Limited Support for Chart Titles as Formulas (#2971)

This is a start in addressing issue #2965 (and earlier issue #749). Chart Titles are usually entered as strings or Rich Text strings, and PhpSpreadsheet supports that. They can also be entered as formulas (typically a pointer to a cell with the title text), and, not only did PhpSpreadsheet not support that, it threw an exception when reading a spreadsheet that did so.

This change does:
- eliminate the exception
- set a static chart title when it can determine it from the Xml

This change does not:
- fully support dynamic titles (e.g. if you change the contents of the source cell, or delete or insert cells or rows or columns)
- permit the user to set the title to a formula
- allow the use of formulas when writing a chart title to a spreadsheet
- provide styling for titles when it has read them as a formula

src/PhpSpreadsheet/Reader/Xlsx/Chart.php

@@ -396,6 +396,7 @@ class Chart
         foreach ($titleDetails as $titleDetailKey => $chartDetail) {
             switch ($titleDetailKey) {
                 case 'tx':
+                    if (isset($chartDetail->rich)) {
                         $titleDetails = $chartDetail->rich->children($this->aNamespace);
                         foreach ($titleDetails as $titleKey => $titleDetail) {
                             switch ($titleKey) {
@@ -404,6 +405,13 @@ class Chart
                                     $caption[] = $this->parseRichText($titleDetailPart);
                             }
                         }
+                    } elseif (isset($chartDetail->strRef->strCache)) {
+                        foreach ($chartDetail->strRef->strCache->pt as $pt) {
+                            if (isset($pt->v)) {
+                                $caption[] = (string) $pt->v;
+                            }
+                        }
+                    }
 
                     break;
                 case 'layout':

tests/PhpSpreadsheetTests/Chart/Issue2965Test.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Chart;
+
+use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
+use PHPUnit\Framework\TestCase;
+
+class Issue2965Test extends TestCase
+{
+    private const DIRECTORY = 'tests' . DIRECTORY_SEPARATOR . 'data' . DIRECTORY_SEPARATOR . 'Reader' . DIRECTORY_SEPARATOR . 'XLSX' . DIRECTORY_SEPARATOR;
+
+    public function testPreliminaries(): void
+    {
+        $file = 'zip://';
+        $file .= self::DIRECTORY . 'issue.2965.xlsx';
+        $file .= '#xl/charts/chart1.xml';
+        $data = file_get_contents($file);
+        // confirm that file contains expected namespaced xml tag
+        if ($data === false) {
+            self::fail('Unable to read file');
+        } else {
+            self::assertStringContainsString('<c:title><c:tx><c:strRef><c:f>Sheet1!$A$1</c:f><c:strCache><c:ptCount val="1"/><c:pt idx="0"><c:v>NewTitle</c:v></c:pt></c:strCache></c:strRef></c:tx>', $data);
+        }
+    }
+
+    public function testChartTitleFormula(): void
+    {
+        $reader = new XlsxReader();
+        $reader->setIncludeCharts(true);
+        $spreadsheet = $reader->load(self::DIRECTORY . 'issue.2965.xlsx');
+        $worksheet = $spreadsheet->getActiveSheet();
+        $charts = $worksheet->getChartCollection();
+        self::assertCount(1, $charts);
+        $originalChart1 = $charts[0];
+        self::assertNotNull($originalChart1);
+        $originalTitle1 = $originalChart1->getTitle();
+        self::assertNotNull($originalTitle1);
+        self::assertSame('NewTitle', $originalTitle1->getCaptionText());
+
+        $spreadsheet->disconnectWorksheets();
+    }
+}