Let embedders override Babylon Native's bgfx configuration

Dependencies/CMakeLists.txt

@@ -40,38 +40,68 @@ set(BGFX_USE_DEBUG_SUFFIX OFF)
 
 FetchContent_MakeAvailable_With_Message(bgfx.cmake)
 
+# Babylon Native tunes a number of bgfx compile-time settings. Every value passed to
+# babylon_native_bgfx_config below is a *default*: an embedder can override any of them
+# by setting the matching BGFX_CONFIG_<name> variable before adding Babylon Native.
+#
+# The value is used as written, so an embedder can spell one the way bgfx spells its own
+# defaults -- (4<<10) and the like. CMake booleans are the one thing that cannot be used,
+# because the C preprocessor has nothing to do with them, and bgfx.cmake declares several
+# of these names as options that can already hold ON or OFF. Those fall back to the
+# default below.
+#
+# These are emitted here rather than left to bgfx.cmake because emitting the resolved
+# value here is what makes overriding work at all: these definitions are added after
+# bgfx.cmake's, so they are last on the compile line and win. Before this indirection they
+# were hard-coded, so an embedder's value produced a conflicting duplicate definition and
+# the hard-coded one took effect.
+function(babylon_native_bgfx_config NAME DEFAULT)
+    set(value "${BGFX_CONFIG_${NAME}}")
+    string(TOUPPER "${value}" value_upper)
+    if(value STREQUAL "" OR value_upper MATCHES "^(ON|OFF|TRUE|FALSE|YES|NO|Y|N|IGNORE|NOTFOUND|.*-NOTFOUND)$")
+        set(value "${DEFAULT}")
+    endif()
+    target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_${NAME}=${value})
+endfunction()
+
 # Turn off debug annotations as it causes an access violation in D3D12.
 # This flag is set using compile definitions because the bgfx.cmake option is ignored in debug configuration.
 # See https://github.com/BabylonJS/bgfx.cmake/blob/0af3c9865a66aff1748a51bb466b24f05a123043/cmake/bgfx/bgfx.cmake#L126.
-target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_DEBUG_ANNOTATION=0)
-
-target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_DEFAULT_MAX_ENCODERS=2)
-target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_MAX_VERTEX_STREAMS=18)
-target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_MIN_RESOURCE_COMMAND_BUFFER_SIZE=16)
-target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_MIN_UNIFORM_BUFFER_SIZE=4096)
-target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_UNIFORM_BUFFER_RESIZE_THRESHOLD_SIZE=256)
-target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_UNIFORM_BUFFER_RESIZE_INCREMENT_SIZE=1024)
+babylon_native_bgfx_config(DEBUG_ANNOTATION 0)
+
+babylon_native_bgfx_config(DEFAULT_MAX_ENCODERS 2)
+babylon_native_bgfx_config(MAX_VERTEX_STREAMS 18)
+babylon_native_bgfx_config(MIN_RESOURCE_COMMAND_BUFFER_SIZE 16)
+babylon_native_bgfx_config(MIN_UNIFORM_BUFFER_SIZE 4096)
+babylon_native_bgfx_config(UNIFORM_BUFFER_RESIZE_THRESHOLD_SIZE 256)
+babylon_native_bgfx_config(UNIFORM_BUFFER_RESIZE_INCREMENT_SIZE 1024)
 target_compile_definitions(bgfx PUBLIC BGFX_PLATFORM_SUPPORTS_WGSL=0)
 
-# Canvas plugin allocates one bgfx framebuffer per JS Canvas object and per
-# text-rendering operation; combined with V8 GC pacing this can exceed the
-# default 128 limit during long playground sweeps. We enforce a floor of 512:
-# CI workflows pass -DBGFX_CONFIG_MAX_FRAME_BUFFERS, and any value below 512
-# (including a smaller CI override) is clamped up so the pool never regresses
-# below the size the Canvas sweeps need.
-if(NOT BGFX_CONFIG_MAX_FRAME_BUFFERS OR BGFX_CONFIG_MAX_FRAME_BUFFERS LESS 512)
-    set(BGFX_CONFIG_MAX_FRAME_BUFFERS 512)
+# The Canvas polyfill allocates one bgfx framebuffer per JS Canvas object and per
+# text-rendering operation; combined with V8 GC pacing this can exceed the default
+# 128 limit during long playground sweeps, so Canvas builds need a floor of 512.
+# That floor is a Canvas requirement, not a universal one: an embedder that disables
+# the polyfill draws into a handful of framebuffers and should be able to select a
+# much smaller pool. Clamp only when Canvas is actually being built, and otherwise
+# leave bgfx on its own default unless the embedder asked for something.
+if(BABYLON_NATIVE_POLYFILL_CANVAS)
+    if(NOT BGFX_CONFIG_MAX_FRAME_BUFFERS OR BGFX_CONFIG_MAX_FRAME_BUFFERS LESS 512)
+        set(BGFX_CONFIG_MAX_FRAME_BUFFERS 512)
+    endif()
+endif()
+
+if(BGFX_CONFIG_MAX_FRAME_BUFFERS)
+    babylon_native_bgfx_config(MAX_FRAME_BUFFERS ${BGFX_CONFIG_MAX_FRAME_BUFFERS})
 endif()
-target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_MAX_FRAME_BUFFERS=${BGFX_CONFIG_MAX_FRAME_BUFFERS})
 
 # Temporary disable uniform debug.
-target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_DEBUG_UNIFORM=0)
+babylon_native_bgfx_config(DEBUG_UNIFORM 0)
 
 # Disable video decoding support (not used by Babylon Native).
-target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_VIDEO=0)
+babylon_native_bgfx_config(VIDEO 0)
 
 # Disable the C99 API (Babylon Native uses the C++ API only); saves binary size.
-target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_C99_API=0)
+babylon_native_bgfx_config(C99_API 0)
 
 if(GRAPHICS_API STREQUAL "D3D11")
     target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_RENDERER_DIRECT3D11=1)