From 031605783e630d46b7294d6ac8bfbf5e4884bb82 Mon Sep 17 00:00:00 2001
From: Leo Prikler <leo.prikler@student.tugraz.at>
Date: Mon, 14 Jun 2021 18:35:33 +0200
Subject: Add support for texture blend modes.

* sdl2/bindings.scm (sdl-set-texture-blend-mode): New variable.
* sdl2/render.scm (set-texture-blend-mode!): New variable.
---
 doc/api.texi      | 5 +++++
 sdl2/bindings.scm | 3 +++
 sdl2/render.scm   | 6 ++++++
 3 files changed, 14 insertions(+)

diff --git a/doc/api.texi b/doc/api.texi
index 288d0a6..8a352a4 100644
--- a/doc/api.texi
+++ b/doc/api.texi
@@ -1254,6 +1254,11 @@ Set the color mod of @var{texture}.
 Set the alpha mod of @var{texture}.
 @end deffn
 
+@deffn {Procedure} set-texture-blend-mode! texture blend-mode
+Set the blend of @var{texture} to @var{blend-mode}.  @xref{Blend
+Modes} for more information.
+@end deffn
+
 @node Blend Modes
 @section Blend Modes
 
diff --git a/sdl2/bindings.scm b/sdl2/bindings.scm
index 8d85c63..7f12b45 100644
--- a/sdl2/bindings.scm
+++ b/sdl2/bindings.scm
@@ -321,6 +321,9 @@ RETURN-TYPE and accept arguments of ARG-TYPES."
 (define-foreign sdl-get-texture-alpha-mod
   int "SDL_GetTextureAlphaMod" '(* *))
 
+(define-foreign sdl-set-texture-blend-mode
+  int "SDL_SetTextureBlendMode" (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 e12fad1..5c3b9b0 100644
--- a/sdl2/render.scm
+++ b/sdl2/render.scm
@@ -403,6 +403,12 @@ TEXTURE."
      (bytevector-uint-ref bv (* 2 (sizeof int)) (native-endianness) (sizeof int))
      (bytevector-uint-ref bv (* 3 (sizeof int)) (native-endianness) (sizeof int)))))
 
+(define (set-texture-blend-mode! texture blend-mode)
+  (unless (zero? (ffi:sdl-set-texture-blend-mode
+                  (unwrap-texture texture)
+                  ((@@ (sdl2 blend-mode) blend-mode-bitmask) blend-mode)))
+    (sdl-error "set-texure-blend-mode!" "Failed to set texture blend mode")))
+
 (define (set-texture-color-mod! texture r g b)
   "Get color mod of TEXTURE as a list of the integers."
   (unless (zero? (ffi:sdl-set-texture-color-mod (unwrap-texture texture) r g b))
-- 
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