ui & desktop: Add a basic “Quit” button.

all-is-cubes-desktop/src/main.rs

@@ -163,7 +163,15 @@ fn main() -> Result<(), anyhow::Error> {
     ));
 
     let start_session_time = Instant::now();
-    let session = runtime.block_on(Session::builder().ui(viewport_cell.as_source()).build());
+    let session = runtime.block_on(
+        Session::builder()
+            .ui(viewport_cell.as_source())
+            .quit(Arc::new(|| {
+                // TODO: command the event loop to exit instead
+                std::process::exit(0)
+            }))
+            .build(),
+    );
     session.graphics_options_mut().set(graphics_options);
     let session_done_time = Instant::now();
     log::debug!(

all-is-cubes-ui/src/apps/session.rs

@@ -531,6 +531,8 @@ pub struct SessionBuilder<I> {
     fullscreen_state: ListenableSource<FullscreenState>,
     set_fullscreen: FullscreenSetter,
 
+    quit: Option<QuitFn>,
+
     _instant: PhantomData<I>,
 }
 
@@ -540,6 +542,7 @@ impl<I> Default for SessionBuilder<I> {
             viewport_for_ui: None,
             fullscreen_state: ListenableSource::constant(None),
             set_fullscreen: None,
+            quit: None,
             _instant: PhantomData,
         }
     }
@@ -556,6 +559,7 @@ impl<I: time::Instant> SessionBuilder<I> {
             viewport_for_ui,
             fullscreen_state,
             set_fullscreen,
+            quit,
             _instant: _,
         } = self;
         let game_universe = Universe::new();
@@ -579,6 +583,7 @@ impl<I: time::Instant> SessionBuilder<I> {
                         viewport,
                         fullscreen_state,
                         set_fullscreen,
+                        quit,
                     )
                     .await,
                 ),
@@ -627,6 +632,15 @@ impl<I: time::Instant> SessionBuilder<I> {
         self.set_fullscreen = setter;
         self
     }
+
+    /// Enable a “quit”/“exit” command in the session's user interface.
+    ///
+    /// This does not cause the session to self-destruct; rather, the provided callback
+    /// function should cause the session’s owner to stop presenting it to the user.
+    pub fn quit(mut self, quit_fn: QuitFn) -> Self {
+        self.quit = Some(quit_fn);
+        self
+    }
 }
 
 // TODO: these should be in one struct or something.
@@ -758,6 +772,20 @@ pub enum CursorIcon {
     PointingHand,
 }
 
+/// TODO: this should be an async fn
+pub(crate) type QuitFn = Arc<dyn Fn() -> Result<QuitSucceeded, QuitCancelled> + Send + Sync>;
+
+/// Return type of a [`SessionBuilder::quit()`] callback on successful quit.
+/// This is uninhabited (cannot happen) since the callback should never be observed to
+/// finish if it successfully quits.
+pub type QuitSucceeded = std::convert::Infallible;
+
+/// Return type of a [`SessionBuilder::quit()`] callback if other considerations cancelled
+/// the quit operation. In this case, the session will return to normal operation.
+#[derive(Clone, Copy, Debug, PartialEq)]
+#[allow(clippy::exhaustive_structs)]
+pub struct QuitCancelled;
+
 #[cfg(test)]
 mod tests {
     use super::*;

all-is-cubes-ui/src/ui_content/hud.rs

@@ -40,6 +40,7 @@ pub(crate) struct HudInputs {
     pub mouselook_mode: ListenableSource<bool>,
     pub fullscreen_mode: ListenableSource<FullscreenState>,
     pub set_fullscreen: FullscreenSetter,
+    pub(crate) quit: Option<crate::apps::QuitFn>,
 }
 
 impl fmt::Debug for HudInputs {

all-is-cubes-ui/src/ui_content/pages.rs

@@ -23,24 +23,40 @@ pub(super) fn new_paused_widget_tree(
 ) -> Result<WidgetTree, InstallVuiError> {
     use parts::{heading, shrink};
 
+    let mut children = vec![
+        // TODO: establish standard resolutions for logo etc
+        LayoutTree::leaf(shrink(u, R16, LayoutTree::leaf(logo_text()))?),
+        LayoutTree::leaf(shrink(u, R32, heading("Paused"))?),
+        LayoutTree::leaf(open_page_button(
+            hud_inputs,
+            VuiPageState::AboutText,
+            hud_inputs.hud_blocks.blocks[UiBlocks::AboutButtonLabel].clone(),
+        )),
+        LayoutTree::leaf(open_page_button(
+            hud_inputs,
+            VuiPageState::Options,
+            hud_inputs.hud_blocks.blocks[UiBlocks::OptionsButtonLabel].clone(),
+        )),
+        LayoutTree::leaf(pause_toggle_button(hud_inputs)),
+    ];
+    if let Some(quit_fn) = hud_inputs.quit.as_ref().cloned() {
+        children.push(LayoutTree::leaf(widgets::ActionButton::new(
+            hud_inputs.hud_blocks.blocks[UiBlocks::QuitButtonLabel].clone(),
+            &hud_inputs.hud_blocks.blocks,
+            // TODO: quit_fn should be an async function, but we don't have a way to
+            // kick off a “Quitting...” task yet.
+            move || match quit_fn() {
+                Ok(s) => match s {},
+                Err(crate::apps::QuitCancelled) => {
+
+                    // TODO: display message indicating failure
+                }
+            },
+        )))
+    }
     let contents = Arc::new(LayoutTree::Stack {
         direction: Face6::NY,
-        children: vec![
-            // TODO: establish standard resolutions for logo etc
-            LayoutTree::leaf(shrink(u, R16, LayoutTree::leaf(logo_text()))?),
-            LayoutTree::leaf(shrink(u, R32, heading("Paused"))?),
-            LayoutTree::leaf(open_page_button(
-                hud_inputs,
-                VuiPageState::AboutText,
-                hud_inputs.hud_blocks.blocks[UiBlocks::AboutButtonLabel].clone(),
-            )),
-            LayoutTree::leaf(open_page_button(
-                hud_inputs,
-                VuiPageState::Options,
-                hud_inputs.hud_blocks.blocks[UiBlocks::OptionsButtonLabel].clone(),
-            )),
-            LayoutTree::leaf(pause_toggle_button(hud_inputs)),
-        ],
+        children,
     });
     Ok(page_modal_backdrop(Arc::new(LayoutTree::Shrink(
         hud_inputs

all-is-cubes-ui/src/ui_content/vui_manager.rs

@@ -14,7 +14,7 @@ use all_is_cubes::time;
 use all_is_cubes::transaction::{self, Transaction};
 use all_is_cubes::universe::{URef, Universe, UniverseStepInfo};
 
-use crate::apps::{ControlMessage, FullscreenSetter, FullscreenState, InputProcessor};
+use crate::apps::{ControlMessage, FullscreenSetter, FullscreenState, InputProcessor, QuitFn};
 use crate::ui_content::hud::{HudBlocks, HudInputs};
 use crate::ui_content::pages;
 use crate::vui::widgets::TooltipState;
@@ -80,6 +80,7 @@ impl Vui {
         viewport_source: ListenableSource<Viewport>,
         fullscreen_source: ListenableSource<FullscreenState>,
         set_fullscreen: FullscreenSetter,
+        quit: Option<QuitFn>,
     ) -> Self {
         let mut universe = Universe::new();
         // TODO: take YieldProgress as a parameter
@@ -111,6 +112,7 @@ impl Vui {
             mouselook_mode: input_processor.mouselook_mode(),
             fullscreen_mode: fullscreen_source,
             set_fullscreen,
+            quit,
         };
         let hud_widget_tree = super::hud::new_hud_widget_tree(
             character_source.clone(),
@@ -471,6 +473,7 @@ mod tests {
             ListenableSource::constant(Viewport::ARBITRARY),
             ListenableSource::constant(None),
             None,
+            None,
         )
         .await;
         (vui, ccrx)

all-is-cubes-ui/src/vui/blocks.rs

@@ -54,6 +54,7 @@ pub enum UiBlocks {
     AboutButtonLabel,
     PauseButtonLabel,
     SaveButtonLabel,
+    QuitButtonLabel,
     OptionsButtonLabel,
     MouselookButtonLabel,
     FullscreenButtonLabel,
@@ -86,6 +87,7 @@ impl fmt::Display for UiBlocks {
             UiBlocks::AboutButtonLabel => write!(f, "about-button"),
             UiBlocks::PauseButtonLabel => write!(f, "pause-button"),
             UiBlocks::SaveButtonLabel => write!(f, "save-button"),
+            UiBlocks::QuitButtonLabel => write!(f, "quit-button"),
             UiBlocks::OptionsButtonLabel => write!(f, "options-button"),
             UiBlocks::MouselookButtonLabel => write!(f, "mouselook-button"),
             UiBlocks::FullscreenButtonLabel => write!(f, "fullscreen-button"),
@@ -203,6 +205,13 @@ impl UiBlocks {
                 )?
                 .build(),
 
+                UiBlocks::QuitButtonLabel => make_button_label_block(
+                    universe,
+                    "Quit",
+                    ButtonIcon::Text(&font::FONT_7X13, "Quit"),
+                )?
+                .build(),
+
                 UiBlocks::OptionsButtonLabel => make_button_label_block(
                     universe,
                     "Options",