Copy doesn't work on Safari

[abey79]

Describe the bug

Copying text from https://egui.rs (e.g. from the text edit widget) or indeed Rerun web doesn't work on Safari. This is particularly annoying for Rerun's new Quick Start guide's code block, which are meant to be copied by the user.

To Reproduce

1. Go to https://egui.rs -> Widget Gallery
2. Enter text in the TextEdit widget
3. Select and copy that text

=> beeps and generate the following error in the console:

ERROR: [eframe::web] eframe/src/web/mod.rs:199: Copy/cut action failed: JsValue(NotAllowedError: The request is not allowed by the user agent or the platform in the current context, possibly because the user denied permission.
writeText@[native code]
@https://www.egui.rs/egui_demo_app.js:941:46
<?>.wasm-function[644]@[wasm code]
<?>.wasm-function[516]@[wasm code]
<?>.wasm-function[2521]@[wasm code]
__wbg_adapter_30@https://www.egui.rs/egui_demo_app.js:226:136
real@https://www.egui.rs/egui_demo_app.js:209:21)

Desktop (please complete the following information):

• OS: macOS Sonoma 14.0
• Browser: Safari 17.0

Related to:

• cannot paste into text fields from mobile safari #501

[lunixbochs]

Triaging this issue, looking to fix it.

1. Copy hits this event listener (and cut the one above it): https://github.com/emilk/egui/blob/0.23.0/crates/eframe/src/web/events.rs#L184
2. repaint_asap is indirect. It just updates NeedsRepaint. This means the "copy" and "cut" document event handlers return without egui actually touching the clipboard. https://github.com/emilk/egui/blob/0.23.0/crates/eframe/src/web/backend.rs#L72
3. Safari probably wants you to access the clipboard during the copy event, in direct response to user input. Instead the clipboard write probably comes from the next rendering tick. This is blocked by security policy.

Here's a better traceback:

ERROR: [eframe::web] eframe/src/web/mod.rs:200: Copy/cut action failed: JsValue(NotAllowedError: The request is not allowed by the user agent or the platform in the current context, possibly because the user denied permission.
writeText@[native code]
@http://127.0.0.1:8080/project-5a43784c0edafe62.js:793:46
<?>.wasm-function[web_sys::features::gen_Clipboard::Clipboard::write_text::h3336955eaeb60a58]@[wasm code]
<?>.wasm-function[eframe::web::set_clipboard_text::he6e87b49ba08fe1b]@[wasm code]
<?>.wasm-function[eframe::web::app_runner::AppRunner::logic::hcf05f7e86b369dbf]@[wasm code]
<?>.wasm-function[eframe::web::events::paint_and_schedule::h38124beb8785c431]@[wasm code]
<?>.wasm-function[<T as wasm_bindgen::closure::WasmClosureFnOnce<(),R>>::into_fn_mut::{{closure}}::hfd84448ff0d2d845]@[wasm code]
<?>.wasm-function[<dyn core::ops::function::FnMut<()>+Output = R as wasm_bindgen::closure::WasmClosure>::describe::invoke::h1d4dabdf8919906c]@[wasm code]
__wbg_adapter_27@http://127.0.0.1:8080/project-5a43784c0edafe62.js:223:136
real@http://127.0.0.1:8080/project-5a43784c0edafe62.js:202:21)