@@ -274,6 +289,8 @@ def write_template(template: str | None, **context_vars: typing.Any):
                 layer_index1=layer_index + 1,
                 layer_id=layer_id,
                 filename=filename,
+                global_index=global_index,
+                global_index1=global_index + 1,
             )
 
             if lines_index != lastlines_index:
@@ -291,7 +308,12 @@ def write_template(template: str | None, **context_vars: typing.Any):
                     layer_index1=layer_index + 1,
                     layer_id=layer_id,
                     filename=filename,
+                    global_index=global_index,
+                    global_index1=global_index + 1,
                 )
+
+            global_index += 1
+
         write_template(
             layer_end,
             x=last_x,
@@ -304,6 +326,8 @@ def write_template(template: str | None, **context_vars: typing.Any):
             layer_index1=layer_index + 1,
             layer_id=layer_id,
             filename=filename,
+            global_index=global_index,
+            global_index1=global_index + 1,
         )
         if layer_index != lastlayer_index:
             write_template(
@@ -318,10 +342,17 @@ def write_template(template: str | None, **context_vars: typing.Any):
                 layer_index1=layer_index + 1,
                 layer_id=layer_id,
                 filename=filename,
+                global_index=global_index,
+                global_index1=global_index + 1,
             )
         current_layer = None
 
-    write_template(document_end, filename=filename)
+    write_template(
+        document_end,
+        filename=filename,
+        global_index=global_index,
+        global_index1=global_index + 1,
+    )
 
     # handle info string
     info = config.get("info", None)