Interaction · Pointer: resize, turn, band selection, and gpui's own drag

Resizable sizes a box from its right and bottom edges and a grip at
its corner, within its least and greatest size; the grip is a Tab stop
whose arrows resize a step. Rotatable turns an svg to its angle inside
a ring whose knob a drag moves, Shift snapping to 15 degrees, with the
arrows turning it a notch. SelectionArea selects items with a band
drawn on empty space, a press, Command or Shift to add, and a cursor
the arrows walk with Space to add or drop; Escape clears and
Command-A takes all. The gallery shows gpui's own drag and drop, drag
preview, double press and wheel zoom, with pointers for Sortable,
LongPress and PanZoom; pinch stays blocked, gpui 0.2.2 forwards no
magnify event.

src/theme/interaction.rs

@@ -0,0 +1,21 @@
+use gpui::Rems;
+
+use super::{Theme, tokens::px_to_rems};
+
+/// Interaction's measures.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct InteractionSizes {
+    /// What an arrow key resizes a box by.
+    pub step: Rems,
+    /// A resize corner's grip, square.
+    pub grip: Rems,
+}
+
+impl Theme {
+    pub fn interaction(&self) -> InteractionSizes {
+        InteractionSizes {
+            step: px_to_rems(8.0),
+            grip: px_to_rems(12.0),
+        }
+    }
+}

src/theme/mod.rs

@@ -4,6 +4,7 @@ mod chart;
 mod dashboard;
 mod files;
 mod generative;
+mod interaction;
 mod media;
 mod messaging;
 mod onboarding;
@@ -22,6 +23,7 @@ pub use chart::ChartSizes;
 pub use dashboard::DashboardSizes;
 pub use files::FileSizes;
 pub use generative::GenerativeSizes;
+pub use interaction::InteractionSizes;
 pub use media::MediaSizes;
 pub use messaging::MessagingSizes;
 pub use onboarding::OnboardingSizes;