Add l10n example

druid/examples/assets/en-US/banana.ftl

@@ -0,0 +1,7 @@
+banana-title = Banana count
+
+bananas = {$count ->
+    [0] No bananas
+    [1] One banana
+   *[other] {$count} bananas
+}

druid/examples/assets/fr-FR/banana.ftl

@@ -0,0 +1,7 @@
+banana-title = Nombre de bananes
+
+bananas = {$count ->
+    [0] Aucune banane
+    [1] Une banane
+   *[other] {$count} bananes
+}

druid/examples/l10n.rs

@@ -0,0 +1,76 @@
+// 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.
+
+//! This is an example of how to translate and localize a druid application.
+//! It uses the fluent (.ftl) files in the asset directory for defining defining messages.
+
+// On Windows platform, don't show a console when opening the app.
+#![windows_subsystem = "windows"]
+
+use druid::widget::{prelude::*, Slider};
+use druid::widget::{Flex, Label};
+use druid::{AppLauncher, Data, Lens, LocalizedString, UnitPoint, WidgetExt, WindowDesc};
+
+const VERTICAL_WIDGET_SPACING: f64 = 20.0;
+const SLIDER_WIDTH: f64 = 200.0;
+
+#[derive(Clone, Data, Lens)]
+struct BananaState {
+    count: f64,
+}
+
+pub fn main() {
+    let main_window = WindowDesc::new(build_root_widget())
+        .title(LocalizedString::new("banana-title"))
+        .window_size((400.0, 400.0));
+
+    let initial_state: BananaState = BananaState { count: 1f64 };
+
+    // start the application, referencing the translation files in /assets.
+    AppLauncher::with_window(main_window)
+        .log_to_console()
+        .localization_resources(vec!["banana.ftl".into()], "assets".into())
+        .launch(initial_state)
+        .expect("Failed to launch application");
+}
+
+fn build_root_widget() -> impl Widget<BananaState> {
+    // create a label with a static translation
+    let title = Label::new(LocalizedString::new("banana-title")).with_text_size(28.0);
+
+    // create a label that uses a translation with dynamic arguments
+    let banana_label = Label::new(|data: &BananaState, env: &Env| {
+        let mut s = LocalizedString::<BananaState>::new("bananas")
+            .with_arg("count", |d, _e| d.count.into());
+        s.resolve(data, env);
+
+        s.localized_str()
+    })
+    .with_text_size(32.0);
+
+    // control the banana count
+    let slider = Slider::new()
+        .with_range(0.0, 3.0)
+        .with_step(1.0)
+        .fix_width(SLIDER_WIDTH)
+        .lens(BananaState::count);
+
+    Flex::column()
+        .with_child(title)
+        .with_spacer(VERTICAL_WIDGET_SPACING * 2.0)
+        .with_child(banana_label)
+        .with_spacer(VERTICAL_WIDGET_SPACING)
+        .with_child(slider)
+        .align_vertical(UnitPoint::CENTER)
+}

druid/examples/readme.md

@@ -86,6 +86,13 @@ cargo run --example invalidation --features="im"
 ```
 A demonstration how to use debug invalidation regions in your own widgets, including some examples of builtin widgets.
 
+## L10n
+```
+cd druid/examples
+LANG=fr-FR cargo run --example l10n
+```
+Shows how to localize and translate text in druid. On Linux, set the LANG environment variable to either "fr-FR" or "en-US".
+
 ## Layout
 ```
 cargo run --example layout