touch: support drag and drop

river/Cursor.zig

@@ -85,6 +85,11 @@ const Image = enum {
 
 const default_size = 24;
 
+const LayoutPoint = struct {
+    lx: f64,
+    ly: f64,
+};
+
 const log = std.log.scoped(.cursor);
 
 /// Current cursor mode as well as any state needed to implement that mode
@@ -107,6 +112,10 @@ hide_cursor_timer: *wl.EventSource,
 hidden: bool = false,
 may_need_warp: bool = false,
 
+/// Keeps track of the last known location of all touch points in layout coordinates.
+/// This information is necessary for proper touch dnd support if there are multiple touch points.
+touch_points: std.AutoHashMapUnmanaged(i32, LayoutPoint) = .{},
+
 axis: wl.Listener(*wlr.Pointer.event.Axis) = wl.Listener(*wlr.Pointer.event.Axis).init(handleAxis),
 frame: wl.Listener(*wlr.Cursor) = wl.Listener(*wlr.Cursor).init(handleFrame),
 button: wl.Listener(*wlr.Pointer.event.Button) =
@@ -459,6 +468,8 @@ fn handleTouchUp(
 
     self.seat.handleActivity();
 
+    _ = self.touch_points.remove(event.touch_id);
+
     self.seat.wlr_seat.touchNotifyUp(event.time_msec, event.touch_id);
 }
 
@@ -474,6 +485,10 @@ fn handleTouchDown(
     var ly: f64 = undefined;
     self.wlr_cursor.absoluteToLayoutCoords(event.device, event.x, event.y, &lx, &ly);
 
+    self.touch_points.putNoClobber(util.gpa, event.touch_id, .{ .lx = lx, .ly = ly }) catch {
+        log.err("out of memory", .{});
+    };
+
     if (surfaceAtCoords(lx, ly)) |result| {
         self.updateKeyboardFocus(result);
 
@@ -503,6 +518,10 @@ fn handleTouchMotion(
     var ly: f64 = undefined;
     self.wlr_cursor.absoluteToLayoutCoords(event.device, event.x, event.y, &lx, &ly);
 
+    self.touch_points.put(util.gpa, event.touch_id, .{ .lx = lx, .ly = ly }) catch {
+        log.err("out of memory", .{});
+    };
+
     if (surfaceAtCoords(lx, ly)) |result| {
         self.seat.wlr_seat.touchNotifyMotion(event.time_msec, event.touch_id, result.sx, result.sy);
     }
@@ -1025,8 +1044,9 @@ fn processMotion(self: *Self, device: *wlr.InputDevice, time: u32, delta_x: f64,
 }
 
 pub fn checkFocusFollowsCursor(self: *Self) void {
-    // Don't do focus-follows-cursor if a drag is in progress as focus change can't occur
+    // Don't do focus-follows-cursor if a pointer drag is in progress as focus
-    if (self.seat.pointer_drag) return;
+    // change can't occur.
+    if (self.seat.drag == .pointer) return;
     if (server.config.focus_follows_cursor == .disabled) return;
     if (self.surfaceAt()) |result| {
         if (server.config.focus_follows_cursor == .always or

river/DragIcon.zig

@@ -29,14 +29,16 @@ const Subsurface = @import("Subsurface.zig");
 seat: *Seat,
 wlr_drag_icon: *wlr.Drag.Icon,
 
+// Accumulated x/y surface offset from the cursor/touch point position.
+sx: i32 = 0,
+sy: i32 = 0,
+
 // Always active
 destroy: wl.Listener(*wlr.Drag.Icon) = wl.Listener(*wlr.Drag.Icon).init(handleDestroy),
 map: wl.Listener(*wlr.Drag.Icon) = wl.Listener(*wlr.Drag.Icon).init(handleMap),
 unmap: wl.Listener(*wlr.Drag.Icon) = wl.Listener(*wlr.Drag.Icon).init(handleUnmap),
-new_subsurface: wl.Listener(*wlr.Subsurface) = wl.Listener(*wlr.Subsurface).init(handleNewSubsurface),
-
-// Only active while mapped
 commit: wl.Listener(*wlr.Surface) = wl.Listener(*wlr.Surface).init(handleCommit),
+new_subsurface: wl.Listener(*wlr.Subsurface) = wl.Listener(*wlr.Subsurface).init(handleNewSubsurface),
 
 pub fn init(drag_icon: *DragIcon, seat: *Seat, wlr_drag_icon: *wlr.Drag.Icon) void {
     drag_icon.* = .{ .seat = seat, .wlr_drag_icon = wlr_drag_icon };
@@ -44,6 +46,7 @@ pub fn init(drag_icon: *DragIcon, seat: *Seat, wlr_drag_icon: *wlr.Drag.Icon) vo
     wlr_drag_icon.events.destroy.add(&drag_icon.destroy);
     wlr_drag_icon.events.map.add(&drag_icon.map);
     wlr_drag_icon.events.unmap.add(&drag_icon.unmap);
+    wlr_drag_icon.surface.events.commit.add(&drag_icon.commit);
     wlr_drag_icon.surface.events.new_subsurface.add(&drag_icon.new_subsurface);
 
     if (wlr_drag_icon.mapped) handleMap(&drag_icon.map, wlr_drag_icon);
@@ -54,36 +57,35 @@ pub fn init(drag_icon: *DragIcon, seat: *Seat, wlr_drag_icon: *wlr.Drag.Icon) vo
 fn handleDestroy(listener: *wl.Listener(*wlr.Drag.Icon), wlr_drag_icon: *wlr.Drag.Icon) void {
     const drag_icon = @fieldParentPtr(DragIcon, "destroy", listener);
 
-    const node = @fieldParentPtr(std.SinglyLinkedList(DragIcon).Node, "data", drag_icon);
+    drag_icon.seat.drag_icon = null;
-    server.root.drag_icons.remove(node);
 
     drag_icon.destroy.link.remove();
     drag_icon.map.link.remove();
     drag_icon.unmap.link.remove();
+    drag_icon.commit.link.remove();
     drag_icon.new_subsurface.link.remove();
 
     Subsurface.destroySubsurfaces(wlr_drag_icon.surface);
 
-    util.gpa.destroy(node);
+    util.gpa.destroy(drag_icon);
 }
 
-fn handleMap(listener: *wl.Listener(*wlr.Drag.Icon), wlr_drag_icon: *wlr.Drag.Icon) void {
+fn handleMap(_: *wl.Listener(*wlr.Drag.Icon), _: *wlr.Drag.Icon) void {
-    const drag_icon = @fieldParentPtr(DragIcon, "map", listener);
-
-    wlr_drag_icon.surface.events.commit.add(&drag_icon.commit);
     var it = server.root.outputs.first;
     while (it) |node| : (it = node.next) node.data.damage.?.addWhole();
 }
 
-fn handleUnmap(listener: *wl.Listener(*wlr.Drag.Icon), _: *wlr.Drag.Icon) void {
+fn handleUnmap(_: *wl.Listener(*wlr.Drag.Icon), _: *wlr.Drag.Icon) void {
-    const drag_icon = @fieldParentPtr(DragIcon, "unmap", listener);
-
-    drag_icon.commit.link.remove();
     var it = server.root.outputs.first;
     while (it) |node| : (it = node.next) node.data.damage.?.addWhole();
 }
 
-fn handleCommit(_: *wl.Listener(*wlr.Surface), _: *wlr.Surface) void {
+fn handleCommit(listener: *wl.Listener(*wlr.Surface), surface: *wlr.Surface) void {
+    const drag_icon = @fieldParentPtr(DragIcon, "commit", listener);
+
+    drag_icon.sx += surface.current.dx;
+    drag_icon.sy += surface.current.dy;
+
     var it = server.root.outputs.first;
     while (it) |node| : (it = node.next) node.data.damage.?.addWhole();
 }

river/Root.zig

@@ -56,8 +56,6 @@ outputs: std.TailQueue(Output) = .{},
 /// It is not advertised to clients.
 noop_output: Output = undefined,
 
-drag_icons: std.SinglyLinkedList(DragIcon) = .{},
-
 /// This list stores all "override redirect" Xwayland windows. This needs to be in root
 /// since X is like the wild west and who knows where these things will place themselves.
 xwayland_override_redirect_views: if (build_options.xwayland)

river/Seat.zig

@@ -87,15 +87,20 @@ focus_stack: ViewStack(*View) = .{},
 /// List of status tracking objects relaying changes to this seat to clients.
 status_trackers: std.SinglyLinkedList(SeatStatus) = .{},
 
-/// True if a pointer drag is currently in progress
+/// The currently in progress drag operation type.
-pointer_drag: bool = false,
+drag: enum {
+    none,
+    pointer,
+    touch,
+} = .none,
+drag_icon: ?*DragIcon = null,
 
 request_set_selection: wl.Listener(*wlr.Seat.event.RequestSetSelection) =
     wl.Listener(*wlr.Seat.event.RequestSetSelection).init(handleRequestSetSelection),
 request_start_drag: wl.Listener(*wlr.Seat.event.RequestStartDrag) =
     wl.Listener(*wlr.Seat.event.RequestStartDrag).init(handleRequestStartDrag),
 start_drag: wl.Listener(*wlr.Drag) = wl.Listener(*wlr.Drag).init(handleStartDrag),
-pointer_drag_destroy: wl.Listener(*wlr.Drag) = wl.Listener(*wlr.Drag).init(handlePointerDragDestroy),
+drag_destroy: wl.Listener(*wlr.Drag) = wl.Listener(*wlr.Drag).init(handleDragDestroy),
 request_set_primary_selection: wl.Listener(*wlr.Seat.event.RequestSetPrimarySelection) =
     wl.Listener(*wlr.Seat.event.RequestSetPrimarySelection).init(handleRequestSetPrimarySelection),
 
@@ -141,7 +146,7 @@ pub fn deinit(self: *Self) void {
     self.request_set_selection.link.remove();
     self.request_start_drag.link.remove();
     self.start_drag.link.remove();
-    if (self.pointer_drag) self.pointer_drag_destroy.link.remove();
+    if (self.drag != .none) self.drag_destroy.link.remove();
     self.request_set_primary_selection.link.remove();
 }
 
@@ -535,50 +540,65 @@ fn handleRequestStartDrag(
 ) void {
     const self = @fieldParentPtr(Self, "request_start_drag", listener);
 
-    if (!self.wlr_seat.validatePointerGrabSerial(event.origin, event.serial)) {
+    // The start_drag request is ignored by wlroots if a drag is currently in progress.
-        log.debug("ignoring request to start drag, " ++
+    assert(self.drag == .none);
-            "failed to validate pointer serial {}", .{event.serial});
-        if (event.drag.source) |source| source.destroy();
-        return;
-    }
-
-    if (self.pointer_drag) {
-        log.debug("ignoring request to start pointer drag, " ++
-            "another pointer drag is already in progress", .{});
-        return;
-    }
 
+    if (self.wlr_seat.validatePointerGrabSerial(event.origin, event.serial)) {
         log.debug("starting pointer drag", .{});
         self.wlr_seat.startPointerDrag(event.drag, event.serial);
+        return;
+    }
+
+    var point: *wlr.TouchPoint = undefined;
+    if (self.wlr_seat.validateTouchGrabSerial(event.origin, event.serial, &point)) {
+        log.debug("starting touch drag", .{});
+        self.wlr_seat.startTouchDrag(event.drag, event.serial, point);
+        return;
+    }
+
+    log.debug("ignoring request to start drag, " ++
+        "failed to validate pointer or touch serial {}", .{event.serial});
+    if (event.drag.source) |source| source.destroy();
 }
 
 fn handleStartDrag(listener: *wl.Listener(*wlr.Drag), wlr_drag: *wlr.Drag) void {
     const self = @fieldParentPtr(Self, "start_drag", listener);
 
-    assert(wlr_drag.grab_type == .keyboard_pointer);
+    assert(self.drag == .none);
-
+    switch (wlr_drag.grab_type) {
-    self.pointer_drag = true;
+        .keyboard_pointer => {
-    wlr_drag.events.destroy.add(&self.pointer_drag_destroy);
+            self.drag = .pointer;
+            self.cursor.mode = .passthrough;
+        },
+        .keyboard_touch => self.drag = .touch,
+        .keyboard => unreachable,
+    }
+    wlr_drag.events.destroy.add(&self.drag_destroy);
 
     if (wlr_drag.icon) |wlr_drag_icon| {
-        const node = util.gpa.create(std.SinglyLinkedList(DragIcon).Node) catch {
+        const drag_icon = util.gpa.create(DragIcon) catch {
             log.err("out of memory", .{});
             wlr_drag.seat_client.client.postNoMemory();
             return;
         };
-        node.data.init(self, wlr_drag_icon);
+        drag_icon.init(self, wlr_drag_icon);
-        server.root.drag_icons.prepend(node);
+        self.drag_icon = drag_icon;
     }
-    self.cursor.mode = .passthrough;
 }
 
-fn handlePointerDragDestroy(listener: *wl.Listener(*wlr.Drag), _: *wlr.Drag) void {
+fn handleDragDestroy(listener: *wl.Listener(*wlr.Drag), _: *wlr.Drag) void {
-    const self = @fieldParentPtr(Self, "pointer_drag_destroy", listener);
+    const self = @fieldParentPtr(Self, "drag_destroy", listener);
-    self.pointer_drag_destroy.link.remove();
+    self.drag_destroy.link.remove();
 
-    self.pointer_drag = false;
+    switch (self.drag) {
+        .none => unreachable,
+        .pointer => {
             self.cursor.checkFocusFollowsCursor();
             self.cursor.updateState();
+        },
+        .touch => {},
+    }
+    self.drag = .none;
 }
 
 fn handleRequestSetPrimarySelection(

river/render.zig

@@ -260,19 +260,33 @@ fn renderDragIcons(output: *const Output, now: *os.timespec) void {
     var output_box: wlr.Box = undefined;
     server.root.output_layout.getBox(output.wlr_output, &output_box);
 
-    var it = server.root.drag_icons.first;
+    var it = server.input_manager.seats.first;
     while (it) |node| : (it = node.next) {
-        const drag_icon = &node.data;
+        const icon = node.data.drag_icon orelse continue;
+
+        var lx: f64 = undefined;
+        var ly: f64 = undefined;
+        switch (icon.wlr_drag_icon.drag.grab_type) {
+            .keyboard_pointer => {
+                lx = icon.seat.cursor.wlr_cursor.x;
+                ly = icon.seat.cursor.wlr_cursor.y;
+            },
+            .keyboard_touch => {
+                const touch_id = icon.wlr_drag_icon.drag.touch_id;
+                const point = icon.seat.cursor.touch_points.get(touch_id) orelse continue;
+                lx = point.lx;
+                ly = point.ly;
+            },
+            .keyboard => unreachable,
+        }
 
         var rdata = SurfaceRenderData{
             .output = output,
-            .output_x = @floatToInt(i32, drag_icon.seat.cursor.wlr_cursor.x) +
+            .output_x = @floatToInt(i32, lx) + icon.sx - output_box.x,
-                drag_icon.wlr_drag_icon.surface.sx - output_box.x,
+            .output_y = @floatToInt(i32, ly) + icon.sy - output_box.y,
-            .output_y = @floatToInt(i32, drag_icon.seat.cursor.wlr_cursor.y) +
-                drag_icon.wlr_drag_icon.surface.sy - output_box.y,
             .when = now,
         };
-        drag_icon.wlr_drag_icon.surface.forEachSurface(*SurfaceRenderData, renderSurfaceIterator, &rdata);
+        icon.wlr_drag_icon.surface.forEachSurface(*SurfaceRenderData, renderSurfaceIterator, &rdata);
     }
 }