Add asset, resource system, mesh formats, color, SDL3 display and example game

Asset directory with CMake add_asset (extension dispatched), plain file asset
access, resource/resource manager with async load thread and text loader,
URI utilities, mesh format helpers, generated color header, and example game
hooks wired through the engine.

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

cmake/asset/asset.cmake

@@ -0,0 +1,65 @@
+# Copyright (c) 2026 Dominic Masters
+#
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+# Asset building. Include this from the root CMakeLists.txt.
+#
+# Assets are registered with add_asset() and built by dusk_assets_finalize().
+# Each asset is dispatched on its file extension to a handler function named
+# dusk_asset_<extension> (e.g. dusk_asset_obj), defined in its own file in this
+# directory. Extensions without a handler fall back to a plain copy.
+
+include(${CMAKE_CURRENT_LIST_DIR}/copy.cmake)
+include(${CMAKE_CURRENT_LIST_DIR}/obj.cmake)
+
+# Registers an asset to be built into the project. The path is relative to the
+# calling CMakeLists.txt, and is kept relative to the root assets directory in
+# the output, so assets/models/a.obj ends up at <build>/assets/models/a.obj.
+#
+# This only records the asset. The build rules are created by
+# dusk_assets_finalize() from the root CMakeLists.txt, because a custom command
+# output can only be used by targets in the directory it was defined in.
+function(add_asset ASSET_PATH)
+  set(ASSET_SOURCE "${CMAKE_CURRENT_SOURCE_DIR}/${ASSET_PATH}")
+  if(NOT EXISTS "${ASSET_SOURCE}")
+    message(FATAL_ERROR "add_asset: ${ASSET_SOURCE} does not exist")
+  endif()
+
+  set_property(GLOBAL APPEND PROPERTY DUSK_ASSET_SOURCES "${ASSET_SOURCE}")
+endfunction()
+
+# Determines the lowercase extension of an asset, without the leading dot.
+function(dusk_asset_extension ASSET_SOURCE OUT_VAR)
+  get_filename_component(ASSET_EXT "${ASSET_SOURCE}" LAST_EXT)
+  string(TOLOWER "${ASSET_EXT}" ASSET_EXT)
+  string(REGEX REPLACE "^\\." "" ASSET_EXT "${ASSET_EXT}")
+  set(${OUT_VAR} "${ASSET_EXT}" PARENT_SCOPE)
+endfunction()
+
+# Creates the TARGET_NAME target, which builds every asset registered with
+# add_asset(). Call once from the root CMakeLists.txt after adding the assets.
+function(dusk_assets_finalize TARGET_NAME)
+  get_property(ASSET_SOURCES GLOBAL PROPERTY DUSK_ASSET_SOURCES)
+
+  set(ASSET_OUTPUTS "")
+  foreach(ASSET_SOURCE IN LISTS ASSET_SOURCES)
+    file(RELATIVE_PATH ASSET_RELATIVE "${DUSK_ASSETS_DIR}" "${ASSET_SOURCE}")
+    dusk_asset_extension("${ASSET_SOURCE}" ASSET_EXT)
+
+    # Dispatch on the extension, falling back to a plain copy.
+    set(ASSET_OUTPUT "")
+    if(COMMAND dusk_asset_${ASSET_EXT})
+      cmake_language(CALL dusk_asset_${ASSET_EXT}
+        "${ASSET_SOURCE}" "${ASSET_RELATIVE}" ASSET_OUTPUT
+      )
+    else()
+      message(STATUS "Asset ${ASSET_RELATIVE}: no handler for '.${ASSET_EXT}', copying")
+      dusk_asset_copy("${ASSET_SOURCE}" "${ASSET_RELATIVE}" ASSET_OUTPUT)
+    endif()
+
+    list(APPEND ASSET_OUTPUTS "${ASSET_OUTPUT}")
+  endforeach()
+
+  add_custom_target(${TARGET_NAME} ALL DEPENDS ${ASSET_OUTPUTS})
+endfunction()

cmake/asset/copy.cmake

@@ -0,0 +1,22 @@
+# Copyright (c) 2026 Dominic Masters
+#
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+# Handler that copies an asset into the built assets directory as is. Every
+# handler has the signature (SOURCE RELATIVE OUT_VAR) and must set OUT_VAR, in
+# the caller's scope, to the file it produces.
+function(dusk_asset_copy ASSET_SOURCE ASSET_RELATIVE OUT_VAR)
+  set(ASSET_OUTPUT "${DUSK_BUILT_ASSETS_DIR}/${ASSET_RELATIVE}")
+
+  add_custom_command(
+    OUTPUT "${ASSET_OUTPUT}"
+    COMMAND ${CMAKE_COMMAND} -E copy_if_different
+      "${ASSET_SOURCE}" "${ASSET_OUTPUT}"
+    DEPENDS "${ASSET_SOURCE}"
+    COMMENT "Copying asset ${ASSET_RELATIVE}"
+    VERBATIM
+  )
+
+  set(${OUT_VAR} "${ASSET_OUTPUT}" PARENT_SCOPE)
+endfunction()

cmake/asset/obj.cmake

@@ -0,0 +1,10 @@
+# Copyright (c) 2026 Dominic Masters
+#
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+# Handler for .obj (Wavefront mesh) assets. Currently just copies the file.
+function(dusk_asset_obj ASSET_SOURCE ASSET_RELATIVE OUT_VAR)
+  dusk_asset_copy("${ASSET_SOURCE}" "${ASSET_RELATIVE}" ASSET_OUTPUT)
+  set(${OUT_VAR} "${ASSET_OUTPUT}" PARENT_SCOPE)
+endfunction()

cmake/option.cmake

@@ -13,6 +13,9 @@ option(DUSK_BUILD_TESTS "Enable tests." OFF)
 option(DUSK_NETWORK "Enable network support." ON)
 
 # Game metadata
+set(DUSK_GAME "duskexample" CACHE STRING
+  "Directory under src/ containing the game to build (provides game/game.c)."
+)
 set(DUSK_GAME_NAME "Dusk" CACHE STRING "Game display name.")
 set(DUSK_GAME_AUTHOR "YourWishes" CACHE STRING "Game author / coder.")
 if(NOT DEFINED DUSK_VERSION)