chore: import upstream snapshot with attribution

pkg/opengl/Framebuffer.zig

@@ -0,0 +1,116 @@
+const Framebuffer = @This();
+
+const std = @import("std");
+const c = @import("c.zig").c;
+const errors = @import("errors.zig");
+const glad = @import("glad.zig");
+const Texture = @import("Texture.zig");
+const Renderbuffer = @import("Renderbuffer.zig");
+
+id: c.GLuint,
+
+/// Create a single buffer.
+pub fn create() !Framebuffer {
+    var fbo: c.GLuint = undefined;
+    glad.context.GenFramebuffers.?(1, &fbo);
+    return .{ .id = fbo };
+}
+
+pub fn destroy(v: Framebuffer) void {
+    glad.context.DeleteFramebuffers.?(1, &v.id);
+}
+
+pub fn bind(v: Framebuffer, target: Target) !Binding {
+    // The default framebuffer is documented as being zero but
+    // on multiple OpenGL drivers its not zero, so we grab it
+    // at runtime.
+    var current: c.GLint = undefined;
+    glad.context.GetIntegerv.?(c.GL_FRAMEBUFFER_BINDING, &current);
+    glad.context.BindFramebuffer.?(@intFromEnum(target), v.id);
+    return .{ .target = target, .previous = @intCast(current) };
+}
+
+/// Enum for possible binding targets.
+pub const Target = enum(c_uint) {
+    framebuffer = c.GL_FRAMEBUFFER,
+    draw = c.GL_DRAW_FRAMEBUFFER,
+    read = c.GL_READ_FRAMEBUFFER,
+    _,
+};
+
+pub const Attachment = enum(c_uint) {
+    color0 = c.GL_COLOR_ATTACHMENT0,
+    depth = c.GL_DEPTH_ATTACHMENT,
+    stencil = c.GL_STENCIL_ATTACHMENT,
+    depth_stencil = c.GL_DEPTH_STENCIL_ATTACHMENT,
+    _,
+};
+
+pub const Status = enum(c_uint) {
+    complete = c.GL_FRAMEBUFFER_COMPLETE,
+    undefined = c.GL_FRAMEBUFFER_UNDEFINED,
+    incomplete_attachment = c.GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT,
+    incomplete_missing_attachment = c.GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT,
+    incomplete_draw_buffer = c.GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER,
+    incomplete_read_buffer = c.GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER,
+    unsupported = c.GL_FRAMEBUFFER_UNSUPPORTED,
+    incomplete_multisample = c.GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE,
+    incomplete_layer_targets = c.GL_FRAMEBUFFER_INCOMPLETE_LAYER_TARGETS,
+    _,
+};
+
+pub const Binding = struct {
+    target: Target,
+    previous: c.GLuint,
+
+    pub fn unbind(self: Binding) void {
+        glad.context.BindFramebuffer.?(
+            @intFromEnum(self.target),
+            self.previous,
+        );
+    }
+
+    pub fn texture2D(
+        self: Binding,
+        attachment: Attachment,
+        textarget: Texture.Target,
+        texture: Texture,
+        level: c.GLint,
+    ) !void {
+        glad.context.FramebufferTexture2D.?(
+            @intFromEnum(self.target),
+            @intFromEnum(attachment),
+            @intFromEnum(textarget),
+            texture.id,
+            level,
+        );
+        try errors.getError();
+    }
+
+    pub fn renderbuffer(
+        self: Binding,
+        attachment: Attachment,
+        buffer: Renderbuffer,
+    ) !void {
+        glad.context.FramebufferRenderbuffer.?(
+            @intFromEnum(self.target),
+            @intFromEnum(attachment),
+            c.GL_RENDERBUFFER,
+            buffer.id,
+        );
+        try errors.getError();
+    }
+
+    pub fn drawBuffers(
+        self: Binding,
+        bufs: []Attachment,
+    ) !void {
+        _ = self;
+        glad.context.DrawBuffers.?(@intCast(bufs.len), bufs.ptr);
+        try errors.getError();
+    }
+
+    pub fn checkStatus(self: Binding) Status {
+        return @enumFromInt(glad.context.CheckFramebufferStatus.?(@intFromEnum(self.target)));
+    }
+};