eframe web: access app from WebHandle (#1886)

Co-authored-by: Stanislav <enomado@users.noreply.github.com>
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

crates/eframe/src/epi.rs

@@ -6,6 +6,9 @@
 
 #![warn(missing_docs)] // Let's keep `epi` well-documented.
 
+#[cfg(target_arch = "wasm32")]
+use std::any::Any;
+
 #[cfg(not(target_arch = "wasm32"))]
 pub use crate::native::run::RequestRepaintEvent;
 #[cfg(not(target_arch = "wasm32"))]
@@ -66,6 +69,15 @@ pub trait App {
     /// To force a repaint, call [`egui::Context::request_repaint`] at any time (e.g. from another thread).
     fn update(&mut self, ctx: &egui::Context, frame: &mut Frame);
 
+    /// Handle to the app.
+    ///
+    /// Can be used from web to interact or other external context
+    /// Implementation is needed, because downcasting Box<dyn App> -> Box<dyn Any> to get &ConcreteApp is not simple in current rust.
+    ///
+    /// Just return &mut *self
+    #[cfg(target_arch = "wasm32")]
+    fn as_any_mut(&mut self) -> &mut dyn Any;
+
     /// Called on shutdown, and perhaps at regular intervals. Allows you to save state.
     ///
     /// Only called when the "persistence" feature is enabled.

crates/eframe/src/web/backend.rs

@@ -265,6 +265,11 @@ impl AppRunner {
         &self.egui_ctx
     }
 
+    /// Get mutable access to the concrete [`App`] we enclose.
+    pub fn app_mut<ConreteApp: 'static + crate::App>(&mut self) -> &mut ConreteApp {
+        self.app.as_any_mut().downcast_mut::<ConreteApp>().unwrap()
+    }
+
     pub fn auto_save(&mut self) {
         let now = now_sec();
         let time_since_last_save = now - self.last_save_time;

crates/egui_demo_app/src/apps/custom3d_glow.rs

@@ -1,5 +1,8 @@
 use std::sync::Arc;
 
+#[cfg(target_arch = "wasm32")]
+use core::any::Any;
+
 use eframe::egui_glow;
 use egui::mutex::Mutex;
 use egui_glow::glow;
@@ -48,6 +51,11 @@ impl eframe::App for Custom3d {
             self.rotating_triangle.lock().destroy(gl);
         }
     }
+
+    #[cfg(target_arch = "wasm32")]
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        &mut *self
+    }
 }
 
 impl Custom3d {

crates/egui_demo_app/src/apps/custom3d_wgpu.rs

@@ -1,5 +1,8 @@
 use std::sync::Arc;
 
+#[cfg(target_arch = "wasm32")]
+use core::any::Any;
+
 use eframe::{
     egui_wgpu::{self, wgpu},
     wgpu::util::DeviceExt,
@@ -117,6 +120,11 @@ impl eframe::App for Custom3d {
                 });
         });
     }
+
+    #[cfg(target_arch = "wasm32")]
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        &mut *self
+    }
 }
 
 impl Custom3d {

crates/egui_demo_app/src/apps/http_app.rs

@@ -1,6 +1,9 @@
 use egui_extras::RetainedImage;
 use poll_promise::Promise;
 
+#[cfg(target_arch = "wasm32")]
+use core::any::Any;
+
 struct Resource {
     /// HTTP response
     response: ehttp::Response,
@@ -106,6 +109,11 @@ impl eframe::App for HttpApp {
             }
         });
     }
+
+    #[cfg(target_arch = "wasm32")]
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        &mut *self
+    }
 }
 
 fn ui_url(ui: &mut egui::Ui, frame: &mut eframe::Frame, url: &mut String) -> bool {

crates/egui_demo_app/src/lib.rs

@@ -32,7 +32,6 @@ pub struct WebHandle {
 #[wasm_bindgen]
 impl WebHandle {
     #[wasm_bindgen]
-    #[cfg(target_arch = "wasm32")]
     pub fn stop_web(&self) -> Result<(), wasm_bindgen::JsValue> {
         let mut app = self.handle.lock();
         let res = app.destroy();
@@ -43,6 +42,12 @@ impl WebHandle {
 
         res
     }
+
+    #[wasm_bindgen]
+    pub fn set_some_content_from_javasript(&mut self, _some_data: &str) {
+        let _app = self.handle.lock().app_mut::<WrapApp>();
+        // _app.data = some_data;
+    }
 }
 
 #[cfg(target_arch = "wasm32")]

crates/egui_demo_app/src/wrap_app.rs

@@ -3,6 +3,9 @@ use egui_demo_lib::is_mobile;
 #[cfg(feature = "glow")]
 use eframe::glow;
 
+#[cfg(target_arch = "wasm32")]
+use core::any::Any;
+
 #[derive(Default)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 struct EasyMarkApp {
@@ -13,6 +16,11 @@ impl eframe::App for EasyMarkApp {
     fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
         self.editor.panels(ctx);
     }
+
+    #[cfg(target_arch = "wasm32")]
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        &mut *self
+    }
 }
 
 // ----------------------------------------------------------------------------
@@ -27,6 +35,11 @@ impl eframe::App for DemoApp {
     fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
         self.demo_windows.ui(ctx);
     }
+
+    #[cfg(target_arch = "wasm32")]
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        &mut *self
+    }
 }
 
 // ----------------------------------------------------------------------------
@@ -46,6 +59,11 @@ impl eframe::App for FractalClockApp {
                     .ui(ui, Some(crate::seconds_since_midnight()));
             });
     }
+
+    #[cfg(target_arch = "wasm32")]
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        &mut *self
+    }
 }
 
 // ----------------------------------------------------------------------------
@@ -70,6 +88,11 @@ impl eframe::App for ColorTestApp {
             });
         });
     }
+
+    #[cfg(target_arch = "wasm32")]
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        &mut *self
+    }
 }
 
 // ----------------------------------------------------------------------------
@@ -225,6 +248,11 @@ impl eframe::App for WrapApp {
             custom3d.on_exit(gl);
         }
     }
+
+    #[cfg(target_arch = "wasm32")]
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        &mut *self
+    }
 }
 
 impl WrapApp {

examples/custom_3d_three-d/src/main.rs

@@ -70,6 +70,11 @@ impl eframe::App for MyApp {
             });
         });
     }
+
+    #[cfg(target_arch = "wasm32")]
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        &mut *self
+    }
 }
 
 /// We get a [`glow::Context`] from `eframe` and we want to construct a [`ThreeDApp`].