From 4e230a869f0b12e7d1cf9159a4900055d31221a1 Mon Sep 17 00:00:00 2001
From: ShenMian <sms_school@outlook.com>
Date: Sat, 20 Jul 2024 02:46:18 +0100
Subject: [PATCH 1/3] feat(camera): add mouse-driven panning

Enable panning of the camera based on
the cursor position relative to the viewport.
---
 src/camera.rs | 51 ++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 40 insertions(+), 11 deletions(-)

diff --git a/src/camera.rs b/src/camera.rs
index 83daf08..4903c98 100644
--- a/src/camera.rs
+++ b/src/camera.rs
@@ -18,23 +18,59 @@ fn spawn(mut commands: Commands) {
 
 pub fn update(
     keys: Res<ButtonInput<KeyCode>>,
-    mut query: Query<(Ref<OrthographicProjection>, &mut Transform), With<Camera2d>>,
+    mut query: Query<(&OrthographicProjection, &mut Transform), With<Camera2d>>,
     time: Res<Time>,
     tilemaps: Res<Assets<Map>>,
     tilemap_query: Query<&Handle<Map>>,
+    window_query: Query<&Window>,
 ) {
+    let Ok((projection, mut transform)) = query.get_single_mut() else {
+        return;
+    };
+
+    let min_speed = 250.;
+    let max_speed = 500.;
+
     let x = keys.any_pressed([KeyCode::ArrowRight, KeyCode::KeyD]) as i8
         - keys.any_pressed([KeyCode::ArrowLeft, KeyCode::KeyA]) as i8;
     let y = keys.any_pressed([KeyCode::ArrowUp, KeyCode::KeyW]) as i8
         - keys.any_pressed([KeyCode::ArrowDown, KeyCode::KeyS]) as i8;
     let dir = Vec2::new(x as f32, y as f32).normalize_or_zero();
 
-    let Ok((projection, mut transform)) = query.get_single_mut() else {
+    if dir != Vec2::ZERO {
+        let speed = if keys.any_pressed([KeyCode::ShiftLeft, KeyCode::ShiftRight]) {
+            max_speed
+        } else {
+            min_speed
+        };
+
+        transform.translation += dir.extend(0.) * time.delta_seconds() * speed;
+    }
+
+    let Ok(window) = window_query.get_single() else {
         return;
     };
 
-    if dir == Vec2::ZERO && !projection.is_changed() {
-        return;
+    if let Some(cursor_position) = window.cursor_position() {
+        fn map_range(from: (f32, f32), to: (f32, f32), value: f32) -> f32 {
+            to.0 + (value - from.0) * (to.1 - to.0) / (from.1 - from.0)
+        }
+
+        let cursor_position = Vec2::new(cursor_position.x, cursor_position.y);
+        let half_viewport_size = window.resolution.size() / 2.;
+        let center_to_cursor = cursor_position - half_viewport_size;
+        let normalized_length = center_to_cursor / half_viewport_size;
+
+        if normalized_length.x.abs() >= 0.8 {
+            transform.translation.x += time.delta_seconds()
+                * map_range((0.8, 1.), (min_speed, max_speed), normalized_length.x.abs())
+                    .copysign(normalized_length.x);
+        }
+        if normalized_length.y.abs() >= 0.8 {
+            transform.translation.y -= time.delta_seconds()
+                * map_range((0.8, 1.), (min_speed, max_speed), normalized_length.y.abs())
+                    .copysign(normalized_length.y);
+        }
     }
 
     let Ok(tilemap_handle) = tilemap_query.get_single() else {
@@ -45,12 +81,6 @@ pub fn update(
         return;
     };
 
-    let speed = if keys.any_pressed([KeyCode::ShiftLeft, KeyCode::ShiftRight]) {
-        500.
-    } else {
-        250.
-    };
-
     let pan_area = tilemap.size_vec2() * crate::tilemap::SCALE * crate::tilemap::TILE_SIZE
         - projection.area.size();
 
@@ -61,7 +91,6 @@ pub fn update(
     let min = pan_area / -2.;
     let max = pan_area / 2.;
 
-    transform.translation += dir.extend(0.) * time.delta_seconds() * speed;
     transform.translation.x = transform.translation.x.clamp(min.x, max.x);
     transform.translation.y = transform.translation.y.clamp(min.y, max.y);
 }

From 2c34285caf96865b0dbe95e89cb8ae98b4aed799 Mon Sep 17 00:00:00 2001
From: ShenMian <sms_school@outlook.com>
Date: Sat, 20 Jul 2024 16:01:40 +0100
Subject: [PATCH 2/3] refactor(camera): replace map_range with remap

Replace the custom map_range function with the remap function from the
glam crate to simplify the code.
---
 src/camera.rs | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/camera.rs b/src/camera.rs
index 4903c98..b85767d 100644
--- a/src/camera.rs
+++ b/src/camera.rs
@@ -52,10 +52,6 @@ pub fn update(
     };
 
     if let Some(cursor_position) = window.cursor_position() {
-        fn map_range(from: (f32, f32), to: (f32, f32), value: f32) -> f32 {
-            to.0 + (value - from.0) * (to.1 - to.0) / (from.1 - from.0)
-        }
-
         let cursor_position = Vec2::new(cursor_position.x, cursor_position.y);
         let half_viewport_size = window.resolution.size() / 2.;
         let center_to_cursor = cursor_position - half_viewport_size;
@@ -63,12 +59,18 @@ pub fn update(
 
         if normalized_length.x.abs() >= 0.8 {
             transform.translation.x += time.delta_seconds()
-                * map_range((0.8, 1.), (min_speed, max_speed), normalized_length.x.abs())
+                * normalized_length
+                    .x
+                    .abs()
+                    .remap(0.8, 1., min_speed, max_speed)
                     .copysign(normalized_length.x);
         }
         if normalized_length.y.abs() >= 0.8 {
             transform.translation.y -= time.delta_seconds()
-                * map_range((0.8, 1.), (min_speed, max_speed), normalized_length.y.abs())
+                * normalized_length
+                    .y
+                    .abs()
+                    .remap(0.8, 1., min_speed, max_speed)
                     .copysign(normalized_length.y);
         }
     }

From 76a5d664a781e656fa234117a2378a53f5d0cdb4 Mon Sep 17 00:00:00 2001
From: ShenMian <sms_school@outlook.com>
Date: Sat, 20 Jul 2024 21:30:41 +0100
Subject: [PATCH 3/3] refactor(camera): replace magic number with constant

---
 src/camera.rs | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/camera.rs b/src/camera.rs
index b85767d..7a2dcb4 100644
--- a/src/camera.rs
+++ b/src/camera.rs
@@ -57,20 +57,21 @@ pub fn update(
         let center_to_cursor = cursor_position - half_viewport_size;
         let normalized_length = center_to_cursor / half_viewport_size;
 
-        if normalized_length.x.abs() >= 0.8 {
+        let threshold = 0.8;
+        if normalized_length.x.abs() >= threshold {
             transform.translation.x += time.delta_seconds()
                 * normalized_length
                     .x
                     .abs()
-                    .remap(0.8, 1., min_speed, max_speed)
+                    .remap(threshold, 1., min_speed, max_speed)
                     .copysign(normalized_length.x);
         }
-        if normalized_length.y.abs() >= 0.8 {
+        if normalized_length.y.abs() >= threshold {
             transform.translation.y -= time.delta_seconds()
                 * normalized_length
                     .y
                     .abs()
-                    .remap(0.8, 1., min_speed, max_speed)
+                    .remap(threshold, 1., min_speed, max_speed)
                     .copysign(normalized_length.y);
         }
     }