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OnMessage trait #257

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OnMessage trait #257

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8df442d
Remove outdated TODO
dhardy Nov 4, 2021
79da5d5
Remove #[widget(update = f)] property
dhardy Nov 4, 2021
e924867
Add OnMessage trait
dhardy Nov 4, 2021
e3724e5
Remove per-widget handler; start migration to OnMessage
dhardy Nov 5, 2021
5286ba8
TODO comments
dhardy Nov 8, 2021
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2 changes: 1 addition & 1 deletion crates/kas-core/src/event/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -97,7 +97,7 @@ pub use enums::{CursorIcon, ModifiersState, MouseButton, VirtualKeyCode};
pub use events::*;
pub use handler::{Handler, SendEvent};
pub use manager::{ConfigureManager, GrabMode, Manager, ManagerState};
pub use response::Response;
pub use response::{OnMessage, Response};
pub use update::UpdateHandle;

/// A type supporting a small number of key bindings
Expand Down
43 changes: 42 additions & 1 deletion crates/kas-core/src/event/response.rs
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Expand Up @@ -5,8 +5,9 @@

//! Event handling: Response type

use super::VoidResponse;
use super::{Manager, VoidResponse};
use crate::geom::{Offset, Rect};
use crate::Widget;

/// Response type from [`Handler::handle`].
///
Expand Down Expand Up @@ -149,3 +150,43 @@ impl<M> From<M> for Response<M> {
Response::Msg(msg)
}
}

/// Configurable message converter / handler
///
/// Parent widgets are expected to implement this to handle or convert messages
/// from child widgets, excepting where the parent and child message types are
/// equal (which is implemented as pass-through).
pub trait OnMessage<M>: Widget {
/// Called on a widget:
///
/// - `mgr`: the event manager
/// - `index`: index of child widget
/// - `msg`: message from child
fn on_msg(&mut self, mgr: &mut Manager, index: usize, msg: M) -> Response<Self::Msg>;
}

// TODO: This impl is required, yet falsely reported to cause conflicts
// Bug report: https://github.com/rust-lang/rust/issues/90587
impl<W: Widget, M: Into<W::Msg>> OnMessage<M> for W {
#[inline]
fn on_msg(&mut self, _mgr: &mut Manager, _index: usize, msg: M) -> Response<W::Msg> {
Response::Msg(msg.into())
}
}

// Below alternatives are not viable: some widgets like CheckBox are generic
// over M and required implementations hit the same conflict.

// impl<W: Widget> OnMessage<VoidMsg> for W {
// #[inline]
// fn on_msg(&mut self, _: &mut Manager, _: usize, _: VoidMsg) -> Response<W::Msg> {
// Response::None
// }
// }

// impl<W: Widget> OnMessage<W::Msg> for W {
// #[inline]
// fn on_msg(&mut self, _: &mut Manager, _: usize, msg: W::Msg) -> Response<W::Msg> {
// Response::Msg(msg)
// }
// }
2 changes: 1 addition & 1 deletion crates/kas-core/src/prelude.rs
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Expand Up @@ -20,7 +20,7 @@ pub use crate::draw::{
};
#[doc(no_inline)]
pub use crate::event::{
Event, Handler, Manager, ManagerState, Response, SendEvent, UpdateHandle, VoidMsg,
Event, Handler, Manager, ManagerState, OnMessage, Response, SendEvent, UpdateHandle, VoidMsg,
};
#[doc(no_inline)]
pub use crate::geom::{Coord, Offset, Rect, Size};
Expand Down
63 changes: 1 addition & 62 deletions crates/kas-macros/src/args.rs
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Expand Up @@ -219,7 +219,6 @@ mod kw {
custom_keyword!(map_msg);
custom_keyword!(use_msg);
custom_keyword!(discard_msg);
custom_keyword!(update);
custom_keyword!(msg);
custom_keyword!(generics);
custom_keyword!(single);
Expand Down Expand Up @@ -312,26 +311,6 @@ impl Parse for WidgetDerive {
}
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub enum Handler {
None,
Use(Ident),
Map(Ident),
FlatMap(Ident),
Discard,
}
impl Handler {
pub fn is_none(&self) -> bool {
*self == Handler::None
}
pub fn any_ref(&self) -> Option<&Ident> {
match self {
Handler::None | Handler::Discard => None,
Handler::Use(n) | Handler::Map(n) | Handler::FlatMap(n) => Some(n),
}
}
}

#[derive(Debug)]
pub struct WidgetAttrArgs {
pub col: Option<Lit>,
Expand All @@ -340,8 +319,6 @@ pub struct WidgetAttrArgs {
pub rspan: Option<Lit>,
pub halign: Option<Ident>,
pub valign: Option<Ident>,
pub update: Option<Ident>,
pub handler: Handler,
}

#[derive(Debug)]
Expand Down Expand Up @@ -409,8 +386,6 @@ impl Parse for WidgetAttrArgs {
rspan: None,
halign: None,
valign: None,
update: None,
handler: Handler::None,
};
if input.is_empty() {
return Ok(args);
Expand Down Expand Up @@ -459,30 +434,11 @@ impl Parse for WidgetAttrArgs {
let _: kw::valign = content.parse()?;
let _: Eq = content.parse()?;
args.valign = Some(content.parse()?);
} else if args.update.is_none() && lookahead.peek(kw::update) {
let _: kw::update = content.parse()?;
let _: Eq = content.parse()?;
args.update = Some(content.parse()?);
} else if args.handler.is_none() && lookahead.peek(kw::flatmap_msg) {
let _: kw::flatmap_msg = content.parse()?;
let _: Eq = content.parse()?;
args.handler = Handler::FlatMap(content.parse()?);
} else if args.handler.is_none() && lookahead.peek(kw::map_msg) {
let _: kw::map_msg = content.parse()?;
let _: Eq = content.parse()?;
args.handler = Handler::Map(content.parse()?);
} else if args.handler.is_none() && lookahead.peek(kw::use_msg) {
let _: kw::use_msg = content.parse()?;
let _: Eq = content.parse()?;
args.handler = Handler::Use(content.parse()?);
} else if args.handler.is_none() && lookahead.peek(kw::discard_msg) {
let _: kw::discard_msg = content.parse()?;
args.handler = Handler::Discard;
} else if lookahead.peek(kw::handler) {
let tok: Ident = content.parse()?;
return Err(Error::new(
tok.span(),
"handler is obsolete; replace with flatmap_msg, map_msg, use_msg or discard_msg",
"handler is obsolete; replace with OnMessage",
));
} else {
return Err(lookahead.error());
Expand All @@ -506,7 +462,6 @@ impl ToTokens for WidgetAttrArgs {
|| self.rspan.is_some()
|| self.halign.is_some()
|| self.valign.is_some()
|| !self.handler.is_none()
{
let comma = TokenTree::from(Punct::new(',', Spacing::Alone));
let mut args = TokenStream::new();
Expand Down Expand Up @@ -543,22 +498,6 @@ impl ToTokens for WidgetAttrArgs {
}
args.append_all(quote! { valign = #ident });
}
if let Some(ref ident) = self.update {
if !args.is_empty() {
args.append(comma.clone());
}
args.append_all(quote! { update = #ident });
}
if !self.handler.is_none() && !args.is_empty() {
args.append(comma);
}
match &self.handler {
Handler::None => (),
Handler::Use(f) => args.append_all(quote! { use_msg = #f }),
Handler::Map(f) => args.append_all(quote! { map_msg = #f }),
Handler::FlatMap(f) => args.append_all(quote! { flatmap_msg = #f }),
Handler::Discard => args.append_all(quote! { discard_msg }),
}
tokens.append_all(quote! { ( #args ) });
}
}
Expand Down
129 changes: 17 additions & 112 deletions crates/kas-macros/src/lib.rs
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Expand Up @@ -8,14 +8,13 @@

extern crate proc_macro;

use self::args::{ChildType, Handler, HandlerArgs};
use self::args::{ChildType, HandlerArgs};
use proc_macro2::{Span, TokenStream};
use proc_macro_error::abort;
use quote::{quote, ToTokens, TokenStreamExt};
use std::collections::HashMap;
use std::fmt::Write;
use syn::punctuated::Punctuated;
use syn::spanned::Spanned;
use syn::Token;
use syn::{parse_macro_input, parse_quote};
use syn::{GenericParam, Ident, Type, TypeParam, TypePath, WhereClause, WherePredicate};
Expand Down Expand Up @@ -380,70 +379,37 @@ pub fn derive(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
quote! { self.#inner.send(mgr, id, event) }
} else {
let mut ev_to_num = TokenStream::new();
for child in args.children.iter() {
for (index, child) in args.children.iter().enumerate() {
#[cfg(feature = "log")]
let log_msg = quote! {
log::trace!(
"Received by {} from {}: {:?}",
"Received by {} from #{}: {:?}",
self.id(),
id,
#index,
::kas::util::TryFormat(&msg)
);
};
#[cfg(not(feature = "log"))]
let log_msg = quote! {};

let ident = &child.ident;
let update = if let Some(f) = child.args.update.as_ref() {
quote! {
if matches!(r, Response::Update) {
self.#f(mgr);
}
}
} else {
quote! {}
};
let handler = match &child.args.handler {
Handler::Use(f) => quote! {
r.try_into().unwrap_or_else(|msg| {
#log_msg
let _: () = self.#f(mgr, msg);
Response::None
})
},
Handler::Map(f) => quote! {
r.try_into().unwrap_or_else(|msg| {
#log_msg
Response::Msg(self.#f(mgr, msg))
})
},
Handler::FlatMap(f) => quote! {
r.try_into().unwrap_or_else(|msg| {
#log_msg
self.#f(mgr, msg)
})
},
Handler::Discard => quote! {
r.try_into().unwrap_or_else(|msg| {
#log_msg
let _ = msg;
Response::None
})
},
Handler::None => quote! { r.into() },
};

ev_to_num.append_all(quote! {
if id <= self.#ident.id() {
let r = self.#ident.send(mgr, id, event);
#update
#handler
match self.#ident.send(mgr, id, event).try_into() {
Ok(r) => r,
Err(msg) => {
#log_msg
self.on_msg(mgr, #index, msg)
}
}
} else
});
}

quote! {
use ::kas::{WidgetCore, event::Response};
use ::kas::WidgetCore;
use ::kas::event::{OnMessage, Response};
if self.is_disabled() {
return Response::Unhandled;
}
Expand Down Expand Up @@ -589,58 +555,6 @@ pub fn derive(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
/// See documentation [in the `kas::macros` module](https://docs.rs/kas/latest/kas/macros#the-make_widget-macro).
#[proc_macro]
pub fn make_widget(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let mut find_handler_ty_buf: Vec<(Ident, Type)> = vec![];
// find type of handler's message; return None on error
let mut find_handler_ty = |handler: &Ident,
impls: &Vec<(Option<TypePath>, Vec<syn::ImplItem>)>|
-> Option<Type> {
// check the buffer in case we did this already
for (ident, ty) in &find_handler_ty_buf {
if ident == handler {
return Some(ty.clone());
}
}

let mut x: Option<(Ident, Type)> = None;

for impl_block in impls {
for f in &impl_block.1 {
match f {
syn::ImplItem::Method(syn::ImplItemMethod { sig, .. })
if sig.ident == *handler =>
{
if let Some(_x) = x {
abort!(
handler.span(), "multiple methods with this name";
help = _x.0.span() => "first method with this name";
help = sig.ident.span() => "second method with this name";
);
}
if sig.inputs.len() != 3 {
abort!(
sig.span(),
"handler functions must have signature: fn handler(&mut self, mgr: &mut Manager, msg: T)"
);
}
let arg = sig.inputs.last().unwrap();
let ty = match arg {
syn::FnArg::Typed(arg) => (*arg.ty).clone(),
_ => panic!("expected typed argument"), // nothing else is possible here?
};
x = Some((sig.ident.clone(), ty));
}
_ => (),
}
}
}
if let Some(x) = x {
find_handler_ty_buf.push((handler.clone(), x.1.clone()));
Some(x.1)
} else {
abort!(handler.span(), "no methods with this name found");
}
};

let mut args = parse_macro_input!(input as args::MakeWidget);

// Used to make fresh identifiers for generic types
Expand Down Expand Up @@ -714,6 +628,7 @@ pub fn make_widget(input: proc_macro::TokenStream) -> proc_macro::TokenStream {

for (index, field) in args.fields.drain(..).enumerate() {
let attr = field.widget_attr;
let is_widget = attr.is_some();

let ident = match &field.ident {
Some(ref ident) => ident.clone(),
Expand All @@ -737,29 +652,19 @@ pub fn make_widget(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
name_buf.write_fmt(format_args!("MWAnon{}", index)).unwrap();
let ty = Ident::new(&name_buf, Span::call_site());

if let Some(ref wattr) = attr {
if is_widget {
if let Some(tyr) = gen_msg {
handler_clauses.push(parse_quote! { #ty: ::kas::Widget<Msg = #tyr> });
} else if let Some(handler) = wattr.args.handler.any_ref() {
// Message passed to a method; exact type required
if let Some(ty_bound) = find_handler_ty(handler, &args.impls) {
handler_clauses
.push(parse_quote! { #ty: ::kas::Widget<Msg = #ty_bound> });
} else {
return quote! {}.into(); // exit after emitting error
}
} else if wattr.args.handler == Handler::Discard {
// No type bound on discarded message
} else {
// Message converted via Into
// Message converted via OnMessage
name_buf.push('R');
let tyr = Ident::new(&name_buf, Span::call_site());
handler
.generics
.params
.push(syn::GenericParam::Type(tyr.clone().into()));
handler_clauses.push(parse_quote! { #ty: ::kas::Widget<Msg = #tyr> });
handler_clauses.push(parse_quote! { #msg: From<#tyr> });
handler_clauses.push(parse_quote! { Self: OnMessage<#tyr, #msg> });
}

if let Some(mut bound) = gen_bound {
Expand Down
1 change: 1 addition & 0 deletions crates/kas-widgets/src/button.rs
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Expand Up @@ -20,6 +20,7 @@ use kas::prelude::*;
#[handler(noauto)]
#[widget(config=noauto)]
#[widget_derive(class_traits)]
// TODO: less restriction on label
pub struct Button<L: Widget<Msg = VoidMsg>, M: 'static> {
#[widget_core]
core: kas::CoreData,
Expand Down
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