From 65bce20d43670d23f433ac11f49f10d2011474b6 Mon Sep 17 00:00:00 2001
From: HampusM <hampus@hampusmat.com>
Date: Sun, 19 Jul 2026 16:30:58 +0200
Subject: feat(engine): add location path to shader binding validation error

---
 engine/Cargo.toml                     |   1 +
 engine/src/rendering/shader/cursor.rs | 103 +++++++++++++++++++++++++++++-----
 2 files changed, 91 insertions(+), 13 deletions(-)

(limited to 'engine')

diff --git a/engine/Cargo.toml b/engine/Cargo.toml
index fa30dd0..df29fd3 100644
--- a/engine/Cargo.toml
+++ b/engine/Cargo.toml
@@ -14,6 +14,7 @@ paste = "1.0.14"
 safer-ffi = "0.1.13"
 crossbeam-queue = "0.3.12"
 parking_lot = "0.12.3"
+circular-buffer = "2.0.0"
 engine-macros = { workspace = true }
 engine-ecs = { workspace = true }
 engine-reflection = { workspace = true }
diff --git a/engine/src/rendering/shader/cursor.rs b/engine/src/rendering/shader/cursor.rs
index 32dee00..ba8bed7 100644
--- a/engine/src/rendering/shader/cursor.rs
+++ b/engine/src/rendering/shader/cursor.rs
@@ -1,5 +1,9 @@
+use std::borrow::Cow;
+use std::fmt::Display;
 use std::hint::cold_path;
 
+use circular_buffer::FixedCircularBuffer;
+
 use crate::color::Color;
 use crate::data_types::matrix::Matrix;
 use crate::data_types::vector::Vec3;
@@ -18,6 +22,7 @@ pub struct Cursor<'a>
 {
     type_layout: TypeLayout<'a>,
     binding_location: BindingLocation,
+    location_path: LocationPath,
 }
 
 impl<'a> Cursor<'a>
@@ -33,12 +38,16 @@ impl<'a> Cursor<'a>
         Self {
             type_layout: var_layout.type_layout().unwrap(),
             binding_location,
+            location_path: LocationPath::default(),
         }
     }
 
-    pub fn field(&self, name: &str) -> Self
+    pub fn field(&self, name: impl Into<Cow<'static, str>>) -> Self
     {
-        let Some(field_var_layout) = self.type_layout.get_field_by_name(name) else {
+        let name = name.into();
+
+        let Some(field_var_layout) = self.type_layout.get_field_by_name(name.as_ref())
+        else {
             panic!("Field '{name}' does not exist");
         };
 
@@ -59,6 +68,10 @@ impl<'a> Cursor<'a>
             type_kind => unimplemented!("Type kind {type_kind:?} is not yet supported"),
         };
 
+        let mut location_path = self.location_path.clone();
+
+        location_path.push(Location::Field(name));
+
         Self {
             type_layout: field_var_layout.type_layout().unwrap(),
             binding_location: BindingLocation {
@@ -76,6 +89,7 @@ impl<'a> Cursor<'a>
                 byte_offset: self.binding_location.byte_offset
                     + field_var_layout.offset(),
             },
+            location_path,
         }
     }
 
@@ -87,19 +101,14 @@ impl<'a> Cursor<'a>
 
         self.type_layout = element_type_layout;
 
-        self
-    }
-
-    pub fn with_field(self, name: &str, func: impl FnOnce(Self) -> Self) -> Self
-    {
-        let _ = func(self.field(name));
+        self.location_path.push(Location::Element(index));
 
         self
     }
 
     pub fn binding(self, value: BindingValue) -> Result<Binding, BindingError>
     {
-        value.validate_for_shader_type(self.type_layout)?;
+        value.validate_for_shader_type(self.type_layout, self.location_path)?;
 
         Ok(Binding {
             location: self.binding_location,
@@ -113,6 +122,66 @@ impl<'a> Cursor<'a>
     }
 }
 
+/// Shader cursor location.
+#[derive(Debug, Clone, Default)]
+pub struct LocationPath
+{
+    locations: FixedCircularBuffer<Location, 16>,
+    is_truncated: bool,
+}
+
+impl LocationPath
+{
+    fn push(&mut self, location: Location)
+    {
+        if self.locations.push_back(location).is_some() {
+            self.is_truncated = true;
+        }
+    }
+}
+
+impl Display for LocationPath
+{
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
+    {
+        if self.is_truncated {
+            write!(formatter, "(...)")?;
+        }
+
+        for location in &self.locations {
+            match location {
+                Location::Field(field) => {
+                    write!(formatter, ".{field}")?;
+                }
+                Location::Element(element) => {
+                    write!(formatter, "[{element}]")?;
+                }
+            }
+        }
+
+        Ok(())
+    }
+}
+
+/// Shader cursor location.
+#[derive(Debug, Clone)]
+pub enum Location
+{
+    Field(Cow<'static, str>),
+    Element(usize),
+}
+
+impl Display for Location
+{
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
+    {
+        match self {
+            Self::Field(field) => <Cow<'static, str> as Display>::fmt(field, formatter),
+            Self::Element(element) => <usize as Display>::fmt(element, formatter),
+        }
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct BindingLocation
 {
@@ -135,7 +204,11 @@ pub enum BindingValue
 
 impl BindingValue
 {
-    fn validate_for_shader_type(&self, ty: TypeLayout<'_>) -> Result<(), BindingError>
+    fn validate_for_shader_type(
+        &self,
+        ty: TypeLayout<'_>,
+        location_path: LocationPath,
+    ) -> Result<(), BindingError>
     {
         match (
             self,
@@ -205,7 +278,10 @@ impl BindingValue
             }
             _ => {
                 cold_path();
-                Err(BindingError::IncorrectValueType { value: self.clone() })
+                Err(BindingError::IncorrectValueType {
+                    value: self.clone(),
+                    location_path,
+                })
             }
         }
     }
@@ -271,9 +347,10 @@ pub struct Binding
 #[non_exhaustive]
 pub enum BindingError
 {
-    #[error("Value {value:?} has incorrect type for shader binding location")]
+    #[error("Value {value:?} has incorrect type for value at {location_path} in shader")]
     IncorrectValueType
     {
-        value: BindingValue
+        value: BindingValue,
+        location_path: LocationPath,
     },
 }
-- 
cgit v1.2.3-18-g5258