Fix multi-selected desktop icons only ever dragging one at a time

Reported live: "try move desktop items all at once somewhere else"
didn't work. Two compounding bugs, both real: CompState::
desktop_icon_drag only ever tracked one icon id, and the click handler
that starts a drag unconditionally collapsed any existing multi-
selection down to just the grabbed icon before the drag even began.

desktop_icon_drag is now Option<DesktopIconDrag> (crates/wayland/src/
desktop_icons.rs, new type): a grab offset, the grabbed icon's own live
position, and a members list - every currently-selected icon (the
grabbed one included), each a fixed offset from the grabbed icon's own
top-left at drag start, so the group moves as one rigid unit.
input/pointer.rs's click handler now only resets to single-selection
when the grabbed icon isn't already part of the current selection --
grabbing one inside an existing multi-selection keeps the whole group
selected and dragging, matching Windows/GNOME/macOS/KDE convention.
end_desktop_icon_drag snaps every dragged icon to its own nearest free
grid cell independently, tracking newly-claimed cells across the group
so two icons landing near each other never claim the same one.

Full workspace build/test/clippy clean, built and installed. Not unit-
testable (this module has no CompState test fixture for its own
selection/drag logic, an already-documented, accepted gap) - needs a
live drag to confirm.

1 files changed, 24 insertions, 0 deletions

diff --git a/crates/wayland/src/desktop_icons.rs b/crates/wayland/src/desktop_icons.rs
index 7cfcbd1..c3b573a 100644
--- a/crates/wayland/src/desktop_icons.rs
+++ b/crates/wayland/src/desktop_icons.rs
@@ -57,6 +57,30 @@ impl DesktopIcon {
     }
 }
 
+/// An in-progress icon drag that may carry more than one icon along
+/// together. `primary` is whichever icon the pointer actually grabbed;
+/// `members` is every icon moving with it (always includes `primary`, at
+/// offset `(0, 0)`), each recorded as a fixed offset from `primary`'s own
+/// top-left at the moment the drag started - the whole group moves as
+/// one rigid unit regardless of where each member's own cell happens to
+/// be, the same way dragging one file in a multi-selection in Windows/
+/// GNOME/macOS/KDE carries every other selected file along with it.
+/// Reported live as missing: "try move desktop items all at once
+/// somewhere else" didn't work at all before this - `members` used to
+/// not exist, a drag only ever carried the one icon it grabbed no matter
+/// how many were selected.
+pub(crate) struct DesktopIconDrag {
+    /// Pointer's grab offset from `primary`'s own top-left at drag start,
+    /// so the icon tracks the pointer smoothly rather than snapping its
+    /// top-left corner straight to the cursor.
+    pub(crate) grab_offset: (i32, i32),
+    /// `primary`'s own live top-left this frame.
+    pub(crate) primary_pos: (i32, i32),
+    /// `(icon id, fixed offset from primary's own top-left at drag
+    /// start)` - primary included at offset `(0, 0)`.
+    pub(crate) members: Vec<(String, (i32, i32))>,
+}
+
 pub(crate) struct DesktopIcons {
     /// Top-left of the grid's own `(0, 0)` cell, in global space, one per
     /// participating monitor - each monitor's own usable-area origin plus