library: vendors/stb_image + vendors/stb_truetype — stb ships with sx

The stb headers move from the repo-root vendors/ (resolvable only
with CWD = sx repo) into library/vendors/ following the sqlite
convention — bindings module + c/ sources + provenance README — so
'#import "vendors/stb_image/stb_image.sx"' (image v2.30 + image_write
v1.16) and '#import "vendors/stb_truetype/stb_truetype.sx"' (v1.26)
work from any consumer via the stdlib search paths. modules/ffi/stb.sx
dissolves into the stb_image vendor; modules/ffi/stb_truetype.sx keeps
its non-stb text-shaping companions and re-imports the vendored unit.
examples/1625 pins a deterministic in-memory BMP decode; examples/1626
pins font init + metric invariants against the system Helvetica.

library/vendors/stb_image/README.md

@@ -0,0 +1,20 @@
+# vendors/stb_image — image decode/encode for sx programs
+
+- stb_image: **v2.30**; stb_image_write: **v1.16** (version comments at
+  the top of each header)
+- Source: <https://github.com/nothings/stb> (`stb_image.h`,
+  `stb_image_write.h`)
+- License: public domain / MIT, dual (see the headers' license blocks)
+- Files: `c/stb_image.h` + `c/stb_image_impl.c`, `c/stb_image_write.h`
+  + `c/stb_image_write_impl.c` (each impl .c defines the
+  `*_IMPLEMENTATION` macro and includes its header)
+
+`#import "vendors/stb_image/stb_image.sx"` resolves through the stdlib
+search paths; the decls (`stbi_load`, `stbi_load_from_memory`,
+`stbi_image_free`, `stbi_write_png`, …) are synthesized from the
+headers, and the implementation compiles once per machine through sx's
+object cache. `examples/1625-vendor-stb-image-decode.sx` pins an
+in-memory BMP decode in the sx suite.
+
+To upgrade: replace the headers under `c/` with newer upstream copies,
+update this file, and rebuild (the object cache keys on source bytes).

library/vendors/stb_image/c/stb_image_impl.c

@@ -0,0 +1,2 @@
+#define STB_IMAGE_IMPLEMENTATION
+#include "stb_image.h"

library/vendors/stb_image/c/stb_image_write_impl.c

@@ -0,0 +1,2 @@
+#define STB_IMAGE_WRITE_IMPLEMENTATION
+#include "stb_image_write.h"

library/vendors/stb_image/stb_image.sx

@@ -0,0 +1,19 @@
+// =====================================================================
+// vendors/stb_image — Sean Barrett's stb_image (decode) and
+// stb_image_write (encode) as one `#import c` unit (c/, see README.md
+// for versions + provenance).
+//
+// `#import "vendors/stb_image/stb_image.sx"` gives any sx program
+// image decode/encode with no system dependency and no build flags:
+// the decls are synthesized from the headers, and the implementation
+// compiles through sx's content-addressed object cache — once per
+// machine, not once per run.
+// =====================================================================
+
+#import c {
+    #include "c/stb_image.h";
+    #source  "c/stb_image_impl.c";
+
+    #include "c/stb_image_write.h";
+    #source  "c/stb_image_write_impl.c";
+};

library/vendors/stb_truetype/README.md

@@ -0,0 +1,20 @@
+# vendors/stb_truetype — font parsing/rasterization for sx programs
+
+- Version: **v1.26** (version comment at the top of the header)
+- Source: <https://github.com/nothings/stb> (`stb_truetype.h`)
+- License: public domain / MIT, dual (see the header's license block)
+- Files: `c/stb_truetype.h` + `c/stb_truetype_impl.c` (the impl .c
+  defines `STB_TRUETYPE_IMPLEMENTATION` and includes the header)
+
+`#import "vendors/stb_truetype/stb_truetype.sx"` resolves through the
+stdlib search paths; the decls (`stbtt_InitFont`,
+`stbtt_ScaleForPixelHeight`, `stbtt_GetFontVMetrics`,
+`stbtt_MakeGlyphBitmap`, …) are synthesized from the header, and the
+implementation compiles once per machine through sx's object cache.
+`stbtt_fontinfo` is opaque on the sx side: allocate a 256-byte blob
+and pass its pointer (modules/ui/glyph_cache.sx is the reference
+consumer; `examples/1626-vendor-stb-truetype-metrics.sx` pins font
+init + metrics in the sx suite).
+
+To upgrade: replace `c/stb_truetype.h` with a newer upstream copy,
+update this file, and rebuild (the object cache keys on source bytes).

library/vendors/stb_truetype/c/stb_truetype_impl.c

@@ -0,0 +1,2 @@
+#define STB_TRUETYPE_IMPLEMENTATION
+#include "stb_truetype.h"

library/vendors/stb_truetype/stb_truetype.sx

@@ -0,0 +1,17 @@
+// =====================================================================
+// vendors/stb_truetype — Sean Barrett's stb_truetype (TTF/TTC
+// parsing, glyph metrics, bitmap rasterization) as a `#import c` unit
+// (c/, see README.md for version + provenance).
+//
+// `#import "vendors/stb_truetype/stb_truetype.sx"` gives any sx
+// program font loading with no system dependency: the decls are
+// synthesized from the header, and the implementation compiles
+// through sx's content-addressed object cache. `stbtt_fontinfo` is
+// opaque on the sx side — allocate a 256-byte blob and pass its
+// pointer (see modules/ui/glyph_cache.sx for the established idiom).
+// =====================================================================
+
+#import c {
+    #include "c/stb_truetype.h";
+    #source  "c/stb_truetype_impl.c";
+};