renderer/opengl: start custom program work

src/renderer/opengl/CustomProgram.zig

@@ -0,0 +1,36 @@
+/// The OpenGL program for custom shaders.
+const CustomProgram = @This();
+
+const std = @import("std");
+const Allocator = std.mem.Allocator;
+const gl = @import("opengl");
+
+program: gl.Program,
+
+pub fn createList(alloc: Allocator, srcs: []const [:0]const u8) ![]const CustomProgram {
+    var programs = std.ArrayList(CustomProgram).init(alloc);
+    defer programs.deinit();
+    errdefer for (programs.items) |program| program.deinit();
+
+    for (srcs) |src| {
+        try programs.append(try CustomProgram.init(src));
+    }
+
+    return try programs.toOwnedSlice();
+}
+
+pub fn init(src: [:0]const u8) !CustomProgram {
+    const program = try gl.Program.createVF(
+        @embedFile("../shaders/custom.v.glsl"),
+        src,
+    );
+    errdefer program.destroy();
+
+    return .{
+        .program = program,
+    };
+}
+
+pub fn deinit(self: CustomProgram) void {
+    self.program.destroy();
+}