Fix missing stdbool.h include / Test headers are kosher

.github/workflows/build_linux.yml

@@ -43,6 +43,29 @@ jobs:
           cmake --build "${{ github.workspace }}/cmake-build" --config "Debug" --target install
           cmake --build "${{ github.workspace }}/cmake-build" --config "Release" --target install
 
+      - name: Check Installed Headers Compile Cleanly
+        run: |
+          mkdir -p header-check
+          cat <<EOF > header-check/CMakeLists.txt
+          cmake_minimum_required(VERSION 3.15)
+          project(HeaderCheck C)
+
+          set(PROJECTM_INCLUDE_DIR "${{ github.workspace }}/install/include")
+          file(GLOB_RECURSE PUBLIC_HEADERS "\${PROJECTM_INCLUDE_DIR}/*.h")
+
+          foreach(header IN LISTS PUBLIC_HEADERS)
+            file(RELATIVE_PATH header_rel "\${PROJECTM_INCLUDE_DIR}" "\${header}")
+            string(MAKE_C_IDENTIFIER "\${header_rel}" safe_name)
+            set(test_source "\${CMAKE_BINARY_DIR}/check_\${safe_name}.c")
+            file(WRITE "\${test_source}" "#include <\${header_rel}>\nint main(void){return 0;}\n")
+            add_executable("check_\${safe_name}" "\${test_source}")
+            target_include_directories("check_\${safe_name}" PRIVATE "\${PROJECTM_INCLUDE_DIR}")
+          endforeach()
+          EOF
+
+          cmake -S header-check -B header-check/build -DCMAKE_C_STANDARD=99
+          cmake --build header-check/build --parallel
+
       - name: Upload Artifact
         uses: actions/upload-artifact@v4
         with:

src/playlist/api/projectM-4/playlist_callbacks.h

@@ -28,6 +28,7 @@
 
 #include "projectM-4/playlist_types.h"
 #include <stdint.h>
+#include <stdbool.h>
 
 #ifdef __cplusplus
 extern "C" {