Add a widget gallery example.

The `Grid` used to display them is also probably useful in other
situations.

druid/examples/web/src/lib.rs

@@ -78,3 +78,4 @@ impl_example!(styled_text.unwrap());
 impl_example!(switches);
 impl_example!(timer);
 impl_example!(view_switcher);
+impl_example!(widget_gallery);

druid/examples/widget_gallery.rs

@@ -0,0 +1,325 @@
+// Copyright 2019 The xi-editor 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.
+
+//! Provides a grid to display the more complex widgets.
+
+use std::sync::Arc;
+
+use druid::{
+    widget::{
+        prelude::*, Button, Checkbox, Flex, Label, List, Painter, ProgressBar, RadioGroup, Scroll,
+        Slider, Stepper, Switch, TextBox,
+    },
+    AppLauncher, Color, Data, Lens, LocalizedString, Rect, Widget, WidgetExt, WidgetPod,
+    WindowDesc,
+};
+
+const XI_IMAGE: &[u8] = include_bytes!("xi.image");
+
+#[derive(Clone, Data, Lens)]
+struct AppData {
+    label_data: String,
+    checkbox_data: bool,
+    clicked_count: u64,
+    list_items: Arc<Vec<String>>,
+    progressbar: f64,
+    radio: MyRadio,
+    stepper: f64,
+    editable_text: String,
+}
+
+#[derive(Clone, Data, PartialEq)]
+enum MyRadio {
+    GaGa,
+    GuGu,
+    BaaBaa,
+}
+
+pub fn main() {
+    let main_window = WindowDesc::new(ui_builder)
+        .title(LocalizedString::new("list-demo-window-title").with_placeholder("List Demo"));
+    // Set our initial data
+    let data = AppData {
+        label_data: "test".into(),
+        checkbox_data: false,
+        clicked_count: 0,
+        list_items: Arc::new(vec!["1".into(), "2".into(), "3".into()]),
+        progressbar: 0.5,
+        radio: MyRadio::GaGa,
+        stepper: 0.0,
+        editable_text: "edit me!".into(),
+    };
+    AppLauncher::with_window(main_window)
+        .use_simple_logger()
+        .launch(data)
+        .expect("launch failed");
+}
+
+fn ui_builder() -> impl Widget<AppData> {
+    Scroll::new(
+        SquaresGrid::new()
+            .with_cell_size(Size::new(200.0, 240.0))
+            .with_spacing(20.0)
+            .with_child(label_widget(
+                Label::new(|data: &AppData, _: &_| data.label_data.clone()),
+                "Label",
+            ))
+            .with_child(label_widget(
+                Flex::column()
+                    .with_child(
+                        Button::new("Click me!")
+                            .on_click(|_, data: &mut AppData, _: &_| data.clicked_count += 1),
+                    )
+                    .with_spacer(4.0)
+                    .with_child(Label::new(|data: &AppData, _: &_| {
+                        format!("Clicked {} times!", data.clicked_count)
+                    })),
+                "Button",
+            ))
+            .with_child(label_widget(
+                Checkbox::new("Check me!").lens(AppData::checkbox_data),
+                "Checkbox",
+            ))
+            .with_child(label_widget(
+                List::new(|| {
+                    Label::new(|data: &String, _: &_| format!("List item: {}", data))
+                        .center()
+                        .background(Color::hlc(230.0, 50.0, 50.0))
+                        .fix_height(40.0)
+                        .expand_width()
+                })
+                .lens(AppData::list_items),
+                "List",
+            ))
+            .with_child(label_widget(
+                Flex::column()
+                    .with_child(ProgressBar::new().lens(AppData::progressbar))
+                    .with_spacer(4.0)
+                    .with_child(Label::new(|data: &AppData, _: &_| {
+                        format!("{:.1}%", data.progressbar * 100.0)
+                    }))
+                    .with_spacer(4.0)
+                    .with_child(
+                        Flex::row()
+                            .with_child(Button::new("<<").on_click(|_, data: &mut AppData, _| {
+                                data.progressbar = (data.progressbar - 0.05).max(0.0);
+                            }))
+                            .with_spacer(4.0)
+                            .with_child(Button::new(">>").on_click(|_, data: &mut AppData, _| {
+                                data.progressbar = (data.progressbar + 0.05).min(1.0);
+                            })),
+                    ),
+                "ProgressBar",
+            ))
+            // The image example here uses hard-coded literal image data included in the binary.
+            // You may also want to load an image at runtime using a crate like `image`.
+            .with_child(label_widget(
+                Painter::new(|ctx, _, _| {
+                    let img = load_xi_image(ctx.render_ctx);
+                    let rect = ctx.size().to_rect();
+                    ctx.draw_image(&img, rect, druid::piet::InterpolationMode::NearestNeighbor);
+                })
+                .fix_size(32.0, 32.0),
+                "Painter",
+            ))
+            .with_child(label_widget(
+                RadioGroup::new(vec![
+                    ("radio gaga", MyRadio::GaGa),
+                    ("radio gugu", MyRadio::GuGu),
+                    ("radio baabaa", MyRadio::BaaBaa),
+                ])
+                .lens(AppData::radio),
+                "RadioGroup",
+            ))
+            .with_child(label_widget(
+                Flex::column()
+                    .with_child(Slider::new().lens(AppData::progressbar))
+                    .with_spacer(4.0)
+                    .with_child(Label::new(|data: &AppData, _: &_| {
+                        format!("{:3.0}%", data.progressbar * 100.0)
+                    })),
+                "Slider",
+            ))
+            .with_child(label_widget(
+                Flex::row()
+                    .with_child(Stepper::new().lens(AppData::stepper))
+                    .with_spacer(4.0)
+                    .with_child(Label::new(|data: &AppData, _: &_| {
+                        format!("{:.1}", data.stepper)
+                    })),
+                "Stepper",
+            ))
+            .with_child(label_widget(
+                TextBox::new().lens(AppData::editable_text),
+                "TextBox",
+            ))
+            .with_child(label_widget(
+                Switch::new().lens(AppData::checkbox_data),
+                "Switch",
+            )),
+    )
+    .vertical()
+}
+
+fn label_widget<T: Data>(widget: impl Widget<T> + 'static, label: &str) -> impl Widget<T> {
+    Flex::column()
+        .must_fill_main_axis(true)
+        .with_flex_child(widget.center(), 1.0)
+        .with_child(
+            Painter::new(|ctx, _: &_, _: &_| {
+                let size = ctx.size().to_rect();
+                ctx.fill(size, &Color::WHITE)
+            })
+            .fix_height(1.0),
+        )
+        .with_child(Label::new(label).center().fix_height(40.0))
+        .border(Color::WHITE, 1.0)
+}
+
+fn load_xi_image<Ctx: druid::RenderContext>(ctx: &mut Ctx) -> Ctx::Image {
+    ctx.make_image(32, 32, XI_IMAGE, druid::piet::ImageFormat::Rgb)
+        .unwrap()
+}
+
+const DEFAULT_GRID_CELL_SIZE: Size = Size::new(100.0, 100.0);
+const DEFAULT_GRID_SPACING: f64 = 10.0;
+
+pub struct SquaresGrid<T> {
+    widgets: Vec<WidgetPod<T, Box<dyn Widget<T>>>>,
+    /// The number of widgets we can fit in the grid given the grid size.
+    drawable_widgets: usize,
+    cell_size: Size,
+    spacing: f64,
+}
+
+impl<T> SquaresGrid<T> {
+    pub fn new() -> Self {
+        SquaresGrid {
+            widgets: vec![],
+            drawable_widgets: 0,
+            cell_size: DEFAULT_GRID_CELL_SIZE,
+            spacing: DEFAULT_GRID_SPACING,
+        }
+    }
+
+    pub fn with_spacing(mut self, spacing: f64) -> Self {
+        self.spacing = spacing;
+        self
+    }
+
+    pub fn with_cell_size(mut self, cell_size: Size) -> Self {
+        self.cell_size = cell_size;
+        self
+    }
+
+    pub fn with_child(mut self, widget: impl Widget<T> + 'static) -> Self {
+        self.widgets.push(WidgetPod::new(Box::new(widget)));
+        self
+    }
+}
+
+impl<T> Default for SquaresGrid<T> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl<T: Data> Widget<T> for SquaresGrid<T> {
+    fn event(&mut self, ctx: &mut EventCtx, event: &Event, data: &mut T, env: &Env) {
+        for widget in self.widgets.iter_mut() {
+            widget.event(ctx, event, data, env);
+        }
+    }
+
+    fn lifecycle(&mut self, ctx: &mut LifeCycleCtx, event: &LifeCycle, data: &T, env: &Env) {
+        for widget in self.widgets.iter_mut() {
+            widget.lifecycle(ctx, event, data, env);
+        }
+    }
+
+    fn update(&mut self, ctx: &mut UpdateCtx, _old_data: &T, data: &T, env: &Env) {
+        for widget in self.widgets.iter_mut() {
+            widget.update(ctx, data, env);
+        }
+    }
+
+    fn layout(&mut self, ctx: &mut LayoutCtx, bc: &BoxConstraints, data: &T, env: &Env) -> Size {
+        let count = self.widgets.len() as f64;
+        // The space needed to lay all elements out on a single line.
+        let ideal_width = (self.cell_size.width + self.spacing + 1.0) * count;
+        // Constrain the width.
+        let width = ideal_width.min(bc.max().width).max(bc.min().width);
+        // Given the width, the space needed to lay out all elements (as many as possible on each
+        // line).
+        let cells_in_row =
+            ((width - self.spacing) / (self.cell_size.width + self.spacing)).floor() as usize;
+        let (height, rows) = if cells_in_row > 0 {
+            let mut rows = (count / cells_in_row as f64).ceil() as usize;
+            let height_from_rows =
+                |rows: usize| (rows as f64) * (self.cell_size.height + self.spacing) + self.spacing;
+            let ideal_height = height_from_rows(rows);
+
+            // Constrain the height
+            let height = ideal_height.max(bc.min().height).min(bc.max().height);
+            // Now calcuate how many rows we can actually fit in
+            while height_from_rows(rows) > height && rows > 0 {
+                rows -= 1;
+            }
+            (height, rows)
+        } else {
+            (bc.min().height, 0)
+        };
+        // Constrain the number of drawn widgets by the number there is space to draw.
+        self.drawable_widgets = self.widgets.len().min(rows * cells_in_row);
+        // Now we have the width and height, we can lay out the children.
+        let mut x_position = self.spacing;
+        let mut y_position = self.spacing;
+        for (idx, widget) in self
+            .widgets
+            .iter_mut()
+            .take(self.drawable_widgets)
+            .enumerate()
+        {
+            let rect = Rect::new(
+                x_position,
+                y_position,
+                x_position + self.cell_size.width,
+                y_position + self.cell_size.height,
+            );
+            let size = widget.layout(
+                ctx,
+                &BoxConstraints::new(self.cell_size, self.cell_size),
+                data,
+                env,
+            );
+            assert_eq!(size, self.cell_size); // todo remove this
+            widget.set_layout_rect(ctx, data, env, rect);
+            // Increment position for the next cell
+            x_position += self.cell_size.width + self.spacing;
+            // If we can't fit in another cell in this row ...
+            if (idx + 1) % cells_in_row == 0 {
+                // ... then start a new row.
+                x_position = self.spacing;
+                y_position += self.cell_size.height + self.spacing;
+            }
+        }
+        Size { width, height }
+    }
+
+    fn paint(&mut self, ctx: &mut PaintCtx, data: &T, env: &Env) {
+        for widget in self.widgets.iter_mut().take(self.drawable_widgets) {
+            widget.paint(ctx, data, env);
+        }
+    }
+}