feat(codec): make BMP support configurable (#500)

BMP support is currently compiled into `skity-codec` unconditionally.
Add `SKITY_ENABLE_CODEC_BMP`, defaulting to `ON` like the existing
GIF/WebP options, so consumers can configure
`-DSKITY_ENABLE_CODEC_BMP=OFF` to omit the built-in BMP implementation
and its codec registration.

Update codec tests to retain BMP coverage when enabled and verify BMP
input is rejected when disabled. The separate Apple ImageIO
implementation is unchanged.

Validation on macOS arm64:
- Default configuration: 47/47 codec unit tests passed via
`tools/test-runner.py`.
- `SKITY_ENABLE_CODEC_BMP=OFF`: 36/36 codec unit tests passed via
`tools/test-runner.py`; BMP source excluded from the build.
- `tools/code_format_check.py`, `tools/cpplint_check.py`, and `git diff
--check`.

Author: Jaden-47

module/codec/CMakeLists.txt

@@ -16,6 +16,7 @@ target_include_directories(skity-codec PRIVATE ${SKITY_ROOT}/include)
 
 option(SKITY_ENABLE_CODEC_WEBP "Enable WebP Codec" ON)
 option(SKITY_ENABLE_CODEC_GIF "Enable GIF Codec" ON)
+option(SKITY_ENABLE_CODEC_BMP "Enable BMP Codec" ON)
 
 target_include_directories(
   skity-codec
@@ -29,8 +30,6 @@ target_sources(
   skity-codec
   PRIVATE
   ${CMAKE_CURRENT_LIST_DIR}/include/skity/codec/codec.hpp
-  ${CMAKE_CURRENT_LIST_DIR}/src/codec/bmp_codec.cc
-  ${CMAKE_CURRENT_LIST_DIR}/src/codec/bmp_codec.hpp
   ${CMAKE_CURRENT_LIST_DIR}/src/codec/codec.cc
   ${CMAKE_CURRENT_LIST_DIR}/src/codec/codec_priv.cc
   ${CMAKE_CURRENT_LIST_DIR}/src/codec/codec_priv.hpp
@@ -39,6 +38,17 @@ target_sources(
   ${CMAKE_CURRENT_LIST_DIR}/src/codec/data_stream.hpp
 )
 
+if (SKITY_ENABLE_CODEC_BMP)
+  target_sources(
+    skity-codec
+    PRIVATE
+    ${CMAKE_CURRENT_LIST_DIR}/src/codec/bmp_codec.cc
+    ${CMAKE_CURRENT_LIST_DIR}/src/codec/bmp_codec.hpp
+  )
+
+  target_compile_definitions(skity-codec PRIVATE -DSKITY_ENABLE_CODEC_BMP=1)
+endif()
+
 if (SKITY_ENABLE_CODEC_WEBP)
   target_sources(
     skity-codec

module/codec/src/codec/codec.cc

@@ -7,10 +7,12 @@
 #include <skity/io/data.hpp>
 #include <vector>
 
+#if SKITY_ENABLE_CODEC_BMP
+#include "src/codec/bmp_codec.hpp"
+#endif
 #if SKITY_ENABLE_CODEC_GIF
 #include "src/codec/gif_codec.hpp"
 #endif
-#include "src/codec/bmp_codec.hpp"
 #include "src/codec/jpeg_codec.hpp"
 #include "src/codec/png_codec.hpp"
 
@@ -26,7 +28,9 @@ static std::mutex codec_mutex = {};
 void Codec::SetupCodecs() {
   codec_list.clear();
 
+#if SKITY_ENABLE_CODEC_BMP
   codec_list.emplace_back(std::make_shared<BMPCodec>());
+#endif
   codec_list.emplace_back(std::make_shared<PNGCodec>());
   codec_list.emplace_back(std::make_shared<JPEGCodec>());
 #if SKITY_ENABLE_CODEC_GIF

test/ut/CMakeLists.txt

@@ -127,6 +127,9 @@ target_link_libraries(skity_unit_test
 )
 
 if (${SKITY_CODEC_MODULE})
+    target_compile_definitions(skity_unit_test PRIVATE
+        SKITY_ENABLE_CODEC_BMP=$<BOOL:${SKITY_ENABLE_CODEC_BMP}>
+    )
     target_sources(skity_unit_test
         PUBLIC
         codec/bmp_codec_test.cc

test/ut/codec/bmp_codec_test.cc

@@ -12,8 +12,6 @@
 #include <skity/render/canvas.hpp>
 
 TEST(BMPCodecTest, RecognizeFileType) {
-  auto png_data = skity::Data::MakeFromFileName(SKITY_TEST_PNG_FILE);
-
   const unsigned char bmp_header[] = {
       'B',  'M',               // signature
       0x36, 0x00, 0x00, 0x00,  // file size = 54
@@ -37,14 +35,21 @@ TEST(BMPCodecTest, RecognizeFileType) {
 
   auto codec = skity::Codec::MakeFromData(bmp_data);
 
+#if SKITY_ENABLE_CODEC_BMP
   ASSERT_TRUE(codec != nullptr) << "MakeFromData returned nullptr for BMP data";
+  auto png_data = skity::Data::MakeFromFileName(SKITY_TEST_PNG_FILE);
+  ASSERT_TRUE(png_data != nullptr);
 
   EXPECT_TRUE(codec->RecognizeFileType(
       reinterpret_cast<const char*>(bmp_header), sizeof(bmp_header)));
   EXPECT_FALSE(codec->RecognizeFileType(
       reinterpret_cast<const char*>(png_data->Bytes()), png_data->Size()));
+#else
+  EXPECT_EQ(codec, nullptr);
+#endif
 }
 
+#if SKITY_ENABLE_CODEC_BMP
 TEST(BMPCodecTest, Decode24Bit) {
   const unsigned char bmp_24bit[] = {
       'B',  'M',               // signature
@@ -425,4 +430,5 @@ TEST(BMPCodecTest, InvalidSize) {
   auto codec = skity::Codec::MakeFromData(data);
 
   EXPECT_TRUE(codec == nullptr);
-}
+}
+#endif

test/ut/codec/codec_scale_test.cc

@@ -522,6 +522,7 @@ TEST(CodecScaleTest, PNGDecodeScaledContent) {
   }
 }
 
+#if SKITY_ENABLE_CODEC_BMP
 TEST(CodecScaleTest, BMPDecodeScaled) {
   // BMP has no native scaling; encode a solid 64x64 image and decode it at
   // half size through the shared resampler. A minimal 1x1 24-bit header is
@@ -563,6 +564,8 @@ TEST(CodecScaleTest, BMPDecodeScaled) {
   }
 }
 
+#endif
+
 TEST(CodecScaleTest, GIFDecodeScaled) {
   // Single-frame GIF (color wheel): intrinsic decode via wuffs, then
   // resampled to the target. Dimensions are asserted relative to the