fix(05-04): fix signature field placement coordinate math

- Use pageInfo.width/height (authoritative rendered canvas size from
  react-pdf) instead of containerRect.width/height for all coordinate
  math; containerRect dimensions could differ if the wrapper div has
  extra decoration not matching the canvas
- Track containerSize in state (updated via useLayoutEffect when
  pageInfo changes) so renderFields() uses stable values from state
  instead of calling getBoundingClientRect() during render
- Refactor screenToPdfCoords/pdfToScreenCoords to take renderedW/H
  as explicit params instead of a DOMRect, making the contract clearer

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

teressa-copeland-homes/src/app/portal/(protected)/documents/[docId]/_components/FieldPlacer.tsx

@@ -1,10 +1,14 @@
 'use client';
-import { useState, useEffect, useRef, useCallback } from 'react';
+import { useState, useEffect, useRef, useCallback, useLayoutEffect } from 'react';
 import {
   DndContext,
   useDraggable,
   useDroppable,
   DragOverlay,
+  MouseSensor,
+  TouchSensor,
+  useSensor,
+  useSensors,
   type DragEndEvent,
 } from '@dnd-kit/core';
 import { CSS } from '@dnd-kit/utilities';
@@ -21,29 +25,28 @@ interface PageInfo {
 // Screen (DOM) → PDF user space. Y-axis flip required.
 // DOM: Y=0 at top, increases downward
 // PDF: Y=0 at bottom, increases upward
+// renderedW/renderedH must be the actual rendered canvas dimensions (from pageInfo.width/height)
 function screenToPdfCoords(
   screenX: number,
   screenY: number,
-  containerRect: DOMRect,
+  renderedW: number,
+  renderedH: number,
   pageInfo: PageInfo,
 ) {
-  // Use containerRect dimensions (current rendered size) not stale pageInfo
-  const renderedW = containerRect.width;
-  const renderedH = containerRect.height;
   const pdfX = (screenX / renderedW) * pageInfo.originalWidth;
   const pdfY = ((renderedH - screenY) / renderedH) * pageInfo.originalHeight;
   return { x: pdfX, y: pdfY };
 }
 
 // PDF user space → screen (for rendering stored fields)
+// renderedW/renderedH must be the actual rendered canvas dimensions (from pageInfo.width/height)
 function pdfToScreenCoords(
   pdfX: number,
   pdfY: number,
-  containerRect: DOMRect,
+  renderedW: number,
+  renderedH: number,
   pageInfo: PageInfo,
 ) {
-  const renderedW = containerRect.width;
-  const renderedH = containerRect.height;
   const left = (pdfX / pageInfo.originalWidth) * renderedW;
   // top is measured from DOM top; pdfY is from PDF bottom — reverse flip
   const top = renderedH - (pdfY / pageInfo.originalHeight) * renderedH;
@@ -125,6 +128,15 @@ export function FieldPlacer({ docId, pageInfo, currentPage, children }: FieldPla
   const [fields, setFields] = useState<SignatureFieldData[]>([]);
   const [isDraggingToken, setIsDraggingToken] = useState(false);
   const containerRef = useRef<HTMLDivElement | null>(null);
+  // Track rendered canvas dimensions in state so renderFields re-runs when they change
+  const [containerSize, setContainerSize] = useState<{ w: number; h: number } | null>(null);
+
+  // Configure sensors: require a minimum drag distance so clicks on delete buttons
+  // are not intercepted as drag starts
+  const sensors = useSensors(
+    useSensor(MouseSensor, { activationConstraint: { distance: 5 } }),
+    useSensor(TouchSensor, { activationConstraint: { delay: 150, tolerance: 5 } }),
+  );
 
   // Load existing fields from server on mount
   useEffect(() => {
@@ -142,11 +154,19 @@ export function FieldPlacer({ docId, pageInfo, currentPage, children }: FieldPla
     loadFields();
   }, [docId]);
 
+  // Update containerSize whenever pageInfo changes (page load or zoom change)
+  // Use pageInfo.width/height (from react-pdf canvas) as the authoritative rendered size.
+  // getBoundingClientRect() is only used for the drop origin (containerRect.left/top).
+  useLayoutEffect(() => {
+    if (!pageInfo) return;
+    setContainerSize({ w: pageInfo.width, h: pageInfo.height });
+  }, [pageInfo]);
+
   const handleDragEnd = useCallback(
     (event: DragEndEvent) => {
       setIsDraggingToken(false);
 
-      const { active, over, activatorEvent, delta } = event;
+      const { over, activatorEvent, delta } = event;
 
       // Only process if dropped onto the PDF zone
       if (!over || over.id !== 'pdf-drop-zone') return;
@@ -155,6 +175,12 @@ export function FieldPlacer({ docId, pageInfo, currentPage, children }: FieldPla
       const containerRect = containerRef.current?.getBoundingClientRect();
       if (!containerRect) return;
 
+      // Use pageInfo.width/height as the authoritative rendered canvas size —
+      // containerRect.width/height could be slightly off if the wrapper div has
+      // any extra decoration that doesn't match the canvas exactly.
+      const renderedW = pageInfo.width;
+      const renderedH = pageInfo.height;
+
       // Compute the final screen position relative to the container
       // activatorEvent is the initial MouseEvent/TouchEvent at drag start
       // delta is the displacement from drag start to drop
@@ -169,24 +195,24 @@ export function FieldPlacer({ docId, pageInfo, currentPage, children }: FieldPla
         clientY = activatorEvent.touches[0].clientY;
       } else {
         // Fallback: use center of container
-        clientX = containerRect.left + containerRect.width / 2;
-        clientY = containerRect.top + containerRect.height / 2;
+        clientX = containerRect.left + renderedW / 2;
+        clientY = containerRect.top + renderedH / 2;
       }
 
       // finalClient = activatorClient + delta (displacement during drag)
       const finalClientX = clientX + delta.x;
       const finalClientY = clientY + delta.y;
 
-      // Convert to coordinates relative to the container
+      // Convert to coordinates relative to the container's top-left corner
       const screenX = finalClientX - containerRect.left;
       const screenY = finalClientY - containerRect.top;
 
-      // Clamp to container bounds
-      const clampedX = Math.max(0, Math.min(screenX, containerRect.width));
-      const clampedY = Math.max(0, Math.min(screenY, containerRect.height));
+      // Clamp to canvas bounds
+      const clampedX = Math.max(0, Math.min(screenX, renderedW));
+      const clampedY = Math.max(0, Math.min(screenY, renderedH));
 
       // Convert screen coords to PDF user-space (Y-flip applied)
-      const { x: pdfX, y: pdfY } = screenToPdfCoords(clampedX, clampedY, containerRect, pageInfo);
+      const { x: pdfX, y: pdfY } = screenToPdfCoords(clampedX, clampedY, renderedW, renderedH, pageInfo);
 
       const newField: SignatureFieldData = {
         id: crypto.randomUUID(),
@@ -205,17 +231,19 @@ export function FieldPlacer({ docId, pageInfo, currentPage, children }: FieldPla
   );
 
   // Render placed fields for the current page
+  // Uses pageInfo.width/height (not getBoundingClientRect) for consistent coordinate math
   const renderFields = () => {
-    if (!pageInfo) return null;
-    const containerRect = containerRef.current?.getBoundingClientRect();
-    if (!containerRect) return null;
+    if (!pageInfo || !containerSize) return null;
+
+    const renderedW = containerSize.w;
+    const renderedH = containerSize.h;
 
     return fields
       .filter((f) => f.page === currentPage)
       .map((field) => {
-        const { left, top } = pdfToScreenCoords(field.x, field.y, containerRect, pageInfo);
-        const widthPx = (field.width / pageInfo.originalWidth) * containerRect.width;
-        const heightPx = (field.height / pageInfo.originalHeight) * containerRect.height;
+        const { left, top } = pdfToScreenCoords(field.x, field.y, renderedW, renderedH, pageInfo);
+        const widthPx = (field.width / pageInfo.originalWidth) * renderedW;
+        const heightPx = (field.height / pageInfo.originalHeight) * renderedH;
 
         return (
           <div
@@ -235,17 +263,25 @@ export function FieldPlacer({ docId, pageInfo, currentPage, children }: FieldPla
               padding: '0 4px',
               fontSize: '10px',
               color: '#2563eb',
+              // Raise above droppable overlay so the delete button is clickable
+              zIndex: 10,
               pointerEvents: 'all',
               boxSizing: 'border-box',
             }}
           >
             <span>Signature</span>
             <button
-              onClick={() => {
+              onClick={(e) => {
+                // Stop dnd-kit from treating this click as a drag activation
+                e.stopPropagation();
                 const next = fields.filter((f) => f.id !== field.id);
                 setFields(next);
                 persistFields(docId, next);
               }}
+              onPointerDown={(e) => {
+                // Prevent dnd-kit sensors from capturing this pointer event
+                e.stopPropagation();
+              }}
               style={{
                 cursor: 'pointer',
                 background: 'none',
@@ -255,6 +291,10 @@ export function FieldPlacer({ docId, pageInfo, currentPage, children }: FieldPla
                 padding: '0 2px',
                 fontSize: '12px',
                 lineHeight: 1,
+                // Ensure the button sits above any overlay that might capture events
+                position: 'relative',
+                zIndex: 11,
+                pointerEvents: 'all',
               }}
               aria-label="Remove field"
             >
@@ -267,6 +307,7 @@ export function FieldPlacer({ docId, pageInfo, currentPage, children }: FieldPla
 
   return (
     <DndContext
+      sensors={sensors}
       onDragStart={() => setIsDraggingToken(true)}
       onDragEnd={handleDragEnd}
     >