completely redesign philosofy of this library

canvas/src/data_provider.rs

@@ -0,0 +1,47 @@
+// src/data_provider.rs
+//! Simplified user interface - only business data, no UI state
+
+use anyhow::Result;
+use async_trait::async_trait;
+
+/// User implements this - only business data, no UI state
+pub trait DataProvider {
+    /// How many fields in the form
+    fn field_count(&self) -> usize;
+    
+    /// Get field label/name
+    fn field_name(&self, index: usize) -> &str;
+    
+    /// Get field value  
+    fn field_value(&self, index: usize) -> &str;
+    
+    /// Set field value (library calls this when text changes)
+    fn set_field_value(&mut self, index: usize, value: String);
+    
+    /// Check if field supports autocomplete (optional)
+    fn supports_autocomplete(&self, _field_index: usize) -> bool {
+        false
+    }
+    
+    /// Get display value (for password masking, etc.) - optional
+    fn display_value(&self, index: usize) -> Option<&str> {
+        None // Default: use actual value
+    }
+}
+
+/// Optional: User implements this for autocomplete data
+#[async_trait]
+pub trait AutocompleteProvider {
+    type SuggestionData: Clone + Send + 'static;
+    
+    /// Fetch autocomplete suggestions (user's business logic)
+    async fn fetch_suggestions(&mut self, field_index: usize, query: &str) 
+        -> Result<Vec<SuggestionItem<Self::SuggestionData>>>;
+}
+
+#[derive(Debug, Clone)]
+pub struct SuggestionItem<T> {
+    pub data: T,
+    pub display_text: String,
+    pub value_to_store: String,
+}