hopefully sound selection rectangle and surface offset logic

main.zig

@@ -27,6 +27,17 @@ const Point = struct {
             .y = self.y * -1,
         };
     }
+
+    fn add(self: *Self, other: Self) void {
+        self.x += other.x;
+        self.y += other.x;
+    }
+
+    fn added(self: *const Self, other: Self) Self {
+        var new = self.*;
+        new.add(other);
+        return new;
+    }
 };
 
 const Size = struct {
@@ -288,8 +299,7 @@ const Box = struct {
     }
 
     fn translate(self: *Self, delta: Point) void {
-        self.position.x += delta.x;
-        self.position.y += delta.y;
+        self.position.add(delta);
     }
 
     fn translated(self: Self, delta: Point) Self {
@@ -712,7 +722,7 @@ const Seat = struct {
 
     pointer: ?struct {
         pointer: *wl.Pointer,
-        button_state: ?wl.Pointer.ButtonState = null,
+        current_surface_offset: ?Point = null,
         selection: SelectionState = SelectionState.None(),
     } = null,
 
@@ -735,6 +745,22 @@ const Seat = struct {
             return SelectionState.none;
         }
 
+        fn translate(self: SelectionState, delta: Point) void {
+            switch (self) {
+                .pre => |*point| {
+                    point.add(delta);
+                },
+                .updating => |*selection| {
+                    selection.start.add(delta);
+                    selection.end.add(delta);
+                },
+                .post => |*box| {
+                    box.translate(delta);
+                },
+                else => {return null;},
+            }
+        }
+
         fn getSelectionBox(self: SelectionState) ?Box {
             switch (self) {
                 .updating => |selection| {
@@ -773,24 +799,35 @@ const Seat = struct {
         _ = pointer;
 
         switch (event) {
-            .enter => {},
-            .leave => {},
+            .enter => |enter| {
+                if (self.state.getOutputForSurface(enter.surface.?)) |output| {
+                    self.pointer.?.current_surface_offset = output.logical_geometry.position;
+                }
+
+                std.debug.print("surface offset: {?}\n", .{self.pointer.?.current_surface_offset});
+            },
+            .leave => {
+                self.pointer.?.current_surface_offset = null;
+            },
             .motion => |motion| {
                 const x = motion.surface_x.toInt();
                 const y = motion.surface_y.toInt();
+                const xy = Point{.x = x, .y = y,};
 
-                const end = Point{.x = x, .y = y,};
+                if (self.pointer.?.current_surface_offset) |offset| {
+                    const point = xy.added(offset);
 
-                switch (self.pointer.?.selection) {
-                    .pre => {
-                        self.pointer.?.selection = .{.updating = .{.start = end, .end = end}};
-                        return self.calculateRedraws();
-                    },
-                    .updating => |*selection| {
-                        selection.end = end;
-                        return self.calculateRedraws();
-                    },
-                    else => {},
+                    switch (self.pointer.?.selection) {
+                        .pre => {
+                            self.pointer.?.selection = .{.updating = .{.start = point, .end = point}};
+                            return self.calculateRedraws();
+                        },
+                        .updating => |*selection| {
+                            selection.end = point;
+                            return self.calculateRedraws();
+                        },
+                        else => {},
+                    }
                 }
             },
             .button => |button| {
@@ -1210,6 +1247,18 @@ const State = struct {
             self.ally.destroy(link);
         }
 
+        fn getOutputForSurface(self: *Self, surface: *wl.Surface) ?*Output {
+            var output_iter = self.outputs.iterator(.forward);
+            while (output_iter.next()) |next| {
+                const output = next.get();
+                if (output.surface == surface) {
+                    return output;
+                }
+            }
+
+            return null;
+        }
+
         fn deinit(self: *Self) void {
             defer self.ally.destroy(self);