fix(web): accept every panel size and row address type the rgbmatrix library does

The Display form capped columns at 128 and chain length at 24, and its
submit handler (fixInvalidNumberInputs) rewrote anything larger to the cap,
so wide panels and long chains silently saved as the wrong size. The config
API checked none of the hardware numbers, so values the library rejects (odd
rows, parallel 4, PWM dither bits 3) saved and the matrix then refused to
start.

- Form limits now match the pinned library: rows even 8-64, cols >= 16 and
  chain_length >= 1 with no upper bound, parallel 1-3, PWM dither bits 0-2,
  PWM LSB nanoseconds 50-3000.
- save_main_config rejects out-of-range rows, cols, chain_length, parallel,
  brightness, scan_mode, pwm_bits, pwm_dither_bits, pwm_lsb_nanoseconds and
  gpio_slowdown with a 400.
- A stored gpio_slowdown or pwm_dither_bits of 0 renders as 0 instead of the
  default, so saving the tab no longer overwrites it.
- Row Address Type offers 5 (SM5368 / B707 row shift register). Verified on a
  Waveshare 96x48 V2 (24S-A1) on a Pi 4 with the Adafruit Triple LED Matrix
  Bonnet: rows 48, cols 96, row address type 5, BGR, GPIO slowdown 8.
- Help text and docs: FM6124-family panels use Panel Type Standard; on a Pi 5
  the library supports only row address types 0 and 2.

No change to the rpi-rgb-led-matrix submodule.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

test/test_api_v3_display_hardware.py

@@ -0,0 +1,214 @@
+"""Display hardware settings accept what the rgbmatrix library accepts.
+
+Held to the ranges in the pinned library (RGBMatrix::Options::Validate in
+lib/options-initialize.cc, the gpio_slowdown check in lib/led-matrix.cc). Two
+ways this used to go wrong:
+
+- The Display form capped cols at 128, chain_length at 24 and
+  pwm_lsb_nanoseconds at 500, and its submit handler (fixInvalidNumberInputs)
+  rewrites anything past an input's min/max to that bound -- so a wide panel or
+  a long chain silently saved as the wrong size.
+- The API checked none of these, so a value the library rejects (odd rows,
+  parallel 4, pwm_dither_bits 3) saved, and the matrix then refused to start.
+
+Row address type 5 is the SM5368 / B707 row shift register the Waveshare 96x48
+V2 needs (Waveshare's own "96X48_1_24_SM5368" panel type in their library fork
+just sets rows/cols, row_address_type=5 and BGR); the API used to stop at 4.
+"""
+import copy
+import json
+import re
+import sys
+from pathlib import Path
+from unittest.mock import MagicMock
+
+import pytest
+from flask import Flask
+
+PROJECT_ROOT = Path(__file__).parent.parent
+sys.path.insert(0, str(PROJECT_ROOT))
+
+from test._api_v3_test_helpers import api_v3_client, api_v3_module  # noqa: F401,E402
+from test.test_web_settings_ui import REALISTIC_CONFIG  # noqa: E402
+
+#: What a Waveshare RGB-Matrix-P2.5-96x48 V2 (back silkscreen 24S-A1) needed on
+#: a Pi 4 with an Adafruit Triple LED Matrix Bonnet, checked on the panel.
+WAVESHARE_96X48_V2 = {
+    'rows': 48, 'cols': 96, 'chain_length': 1, 'parallel': 1,
+    'hardware_mapping': 'regular', 'panel_type': '', 'row_address_type': 5,
+    'led_rgb_sequence': 'BGR', 'gpio_slowdown': 8,
+}
+
+#: Fields stored under display.runtime; the rest go under display.hardware.
+RUNTIME_FIELDS = {'gpio_slowdown'}
+
+
+def _stored(config, field):
+    section = 'runtime' if field in RUNTIME_FIELDS else 'hardware'
+    return config['display'][section][field]
+
+
+def _post(client, body):
+    return client.post('/api/v3/config/main', data=json.dumps(body),
+                       content_type='application/json')
+
+
+@pytest.fixture
+def saved(api_v3_module, monkeypatch):
+    """Capture what save_main_config would write.
+
+    Asserting on the stored value, not just the status code, is what shows the
+    value passed validation and landed where DisplayManager reads it.
+    """
+    captured = {}
+    api_v3_module.api_v3.config_manager.load_config.return_value = {}
+
+    def fake_save(_manager, config, **_kwargs):
+        captured['config'] = config
+        return True, ''
+
+    monkeypatch.setattr(api_v3_module, '_save_config_atomic', fake_save)
+    return captured
+
+
+@pytest.mark.parametrize('as_strings', [False, True], ids=['json-numbers', 'form-strings'])
+def test_waveshare_96x48_v2_settings_all_save(api_v3_client, saved, as_strings):
+    """The Display form posts every value as a string (json-enc); API clients send numbers."""
+    body = {k: str(v) if as_strings else v for k, v in WAVESHARE_96X48_V2.items()}
+    response = _post(api_v3_client, body)
+    assert response.status_code == 200, response.get_data(as_text=True)[:200]
+    for field, value in WAVESHARE_96X48_V2.items():
+        assert _stored(saved['config'], field) == value, field
+
+
+@pytest.mark.parametrize('field,value', [
+    ('rows', 8), ('rows', 64),
+    ('cols', 16), ('cols', 192), ('cols', 512),
+    ('chain_length', 1), ('chain_length', 32),
+    ('parallel', 3),
+    ('row_address_type', 0), ('row_address_type', 5),
+    ('gpio_slowdown', 0), ('gpio_slowdown', 10),
+    ('pwm_bits', 1), ('pwm_bits', 11),
+    ('pwm_dither_bits', 0), ('pwm_dither_bits', 2),
+    ('pwm_lsb_nanoseconds', 50), ('pwm_lsb_nanoseconds', 3000),
+    ('scan_mode', 1),
+    ('brightness', 1), ('brightness', 100),
+])
+def test_values_the_library_accepts_are_saved(api_v3_client, saved, field, value):
+    response = _post(api_v3_client, {field: value})
+    assert response.status_code == 200, response.get_data(as_text=True)[:200]
+    assert _stored(saved['config'], field) == value
+
+
+@pytest.mark.parametrize('field,value', [
+    ('rows', 6), ('rows', 47), ('rows', 66), ('rows', '48.5'),
+    ('cols', 15), ('cols', 96.5), ('cols', True), ('cols', 'wide'),
+    ('chain_length', 0),
+    ('parallel', 0), ('parallel', 4),
+    ('row_address_type', -1), ('row_address_type', 6),
+    ('gpio_slowdown', -1), ('gpio_slowdown', 11),
+    ('pwm_bits', 0), ('pwm_bits', 12),
+    ('pwm_dither_bits', 3),
+    ('pwm_lsb_nanoseconds', 49), ('pwm_lsb_nanoseconds', 3001),
+    ('scan_mode', 2),
+    ('brightness', 0), ('brightness', 101),
+])
+def test_values_the_library_rejects_are_refused(api_v3_client, saved, field, value):
+    """Refused with a message naming the field, and nothing written."""
+    response = _post(api_v3_client, {field: value})
+    assert response.status_code == 400
+    assert field in response.get_json()['message']
+    assert 'config' not in saved
+
+
+@pytest.fixture
+def display_page(monkeypatch):
+    """Render the Display settings partial for a given config."""
+    from web_interface.blueprints import pages_v3 as pv
+
+    def render(config):
+        base = PROJECT_ROOT / 'web_interface'
+        app = Flask(__name__, template_folder=str(base / 'templates'),
+                    static_folder=str(base / 'static'))
+        app.config['TESTING'] = True
+        config_manager = MagicMock()
+        config_manager.load_config.return_value = config
+        config_manager.get_raw_file_content.return_value = config
+        config_manager.get_config_path.return_value = 'config/config.json'
+        config_manager.get_secrets_path.return_value = 'config/config_secrets.json'
+        monkeypatch.setattr(pv.pages_v3, 'config_manager', config_manager, raising=False)
+        monkeypatch.setattr(pv.pages_v3, 'plugin_manager', MagicMock(plugins={}), raising=False)
+        app.register_blueprint(pv.pages_v3, url_prefix='/v3')
+        response = app.test_client().get('/v3/partials/display')
+        assert response.status_code == 200
+        return response.get_data(as_text=True)
+
+    return render
+
+
+def _config_with(hardware=None, runtime=None):
+    config = copy.deepcopy(REALISTIC_CONFIG)
+    config['display']['hardware'].update(hardware or {})
+    config['display']['runtime'].update(runtime or {})
+    return config
+
+
+def _input_tag(body, input_id):
+    match = re.search(r'<input[^>]*\bid="%s"[^>]*>' % re.escape(input_id), body)
+    assert match, f'no <input id="{input_id}">'
+    return match.group(0)
+
+
+def _attr(tag, name):
+    match = re.search(r'\s%s="([^"]*)"' % name, tag)
+    return match.group(1) if match else None
+
+
+def _selected_option(body, select_id):
+    select = re.search(r'<select id="%s".*?</select>' % select_id, body, re.S)
+    assert select, f'no <select id="{select_id}">'
+    return re.findall(r'<option value="([^"]*)"\s+selected\s*>', select.group(0))
+
+
+@pytest.mark.parametrize('input_id,expected', [
+    ('rows', {'min': '8', 'max': '64', 'step': '2'}),
+    ('cols', {'min': '16', 'max': None}),
+    ('chain_length', {'min': '1', 'max': None}),
+    ('parallel', {'min': '1', 'max': '3'}),
+    ('gpio_slowdown', {'min': '0', 'max': '10'}),
+    ('pwm_bits', {'min': '1', 'max': '11'}),
+    ('pwm_dither_bits', {'min': '0', 'max': '2'}),
+    ('pwm_lsb_nanoseconds', {'min': '50', 'max': '3000'}),
+])
+def test_form_limits_match_the_library(display_page, input_id, expected):
+    """fixInvalidNumberInputs rewrites a value past min/max on submit, so these
+    attributes are the real limits: a max below the library's clamps panels
+    that would work, and one above it saves a value the matrix rejects."""
+    tag = _input_tag(display_page(_config_with()), input_id)
+    for name, value in expected.items():
+        assert _attr(tag, name) == value, f'{input_id} {name}'
+
+
+def test_waveshare_96x48_v2_config_renders_back_unchanged(display_page):
+    """Saving the Display tab posts what it rendered, so each value must render as stored.
+
+    Before row address type 5 was in the dropdown no option was selected, the
+    browser posted the first one (0), and one save scrambled the panel again.
+    """
+    hardware = {k: v for k, v in WAVESHARE_96X48_V2.items() if k not in RUNTIME_FIELDS}
+    body = display_page(_config_with(hardware=hardware, runtime={'gpio_slowdown': 8}))
+
+    assert _selected_option(body, 'row_address_type') == ['5']
+    assert _selected_option(body, 'led_rgb_sequence') == ['BGR']
+    assert _selected_option(body, 'hardware_mapping') == ['regular']
+    for input_id in ('rows', 'cols', 'chain_length', 'parallel', 'gpio_slowdown'):
+        assert _attr(_input_tag(body, input_id), 'value') == str(WAVESHARE_96X48_V2[input_id]), input_id
+
+
+@pytest.mark.parametrize('field,section', [
+    ('gpio_slowdown', 'runtime'), ('pwm_dither_bits', 'hardware'),
+])
+def test_a_stored_zero_renders_as_zero(display_page, field, section):
+    """`value or default` showed a stored 0 as the default, and the next save wrote it back."""
+    body = display_page(_config_with(**{section: {field: 0}}))
+    assert _attr(_input_tag(body, field), 'value') == '0'