From c5670840cc6eae4c239f3320ed3c0bba8fb771f8 Mon Sep 17 00:00:00 2001
From: Jasen Borisov <40234599+jamadazi@users.noreply.github.com>
Date: Mon, 15 Feb 2021 18:59:23 +0100
Subject: [PATCH] Use System Chains to handle Buttons (#12)

* Use System Chains to handle Buttons

* cargo fmt
---
 src/main.rs           | 22 ++++++++++++++++++++--
 src/menu/main_menu.rs | 27 +++++++++++++++++++++++----
 src/menu/mod.rs       | 40 ++++++++++++++++++++--------------------
 src/menu/settings.rs  | 10 ++++++++--
 4 files changed, 71 insertions(+), 28 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index b08e26f..ca2c183 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -57,7 +57,23 @@ fn main() {
         .on_state_update(
             APPSTATES,
             AppState::MainMenu,
-            menu::button_interact.system(),
+            menu::button_interact::<menu::button::ExitApp>
+                .system()
+                .chain(menu::main_menu::button_exit_app.system()),
+        )
+        .on_state_update(
+            APPSTATES,
+            AppState::MainMenu,
+            menu::button_interact::<menu::button::EnterGame>
+                .system()
+                .chain(menu::main_menu::button_enter_game.system()),
+        )
+        .on_state_update(
+            APPSTATES,
+            AppState::MainMenu,
+            menu::button_interact::<menu::button::OpenSettingsMenu>
+                .system()
+                .chain(menu::main_menu::button_open_settings_menu.system()),
         )
         .on_state_exit(
             APPSTATES,
@@ -73,7 +89,9 @@ fn main() {
         .on_state_update(
             APPSTATES,
             AppState::SettingsMenu,
-            menu::button_interact.system(),
+            menu::button_interact::<menu::button::ExitSettingsMenu>
+                .system()
+                .chain(menu::settings::button_exit_settings_menu.system()),
         )
         .on_state_exit(
             APPSTATES,
diff --git a/src/menu/main_menu.rs b/src/menu/main_menu.rs
index d058038..f705de2 100644
--- a/src/menu/main_menu.rs
+++ b/src/menu/main_menu.rs
@@ -1,11 +1,30 @@
+use bevy::app::AppExit;
 use bevy::prelude::*;
 
-use crate::menu::{ClickAction, MenuAssets};
+use crate::menu::{button, MenuAssets};
 use crate::AppState;
 
 /// Marker for despawning when exiting `AppState::MainMenu`
 pub struct StateCleanup;
 
+pub fn button_exit_app(In(clicked): In<bool>, mut app_exit: ResMut<Events<AppExit>>) {
+    if clicked {
+        app_exit.send(AppExit);
+    }
+}
+
+pub fn button_enter_game(In(clicked): In<bool>, mut state: ResMut<State<AppState>>) {
+    if clicked {
+        state.set_next(AppState::Overworld).unwrap();
+    }
+}
+
+pub fn button_open_settings_menu(In(clicked): In<bool>, mut state: ResMut<State<AppState>>) {
+    if clicked {
+        state.set_next(AppState::SettingsMenu).unwrap();
+    }
+}
+
 pub fn setup(commands: &mut Commands, assets: Res<MenuAssets>) {
     let button_style = Style {
         size: Size::new(Val::Auto, Val::Auto),
@@ -98,7 +117,7 @@ pub fn setup(commands: &mut Commands, assets: Res<MenuAssets>) {
                             style: button_style.clone(),
                             ..Default::default()
                         })
-                        .with(ClickAction::ChangeState(AppState::Overworld))
+                        .with(button::EnterGame)
                         .with_children(|button| {
                             button.spawn(TextBundle {
                                 text: Text::with_section(
@@ -124,7 +143,7 @@ pub fn setup(commands: &mut Commands, assets: Res<MenuAssets>) {
                             style: button_style.clone(),
                             ..Default::default()
                         })
-                        .with(ClickAction::ChangeState(AppState::SettingsMenu))
+                        .with(button::OpenSettingsMenu)
                         .with_children(|button| {
                             button.spawn(TextBundle {
                                 text: Text::with_section(
@@ -141,7 +160,7 @@ pub fn setup(commands: &mut Commands, assets: Res<MenuAssets>) {
                             style: button_style.clone(),
                             ..Default::default()
                         })
-                        .with(ClickAction::Exit)
+                        .with(button::ExitApp)
                         .with_children(|button| {
                             button.spawn(TextBundle {
                                 text: Text::with_section(
diff --git a/src/menu/mod.rs b/src/menu/mod.rs
index b3b726c..19c1c95 100644
--- a/src/menu/mod.rs
+++ b/src/menu/mod.rs
@@ -1,11 +1,18 @@
-use bevy::app::AppExit;
 use bevy::prelude::*;
 
-use crate::AppState;
-
 pub mod main_menu;
 pub mod settings;
 
+/// Every logical action for which we can have a UI button
+///
+/// Use as marker components to identify the buttons.
+pub mod button {
+    pub struct EnterGame;
+    pub struct ExitApp;
+    pub struct OpenSettingsMenu;
+    pub struct ExitSettingsMenu;
+}
+
 pub struct MenuAssets {
     button_normal: Handle<ColorMaterial>,
     button_hover: Handle<ColorMaterial>,
@@ -47,32 +54,25 @@ impl FromResources for MenuAssets {
     }
 }
 
-pub enum ClickAction {
-    ChangeState(AppState),
-    Exit,
-}
-
-pub fn button_interact(
-    mut state: ResMut<State<AppState>>,
-    mut app_exit: ResMut<Events<AppExit>>,
+pub fn button_interact<B: Component>(
     materials: Res<MenuAssets>,
     mut query: Query<
-        (&Interaction, &mut Handle<ColorMaterial>, &ClickAction),
-        (Mutated<Interaction>, With<Button>),
+        (&Interaction, &mut Handle<ColorMaterial>),
+        (Mutated<Interaction>, With<Button>, With<B>),
     >,
-) {
-    for (interaction, mut material, action) in query.iter_mut() {
+) -> bool {
+    let mut clicked = false;
+
+    for (interaction, mut material) in query.iter_mut() {
         match interaction {
             Interaction::Clicked => {
                 *material = materials.button_active.clone();
-
-                match action {
-                    ClickAction::ChangeState(next) => state.set_next(*next).unwrap(),
-                    ClickAction::Exit => app_exit.send(AppExit),
-                }
+                clicked = true;
             }
             Interaction::Hovered => *material = materials.button_hover.clone(),
             Interaction::None => *material = materials.button_normal.clone(),
         }
     }
+
+    clicked
 }
diff --git a/src/menu/settings.rs b/src/menu/settings.rs
index 4b1478e..eb9e9a9 100644
--- a/src/menu/settings.rs
+++ b/src/menu/settings.rs
@@ -1,11 +1,17 @@
 use bevy::prelude::*;
 
-use crate::menu::{ClickAction, MenuAssets};
+use crate::menu::{button, MenuAssets};
 use crate::AppState;
 
 /// Marker for despawning when exiting `AppState::SettingsMenu`
 pub struct StateCleanup;
 
+pub fn button_exit_settings_menu(In(clicked): In<bool>, mut state: ResMut<State<AppState>>) {
+    if clicked {
+        state.set_next(AppState::MainMenu).unwrap();
+    }
+}
+
 pub fn setup(commands: &mut Commands, assets: Res<MenuAssets>) {
     let button_style = Style {
         size: Size::new(Val::Auto, Val::Auto),
@@ -121,7 +127,7 @@ pub fn setup(commands: &mut Commands, assets: Res<MenuAssets>) {
                             style: button_style.clone(),
                             ..Default::default()
                         })
-                        .with(ClickAction::ChangeState(AppState::MainMenu))
+                        .with(button::ExitSettingsMenu)
                         .with_children(|button| {
                             button.spawn(TextBundle {
                                 text: Text::with_section(