Add simple page shader

builtin-programs/gpu/page-shader.folk

@@ -0,0 +1,35 @@
+set cc [C]
+$cc include <string.h>
+$cc include <openssl/sha.h>
+$cc proc sha1 {char* d} Jim_Obj* {
+    unsigned char md[20];
+    SHA1((unsigned char *)d, strlen(d), md);
+    return Jim_NewStringObj(interp, (char *)md, 20);
+}
+$cc endcflags -lssl -lcrypto
+set sha1Lib [$cc compile]
+
+
+When /someone/ wishes /p/ draws shader /shaderCode/ {
+    binary scan [$sha1Lib sha1 $shaderCode] H* sha1
+
+    Wish the GPU compiles pipeline $sha1 [list \
+        {vec2 viewport mat3 surfaceToClip} {
+            vec2 vertices[6] = vec2[6](
+                vec2(0.0, 0.0), vec2(1.0, 0.0), vec2(1.0, 1.0),
+                vec2(0.0, 0.0), vec2(1.0, 1.0), vec2(0.0, 1.0)
+            );
+            vec3 v = surfaceToClip * vec3(vertices[gl_VertexIndex], 1.0);
+            return vec4(v.xy/v.z, 0.0, 1.0);
+        } $shaderCode]
+
+    When the GPU compiles pipeline $sha1 to /anything/ & \
+         $p has canvas /id/ with /...wiOptions/ & \
+         $p has canvas projection /surfaceToClip/ {
+        puts "the GPU compiled the pipeline"
+        set wiResolution [list [dict get $wiOptions width] [dict get $wiOptions height]]
+
+        Wish the GPU draws pipeline $sha1 onto canvas $id \
+            with arguments [list $wiResolution $surfaceToClip ]
+    }
+}