Scale bar for map view

rgis-settings/src/lib.rs

@@ -22,6 +22,7 @@ pub enum Tool {
 pub struct RgisSettings {
     pub target_crs: String,
     pub current_tool: Tool,
+    pub show_scale: bool,
 }
 
 pub struct Plugin;
@@ -31,6 +32,7 @@ impl bevy::prelude::Plugin for Plugin {
         app.insert_resource(RgisSettings {
             target_crs: DEFAULT_TARGET_CRS.into(),
             current_tool: Tool::Pan,
+            show_scale: true,
         })
         .add_system(systems::handle_crs_changed_events);
     }

rgis-ui/src/lib.rs

@@ -17,6 +17,7 @@ mod feature_properties_window;
 mod manage_layer_window;
 mod message_window;
 mod operation_window;
+mod scale_bar;
 mod side_panel;
 mod systems;
 mod top_panel;

rgis-ui/src/scale_bar.rs

@@ -0,0 +1,96 @@
+use bevy::prelude::*;
+use bevy_egui::egui::{self, Widget};
+
+pub fn render_map_scale(
+    query: Query<
+        &bevy::transform::components::Transform,
+        bevy::ecs::query::With<bevy::render::camera::Camera>,
+    >,
+    mut bevy_egui_ctx: ResMut<bevy_egui::EguiContext>,
+    rgis_settings: Res<rgis_settings::RgisSettings>,
+) {
+    if !rgis_settings.show_scale {
+        return;
+    }
+    let transform = query.single();
+    let scale = transform.scale.x;
+
+    let bar_max_width = 100.;
+    let bar_in_meter = desired_bar_length(scale * bar_max_width);
+    let bar_width = bar_in_meter / scale;
+    let bar_text = distance_to_readable_string(bar_in_meter);
+
+    egui::Window::new("Scale")
+        .frame(egui::Frame::none())
+        .open(&mut true)
+        .title_bar(false)
+        .anchor(egui::Align2::LEFT_BOTTOM, [4., -2.])
+        .fixed_size(egui::Vec2 {
+            x: bar_max_width,
+            y: 0.,
+        })
+        .show(bevy_egui_ctx.ctx_mut(), |ui| {
+            ui.horizontal(|ui| {
+                ui.spacing_mut().item_spacing = egui::Vec2 { x: 4., y: 0. };
+
+                egui::Button::new("")
+                    .min_size(egui::Vec2 {
+                        x: bar_width,
+                        y: 0.,
+                    })
+                    .small()
+                    .frame(false)
+                    .sense(egui::Sense::hover())
+                    .fill(egui::Color32::GRAY)
+                    .ui(ui);
+
+                ui.label(
+                    egui::RichText::new(bar_text)
+                        // .small()
+                        .background_color(ui.visuals().window_fill()), // .strong(),
+                );
+            });
+        });
+}
+
+fn desired_bar_length(full_bar_length: f32) -> f32 {
+    let mut desired_length = 2e38;
+
+    for i in full_bar_length.log10().floor() as i32..=f32::MAX_10_EXP {
+        for j in [1., 2., 5.] {
+            let length = 10_f32.powi(i) * j;
+            if full_bar_length < length {
+                break;
+            }
+            desired_length = length;
+        }
+    }
+    desired_length
+}
+
+fn distance_to_readable_string(distance: f32) -> String {
+    let res = get_proper_distance_unit(distance);
+    format!("{}{}m", (res.1 * distance).round(), res.0)
+}
+
+fn get_proper_distance_unit(distance: f32) -> (&'static str, f32) {
+    match distance.log10().floor() as i32 {
+        i32::MIN..=-16 => ("a", 1e18),
+        -15..=-13 => ("f", 1e15),
+        -12..=-10 => ("p", 1e12),
+        -9..=-7 => ("n", 1e9),
+        -6..=-4 => ("µ", 1e6),
+        -3..=-3 => ("m", 1e3),
+        -2..=-1 => ("c", 1e2),
+        0..=2 => ("", 1e0),
+        3..=8 => ("k", 1e-3), //human readable
+        // 6..=8 => ("M", 1e-6),
+        9..=11 => ("G", 1e-9),
+        12..=14 => ("T", 1e-12),
+        15..=17 => ("P", 1e-15),
+        18..=20 => ("E", 1e-18),
+        21..=23 => ("Z", 1e-21),
+        24..=26 => ("Y", 1e-24),
+        27..=i32::MAX => ("Y", 1e-24),
+    }
+}

rgis-ui/src/systems.rs

@@ -349,6 +349,7 @@ pub fn system_sets() -> [SystemSet; 2] {
             .with_system(render_feature_properties_window.after(render_change_crs_window))
             .with_system(render_operation_window.after(render_feature_properties_window))
             .with_system(render_in_progress.after("top_bottom_panels"))
+            .with_system(crate::scale_bar::render_map_scale.after(render_side_panel))
             .label("rgis_ui"),
     ]
 }

rgis-ui/src/top_panel.rs

@@ -26,6 +26,19 @@ impl<'a> TopPanel<'a> {
                         ui.add(FullScreenButton {
                             windows: self.windows,
                         });
+
+                        if ui
+                            .button(format!(
+                                "{} scale",
+                                match self.app_settings.show_scale {
+                                    true => "Hide",
+                                    false => "Show",
+                                }
+                            ))
+                            .clicked()
+                        {
+                            self.app_settings.show_scale = !self.app_settings.show_scale;
+                        }
                     });
                     ui.menu_button("Help", |ui| {
                         if ui.button("Debug stats").clicked() {