provide nicer error types

packages/html/src/events/mounted.rs

@@ -2,30 +2,34 @@
 
 use euclid::Rect;
 
-use std::{any::Any, rc::Rc};
+use std::{
+    any::Any,
+    fmt::{Display, Formatter},
+    rc::Rc,
+};
 
 /// An Element that has been rendered and allows reading and modifying information about it.
 ///
 /// Different platforms will have different implementations and different levels of support for this trait. Renderers that do not support specific features will return `None` for those queries.
 pub trait RenderedElementBacking {
     /// Get the renderer specific element for the given id
-    fn get_raw_element(&self) -> Option<&dyn Any> {
-        None
+    fn get_raw_element(&self) -> MountedResult<&dyn Any> {
+        Err(MountedError::NotSupported)
     }
 
     /// Get the bounding rectangle of the element relative to the viewport (this does not include the scroll position)
-    fn get_client_rect(&self) -> Option<Rect<f64, f64>> {
-        None
+    fn get_client_rect(&self) -> MountedResult<Rect<f64, f64>> {
+        Err(MountedError::NotSupported)
     }
 
     /// Scroll to make the element visible
-    fn scroll_to(&self, _behavior: ScrollBehavior) -> Option<()> {
-        None
+    fn scroll_to(&self, _behavior: ScrollBehavior) -> MountedResult<()> {
+        Err(MountedError::NotSupported)
     }
 
     /// Set the focus on the element
-    fn set_focus(&self, _focus: bool) -> Option<()> {
-        None
+    fn set_focus(&self, _focus: bool) -> MountedResult<()> {
+        Err(MountedError::NotSupported)
     }
 }
 
@@ -53,22 +57,22 @@ impl MountedData {
     }
 
     /// Get the renderer specific element for the given id
-    pub fn get_raw_element(&self) -> Option<&dyn Any> {
+    pub fn get_raw_element(&self) -> MountedResult<&dyn Any> {
         self.inner.get_raw_element()
     }
 
     /// Get the bounding rectangle of the element relative to the viewport (this does not include the scroll position)
-    pub fn get_client_rect(&self) -> Option<Rect<f64, f64>> {
+    pub fn get_client_rect(&self) -> MountedResult<Rect<f64, f64>> {
         self.inner.get_client_rect()
     }
 
     /// Scroll to make the element visible
-    pub fn scroll_to(&self, behavior: ScrollBehavior) -> Option<()> {
+    pub fn scroll_to(&self, behavior: ScrollBehavior) -> MountedResult<()> {
         self.inner.scroll_to(behavior)
     }
 
     /// Set the focus on the element
-    pub fn set_focus(&self, focus: bool) -> Option<()> {
+    pub fn set_focus(&self, focus: bool) -> MountedResult<()> {
         self.inner.set_focus(focus)
     }
 }
@@ -83,3 +87,30 @@ impl_event! [
     /// mounted
     onmounted
 ];
+
+/// The MountedResult type for the MountedData
+pub type MountedResult<T> = Result<T, MountedError>;
+
+#[derive(Debug)]
+/// The error type for the MountedData
+pub enum MountedError {
+    /// The renderer does not support the requested operation
+    NotSupported,
+    /// The element was not found
+    OperationFailed(Box<dyn std::error::Error>),
+}
+
+impl Display for MountedError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            MountedError::NotSupported => {
+                write!(f, "The renderer does not support the requested operation")
+            }
+            MountedError::OperationFailed(e) => {
+                write!(f, "The operation failed: {}", e)
+            }
+        }
+    }
+}
+
+impl std::error::Error for MountedError {}