bug fixes & improvements & missing features & font loader

layout-engine/src/font_provider.rs

@@ -0,0 +1,51 @@
+use crate::font_meta::FontFamilyInfo;
+use crate::FontData;
+
+/// Font resolution trait — host apps implement this to provide fonts.
+/// Backend implements it with a file-based registry, WASM side with API fetching.
+pub trait FontProvider: Send + Sync {
+    /// List all available font families with their variants.
+    fn list_families(&self) -> Vec<FontFamilyInfo>;
+
+    /// Load a specific font variant. Returns None if not found.
+    fn load_font(&self, family: &str, weight: u16, italic: bool) -> Option<FontData>;
+
+    /// The default/fallback font family name.
+    fn default_family(&self) -> &str {
+        "Noto Sans"
+    }
+
+    /// Load all variants of the given families. Falls back to default family if a family is not found.
+    /// Always includes the default family.
+    fn load_families(&self, families: &[String]) -> Vec<FontData> {
+        let mut result = Vec::new();
+        let mut loaded_families = std::collections::HashSet::new();
+
+        // Always include default family
+        let mut all_families: Vec<String> = vec![self.default_family().to_string()];
+        for f in families {
+            if !all_families.iter().any(|af| af.eq_ignore_ascii_case(f)) {
+                all_families.push(f.clone());
+            }
+        }
+
+        for family in &all_families {
+            let family_lower = family.to_lowercase();
+            if loaded_families.contains(&family_lower) {
+                continue;
+            }
+
+            let infos = self.list_families();
+            if let Some(info) = infos.iter().find(|i| i.family.to_lowercase() == family_lower) {
+                for variant in &info.variants {
+                    if let Some(fd) = self.load_font(&info.family, variant.weight, variant.italic) {
+                        result.push(fd);
+                    }
+                }
+                loaded_families.insert(family_lower);
+            }
+        }
+
+        result
+    }
+}