feat(engine): add logging OpenGL debug messages

6 files changed, 240 insertions, 1 deletions

diff --git a/engine/Cargo.toml b/engine/Cargo.toml
index 40b2e9f..ff52cce 100644
--- a/engine/Cargo.toml
+++ b/engine/Cargo.toml
@@ -3,8 +3,12 @@ name = "engine"
 version = "0.1.0"
 edition = "2021"
 
+[features]
+debug = ["dep:tracing"]
+
 [dependencies]
 glfw = { path = "../glfw" }
 thiserror = "1.0.49"
 gl = "0.14.0"
 bitflags = "2.4.0"
+tracing = { version = "0.1.39", optional = true }
diff --git a/engine/src/lib.rs b/engine/src/lib.rs
index 407df32..dc76b37 100644
--- a/engine/src/lib.rs
+++ b/engine/src/lib.rs
@@ -29,7 +29,13 @@ impl Engine
     /// Will return `Err` if window creation or window configuration fails.
     pub fn new(window_size: &WindowSize, window_title: &str) -> Result<Self, Error>
     {
-        let window = WindowBuilder::new()
+        let window_builder = WindowBuilder::new();
+
+        #[cfg(feature = "debug")]
+        let window_builder =
+            window_builder.hint(glfw::window::Hint::OpenGLDebugContext, 1);
+
+        let window = window_builder
             .create(window_size, window_title)
             .map_err(Error::CreateWindowFailed)?;
 
diff --git a/engine/src/opengl/debug.rs b/engine/src/opengl/debug.rs
new file mode 100644
index 0000000..203590a
--- /dev/null
+++ b/engine/src/opengl/debug.rs
@@ -0,0 +1,145 @@
+use std::ffi::c_void;
+use std::io::{stderr, Write};
+use std::panic::catch_unwind;
+use std::ptr::null_mut;
+use std::sync::Mutex;
+
+use crate::opengl::util::gl_enum;
+
+pub type MessageCallback = fn(
+    source: MessageSource,
+    ty: MessageType,
+    id: u32,
+    severity: MessageSeverity,
+    message: &str,
+);
+
+pub fn enable_debug_output()
+{
+    unsafe {
+        gl::Enable(gl::DEBUG_OUTPUT);
+        gl::Enable(gl::DEBUG_OUTPUT_SYNCHRONOUS);
+    }
+}
+
+pub fn set_debug_message_callback(cb: MessageCallback)
+{
+    *DEBUG_MESSAGE_CB.lock().unwrap() = Some(cb);
+
+    unsafe {
+        gl::DebugMessageCallback(Some(debug_message_cb), null_mut());
+    }
+}
+
+pub fn set_debug_message_control(
+    source: Option<MessageSource>,
+    ty: Option<MessageType>,
+    severity: Option<MessageSeverity>,
+    ids: &[u32],
+    ids_action: MessageIdsAction,
+)
+{
+    // Ids shouldn't realistically be large enough to cause a panic here
+    let ids_len: i32 = ids.len().try_into().unwrap();
+
+    unsafe {
+        gl::DebugMessageControl(
+            source.map_or(gl::DONT_CARE, |source| source as u32),
+            ty.map_or(gl::DONT_CARE, |ty| ty as u32),
+            severity.map_or(gl::DONT_CARE, |severity| severity as u32),
+            ids_len,
+            ids.as_ptr(),
+            ids_action as u8,
+        );
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+#[allow(dead_code)]
+pub enum MessageIdsAction
+{
+    Enable = 1,
+    Disable = 0,
+}
+
+gl_enum! {
+pub enum MessageSource
+{
+    Api = gl::DEBUG_SOURCE_API,
+    WindowSystem = gl::DEBUG_SOURCE_WINDOW_SYSTEM,
+    ShaderCompiler = gl::DEBUG_SOURCE_SHADER_COMPILER,
+    ThirdParty = gl::DEBUG_SOURCE_THIRD_PARTY,
+    Application = gl::DEBUG_SOURCE_APPLICATION,
+    Other = gl::DEBUG_SOURCE_OTHER,
+}
+}
+
+gl_enum! {
+pub enum MessageType
+{
+    DeprecatedBehavior = gl::DEBUG_TYPE_DEPRECATED_BEHAVIOR,
+    Error = gl::DEBUG_TYPE_ERROR,
+    Marker = gl::DEBUG_TYPE_MARKER,
+    Other = gl::DEBUG_TYPE_OTHER,
+    Performance = gl::DEBUG_TYPE_PERFORMANCE,
+    PopGroup = gl::DEBUG_TYPE_POP_GROUP,
+    PushGroup = gl::DEBUG_TYPE_PUSH_GROUP,
+    Portability = gl::DEBUG_TYPE_PORTABILITY,
+    UndefinedBehavior = gl::DEBUG_TYPE_UNDEFINED_BEHAVIOR,
+}
+}
+
+gl_enum! {
+pub enum MessageSeverity
+{
+    High = gl::DEBUG_SEVERITY_HIGH,
+    Medium = gl::DEBUG_SEVERITY_MEDIUM,
+    Low = gl::DEBUG_SEVERITY_LOW,
+    Notification = gl::DEBUG_SEVERITY_NOTIFICATION,
+}
+}
+
+static DEBUG_MESSAGE_CB: Mutex<Option<MessageCallback>> = Mutex::new(None);
+
+extern "system" fn debug_message_cb(
+    source: gl::types::GLenum,
+    ty: gl::types::GLenum,
+    id: gl::types::GLuint,
+    severity: gl::types::GLenum,
+    message_length: gl::types::GLsizei,
+    message: *const gl::types::GLchar,
+    _user_param: *mut c_void,
+)
+{
+    // Unwinds are catched because unwinding from Rust code into foreign code is UB.
+    let res = catch_unwind(|| {
+        let cb_lock = DEBUG_MESSAGE_CB.lock().unwrap();
+
+        if let Some(cb) = *cb_lock {
+            let msg_source = MessageSource::from_gl(source).unwrap();
+            let msg_type = MessageType::from_gl(ty).unwrap();
+            let msg_severity = MessageSeverity::from_gl(severity).unwrap();
+
+            let msg_length = usize::try_from(message_length).unwrap();
+
+            // SAFETY: The received message should be a valid ASCII string
+            let message = unsafe {
+                std::str::from_utf8_unchecked(std::slice::from_raw_parts(
+                    message.cast(),
+                    msg_length,
+                ))
+            };
+
+            cb(msg_source, msg_type, id, msg_severity, message);
+        }
+    });
+
+    if res.is_err() {
+        // eprintln is not used since it can panic and unwinds are unwanted because
+        // unwinding from Rust code into foreign code is UB.
+        stderr()
+            .write_all(b"ERROR: Panic in debug message callback")
+            .ok();
+        println!();
+    }
+}
diff --git a/engine/src/opengl/mod.rs b/engine/src/opengl/mod.rs
index a58e72e..ce375f5 100644
--- a/engine/src/opengl/mod.rs
+++ b/engine/src/opengl/mod.rs
@@ -8,6 +8,11 @@ pub mod shader;
 pub mod vertex_array;
 pub mod vertex_buffer;
 
+mod util;
+
+#[cfg(feature = "debug")]
+pub mod debug;
+
 pub fn set_viewport(position: &Vec2<u32>, size: &WindowSize)
 {
     unsafe {
diff --git a/engine/src/opengl/util.rs b/engine/src/opengl/util.rs
new file mode 100644
index 0000000..e60778f
--- /dev/null
+++ b/engine/src/opengl/util.rs
@@ -0,0 +1,30 @@
+// May only be used when certain crate features are enabled
+#![allow(unused_macros, unused_imports)]
+
+macro_rules! gl_enum {
+    (
+        $visibility: vis enum $name: ident
+        {$(
+            $variant: ident = gl::$gl_enum: ident,
+        )+}
+    ) => {
+        #[derive(Debug, Clone, Copy)]
+        #[repr(u32)]
+        $visibility enum $name
+        {$(
+            $variant = gl::$gl_enum,
+        )+}
+
+        impl $name {
+            fn from_gl(num: gl::types::GLenum) -> Option<Self>
+            {
+                match num {
+                    $(gl::$gl_enum => Some(Self::$variant),)+
+                    _ => None
+                }
+            }
+        }
+    };
+}
+
+pub(crate) use gl_enum;
diff --git a/engine/src/renderer/mod.rs b/engine/src/renderer/mod.rs
index 4ed3c0a..cc1631f 100644
--- a/engine/src/renderer/mod.rs
+++ b/engine/src/renderer/mod.rs
@@ -3,6 +3,8 @@ use std::process::abort;
 
 use glfw::WindowSize;
 
+#[cfg(feature = "debug")]
+use crate::opengl::debug::{MessageSeverity, MessageSource, MessageType};
 use crate::opengl::shader::Program as ShaderProgram;
 use crate::opengl::vertex_array::{PrimitiveKind, VertexArray};
 use crate::opengl::vertex_buffer::{BufferUsage, VertexBuffer};
@@ -28,6 +30,22 @@ pub fn initialize(window: &glfw::Window) -> Result<(), Error>
         }
     });
 
+    #[cfg(feature = "debug")]
+    {
+        use crate::opengl::debug::{
+            enable_debug_output,
+            set_debug_message_callback,
+            set_debug_message_control,
+            MessageIdsAction,
+        };
+
+        enable_debug_output();
+
+        set_debug_message_callback(opengl_debug_message_cb);
+
+        set_debug_message_control(None, None, None, &[], MessageIdsAction::Disable);
+    }
+
     let window_size = window.size().map_err(Error::GetWindowSizeFailed)?;
 
     set_viewport(&Vec2 { x: 0, y: 0 }, &window_size);
@@ -35,6 +53,37 @@ pub fn initialize(window: &glfw::Window) -> Result<(), Error>
     Ok(())
 }
 
+#[cfg(feature = "debug")]
+#[tracing::instrument(skip_all)]
+fn opengl_debug_message_cb(
+    source: MessageSource,
+    ty: MessageType,
+    id: u32,
+    severity: MessageSeverity,
+    message: &str,
+)
+{
+    use tracing::{event, Level};
+
+    macro_rules! create_event {
+        ($level: expr) => {
+            event!($level, ?source, ?ty, id, ?severity, message);
+        };
+    }
+
+    match ty {
+        MessageType::Error => {
+            create_event!(Level::ERROR);
+        }
+        MessageType::Other => {
+            create_event!(Level::INFO);
+        }
+        _ => {
+            create_event!(Level::WARN);
+        }
+    };
+}
+
 pub fn render<'renderable>(renderables: impl IntoIterator<Item = &'renderable Renderable>)
 {
     clear_buffers(BufferClearMask::COLOR);