fix(snic): make image follow pieces when offset > 0

Store per-piece offset_dx/offset_dy during tessellation positioning and
accumulate through repel translations, then use these offsets to position
the image element inside each piece's clipPath group. Also use original
(pre-expansion) canvas size for image dimensions so the image covers only
the puzzle area, not the expanded offset canvas.

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

Author: pjt222

R/image_fill_rendering.R

@@ -88,14 +88,16 @@ render_image_filled_pieces <- function(pieces, image_data_uri, canvas_size,
                                         canvas_offset = c(0, 0),
                                         stroke_width = 1.5, colors = "black",
                                         opacity = 1.0,
-                                        image_width = NULL, image_height = NULL) {
+                                        image_width = NULL, image_height = NULL,
+                                        original_canvas_size = NULL) {
   if (length(colors) == 1) {
     colors <- rep(colors, length(pieces))
   }
 
-  # Image dimensions in canvas mm units — canvas_size is always c(width, height)
-  img_w <- canvas_size[1]  # width
-  img_h <- canvas_size[2]  # height
+  # Use original (pre-offset-expansion) canvas for image dimensions
+  orig <- original_canvas_size %||% canvas_size
+  img_w <- orig[1]  # width
+  img_h <- orig[2]  # height
 
   sapply(seq_along(pieces), function(i) {
     piece <- pieces[[i]]
@@ -104,19 +106,23 @@ render_image_filled_pieces <- function(pieces, image_data_uri, canvas_size,
 
     opacity_attr <- if (opacity < 1.0) sprintf(' opacity="%.2f"', opacity) else ""
 
+    # Per-piece image offset (tracks radial/repel translation)
+    img_x <- piece$offset_dx %||% 0
+    img_y <- piece$offset_dy %||% 0
+
     # Clipped image group + stroke outline
     sprintf(paste0(
       '<g%s>\n',
       '  <clipPath id="piece-%d-clip"><path d="%s" /></clipPath>\n',
       '  <g clip-path="url(#piece-%d-clip)">\n',
-      '    <image href="%s" x="0" y="0" width="%.1f" height="%.1f" preserveAspectRatio="none" />\n',
+      '    <image href="%s" x="%.4f" y="%.4f" width="%.1f" height="%.1f" preserveAspectRatio="none" />\n',
       '  </g>\n',
       '  <path d="%s" fill="none" stroke="%s" stroke-width="%.1f" />\n',
       '</g>'),
       opacity_attr,
       piece_id, piece$path,
       piece_id,
-      image_data_uri, img_w, img_h,
+      image_data_uri, img_x, img_y, img_w, img_h,
       piece$path, color, stroke_width
     )
   })

R/piece_positioning.R

@@ -397,7 +397,9 @@ apply_tessellation_positioning <- function(piece_result, offset) {
       is_boundary = piece$is_boundary,
       fusion_group = piece$fusion_group,
       fused_edges = piece$fused_edges,
-      fused_neighbor_ids = piece$fused_neighbor_ids
+      fused_neighbor_ids = piece$fused_neighbor_ids,
+      offset_dx = dx,
+      offset_dy = dy
     )
 
     # Copy the type-specific position data
@@ -958,6 +960,10 @@ translate_piece <- function(piece, dx, dy) {
     }
   }
 
+  # Accumulate offset tracking for image fill positioning
+  piece$offset_dx <- (piece$offset_dx %||% 0) + dx
+  piece$offset_dy <- (piece$offset_dy %||% 0) + dy
+
   piece
 }
 

R/renderer_main.R

@@ -192,12 +192,15 @@ render_puzzle_svg <- function(positioned, fill = "none", fills = NULL,
     # Get image dimensions from parameters
     img_w <- positioned$parameters$image_width
     img_h <- positioned$parameters$image_height
+    # Original canvas size before offset expansion — size is c(height, width)
+    original_canvas_size <- c(positioned$parameters$size[2], positioned$parameters$size[1])
     piece_elements <- render_image_filled_pieces(
       positioned$pieces, image_data_uri, positioned$canvas_size,
       canvas_offset = if (!is.null(positioned$canvas_offset)) positioned$canvas_offset else c(0, 0),
       stroke_width = stroke_width, colors = colors,
       opacity = opacity,
-      image_width = img_w, image_height = img_h
+      image_width = img_w, image_height = img_h,
+      original_canvas_size = original_canvas_size
     )
   }