Selector Widget error

[giannissc]

the trait bound `Destination: druid::data::Data` is not satisfied
  --> src\main.rs:45:46
   |
45 |           Scroll::new(ListSelect::build_widget(vec![
   |  ______________________________________________^
46 | |             ("to Sydney", Destination::Sydney),
47 | |             ("to Petaluma", Destination::Petaluma),
48 | |             ("to Tokyo", Destination::Tokyo),
49 | |             ("to Paris", Destination::Paris),
50 | |         ]))
   | |_________^ the trait `druid::data::Data` is not implemented for `Destination`

[giannissc]

This happens when extracting example and running it as an isolated instance @maan2003

[richard-uk1]

Have you tried deriving Data for your type?

[giannissc]

I have done so but when it didn't work I copied the example from nursury and it didn't work either.

dropdown_test.zip

[richard-uk1]

Try replacing vec![..] with Arc::new(vec![..]). Data::same needs to run quickly, and so isn't implemented for Vec<_>, only for Arc<Vec<_>>

[giannissc]

Is it compatible with the im crate as well?

[richard-uk1]

So because im::Vector is immutable, using b-trees internally, it is as cheap to compare as Arc (a pointer equality check). So Data is implemented for im types.

Rather than import the im crate directly, it's best to turn on the im feature of druid and use the types that way, to ensure the version of im that has the traits implemented is the same as the one you're using. Version conflicts when using traits can lead to very confusing error messages.

[giannissc]

Well I used vector but I am getting the following errors

error[E0277]: the trait bound `Destination: druid::data::Data` is not satisfied
  --> src\main.rs:46:37
   |
46 |           Scroll::new(ListSelect::new(vector![
   |  _____________________________________^
47 | |             ("to Sydney", Destination::Sydney),
48 | |             ("to Petaluma", Destination::Petaluma),
49 | |             ("to Tokyo", Destination::Tokyo),
50 | |             ("to Paris", Destination::Paris),
51 | |         ]))
   | |_________^ the trait `druid::data::Data` is not implemented for `Destination`
   | 
  ::: C:\Users\John\.cargo\git\checkouts\druid-widget-nursery-63e9f3f67c4f288a\5e4a8d7\src\list_select.rs:36:48
   |
36 |           values: impl IntoIterator<Item = (impl Into<LabelText<T>> + 'static, T)>,
   |                                                  ------------------ required by this bound in `ListSelect::<T>::new`
   |
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0277]: the trait bound `impl druid::widget::widget::Widget<Destination>: druid::Widget<_>` is not satisfied
  --> src\main.rs:46:21
   |
46 |           Scroll::new(ListSelect::new(vector![
   |  _____________________^
47 | |             ("to Sydney", Destination::Sydney),
48 | |             ("to Petaluma", Destination::Petaluma),
49 | |             ("to Tokyo", Destination::Tokyo),
50 | |             ("to Paris", Destination::Paris),
51 | |         ]))
   | |__________^ the trait `druid::Widget<_>` is not implemented for `impl druid::widget::widget::Widget<Destination>`
   |
   = note: required by `Scroll::<T, W>::new`

error[E0599]: no method named `vertical` found for struct `Scroll<_, impl druid::widget::widget::Widget<Destination>>` in the current scope
  --> src\main.rs:52:10
   |
52 |         .vertical()
   |          ^^^^^^^^ method not found in `Scroll<_, impl druid::widget::widget::Widget<Destination>>`
   |
   = note: the method `vertical` exists but the following trait bounds were not satisfied:
           `impl druid::widget::widget::Widget<Destination>: druid::Widget<_>`

error[E0277]: the trait bound `Transportation: druid::data::Data` is not satisfied
  --> src\main.rs:58:29
   |
58 |           DropdownSelect::new(vector![
   |  _____________________________^
59 | |             ("by car", Transportation::Car),
60 | |             ("by train", Transportation::Train),
61 | |             ("by plane", Transportation::Plane),
62 | |             ("in a yellow submarine", Transportation::Submarine),
63 | |         ])
   | |_________^ the trait `druid::data::Data` is not implemented for `Transportation`
   | 
  ::: C:\Users\John\.cargo\git\checkouts\druid-widget-nursery-63e9f3f67c4f288a\5e4a8d7\src\dropdown_select.rs:43:48
   |
43 |           values: impl IntoIterator<Item = (impl Into<LabelText<T>> + 'static, T)> + Clone + 'static,
   |                                                  ------------------ required by this bound in `DropdownSelect::<T>::new`
   |
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0599]: no method named `align_left` found for opaque type `impl druid::widget::widget::Widget<Transportation>` in the current scope
  --> src\main.rs:64:10
   |
64 |         .align_left()
   |          ^^^^^^^^^^ method not found in `impl druid::widget::widget::Widget<Transportation>`
   |
   = note: the method `align_left` exists but the following trait bounds were not satisfied:
           `impl druid::widget::widget::Widget<Transportation>: druid::Widget<_>`
           which is required by `impl druid::widget::widget::Widget<Transportation>: WidgetExt<_>`
           `&impl druid::widget::widget::Widget<Transportation>: druid::Widget<_>`
           which is required by `&impl druid::widget::widget::Widget<Transportation>: WidgetExt<_>`
           `&mut impl druid::widget::widget::Widget<Transportation>: druid::Widget<_>`
           which is required by `&mut impl druid::widget::widget::Widget<Transportation>: WidgetExt<_>`
   = help: items from traits can only be used if the trait is in scope
help: the following trait is implemented but not in scope; perhaps add a `use` for it:
   |
15 | use druid::widget::widget_ext::WidgetExt;
   |

error: aborting due to 5 previous errors; 1 warning emitted

Some errors have detailed explanations: E0277, E0599.
For more information about an error, try `rustc --explain E0277`.
error: could not compile `dropdown_test`

[giannissc]

Can you help me out @derekdreery ?

[richard-uk1]

So your error messages mention that the trait Data is not implemented for your data types. Any data types that you use in druid need to have Data implemented for them. Fortunately you can just do use druid::Data and then #[derive(Data)] on your data types to get the impl.

The last error is there because you haven't done use druid::WidgetExt when you need to for the function you use.

[giannissc]

But already have all that. This is a copy from the example of the widget

[giannissc]

Here is the code:

// Copyright 2019 The Druid Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use druid::widget::{CrossAxisAlignment, Flex, Label, Scroll};
use druid::{AppLauncher, Data, Env, Insets, Lens, Widget, WidgetExt, WindowDesc};
use druid_widget_nursery::{DropdownSelect, ListSelect};
use druid::im::{vector};

#[derive(Clone, Copy, Data, Debug, PartialEq)]
enum Destination {
    Sydney,
    Petaluma,
    Tokyo,
    Paris,
}

//#[derive(Clone, Copy, Data, Debug, PartialEq)]
#[derive(Data, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Debug)]
enum Transportation {
    Car,
    Train,
    Plane,
    Submarine,
}

#[derive(Data, Clone, Lens)]
struct AppData {
    destination: Destination,
    transportation: Transportation,
}

fn main_widget() -> impl Widget<AppData> {
    let mut row = Flex::row().cross_axis_alignment(CrossAxisAlignment::Start);
    row.add_flex_child(
        Scroll::new(ListSelect::new(vector![
            ("to Sydney", Destination::Sydney),
            ("to Petaluma", Destination::Petaluma),
            ("to Tokyo", Destination::Tokyo),
            ("to Paris", Destination::Paris),
        ]))
        .vertical()
        .lens(AppData::destination),
        1.0,
    );
    row.add_default_spacer();
    row.add_flex_child(
        DropdownSelect::new(vector![
            ("by car", Transportation::Car),
            ("by train", Transportation::Train),
            ("by plane", Transportation::Plane),
            ("in a yellow submarine", Transportation::Submarine),
        ])
        .align_left()
        .lens(AppData::transportation),
        1.0,
    );

    let mut col = Flex::column().cross_axis_alignment(CrossAxisAlignment::Start);
    col.add_child(
        Label::new(|d: &AppData, _: &Env| {
            format!("Let's go to {:?} by {:?}", d.destination, d.transportation)
        })
        .padding(Insets::uniform_xy(5., 5.)),
    );
    col.add_child(row);
    col
}

fn main() {
    let main_window = WindowDesc::new(main_widget())
        .title("Select")
        .window_size((250., 300.));

    // create the initial app state
    let app_data = AppData {
        transportation: Transportation::Car,
        destination: Destination::Tokyo,
    };

    // start the application
    AppLauncher::with_window(main_window)
        .use_env_tracing()
        .launch(app_data)
        .expect("Failed to launch application");
}

[richard-uk1]

Could you post a full version that you expect to work (ideally in a git repository I can clone). Also, you may get quicker (and more varied) answers at https://xi.zulipchat.com/

[giannissc]

The repository: https://github.com/giannissc/dropdown-widget-test @derekdreery