Inertial movement

CHANGELOG.md

@@ -6,6 +6,10 @@ All notable changes to this project will be documented in this file.
 
 ### Breaking
 
+ * New `Center` variant - `Inertia`. It means that the map is moving due to inertia and
+  soon will stop with `Center` switching to `Exact`. To keep things easy, `Center` now
+  has new method `detached`, will returns a position the map is currently at, or `None`
+  if it just follows `my_position`.
  * `openstreetmap` is now in `walkers::providers` module.
  * `osm` example is now called `myapp` and it shows a small windows with an orthophotomap
    layer from <https://geoportal.gov.pl>.

examples/myapp.rs

@@ -14,6 +14,7 @@ struct MyApp {
     tiles: Tiles,
     geoportal_tiles: Tiles,
     map_memory: MapMemory,
+    satellite: bool,
 }
 
 impl MyApp {
@@ -22,6 +23,7 @@ impl MyApp {
             tiles: Tiles::new(walkers::providers::openstreetmap, egui_ctx.to_owned()),
             geoportal_tiles: Tiles::new(walkers::providers::geoportal, egui_ctx),
             map_memory: MapMemory::default(),
+            satellite: false,
         }
     }
 }
@@ -39,8 +41,15 @@ impl eframe::App for MyApp {
                 // Typically this would be a GPS acquired position which is tracked by the map.
                 let my_position = places::wroclaw_glowny();
 
+                // Select either OSM standard map or satellite.
+                let tiles = if self.satellite {
+                    &mut self.geoportal_tiles
+                } else {
+                    &mut self.tiles
+                };
+
                 // In egui, widgets are constructed and consumed in each frame.
-                let map = Map::new(Some(&mut self.tiles), &mut self.map_memory, my_position);
+                let map = Map::new(Some(tiles), &mut self.map_memory, my_position);
 
                 // Optionally, a function which draw custom stuff on the map can be attached.
                 let ctx_clone = ctx.clone();
@@ -57,14 +66,7 @@ impl eframe::App for MyApp {
 
                     zoom(ui, &mut self.map_memory);
                     go_to_my_position(ui, &mut self.map_memory);
-
-                    orthophotomap(
-                        ui,
-                        &mut self.geoportal_tiles,
-                        &mut self.map_memory,
-                        my_position,
-                    );
-
+                    satellite(ui, &mut self.satellite);
                     acknowledge(ui);
                 }
             });
@@ -122,7 +124,7 @@ fn draw_custom_shapes(ctx: Context, painter: Painter, projector: &Projector) {
 
 mod windows {
     use egui::{Align2, RichText, Ui, Window};
-    use walkers::{Center, Map, MapMemory, Position, Tiles};
+    use walkers::{Center, MapMemory};
 
     pub fn acknowledge(ui: &Ui) {
         Window::new("Acknowledge")
@@ -139,20 +141,15 @@ mod windows {
             });
     }
 
-    pub fn orthophotomap(
-        ui: &Ui,
-        tiles: &mut Tiles,
-        map_memory: &mut MapMemory,
-        my_position: Position,
-    ) {
-        Window::new("Orthophotomap")
+    pub fn satellite(ui: &Ui, satellite: &mut bool) {
+        Window::new("Satellite")
             .collapsible(false)
             .resizable(false)
             .title_bar(false)
             .anchor(Align2::RIGHT_TOP, [-10., 10.])
             .fixed_size([150., 150.])
             .show(ui.ctx(), |ui| {
-                ui.add(Map::new(Some(tiles), map_memory, my_position));
+                ui.checkbox(satellite, "satellite view");
             });
     }
 
@@ -178,7 +175,7 @@ mod windows {
 
     /// When map is "detached", show a windows with an option to go back to my position.
     pub fn go_to_my_position(ui: &Ui, map_memory: &mut MapMemory) {
-        if let Center::Exact(position) = map_memory.center_mode {
+        if let Some(position) = map_memory.center_mode.detached() {
             Window::new("Center")
                 .collapsible(false)
                 .resizable(false)

src/map.rs

@@ -1,6 +1,6 @@
 use std::collections::{hash_map::Entry, HashMap};
 
-use egui::{Mesh, Painter, Pos2, Rect, Response, Sense, Ui, Vec2, Widget};
+use egui::{Context, Mesh, Painter, Pos2, Rect, Response, Sense, Ui, Vec2, Widget};
 
 use crate::{
     mercator::{screen_to_position, PositionExt, TileId},
@@ -83,22 +83,27 @@ impl Widget for Map<'_, '_> {
     fn ui(self, ui: &mut Ui) -> Response {
         let (rect, response) = ui.allocate_exact_size(ui.available_size(), Sense::drag());
 
-        if response.hovered() {
-            let zoom_delta = ui.input(|input| input.zoom_delta());
+        //if response.hovered() {
+        let zoom_delta = ui.input(|input| input.zoom_delta());
 
-            // Zooming and dragging need to be exclusive, otherwise the map will get dragged when
-            // pinch gesture is used.
-            if !(0.99..=1.01).contains(&zoom_delta) {
-                // Shift by 1 because of the values given by zoom_delta(). Multiple by 2, because
-                // then it felt right with both mouse wheel, and an Android phone.
-                self.memory.zoom.zoom_by((zoom_delta - 1.) * 2.);
-            } else {
-                self.memory
-                    .center_mode
-                    .drag(&response, self.my_position, self.memory.zoom.round());
-            }
+        // Zooming and dragging need to be exclusive, otherwise the map will get dragged when
+        // pinch gesture is used.
+        if !(0.99..=1.01).contains(&zoom_delta) {
+            // Shift by 1 because of the values given by zoom_delta(). Multiple by 2, because
+            // then it felt right with both mouse wheel, and an Android phone.
+            self.memory.zoom.zoom_by((zoom_delta - 1.) * 2.);
+        } else {
+            self.memory
+                .center_mode
+                .recalculate_drag(&response, self.my_position);
         }
 
+        self.memory.center_mode.recalculate_inertial_movement(
+            ui.ctx(),
+            self.my_position,
+            self.memory.zoom.round(),
+        );
+
         let map_center = self.memory.center_mode.position(self.my_position);
         let painter = ui.painter().with_clip_rect(rect);
 
@@ -140,32 +145,76 @@ impl Widget for Map<'_, '_> {
 /// [`Center::MyPosition`].
 #[derive(Clone, PartialEq, Default)]
 pub enum Center {
-    /// Center at `my_position` argument of the [`Map::new()`] function.
+    /// Centered at `my_position` argument of the [`Map::new()`] function.
     #[default]
     MyPosition,
 
-    /// Center at the exact position.
+    /// Centered at the exact position.
     Exact(Position),
+
+    /// Map's currently moving due to inertia, and will slow down and stop after a short while.
+    Inertia {
+        position: Position,
+        direction: Vec2,
+        amount: f32,
+    },
 }
 
 impl Center {
-    fn drag(&mut self, response: &Response, my_position: Position, zoom: u8) {
+    fn recalculate_drag(&mut self, response: &Response, my_position: Position) {
         if response.dragged_by(egui::PointerButton::Primary) {
-            // We always end up in some exact, "detached" position, regardless of the current mode.
-            *self = Center::Exact(screen_to_position(
-                self.position(my_position).project(zoom) - response.drag_delta(),
-                zoom,
-            ));
+            *self = Center::Inertia {
+                position: self.position(my_position),
+                direction: response.drag_delta(),
+                amount: 1.0,
+            };
         }
     }
 
-    /// Get the real position at the map's center.
-    pub fn position(&self, my_position: Position) -> Position {
+    fn recalculate_inertial_movement(&mut self, ctx: &Context, my_position: Position, zoom: u8) {
+        if let Center::Inertia {
+            position,
+            direction,
+            amount,
+        } = &self
+        {
+            *self = if amount <= &mut 0.0 {
+                Center::Exact(*position)
+            } else {
+                Center::Inertia {
+                    position: screen_to_position(
+                        self.position(my_position).project(zoom) - (*direction * *amount),
+                        zoom,
+                    ),
+                    direction: *direction,
+                    amount: *amount - 0.03,
+                }
+            };
+
+            // Map is moving due to interia, therefore we need to recalculate in the next frame.
+            log::trace!("Requesting repaint due to non-zero inertia.");
+            ctx.request_repaint();
+        }
+    }
+
+    /// Returns exact position if map is detached (i.e. not following `my_position`),
+    /// `None` otherwise.
+    pub fn detached(&self) -> Option<Position> {
         match self {
-            Center::MyPosition => my_position,
-            Center::Exact(position) => *position,
+            Center::MyPosition => None,
+            Center::Exact(position) => Some(*position),
+            Center::Inertia {
+                position,
+                direction: _,
+                amount: _,
+            } => Some(*position),
         }
     }
+
+    /// Get the real position at the map's center.
+    pub fn position(&self, my_position: Position) -> Position {
+        self.detached().unwrap_or(my_position)
+    }
 }
 
 /// State of the map widget which must persist between frames.