avm1: Add EditText variable property

Add `EditText::variable` as well as `TextField.variable` property.
This commit only adds the getter/setter and does not yet add the
binding functionality.

core/src/avm1/globals/text_field.rs

@@ -312,6 +312,46 @@ pub fn set_multiline<'gc>(
     Ok(Value::Undefined.into())
 }
 
+fn variable<'gc>(
+    _avm: &mut Avm1<'gc>,
+    _context: &mut UpdateContext<'_, 'gc, '_>,
+    this: Object<'gc>,
+    _args: &[Value<'gc>],
+) -> Result<ReturnValue<'gc>, Error<'gc>> {
+    if let Some(etext) = this
+        .as_display_object()
+        .and_then(|dobj| dobj.as_edit_text())
+    {
+        if let Some(variable) = etext.variable() {
+            return Ok(variable.to_string().into());
+        }
+    }
+
+    // Unset `variable` retuns null, not undefined
+    Ok(Value::Null.into())
+}
+
+fn set_variable<'gc>(
+    avm: &mut Avm1<'gc>,
+    context: &mut UpdateContext<'_, 'gc, '_>,
+    this: Object<'gc>,
+    args: &[Value<'gc>],
+) -> Result<ReturnValue<'gc>, Error<'gc>> {
+    let variable = match args.get(0) {
+        None | Some(Value::Undefined) | Some(Value::Null) => None,
+        Some(v) => Some(v.coerce_to_string(avm, context)?),
+    };
+
+    if let Some(etext) = this
+        .as_display_object()
+        .and_then(|dobj| dobj.as_edit_text())
+    {
+        etext.set_variable(variable.map(|v| v.into_owned()), context);
+    }
+
+    Ok(Value::Undefined.into())
+}
+
 pub fn word_wrap<'gc>(
     _avm: &mut Avm1<'gc>,
     _context: &mut UpdateContext<'_, 'gc, '_>,
@@ -469,6 +509,13 @@ pub fn attach_virtual_properties<'gc>(gc_context: MutationContext<'gc, '_>, obje
         Some(Executable::Native(set_multiline)),
         ReadOnly.into(),
     );
+    object.add_property(
+        gc_context,
+        "variable",
+        Executable::Native(variable),
+        Some(Executable::Native(set_variable)),
+        DontDelete | ReadOnly | DontEnum,
+    );
     object.add_property(
         gc_context,
         "wordWrap",

core/src/display_object/edit_text.rs

@@ -12,7 +12,7 @@ use crate::tag_utils::SwfMovie;
 use crate::transform::Transform;
 use crate::xml::XMLDocument;
 use gc_arena::{Collect, Gc, GcCell, MutationContext};
-use std::sync::Arc;
+use std::{cell::Ref, sync::Arc};
 use swf::Twips;
 
 /// Boxed error type.
@@ -99,6 +99,9 @@ pub struct EditTextData<'gc> {
 
     /// The AVM1 object handle
     object: Option<Object<'gc>>,
+
+    /// The variable path that this text field is bound to (AVM1 only).
+    variable: Option<String>,
 }
 
 impl<'gc> EditText<'gc> {
@@ -146,6 +149,12 @@ impl<'gc> EditText<'gc> {
         base.matrix_mut(context.gc_context).tx = bounds.x_min;
         base.matrix_mut(context.gc_context).ty = bounds.y_min;
 
+        let variable = if !swf_tag.variable_name.is_empty() {
+            Some(swf_tag.variable_name.clone())
+        } else {
+            None
+        };
+
         let et = EditText(GcCell::allocate(
             context.gc_context,
             EditTextData {
@@ -169,6 +178,7 @@ impl<'gc> EditText<'gc> {
                 intrinsic_bounds,
                 bounds,
                 autosize: AutoSizeMode::None,
+                variable,
             },
         ));
 
@@ -405,6 +415,26 @@ impl<'gc> EditText<'gc> {
         base_width
     }
 
+    /// Returns the variable that this text field is bound to.
+    pub fn variable(&self) -> Option<Ref<str>> {
+        let text = self.0.read();
+        if text.variable.is_some() {
+            Some(Ref::map(text, |text| text.variable.as_deref().unwrap()))
+        } else {
+            None
+        }
+    }
+
+    pub fn set_variable(self, variable: Option<String>, context: &mut UpdateContext<'_, 'gc, '_>) {
+        self.0.write(context.gc_context).variable = variable
+    }
+
+    /// Construct a base text transform for this `EditText`, to be used for
+    /// evaluating fonts.
+    ///
+    /// The `text_transform` constitutes the base transform that all text is
+    /// written into.
+
     /// Redraw the border of this `EditText`.
     fn redraw_border(self, context: MutationContext<'gc, '_>) {
         let mut write = self.0.write(context);