fix(ltk_ritobin): transpose Mat4 for correct row-major text output

[budlibu500]

Changes

• Add .transpose() in the ritobin text writer before to_cols_array() so matrices are output in row-major order
• Add .transpose() in the ritobin text parser after from_cols_array() to convert row-major text input into glam's column-major Mat4

Root Cause
The text writer called to_cols_array() without transposing, outputting column-major order instead of row-major. Translation values appeared in the wrong row.
The binary reader/writer already handle this correctly — only the text path was missing it.

[alanpq]

Agreed — keeping Mat4 and just transposing/reordering is cleaner than switching to [f32; 16].

The PR needs to be reworded/renamed to match the new changes — but other than that it LGTM — Let's keep cooking 🔥 🚀

[Crauzer]

Can you also write tests to make sure that the ordering is correct when doing a parsing round-trip ?

[Crauzer]

I think this might be in reverse ?

[Copilot]

Pull request overview

Fixes mtx44 handling in the ritobin text path so glam::Mat4 values are written and read in row-major order (matching the text format expectations), by transposing at the serialization/deserialization boundaries.

Changes:

• Transpose Mat4 before to_cols_array() when writing text to emit row-major ordering.
• Transpose Mat4 after from_cols_array() when parsing text to convert row-major input into glam’s column-major representation.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
crates/ltk_ritobin/src/writer.rs	Adjusts mtx44 text output to row-major order via transpose-before-write.
crates/ltk_ritobin/src/parser.rs	Adjusts mtx44 text parsing to interpret row-major input via transpose-after-read.

---

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[Copilot]

The matrix text serialization order is subtle (ritobin text appears to be row-major while glam::Mat4 is column-major). Please add an inline comment here explaining why .transpose() is required before to_cols_array() so future refactors don’t accidentally remove/double-apply it.

Suggested change

	self.indent();
	self.indent();
	// ritobin text stores matrices in row-major order, but glam::Mat4 is column-major.
	// Transpose before to_cols_array() so the serialized values are written row by row.

[Copilot]

This change fixes a correctness issue in matrix formatting, but there are no tests covering mtx44 write behavior. Please add a unit/integration test that writes a known Mat4 (e.g., a translation matrix) and asserts the emitted 16 floats are in the expected row-major order (and/or that parse->write roundtrips preserve the matrix).

[Copilot]

Similar to the writer side, please document why this .transpose() is necessary (row-major text input vs glam::Mat4 column-major storage). Without a note, it’s easy to remove this during cleanup and reintroduce the bug.

Suggested change

	// The text format stores the 16 matrix elements in row-major order, but
	// `Mat4::from_cols_array` interprets the slice as column-major. Transpose
	// here to convert from the row-major input layout to glam's column-major
	// internal storage. Without this, matrices will be interpreted incorrectly.

[Copilot]

There are parser tests for several value kinds, but none for mtx44. Please add a test that parses a row-major 4x4 (ideally one with non-symmetric values, e.g. translation + scaling) and asserts the resulting Mat4 matches the expected transform; this will lock in the corrected transpose behavior.

Suggested change

	#[cfg(test)]
	mod mtx44_tests {
	use super::{parse_mtx44, Span};
	use glam::{Mat4, Quat, Vec3};
	#[test]
	fn parse_mtx44_row_major_translation_and_scaling() {
	// Construct an expected transform using glam's column-major API:
	// scaling (2, 3, 4) and translation (10, 20, 30), with no rotation.
	let scale = Vec3::new(2.0, 3.0, 4.0);
	let translation = Vec3::new(10.0, 20.0, 30.0);
	let expected: Mat4 =
	Mat4::from_scale_rotation_translation(scale, Quat::IDENTITY, translation);
	// Derive a row-major representation of `expected`.
	// `to_cols_array` returns column-major elements of its receiver,
	// so using `expected.transpose()` yields the rows of `expected`.
	let row_major = expected.transpose().to_cols_array();
	// Format the row-major values into the text format expected by `parse_mtx44`.
	let input_str = format!(
	"{{ {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {} }}",
	row_major[0],
	row_major[1],
	row_major[2],
	row_major[3],
	row_major[4],
	row_major[5],
	row_major[6],
	row_major[7],
	row_major[8],
	row_major[9],
	row_major[10],
	row_major[11],
	row_major[12],
	row_major[13],
	row_major[14],
	row_major[15],
	);
	let span = Span::new(&input_str);
	let (remaining, parsed) = parse_mtx44(span).expect("parse_mtx44 should succeed");
	// Ensure we've consumed all significant input.
	assert!(remaining.fragment().trim().is_empty());
	// The parsed matrix should match the original column-major transform.
	assert_eq!(parsed, expected);
	}
	}