From d949a952bb804b8423a8155d6be1503488d5ee9e Mon Sep 17 00:00:00 2001
From: Thom Bruce <thom@thombruce.com>
Date: Wed, 25 Oct 2023 03:02:04 +0100
Subject: [PATCH 1/4] show damage at ship position when hit

---
 CHANGELOG.md     |  4 +++
 src/ui/damage.rs | 64 ++++++++++++++++++++++++++++++++++++++++++++++++
 src/ui/mod.rs    |  3 +++
 3 files changed, 71 insertions(+)
 create mode 100644 src/ui/damage.rs

diff --git a/CHANGELOG.md b/CHANGELOG.md
index de39dc6..7981bc4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- UI damage indicators appear when a ship is hit
+
 ### Changed
 
 - Camera scaling to 1.5, more zoomed out, see enemies on screen for longer
diff --git a/src/ui/damage.rs b/src/ui/damage.rs
new file mode 100644
index 0000000..24ca094
--- /dev/null
+++ b/src/ui/damage.rs
@@ -0,0 +1,64 @@
+use bevy::prelude::*;
+
+use crate::{
+    core::resources::{assets::UiAssets, state::GameState},
+    ships::{
+        bullet::BulletShipContactEvent,
+        ship::{AttackSet, Ship},
+    },
+};
+
+pub struct UiDamagePlugin;
+impl Plugin for UiDamagePlugin {
+    fn build(&self, app: &mut App) {
+        app.add_systems(
+            Update,
+            (ui_spawn_damage, ui_update_damage)
+                .after(AttackSet)
+                .run_if(in_state(GameState::Active)),
+        );
+    }
+}
+
+fn ui_spawn_damage(
+    mut commands: Commands,
+    mut bullet_ship_contact_events: EventReader<BulletShipContactEvent>,
+    ship_transform: Query<&Transform, With<Ship>>,
+    camera_query: Query<(&Camera, &GlobalTransform)>,
+    ui: Res<UiAssets>,
+) {
+    for event in bullet_ship_contact_events.iter() {
+        if let Ok(transform) = ship_transform.get(event.ship) {
+            // Use camera.world_to_viewport() and camera GlobalTransform to translate
+            // a world position into UI coordinates
+            let (camera, camera_transform) = camera_query.single();
+            let coords = camera
+                .world_to_viewport(camera_transform, transform.translation)
+                .unwrap();
+
+            commands.spawn(TextBundle {
+                text: Text::from_section(
+                    "100",
+                    TextStyle {
+                        font: ui.font.clone(),
+                        font_size: 25.0,
+                        color: Color::RED,
+                        ..default()
+                    },
+                ),
+                style: Style {
+                    position_type: PositionType::Absolute,
+                    top: Val::Px(coords.y),
+                    left: Val::Px(coords.x),
+                    ..default()
+                },
+                ..default()
+            });
+        }
+    }
+}
+
+fn ui_update_damage() {
+    // TODO: Update damage text position
+    // TODO: Despawn damage on a timer (maybe reuse the bullet despawn timer for this?)
+}
diff --git a/src/ui/mod.rs b/src/ui/mod.rs
index 392c20d..832bc0c 100644
--- a/src/ui/mod.rs
+++ b/src/ui/mod.rs
@@ -1,11 +1,13 @@
 use bevy::prelude::*;
 
 pub mod camera;
+pub mod damage;
 pub mod hud;
 pub mod menus;
 
 use self::{
     camera::CameraPlugin,
+    damage::UiDamagePlugin,
     hud::HudPlugin,
     menus::{credits::CreditsPlugin, pause::PausePlugin, start_menu::MenuPlugin},
 };
@@ -19,6 +21,7 @@ impl Plugin for UiPlugin {
             CreditsPlugin,
             PausePlugin,
             CameraPlugin,
+            UiDamagePlugin,
         ));
     }
 }

From 92347cfbe59839c2c1f8567eb884e3d78e4c8a67 Mon Sep 17 00:00:00 2001
From: Thom Bruce <thom@thombruce.com>
Date: Wed, 25 Oct 2023 03:20:43 +0100
Subject: [PATCH 2/4] despawn UI damage after half a second

---
 src/core/mod.rs                     | 10 ++++++--
 src/core/resources/despawn_timer.rs | 26 +++++++++++++++++++++
 src/core/resources/mod.rs           |  1 +
 src/ships/bullet.rs                 | 26 ++++-----------------
 src/ui/damage.rs                    | 36 +++++++++++++++--------------
 5 files changed, 59 insertions(+), 40 deletions(-)
 create mode 100644 src/core/resources/despawn_timer.rs

diff --git a/src/core/mod.rs b/src/core/mod.rs
index e1b3993..fd54b3b 100644
--- a/src/core/mod.rs
+++ b/src/core/mod.rs
@@ -5,12 +5,18 @@ pub mod resources;
 
 use self::{
     effects::{animate::AnimatePlugin, blink::EffectsPlugin},
-    resources::{game_time::GameTimePlugin, state::StatePlugin},
+    resources::{despawn_timer::DespawnTimerPlugin, game_time::GameTimePlugin, state::StatePlugin},
 };
 
 pub struct CorePlugin;
 impl Plugin for CorePlugin {
     fn build(&self, app: &mut App) {
-        app.add_plugins((GameTimePlugin, StatePlugin, EffectsPlugin, AnimatePlugin));
+        app.add_plugins((
+            GameTimePlugin,
+            StatePlugin,
+            EffectsPlugin,
+            AnimatePlugin,
+            DespawnTimerPlugin,
+        ));
     }
 }
diff --git a/src/core/resources/despawn_timer.rs b/src/core/resources/despawn_timer.rs
new file mode 100644
index 0000000..9ce31d0
--- /dev/null
+++ b/src/core/resources/despawn_timer.rs
@@ -0,0 +1,26 @@
+use bevy::prelude::*;
+
+use crate::core::resources::state::GameState;
+
+#[derive(Component)]
+pub struct DespawnTimer(pub Timer);
+
+pub struct DespawnTimerPlugin;
+impl Plugin for DespawnTimerPlugin {
+    fn build(&self, app: &mut App) {
+        app.add_systems(Update, despawn_system.run_if(in_state(GameState::Active)));
+    }
+}
+
+fn despawn_system(
+    mut commands: Commands,
+    time: Res<Time>,
+    mut query: Query<(Entity, &mut DespawnTimer)>,
+) {
+    for (entity, mut bullet) in query.iter_mut() {
+        bullet.0.tick(time.delta());
+        if bullet.0.finished() {
+            commands.entity(entity).despawn();
+        }
+    }
+}
diff --git a/src/core/resources/mod.rs b/src/core/resources/mod.rs
index 4807e9f..87960ac 100644
--- a/src/core/resources/mod.rs
+++ b/src/core/resources/mod.rs
@@ -1,3 +1,4 @@
 pub mod assets;
+pub mod despawn_timer;
 pub mod game_time;
 pub mod state;
diff --git a/src/ships/bullet.rs b/src/ships/bullet.rs
index 7b49ad4..6d1c0d5 100644
--- a/src/ships/bullet.rs
+++ b/src/ships/bullet.rs
@@ -3,15 +3,14 @@ use bevy_rapier2d::prelude::*;
 
 use crate::core::resources::{
     assets::{AudioAssets, SpriteAssets},
+    despawn_timer::DespawnTimer,
     state::{ForState, GameState},
 };
 
 use super::ship::MovementSet;
 
 #[derive(Component)]
-pub struct Bullet {
-    pub despawn_timer: Timer,
-}
+pub struct Bullet;
 
 #[derive(Event)]
 pub struct BulletSpawnEvent {
@@ -34,8 +33,7 @@ impl Plugin for BulletPlugin {
             .add_event::<BulletShipContactEvent>()
             .add_systems(
                 Update,
-                (spawn_bullet.after(MovementSet), bullet_despawn_system)
-                    .run_if(in_state(GameState::Active)),
+                (spawn_bullet.after(MovementSet)).run_if(in_state(GameState::Active)),
             );
     }
 }
@@ -63,9 +61,8 @@ fn spawn_bullet(
                 texture: handles.bullet.clone(),
                 ..default()
             },
-            Bullet {
-                despawn_timer: Timer::from_seconds(2.0, TimerMode::Once),
-            },
+            Bullet,
+            DespawnTimer(Timer::from_seconds(2.0, TimerMode::Once)),
             ForState {
                 states: GameState::IN_GAME_STATE.to_vec(),
             },
@@ -81,16 +78,3 @@ fn spawn_bullet(
         ));
     }
 }
-
-fn bullet_despawn_system(
-    mut commands: Commands,
-    time: Res<Time>,
-    mut query: Query<(Entity, &mut Bullet)>,
-) {
-    for (entity, mut bullet) in query.iter_mut() {
-        bullet.despawn_timer.tick(time.delta());
-        if bullet.despawn_timer.finished() {
-            commands.entity(entity).despawn();
-        }
-    }
-}
diff --git a/src/ui/damage.rs b/src/ui/damage.rs
index 24ca094..07743f4 100644
--- a/src/ui/damage.rs
+++ b/src/ui/damage.rs
@@ -1,7 +1,7 @@
 use bevy::prelude::*;
 
 use crate::{
-    core::resources::{assets::UiAssets, state::GameState},
+    core::resources::{assets::UiAssets, despawn_timer::DespawnTimer, state::GameState},
     ships::{
         bullet::BulletShipContactEvent,
         ship::{AttackSet, Ship},
@@ -36,29 +36,31 @@ fn ui_spawn_damage(
                 .world_to_viewport(camera_transform, transform.translation)
                 .unwrap();
 
-            commands.spawn(TextBundle {
-                text: Text::from_section(
-                    "100",
-                    TextStyle {
-                        font: ui.font.clone(),
-                        font_size: 25.0,
-                        color: Color::RED,
+            commands.spawn((
+                TextBundle {
+                    text: Text::from_section(
+                        "100",
+                        TextStyle {
+                            font: ui.font.clone(),
+                            font_size: 25.0,
+                            color: Color::RED,
+                            ..default()
+                        },
+                    ),
+                    style: Style {
+                        position_type: PositionType::Absolute,
+                        top: Val::Px(coords.y),
+                        left: Val::Px(coords.x),
                         ..default()
                     },
-                ),
-                style: Style {
-                    position_type: PositionType::Absolute,
-                    top: Val::Px(coords.y),
-                    left: Val::Px(coords.x),
                     ..default()
                 },
-                ..default()
-            });
+                DespawnTimer(Timer::from_seconds(0.5, TimerMode::Once)),
+            ));
         }
     }
 }
 
 fn ui_update_damage() {
-    // TODO: Update damage text position
-    // TODO: Despawn damage on a timer (maybe reuse the bullet despawn timer for this?)
+    // TODO: Update damage text position, maybe fade out over time until disappearance
 }

From 9b6feb33242b244944e5018ca60fb357e5b9b89a Mon Sep 17 00:00:00 2001
From: Thom Bruce <thom@thombruce.com>
Date: Wed, 25 Oct 2023 04:26:55 +0100
Subject: [PATCH 3/4] fade UI damage text for the duration it's on screen

---
 src/ui/damage.rs | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/ui/damage.rs b/src/ui/damage.rs
index 07743f4..bf55f9f 100644
--- a/src/ui/damage.rs
+++ b/src/ui/damage.rs
@@ -8,12 +8,15 @@ use crate::{
     },
 };
 
+#[derive(Component)]
+struct UiTextFadeOut;
+
 pub struct UiDamagePlugin;
 impl Plugin for UiDamagePlugin {
     fn build(&self, app: &mut App) {
         app.add_systems(
             Update,
-            (ui_spawn_damage, ui_update_damage)
+            (ui_spawn_damage, ui_text_fade_out)
                 .after(AttackSet)
                 .run_if(in_state(GameState::Active)),
         );
@@ -56,11 +59,20 @@ fn ui_spawn_damage(
                     ..default()
                 },
                 DespawnTimer(Timer::from_seconds(0.5, TimerMode::Once)),
+                UiTextFadeOut,
             ));
         }
     }
 }
 
-fn ui_update_damage() {
-    // TODO: Update damage text position, maybe fade out over time until disappearance
+fn ui_text_fade_out(time: Res<Time>, mut text: Query<&mut Text, With<UiTextFadeOut>>) {
+    for mut txt in text.iter_mut() {
+        for section in txt.sections.iter_mut() {
+            let current_alpha = section.style.color.a();
+            section
+                .style
+                .color
+                .set_a(current_alpha - (2.0 * time.delta_seconds()));
+        }
+    }
 }

From 50cf59a3da9218eac54d1480e21cb1c2e152a437 Mon Sep 17 00:00:00 2001
From: Thom Bruce <thom@thombruce.com>
Date: Thu, 26 Oct 2023 02:53:42 +0100
Subject: [PATCH 4/4] move UI damage indicator upwards each frame until
 despawned

---
 src/ui/damage.rs        | 15 +++++++++++++--
 src/ui/menus/credits.rs | 12 ++++++------
 src/ui/mod.rs           |  1 +
 src/ui/resources/mod.rs |  1 +
 src/ui/resources/top.rs | 28 ++++++++++++++++++++++++++++
 5 files changed, 49 insertions(+), 8 deletions(-)
 create mode 100644 src/ui/resources/mod.rs
 create mode 100644 src/ui/resources/top.rs

diff --git a/src/ui/damage.rs b/src/ui/damage.rs
index bf55f9f..956746f 100644
--- a/src/ui/damage.rs
+++ b/src/ui/damage.rs
@@ -8,6 +8,8 @@ use crate::{
     },
 };
 
+use super::resources::top::Top;
+
 #[derive(Component)]
 struct UiTextFadeOut;
 
@@ -60,13 +62,22 @@ fn ui_spawn_damage(
                 },
                 DespawnTimer(Timer::from_seconds(0.5, TimerMode::Once)),
                 UiTextFadeOut,
+                Top(coords.y),
             ));
         }
     }
 }
 
-fn ui_text_fade_out(time: Res<Time>, mut text: Query<&mut Text, With<UiTextFadeOut>>) {
-    for mut txt in text.iter_mut() {
+fn ui_text_fade_out(
+    time: Res<Time>,
+    mut text: Query<(&mut Text, &mut Style, &mut Top), With<UiTextFadeOut>>,
+) {
+    for (mut txt, mut style, mut top) in text.iter_mut() {
+        // Moves the damage text upwards every frame
+        top.0 -= 100.0 * time.delta_seconds();
+        style.top = Val::Px(top.0);
+
+        // Fades the damage text out every frame
         for section in txt.sections.iter_mut() {
             let current_alpha = section.style.color.a();
             section
diff --git a/src/ui/menus/credits.rs b/src/ui/menus/credits.rs
index 8c55965..43b7ef7 100644
--- a/src/ui/menus/credits.rs
+++ b/src/ui/menus/credits.rs
@@ -1,8 +1,11 @@
 use bevy::prelude::*;
 
-use crate::core::resources::{
-    assets::UiAssets,
-    state::{ForState, GameState},
+use crate::{
+    core::resources::{
+        assets::UiAssets,
+        state::{ForState, GameState},
+    },
+    ui::resources::top::Top,
 };
 
 pub struct CreditsPlugin;
@@ -16,9 +19,6 @@ impl Plugin for CreditsPlugin {
 #[derive(Component)]
 pub struct Credits;
 
-#[derive(Component)]
-pub struct Top(pub f32);
-
 fn setup(mut commands: Commands, ui: Res<UiAssets>) {
     commands
         .spawn((
diff --git a/src/ui/mod.rs b/src/ui/mod.rs
index 832bc0c..6dd589e 100644
--- a/src/ui/mod.rs
+++ b/src/ui/mod.rs
@@ -4,6 +4,7 @@ pub mod camera;
 pub mod damage;
 pub mod hud;
 pub mod menus;
+pub mod resources;
 
 use self::{
     camera::CameraPlugin,
diff --git a/src/ui/resources/mod.rs b/src/ui/resources/mod.rs
new file mode 100644
index 0000000..f6229ea
--- /dev/null
+++ b/src/ui/resources/mod.rs
@@ -0,0 +1 @@
+pub mod top;
diff --git a/src/ui/resources/top.rs b/src/ui/resources/top.rs
new file mode 100644
index 0000000..c87a0ea
--- /dev/null
+++ b/src/ui/resources/top.rs
@@ -0,0 +1,28 @@
+use bevy::prelude::*;
+
+// TODO: This is actually just some arbitrary value we wanted to be able to change.
+//       It was originally created for credits scrolling and ported from there,
+//       and is now also being used in the ui/damage.rs system.
+//       Both systems wanted to be able to change the "top" value of a UI
+//       element, set as a Val::[Px, Percent, VMax, VMin, VH, VW](f32) which
+//       it seems we can't otherwise perform calculations on.
+//       So what this is, really, is a wrapper around some f32 intended to be used
+//       in some other UI element.
+//
+//       We might therefore think about renaming it to something like Uif32 so that it
+//       could be used more generally for Top, Bottom, Left, Right, Margin, Padding, etc.
+//
+//       But what if we wanted to change two or more such values? An entity can't have
+//       more than one of a single component, can it?
+//
+//       No, but... we should create more of these and determine what's common about them,
+//       see if we can implement some kind of inheritence, and also generalise the system(s)
+//       that are responsible for converting these values into Val::* ones.
+//
+//       Though, I'm not certain how possible that is... Are these values always in a
+//       Style component? And how do we determine what kind of Val to set?
+//
+//       Perhaps 'Top'/'Uif32Top'/* should have a secondary value indicating type?
+//       Following this, the conversions could be handled in a single system here.
+#[derive(Component)]
+pub struct Top(pub f32);