From 697a403617b97b4ce333132dae89cb009f6b6e3b Mon Sep 17 00:00:00 2001
From: Ekaitz Zarraga <ekaitz@elenq.tech>
Date: Wed, 6 Jul 2022 20:25:30 +0200
Subject: Add SDL_UpdateTexture binding.

---
 doc/api.texi      |  8 ++++++++
 sdl2/bindings.scm |  3 +++
 sdl2/render.scm   | 16 ++++++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/doc/api.texi b/doc/api.texi
index 204db9e..8e0fe73 100644
--- a/doc/api.texi
+++ b/doc/api.texi
@@ -1242,6 +1242,14 @@ Convert @var{surface} to a texture suitable for @var{renderer}.
 Free the memory used by @var{texture}.
 @end deffn
 
+@deffn {Procedure} update-texture texture rect pixels pitch
+Update the subsection of @var{texture} defined by @var{rect} with new
+pixel data in the @var{pixels} bytevector.  @var{pitch} represents the
+number of bytes in a row of pixel data, including any padding between
+rows.  This is a fairly slow process: Better to use the lock/unlock
+mechanism in streaming textures.
+@end deffn
+
 @deffn {Procedure} texture-color-mod texture
 Get color mod of @var{texture} as a list of the integers.
 @end deffn
diff --git a/sdl2/bindings.scm b/sdl2/bindings.scm
index 5a63636..897a0dc 100644
--- a/sdl2/bindings.scm
+++ b/sdl2/bindings.scm
@@ -327,6 +327,9 @@ RETURN-TYPE and accept arguments of ARG-TYPES."
 (define-foreign sdl-set-texture-blend-mode
   int "SDL_SetTextureBlendMode" (list '* int))
 
+(define-foreign sdl-update-texture
+  int "SDL_UpdateTexture" (list '* '* '* int))
+
 (define-foreign sdl-set-render-draw-blend-mode
   int "SDL_SetRenderDrawBlendMode" (list '* int))
 
diff --git a/sdl2/render.scm b/sdl2/render.scm
index 5c3b9b0..94e115a 100644
--- a/sdl2/render.scm
+++ b/sdl2/render.scm
@@ -66,6 +66,7 @@
             set-texture-alpha-mod!
 
             make-texture
+            update-texture
             delete-texture!
             surface->texture
             query-texture))
@@ -332,6 +333,21 @@ created with 'texture')"
         (sdl-error "make-texture" "Failed to create texture")
         (wrap-texture ptr))))
 
+(define (update-texture texture rect pixels pitch)
+  "Update the subsection of TEXTURE defined by RECT with new pixel
+data in the PIXELS bytevector.  PITCH represents the number of bytes
+in a row of pixel data, including any padding between rows.  This is a
+fairly slow process: Better to use the lock/unlock mechanism in
+streaming textures."
+  (let ((ret (ffi:sdl-update-texture
+                (unwrap-texture texture)
+                ((@@ (sdl2 rect) unwrap-rect) rect)
+                (bytevector->pointer pixels)
+                pitch)))
+    (if (> 0 ret)
+      (sdl-error "update-texture" "failed to update texture")
+      ret)))
+
 (define (surface->texture renderer surface)
   "Convert SURFACE to a texture suitable for RENDERER."
   (let ((ptr (ffi:sdl-create-texture-from-surface
-- 
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