opengl: glad helpers

src/App.zig

@@ -34,16 +34,10 @@ pub fn init(alloc: std.mem.Allocator) !App {
     try glfw.swapInterval(1);
 
     // Load OpenGL bindings
-    const version = gl.c.gladLoadGL(@ptrCast(
-        fn ([*c]const u8) callconv(.C) ?fn () callconv(.C) void,
-        glfw.getProcAddress,
-    ));
-    if (version == 0) {
-        return error.OpenGLInitFailed;
-    }
+    const version = try gl.glad.load(glfw.getProcAddress);
     log.info("loaded OpenGL {}.{}", .{
-        gl.c.GLAD_VERSION_MAJOR(@intCast(c_uint, version)),
-        gl.c.GLAD_VERSION_MINOR(@intCast(c_uint, version)),
+        gl.glad.versionMajor(version),
+        gl.glad.versionMinor(version),
     });
 
     // Blending for text

src/opengl.zig

@@ -12,9 +12,11 @@
 //! comptime help. I'm deferring this until later but have some fun ideas.
 
 pub const c = @import("opengl/c.zig");
+pub const glad = @import("opengl/glad.zig");
+pub usingnamespace @import("opengl/draw.zig");
+
 pub const Buffer = @import("opengl/Buffer.zig");
 pub const Program = @import("opengl/Program.zig");
 pub const Shader = @import("opengl/Shader.zig");
 pub const Texture = @import("opengl/Texture.zig");
 pub const VertexArray = @import("opengl/VertexArray.zig");
-pub usingnamespace @import("opengl/draw.zig");

src/opengl/glad.zig

@@ -0,0 +1,29 @@
+const c = @import("c.zig");
+
+/// Initialize Glad. This is guaranteed to succeed if no errors are returned.
+/// The getProcAddress param is an anytype so that we can accept multiple
+/// forms of the function depending on what we're interfacing with.
+pub fn load(getProcAddress: anytype) !c_int {
+    const res = switch (@TypeOf(getProcAddress)) {
+        // glfw
+        fn ([*:0]const u8) callconv(.C) ?fn () callconv(.C) void => c.gladLoadGL(@ptrCast(
+            fn ([*c]const u8) callconv(.C) ?fn () callconv(.C) void,
+            getProcAddress,
+        )),
+
+        // try as-is. If this introduces a compiler error, then add a new case.
+        else => c.gladLoadGL(getProcAddress),
+    };
+    if (res == 0) return error.GLInitFailed;
+    return res;
+}
+
+pub fn versionMajor(res: c_int) c_uint {
+    // The intcast here is due to translate-c weirdness
+    return c.GLAD_VERSION_MAJOR(@intCast(c_uint, res));
+}
+
+pub fn versionMinor(res: c_int) c_uint {
+    // The intcast here is due to translate-c weirdness
+    return c.GLAD_VERSION_MINOR(@intCast(c_uint, res));
+}