T13a Lists: ListItem, List, SelectableList, VirtualList, InfiniteList, GroupedList, SortableList, SwipeableListItem (review pending: codex 401)

examples/gallery/swipe.rs

@@ -0,0 +1,91 @@
+use anyhow::Result;
+use gpui::{AsyncApp, Pixels, Point, WindowHandle};
+
+use crate::{capture::number, shell::Gallery};
+
+/// A scroll's phase, as AppKit numbers them.
+pub const BEGAN: i64 = 1;
+pub const CHANGED: i64 = 2;
+pub const ENDED: i64 = 4;
+
+pub fn swipe(
+    window: WindowHandle<Gallery>,
+    at: Point<Pixels>,
+    across: f32,
+    phase: i64,
+    cx: &mut AsyncApp,
+) -> Result<()> {
+    let (height, number) = window.update(cx, |_, window, _| {
+        (window.viewport_size().height, number(window))
+    })?;
+    post_scroll(
+        f64::from(at.x),
+        f64::from(height - at.y),
+        across,
+        phase,
+        number?,
+    )
+}
+
+/// Sends a real trackpad scroll to the window, sideways by `across` points, with its phase. Quartz scrolls carry no window, so AppKit reads their location as window points and the window takes them directly.
+#[cfg(target_os = "macos")]
+fn post_scroll(x: f64, y: f64, across: f32, phase: i64, number: u32) -> Result<()> {
+    use cocoa::{
+        appkit::NSApp,
+        base::{id, nil},
+        foundation::NSRect,
+    };
+    use objc::{class, msg_send, sel, sel_impl};
+    type Event = *mut std::ffi::c_void;
+    #[repr(C)]
+    struct Spot {
+        x: f64,
+        y: f64,
+    }
+    unsafe extern "C" {
+        fn CGEventCreateScrollWheelEvent2(
+            source: *const std::ffi::c_void,
+            units: u32,
+            count: u32,
+            wheel1: i32,
+            wheel2: i32,
+            wheel3: i32,
+        ) -> Event;
+        fn CGEventSetIntegerValueField(event: Event, field: u32, value: i64);
+        fn CGEventSetLocation(event: Event, at: Spot);
+        fn CFRelease(object: *const std::ffi::c_void);
+    }
+    const PIXELS: u32 = 0;
+    const CONTINUOUS: u32 = 88;
+    const PHASE: u32 = 99;
+    unsafe {
+        let window: id = msg_send![NSApp(), windowWithWindowNumber: i64::from(number)];
+        anyhow::ensure!(window != nil, "no window numbered {number}");
+        let screens: id = msg_send![class!(NSScreen), screens];
+        let primary: id = msg_send![screens, objectAtIndex: 0usize];
+        let frame: NSRect = msg_send![primary, frame];
+        let event = CGEventCreateScrollWheelEvent2(
+            std::ptr::null(),
+            PIXELS,
+            2,
+            0,
+            across.round() as i32,
+            0,
+        );
+        anyhow::ensure!(!event.is_null(), "Quartz refused a scroll event");
+        CGEventSetLocation(
+            event,
+            Spot {
+                x,
+                y: frame.size.height - y,
+            },
+        );
+        CGEventSetIntegerValueField(event, CONTINUOUS, 1);
+        CGEventSetIntegerValueField(event, PHASE, phase);
+        let scroll: id = msg_send![class!(NSEvent), eventWithCGEvent: event];
+        CFRelease(event);
+        anyhow::ensure!(scroll != nil, "AppKit refused a scroll event");
+        let _: () = msg_send![window, sendEvent: scroll];
+    }
+    Ok(())
+}