Allow disabling STB_*_IMPLEMENTATION (#578)

When having stb_rect_pack or stb_truetype used elsewhere in your project, Nuklear could cause conflicts. This change adds `NK_NO_STB_RECT_PACK_IMPLEMENTATION` or `NK_NO_STB_TRUETYPE_IMPLEMENTATION` to allow disabling adding `STB_RECT_PACK_IMPLEMENTATION` or `STB_TRUETYPE_IMPLEMENTATION`.

nuklear.h

@@ -6103,8 +6103,23 @@ NK_LIB void nk_property(struct nk_context *ctx, const char *name, struct nk_prop
 
 #ifdef NK_INCLUDE_FONT_BAKING
 
+/**
+ * @def NK_NO_STB_RECT_PACK_IMPLEMENTATION
+ *
+ * When defined, will avoid enabling STB_RECT_PACK_IMPLEMENTATION for when stb_rect_pack.h is already implemented elsewhere.
+ */
+#ifndef NK_NO_STB_RECT_PACK_IMPLEMENTATION
 #define STB_RECT_PACK_IMPLEMENTATION
+#endif /* NK_NO_STB_RECT_PACK_IMPLEMENTATION */
+
+/**
+ * @def NK_NO_STB_TRUETYPE_IMPLEMENTATION
+ *
+ * When defined, will avoid enabling STB_TRUETYPE_IMPLEMENTATION for when stb_truetype.h is already implemented elsewhere.
+ */
+#ifndef NK_NO_STB_TRUETYPE_IMPLEMENTATION
 #define STB_TRUETYPE_IMPLEMENTATION
+#endif /* NK_NO_STB_TRUETYPE_IMPLEMENTATION */
 
 /* Allow consumer to define own STBTT_malloc/STBTT_free, and use the font atlas' allocator otherwise */
 #ifndef STBTT_malloc

src/nuklear_internal.h

@@ -328,8 +328,23 @@ NK_LIB void nk_property(struct nk_context *ctx, const char *name, struct nk_prop
 
 #ifdef NK_INCLUDE_FONT_BAKING
 
+/**
+ * @def NK_NO_STB_RECT_PACK_IMPLEMENTATION
+ *
+ * When defined, will avoid enabling STB_RECT_PACK_IMPLEMENTATION for when stb_rect_pack.h is already implemented elsewhere.
+ */
+#ifndef NK_NO_STB_RECT_PACK_IMPLEMENTATION
 #define STB_RECT_PACK_IMPLEMENTATION
+#endif /* NK_NO_STB_RECT_PACK_IMPLEMENTATION */
+
+/**
+ * @def NK_NO_STB_TRUETYPE_IMPLEMENTATION
+ *
+ * When defined, will avoid enabling STB_TRUETYPE_IMPLEMENTATION for when stb_truetype.h is already implemented elsewhere.
+ */
+#ifndef NK_NO_STB_TRUETYPE_IMPLEMENTATION
 #define STB_TRUETYPE_IMPLEMENTATION
+#endif /* NK_NO_STB_TRUETYPE_IMPLEMENTATION */
 
 /* Allow consumer to define own STBTT_malloc/STBTT_free, and use the font atlas' allocator otherwise */
 #ifndef STBTT_malloc