From 2855edbb81f64ffadb93576e0800066f71880746 Mon Sep 17 00:00:00 2001
From: tali <iitalics@gmail.com>
Date: Fri, 19 Jan 2024 16:22:10 -0500
Subject: [PATCH] add basic texture rendering (no clips, no instances)

---
 assets/shaders/sprite.frag | 12 ++++++++
 assets/shaders/sprite.vert | 25 ++++++++++++++++
 src/main.ml                |  4 +++
 src/s2/renderer.ml         | 58 ++++++++++++++++++++++++++++++--------
 src/s2/s2.mli              |  2 +-
 5 files changed, 89 insertions(+), 12 deletions(-)
 create mode 100644 assets/shaders/sprite.frag
 create mode 100644 assets/shaders/sprite.vert

diff --git a/assets/shaders/sprite.frag b/assets/shaders/sprite.frag
new file mode 100644
index 0000000..5bea912
--- /dev/null
+++ b/assets/shaders/sprite.frag
@@ -0,0 +1,12 @@
+#version 150 core
+
+uniform sampler2D Texture;
+uniform vec4 Tint;
+
+in vec2 TextureCoord;
+
+out vec4 FragColor;
+
+void main() {
+  FragColor = texture2D(Texture, TextureCoord) * Tint;
+}
diff --git a/assets/shaders/sprite.vert b/assets/shaders/sprite.vert
new file mode 100644
index 0000000..9b413ca
--- /dev/null
+++ b/assets/shaders/sprite.vert
@@ -0,0 +1,25 @@
+#version 150 core
+
+uniform ivec2 Viewport;
+uniform mat3  Transform;
+uniform vec4  BoundingBox;
+
+in vec2 Vert;
+
+/* TODO: instances */
+// in vec4 Rect;
+// in vec4 Clip;
+
+out vec2 TextureCoord;
+
+void main() {
+  vec2 vert = mix(BoundingBox.xy, BoundingBox.zw, Vert);
+  vec3 pos = Transform * vec3(vert, 1.0);
+
+  // TextureCoord = mix(Clip.st, Clip.pq, Vert) / textureSize(T, 0);
+  TextureCoord = Vert;
+
+  gl_Position.xy = pos.xy * vec2(2.0, -2.0) / Viewport + vec2(-1.0, 1.0);
+  gl_Position.z = 0.0;
+  gl_Position.w = 1.0;
+}
diff --git a/src/main.ml b/src/main.ml
index 40010c3..675a8dd 100644
--- a/src/main.ml
+++ b/src/main.ml
@@ -45,6 +45,10 @@ let main () =
       TG.update tg;
       SG.render sg ~ren;
 
+      Renderer.draw_texture ren cat
+        ~tf
+        ~bb:(aabb 0.0 0.0 (200.0) (200.0));
+
       Renderer.post_draw ren;
 
       Gc.minor ();
diff --git a/src/s2/renderer.ml b/src/s2/renderer.ml
index 88926e9..e3014ce 100644
--- a/src/s2/renderer.ml
+++ b/src/s2/renderer.ml
@@ -216,6 +216,13 @@ let make_texture ~size ~format (pixels : pixel_array) =
   Gl.bind_texture Gl.texture_2d 0;
   { tid; tsize = size }
 
+let set_tex : texture set_fn =
+  fun (U l) { tid; _ } ->
+  (* TODO: in order to allow multiple textures, there should something like a LRU cache of
+     which texture unit each is bound to. *)
+  Gl.bind_texture Gl.texture_2d tid;
+  Gl.uniform1i l 0
+
 
 (* Renderer *)
 
@@ -224,7 +231,11 @@ type t = {
   gl_ctx : Sdl.gl_context;
 
   polygon : shader;
-  rect : geometry;
+  polygon_rect : geometry;
+
+  sprite : shader;
+  sprite_rect : geometry;
+  (* sprite_instances : vertex_buffer; *)
 }
 
 let unit_square =
@@ -269,12 +280,8 @@ let make ~(wnd : Sdl.window) : t =
   Gl.blend_func Gl.one Gl.one_minus_src_alpha;
   Gl.check_error "setup";
 
-  let polygon =
-    load_shader
-      ~name:"polygon"
-  in
-
-  let rect =
+  let polygon = load_shader ~name:"polygon" in
+  let polygon_rect =
     make_geometry [
       make_static_vertex_buffer unit_square_with_norm [
         attr polygon "Vert" `float 2;
@@ -285,11 +292,25 @@ let make ~(wnd : Sdl.window) : t =
       ~index:(`count 4)
   in
 
+  let sprite = load_shader ~name:"sprite" in
+  let sprite_rect =
+    make_geometry [
+      make_static_vertex_buffer unit_square [
+        attr polygon "Vert" `float 2;
+      ]
+      (* sprite_instances *)
+    ]
+      ~draw_mode:Gl.triangle_strip
+      ~index:(`count 4)
+  in
+
   {
     window = wnd;
     gl_ctx;
     polygon;
-    rect;
+    polygon_rect;
+    sprite;
+    sprite_rect;
   }
 
 let destroy t =
@@ -299,7 +320,8 @@ let pre_draw t =
   let viewport = Sdl.get_window_size t.window in
   begin
     Sdl.gl_make_current_exn t.window t.gl_ctx;
-    set_ivec2 (uniform t.polygon "Viewport") viewport;
+    use t.polygon; set_ivec2 (uniform t.polygon "Viewport") viewport;
+    use t.sprite; set_ivec2 (uniform t.sprite "Viewport") viewport;
   end
 
 let post_draw t =
@@ -313,7 +335,7 @@ let clear _t (bg : color) =
     Gl.clear Gl.color_buffer_bit;
   end
 
-let draw_rect t ~(tf : mat2a) ~(bb : aabb) ~(fill : color) =
+let draw_rect t ~tf ~bb ~fill =
   let sh = t.polygon in
   begin
     (* TODO: cache/store uniform locations in some way *)
@@ -322,5 +344,19 @@ let draw_rect t ~(tf : mat2a) ~(bb : aabb) ~(fill : color) =
     set_aabb  (uniform sh "BoundingBox") bb;
     set_int   (uniform sh "Border") 0;
     set_color (uniform sh "Fill") fill;
-    draw_geometry t.rect;
+    draw_geometry t.polygon_rect;
+  end
+
+let _white = Color.white ()
+
+let draw_texture t ~tf ~bb ?(tint = _white) tex =
+  let sh = t.sprite in
+  begin
+    (* TODO: cache/store uniform locations in some way *)
+    use sh;
+    set_mat2a (uniform sh "Transform") tf;
+    set_aabb  (uniform sh "BoundingBox") bb;
+    set_tex   (uniform sh "Texture") tex;
+    set_color (uniform sh "Tint") tint;
+    draw_geometry t.sprite_rect;
   end
diff --git a/src/s2/s2.mli b/src/s2/s2.mli
index 38ed3e4..4a6d145 100644
--- a/src/s2/s2.mli
+++ b/src/s2/s2.mli
@@ -31,7 +31,7 @@ module Renderer : sig
   val post_draw : t -> unit
   val clear : t -> color -> unit
   val draw_rect : t -> tf:mat2a -> bb:aabb -> fill:color -> unit
-  (* val draw_texture : t -> tf:mat2a -> bb:aabb -> tex:Texture.t -> unit *)
+  val draw_texture : t -> tf:mat2a -> bb:aabb -> ?tint:color -> Texture.t -> unit
 end
 
 module Asset : sig