terminal/kitty: parse relative placement fields

src/terminal/kitty/graphics_command.zig

@@ -462,6 +462,10 @@ pub const Display = struct {
     rows: u32 = 0, // r
     cursor_movement: CursorMovement = .after, // C
     virtual_placement: bool = false, // U
+    parent_id: u32 = 0, // P
+    parent_placement_id: u32 = 0, // Q
+    horizontal_offset: u32 = 0, // H
+    vertical_offset: u32 = 0, // V
     z: i32 = 0, // z
 
     pub const CursorMovement = enum {
@@ -537,6 +541,22 @@ pub const Display = struct {
             result.z = @bitCast(v);
         }
 
+        if (kv.get('P')) |v| {
+            result.parent_id = v;
+        }
+
+        if (kv.get('Q')) |v| {
+            result.parent_placement_id = v;
+        }
+
+        if (kv.get('H')) |v| {
+            result.horizontal_offset = v;
+        }
+
+        if (kv.get('V')) |v| {
+            result.vertical_offset = v;
+        }
+
         return result;
     }
 };

src/terminal/kitty/graphics_exec.zig

@@ -187,7 +187,14 @@ fn display(
     // Location where the placement will go.
     const location: ImageStorage.Placement.Location = location: {
         // Virtual placements are not tracked
-        if (d.virtual_placement) break :location .{ .virtual = {} };
+        if (d.virtual_placement) {
+            if (d.parent_id > 0) {
+                result.message = "EINVAL: virtual placement cannot refer to a parent";
+                return result;
+            }
+
+            break :location .{ .virtual = {} };
+        }
 
         // Track a new pin for our cursor. The cursor is always tracked but we
         // don't want this one to move with the cursor.