Add Servo scroll snapshots

crates/ely_app/src/shell/web_surface_geometry.rs

@@ -0,0 +1,95 @@
+use gpui::{Bounds, Pixels, Point};
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub(super) struct WebSurfaceSize {
+    pub(super) width: u32,
+    pub(super) height: u32,
+}
+
+impl WebSurfaceSize {
+    pub(super) fn from_bounds(bounds: Bounds<Pixels>) -> Option<Self> {
+        Some(Self {
+            width: viewport_dimension(bounds.size.width)?,
+            height: viewport_dimension(bounds.size.height)?,
+        })
+    }
+}
+
+#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
+pub(super) struct WebSurfaceScrollOffset {
+    x: i32,
+    y: i32,
+}
+
+impl WebSurfaceScrollOffset {
+    pub(super) fn scrolled_by(self, delta: WebSurfaceScrollDelta) -> Self {
+        Self {
+            x: positive_scroll_component(self.x, delta.x),
+            y: positive_scroll_component(self.y, delta.y),
+        }
+    }
+
+    pub(super) fn detail_label(self, size: WebSurfaceSize) -> String {
+        match (self.x, self.y) {
+            (0, 0) => format!("{}x{}", size.width, size.height),
+            (0, y) => format!("{}x{} y={y}", size.width, size.height),
+            (x, y) => format!("{}x{} x={x} y={y}", size.width, size.height),
+        }
+    }
+
+    pub(super) fn x(self) -> i32 {
+        self.x
+    }
+
+    pub(super) fn y(self) -> i32 {
+        self.y
+    }
+}
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub(super) struct WebSurfaceScrollDelta {
+    x: i32,
+    y: i32,
+}
+
+impl WebSurfaceScrollDelta {
+    pub(super) fn from_point(delta: Point<Pixels>) -> Option<Self> {
+        let x = scroll_dimension(delta.x)?;
+        let y = scroll_dimension(delta.y)?;
+        if x == 0 && y == 0 {
+            return None;
+        }
+
+        Some(Self { x, y })
+    }
+}
+
+fn viewport_dimension(pixels: Pixels) -> Option<u32> {
+    let value = f32::from(pixels.round());
+    if !value.is_finite() || value < 1.0 || value > u32::MAX as f32 {
+        return None;
+    }
+
+    Some(value as u32)
+}
+
+fn scroll_dimension(pixels: Pixels) -> Option<i32> {
+    let value = f32::from(pixels.round());
+    if !value.is_finite() {
+        return None;
+    }
+    if value > i32::MAX as f32 {
+        return Some(i32::MAX);
+    }
+    if value < i32::MIN as f32 {
+        return Some(i32::MIN);
+    }
+
+    Some(value as i32)
+}
+
+fn positive_scroll_component(current: i32, delta: i32) -> i32 {
+    let value = i64::from(current) + i64::from(delta);
+    let clamped = value.clamp(0, i64::from(i32::MAX));
+    clamped as i32
+}