svg-filters: get bare basic xml generation going

crates/svg-filters/src/types/nodes/primitives/blend.rs

@@ -1,6 +1,6 @@
 /// [feBlend](https://www.w3.org/TR/SVG11/filters.html#feBlendElement)
 #[derive(Debug)]
-pub(in crate::types::nodes) struct Blend {
+pub struct Blend {
     mode: BlendMode,
 }
 

crates/svg-filters/src/types/nodes/primitives/color_matrix.rs

@@ -1,3 +1,9 @@
+use std::borrow::Cow;
+
+use quick_xml::{events::attributes::Attribute, name::QName, se::to_string};
+
+use super::WriteElement;
+
 /// [feColorMatrix](https://www.w3.org/TR/SVG11/filters.html#feColorMatrixElement)
 #[derive(Debug)]
 pub struct ColorMatrix {
@@ -10,6 +16,34 @@ impl ColorMatrix {
     }
 }
 
+impl WriteElement for ColorMatrix {
+    fn attrs(&self) -> Vec<quick_xml::events::attributes::Attribute> {
+        match &self.cm_type {
+            ColorMatrixType::Matrix(v) => vec![Attribute {
+                key: QName(b"values"),
+                value: Cow::from(
+                    v.iter()
+                        .map(|v| v.to_string())
+                        .reduce(|mut acc, e| {
+                            acc.push(' ');
+                            acc.push_str(&e);
+                            acc
+                        })
+                        .expect("Should be able to concatenate the thingies")
+                        .into_bytes(),
+                ),
+            }],
+            ColorMatrixType::Saturate(v) => todo!(),
+            ColorMatrixType::HueRotate(v) => todo!(),
+            ColorMatrixType::LuminanceToAlpha => todo!(),
+        }
+    }
+
+    fn tag_name(&self) -> &'static str {
+        "feColorMatrix"
+    }
+}
+
 #[derive(Debug)]
 pub enum ColorMatrixType {
     Matrix(Box<[f32; 20]>),