1 files changed, 47 insertions, 0 deletions
diff --git a/examples/statetracker/src/formatter.rs b/examples/statetracker/src/formatter.rs
new file mode 100644
index 0000000..4ceb68f
--- /dev/null
+++ b/examples/statetracker/src/formatter.rs
@@ -0,0 +1,47 @@
+use druid::text::{Formatter, Validation, ValidationError};
+
+pub struct U16Formatter;
+
+impl Formatter<u16> for U16Formatter {
+    fn format(&self, value: &u16) -> String {
+        value.to_string()
+    }
+
+    fn validate_partial_input(&self, input: &str, _sel: &druid::text::Selection) -> Validation {
+        if input.is_empty() {
+            return Validation::success();
+        }
+
+        if input.len() > 6 {
+            return Validation::failure(U16ValidationError::WrongNumberOfCharacters);
+        }
+
+        match input.parse::<u16>() {
+            Ok(_) => Validation::success(),
+            Err(err) => Validation::failure(err),
+        }
+    }
+
+    fn value(&self, input: &str) -> Result<u16, ValidationError> {
+        if input.is_empty() || input.len() > 5 {
+            return Err(ValidationError::new(
+                U16ValidationError::WrongNumberOfCharacters,
+            ));
+        }
+
+        input.parse().map_err(|err| ValidationError::new(err))
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum U16ValidationError {
+    WrongNumberOfCharacters,
+}
+
+impl std::fmt::Display for U16ValidationError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", std::any::type_name_of_val(self))
+    }
+}
+
+impl std::error::Error for U16ValidationError {}