T20 round 1 fixes

- the hex demo's selection stops at memory's end
- a disassembly gutter fills its row, so an empty one takes a press
- a breakpoint's box keeps its press from the row
- ruler ticks keep the places their step needs
- the toolbar names each usual key for the platform; the app binds them
- tests: gutter press, box press, tick places

src/debug/tests.rs

@@ -0,0 +1,97 @@
+use std::{cell::RefCell, rc::Rc};
+
+use gpui::{
+    Context, IntoElement, Modifiers, ParentElement, Render, Styled, TestAppContext,
+    VisualTestContext, Window, div, point, px,
+};
+
+use super::{Breakpoint, BreakpointList, Disassembly, Instruction};
+use crate::theme::Theme;
+
+fn settle(cx: &mut VisualTestContext) {
+    cx.run_until_parked();
+    cx.update(|window, _| window.refresh());
+    cx.run_until_parked();
+}
+
+/// Two plain instructions; it keeps the gutter presses.
+struct Listing(Rc<RefCell<Vec<usize>>>);
+
+impl Render for Listing {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        let store = self.0.clone();
+        let plain = |address| Instruction {
+            address,
+            bytes: vec![0x90],
+            mnemonic: "nop".into(),
+            operands: "".into(),
+            comment: None,
+            source: None,
+        };
+        div().w(px(400.0)).h(px(200.0)).child(
+            Disassembly::new("listing", vec![plain(0x10), plain(0x11)])
+                .on_breakpoint(move |ix, _, _| store.borrow_mut().push(ix)),
+        )
+    }
+}
+
+#[gpui::test]
+fn an_empty_gutter_takes_a_press_across_its_row(cx: &mut TestAppContext) {
+    cx.update(Theme::init);
+    let seen = Rc::new(RefCell::new(Vec::new()));
+    let store = seen.clone();
+    let (_, cx) = cx.add_window_view(|_, _| Listing(store));
+    settle(cx);
+    cx.simulate_click(point(px(10.0), px(2.0)), Modifiers::none());
+    settle(cx);
+    assert_eq!(*seen.borrow(), [0]);
+}
+
+/// One breakpoint; it keeps what its toggle and open report.
+struct Points {
+    toggles: Rc<RefCell<Vec<(usize, bool)>>>,
+    opens: Rc<RefCell<Vec<usize>>>,
+}
+
+impl Render for Points {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        let (toggles, opens) = (self.toggles.clone(), self.opens.clone());
+        let point = Breakpoint {
+            path: "src/lift.rs".into(),
+            line: 3,
+            enabled: true,
+            condition: None,
+            hits: 0,
+        };
+        div().w(px(400.0)).child(
+            BreakpointList::new("points", [point])
+                .on_toggle(move |ix, on, _, _| toggles.borrow_mut().push((ix, on)))
+                .on_open(move |ix, _, _| opens.borrow_mut().push(ix)),
+        )
+    }
+}
+
+#[gpui::test]
+fn a_breakpoints_box_toggles_without_opening_it(cx: &mut TestAppContext) {
+    cx.update(Theme::init);
+    let (toggles, opens) = (
+        Rc::new(RefCell::new(Vec::new())),
+        Rc::new(RefCell::new(Vec::new())),
+    );
+    let view = Points {
+        toggles: toggles.clone(),
+        opens: opens.clone(),
+    };
+    let (_, cx) = cx.add_window_view(|_, _| view);
+    settle(cx);
+    cx.simulate_click(point(px(14.0), px(12.0)), Modifiers::none());
+    settle(cx);
+    assert_eq!(*toggles.borrow(), [(0, false)]);
+    assert!(
+        opens.borrow().is_empty(),
+        "the box press stays with the box"
+    );
+    cx.simulate_click(point(px(200.0), px(12.0)), Modifiers::none());
+    settle(cx);
+    assert_eq!(*opens.borrow(), [0], "the row still opens");
+}