Update guidelines about adding layouts

to reflect the recent changes. Also, change `gen_layouts.py` to not
generate warnings for file that are known not to be layouts.

CONTRIBUTING.md

@@ -77,16 +77,22 @@ make installd
 
 ### Adding a layout
 
-Layouts are defined in XML, see `res/xml/qwerty.xml`.
+Layouts are defined in XML, see `res/xml/latn_qwerty_us.xml`.
 An online tool for editing layout files written by @Lixquid is available
 [here](https://unexpected-keyboard-layout-editor.lixquid.com/).
 
-An entry must be added to the layout option in `res/values/arrays.xml`, to both
-`pref_layout_values` (correspond to the file name) and `pref_layout_entries`
-(display name).
+Makes sure to specify the `name` attribute like in `latn_qwerty_us.xml`,
+otherwise the layout won't be added to the app.
 
-The layout must also be referenced in `srcs/juloo.keyboard2/Config.java` in
-`layout_of_string`.
+The layout file must be placed in the `res/xml/` directory and named according to:
+- script (`latn` for latin, etc..)
+- layout name (eg. the name of a standard)
+- country code (or language code if more adequate)
+
+Then, run `make gen_layouts` to add the layout to the app.
+
+The last step will update the file `res/values/layouts.xml`, that you should
+not edit directly.
 
 Run `make check_layouts` to check some properties about your layout. This will
 change the file `check_layout.output`, which you should commit.

gen_layouts.py

@@ -11,6 +11,11 @@ import xml.etree.ElementTree as XML
 # are sorted alphabetically.
 FIRST_LAYOUTS = [ "latn_qwerty_us", "latn_colemak", "latn_dvorak" ]
 
+# File names that are known not to be layouts. Avoid warning about them.
+KNOWN_NOT_LAYOUT = set([
+    "number_row", "numpad", "pin", "bottom_row", "settings", "method",
+    "greekmath", "numeric" ])
+
 # Read a layout from a file. Returns [None] if [fname] is not a layout.
 def read_layout(fname):
     root = XML.parse(fname).getroot()
@@ -23,7 +28,9 @@ def read_layouts(files):
     for layout_file in files:
         layout_id, _ = os.path.splitext(os.path.basename(layout_file))
         layout = read_layout(layout_file)
-        if layout == None:
+        if layout_id in KNOWN_NOT_LAYOUT:
+            continue
+        elif layout == None:
             print("Not a layout file: %s" % layout_file)
         elif layout["name"] == None:
             print("Layout doesn't have a name: %s" % layout_id)