--- /dev/null
+<?php
+
+namespace Drupal\Core\Layout\Icon;
+
+use Drupal\Component\Utility\Html;
+
+/**
+ * Builds SVG layout icons.
+ */
+class SvgIconBuilder implements IconBuilderInterface {
+
+ /**
+ * The machine name of the layout.
+ *
+ * @var string
+ */
+ protected $id;
+
+ /**
+ * The label of the layout.
+ *
+ * @var string
+ */
+ protected $label;
+
+ /**
+ * The width of the SVG.
+ *
+ * @var int
+ */
+ protected $width = 125;
+
+ /**
+ * The height of the SVG.
+ *
+ * @var int
+ */
+ protected $height = 150;
+
+ /**
+ * The padding between regions.
+ *
+ * @var int
+ */
+ protected $padding = 4;
+
+ /**
+ * The width of region borders.
+ *
+ * @var int|null
+ */
+ protected $strokeWidth = 1;
+
+ /**
+ * {@inheritdoc}
+ */
+ public function build(array $icon_map) {
+ $regions = $this->calculateSvgValues($icon_map, $this->width, $this->height, $this->strokeWidth, $this->padding);
+ return $this->buildRenderArray($regions, $this->width, $this->height, $this->strokeWidth);
+ }
+
+ /**
+ * Builds a render array representation of an SVG.
+ *
+ * @param mixed[] $regions
+ * An array keyed by region name, with each element containing the 'height',
+ * 'width', and 'x' and 'y' offsets of each region.
+ * @param int $width
+ * The width of the SVG.
+ * @param int $height
+ * The height of the SVG.
+ * @param int|null $stroke_width
+ * The width of region borders.
+ *
+ * @return array
+ * A render array representing a SVG icon.
+ */
+ protected function buildRenderArray(array $regions, $width, $height, $stroke_width) {
+ $build = [
+ '#type' => 'html_tag',
+ '#tag' => 'svg',
+ '#attributes' => [
+ 'width' => $width,
+ 'height' => $height,
+ 'class' => [
+ 'layout-icon',
+ ],
+ ],
+ ];
+
+ if ($this->id) {
+ $build['#attributes']['class'][] = Html::getClass('layout-icon--' . $this->id);
+ }
+
+ if ($this->label) {
+ $build['title'] = [
+ '#type' => 'html_tag',
+ '#tag' => 'title',
+ '#value' => $this->label,
+ ];
+ }
+
+ // Append each polygon to the SVG.
+ foreach ($regions as $region => $attributes) {
+ // Wrapping with a <g> element allows for metadata to exist alongside the
+ // rectangle.
+ $build['region'][$region] = [
+ '#type' => 'html_tag',
+ '#tag' => 'g',
+ ];
+
+ $build['region'][$region]['title'] = [
+ '#type' => 'html_tag',
+ '#tag' => 'title',
+ '#value' => $region,
+ ];
+
+ // Assemble the rectangle SVG element.
+ $build['region'][$region]['rect'] = [
+ '#type' => 'html_tag',
+ '#tag' => 'rect',
+ '#attributes' => [
+ 'x' => $attributes['x'],
+ 'y' => $attributes['y'],
+ 'width' => $attributes['width'],
+ 'height' => $attributes['height'],
+ 'stroke-width' => $stroke_width,
+ 'class' => [
+ 'layout-icon__region',
+ Html::getClass('layout-icon__region--' . $region),
+ ],
+ ],
+ ];
+ }
+
+ return $build;
+ }
+
+ /**
+ * Calculates the dimensions and offsets of all regions.
+ *
+ * @param string[][] $rows
+ * A two-dimensional array representing the visual output of the layout. See
+ * the documentation for the $icon_map parameter of
+ * \Drupal\Core\Layout\Icon\IconBuilderInterface::build().
+ * @param int $width
+ * The width of the SVG.
+ * @param int $height
+ * The height of the SVG.
+ * @param int $stroke_width
+ * The width of region borders.
+ * @param int $padding
+ * The padding between regions.
+ *
+ * @return mixed[][]
+ * An array keyed by region name, with each element containing the 'height',
+ * 'width', and 'x' and 'y' offsets of each region.
+ */
+ protected function calculateSvgValues(array $rows, $width, $height, $stroke_width, $padding) {
+ $region_rects = [];
+
+ $row_height = $this->getLength(count($rows), $height, $stroke_width, $padding);
+ foreach ($rows as $row => $cols) {
+ $column_width = $this->getLength(count($cols), $width, $stroke_width, $padding);
+ $vertical_offset = $this->getOffset($row, $row_height, $stroke_width, $padding);
+ foreach ($cols as $col => $region) {
+ $horizontal_offset = $this->getOffset($col, $column_width, $stroke_width, $padding);
+
+ // Check if this region is new, or already exists in the rectangle.
+ if (!isset($region_rects[$region])) {
+ $region_rects[$region] = [
+ 'x' => $horizontal_offset,
+ 'y' => $vertical_offset,
+ 'width' => $column_width,
+ 'height' => $row_height,
+ ];
+ }
+ else {
+ // In order to include the area of the previous region and any padding
+ // or border, subtract the calculated offset from the original offset.
+ $region_rects[$region]['width'] = $column_width + ($horizontal_offset - $region_rects[$region]['x']);
+ $region_rects[$region]['height'] = $row_height + ($vertical_offset - $region_rects[$region]['y']);
+ }
+ }
+ }
+
+ return $region_rects;
+ }
+
+ /**
+ * Gets the offset for this region.
+ *
+ * @param int $delta
+ * The zero-based delta of the region.
+ * @param int $length
+ * The height or width of the region.
+ * @param int $stroke_width
+ * The width of the region borders.
+ * @param int $padding
+ * The padding between regions.
+ *
+ * @return int
+ * The offset for this region.
+ */
+ protected function getOffset($delta, $length, $stroke_width, $padding) {
+ // Half of the stroke width is drawn outside the dimensions.
+ $stroke_width /= 2;
+ // For every region in front of this add two strokes, as well as one
+ // directly in front.
+ $num_of_strokes = 2 * $delta + 1;
+ return ($num_of_strokes * $stroke_width) + ($delta * ($length + $padding));
+ }
+
+ /**
+ * Gets the height or width of a region.
+ *
+ * @param int $number_of_regions
+ * The total number of regions.
+ * @param int $length
+ * The total height or width of the icon.
+ * @param int $stroke_width
+ * The width of the region borders.
+ * @param int $padding
+ * The padding between regions.
+ *
+ * @return float|int
+ * The height or width of a region.
+ */
+ protected function getLength($number_of_regions, $length, $stroke_width, $padding) {
+ if ($number_of_regions === 0) {
+ return 0;
+ }
+
+ // Half of the stroke width is drawn outside the dimensions.
+ $total_stroke = $number_of_regions * $stroke_width;
+ // Padding does not precede the first region.
+ $total_padding = ($number_of_regions - 1) * $padding;
+ // Divide the remaining length by the number of regions.
+ return ($length - $total_padding - $total_stroke) / $number_of_regions;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function setId($id) {
+ $this->id = $id;
+ return $this;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function setLabel($label) {
+ $this->label = $label;
+ return $this;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function setWidth($width) {
+ $this->width = $width;
+ return $this;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function setHeight($height) {
+ $this->height = $height;
+ return $this;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function setPadding($padding) {
+ $this->padding = $padding;
+ return $this;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function setStrokeWidth($stroke_width) {
+ $this->strokeWidth = $stroke_width;
+ return $this;
+ }
+
+}