Override system files for a device

.claude/rules/key-conventions.md

@@ -6,5 +6,6 @@
 - `Modules/` contains cross-cutting modules. e.g.`lvgl-module` (LVGL task management).
 - `Data/data/` is flashed as a FAT filesystem image on ESP32 devices that don't have an SD card.
 - `Data/system/` is embedded in the Tactility project as generated C byte arrays (`generated_assets.h`, see `Buildscripts/generate-assets.py`).
+  A device overrides a file by placing one at the same relative path in `Devices/<id>/system/` (e.g. `system/app/Boot/assets/logo.png`).
 - The binfont files of the default font size are generated at build time into `generated_fonts.h` (see `Buildscripts/generate-fonts.py`).
 - Translations are in `Translations/` as CSV files, generated via `generate.py`.

Buildscripts/generate-assets.py

@@ -2,12 +2,14 @@
 """
 Embeds every file of an asset folder as a C byte array.
 
-Usage: generate-assets.py <asset-folder> <output-folder>
+Usage: generate-assets.py <asset-folder> <output-folder> [<overlay-folder>...]
 
 Writes generated_assets.h and generated_assets.c. A file "fonts/AdwaitaSans.ttf" becomes the symbols
 asset_fonts_AdwaitaSans_ttf (the bytes) and asset_fonts_AdwaitaSans_ttf_size (the byte count).
 The size is also available as the constant asset_fonts_AdwaitaSans_ttf_SIZE for use in constant initializers.
 Text files get an extra terminating 0 byte that is not part of the size, so they can be used as C strings.
+A file in an overlay folder replaces the file with the same relative path in the asset folder.
+Overlay folders that don't exist are skipped.
 Output files are only rewritten when their content changes, to avoid needless recompiles.
 """
 import os
@@ -31,18 +33,21 @@ def write_if_changed(path: str, content: str):
 
 
 def main():
-    if len(sys.argv) != 3:
-        print(f"Usage: {sys.argv[0]} <asset-folder> <output-folder>")
+    if len(sys.argv) < 3:
+        print(f"Usage: {sys.argv[0]} <asset-folder> <output-folder> [<overlay-folder>...]")
         sys.exit(1)
-    asset_folder = os.path.abspath(sys.argv[1])
+    asset_folders = [os.path.abspath(sys.argv[1])] + [os.path.abspath(folder) for folder in sys.argv[3:]]
     output_folder = os.path.abspath(sys.argv[2])
     os.makedirs(output_folder, exist_ok=True)
 
-    relative_paths = []
-    for directory, _, file_names in os.walk(asset_folder):
-        for file_name in file_names:
-            relative_paths.append(os.path.relpath(os.path.join(directory, file_name), asset_folder).replace(os.sep, "/"))
-    relative_paths.sort()
+    # Maps each relative path to the folder that provides it: later folders win
+    asset_paths = {}
+    for asset_folder in asset_folders:
+        for directory, _, file_names in os.walk(asset_folder):
+            for file_name in file_names:
+                relative_path = os.path.relpath(os.path.join(directory, file_name), asset_folder).replace(os.sep, "/")
+                asset_paths[relative_path] = asset_folder
+    relative_paths = sorted(asset_paths)
 
     header = [
         "// Generated by Buildscripts/generate-assets.py. Do not edit.",
@@ -62,7 +67,7 @@ def main():
         "",
     ]
     for relative_path in relative_paths:
-        with open(os.path.join(asset_folder, relative_path), "rb") as file:
+        with open(os.path.join(asset_paths[relative_path], relative_path), "rb") as file:
             data = file.read()
         symbol = symbol_name(relative_path)
         size = len(data)

Tactility/CMakeLists.txt

@@ -224,10 +224,10 @@ add_dependencies(${COMPONENT_LIB} Generated)
 #
 
 # Rewrites its outputs only when the content changes. The assets are the whole Data/system tree,
-# so no fixed DEPENDS list is kept.
+# so no fixed DEPENDS list is kept. Files in the device's system/ folder replace the ones with the same path.
 add_custom_target(GeneratedAssets ALL
     COMMAND python "${CMAKE_SOURCE_DIR}/Buildscripts/generate-assets.py"
-        "${CMAKE_SOURCE_DIR}/Data/system" "${GENERATED_DIR}"
+        "${CMAKE_SOURCE_DIR}/Data/system" "${GENERATED_DIR}" "${DEVICETREE_LOCATION}/system"
     BYPRODUCTS "${GENERATED_DIR}/generated_assets.c" "${GENERATED_DIR}/generated_assets.h"
     WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
     COMMENT "Generating asset source files..."