Add BG offset

packages/vitec/Classes/UserFunc/ContainerBackgroundRenderer.php

@@ -74,7 +74,7 @@ class ContainerBackgroundRenderer
             return (string)json_encode([
                 'image' => $image,
                 'size' => $this->resolveSize($row),
-                'position' => (string)($row['tx_vitec_bg_position'] ?? 'center center'),
+                'position' => $this->resolvePosition($row),
             ]);
         } catch (\Throwable $e) {
             return '';
@@ -101,4 +101,54 @@ class ContainerBackgroundRenderer
         $percent = (int)($row['tx_vitec_bg_size_percent'] ?? 0);
         return $percent > 0 ? $percent . '%' : 'auto';
     }
+
+    /**
+     * The stored position, again resolved into one CSS-ready value.
+     *
+     * The four custom fields are edge offsets, but CSS cannot take a top AND a
+     * bottom offset at once, so they are folded into the percentage form. That
+     * form says exactly the same thing: in `background-position` a percentage
+     * aligns the same point of image and container, so "10% from the right edge"
+     * IS `90%`. Nothing is lost in the translation.
+     *
+     * Per axis the near edge wins when both are filled - `left` over `right`,
+     * `top` over `bottom` - because two opposing offsets contradict each other
+     * and silently picking one beats emitting something invalid.
+     *
+     * @param array<string,mixed> $row
+     */
+    private function resolvePosition(array $row): string
+    {
+        $position = (string)($row['tx_vitec_bg_position'] ?? 'center center');
+        if ($position !== 'custom') {
+            return $position;
+        }
+
+        $x = $this->axisPercent($row, 'tx_vitec_bg_pos_left', 'tx_vitec_bg_pos_right');
+        $y = $this->axisPercent($row, 'tx_vitec_bg_pos_top', 'tx_vitec_bg_pos_bottom');
+
+        return $x . '% ' . $y . '%';
+    }
+
+    /**
+     * One axis as a percentage. An empty field means "centred on this axis" -
+     * which is why the columns are nullable: 0 is a legitimate offset (flush
+     * against that edge) and has to stay distinguishable from "not set".
+     *
+     * @param array<string,mixed> $row
+     */
+    private function axisPercent(array $row, string $nearField, string $farField): int
+    {
+        $near = $row[$nearField] ?? null;
+        if ($near !== null && $near !== '') {
+            return (int)$near;
+        }
+
+        $far = $row[$farField] ?? null;
+        if ($far !== null && $far !== '') {
+            return 100 - (int)$far;
+        }
+
+        return 50;
+    }
 }