Fix handling of multiple consecutive tabs with HTML text rendering

Refs #60098

src/core/textrenderer/qgstextdocument.cpp

@@ -52,7 +52,7 @@ QgsTextDocument QgsTextDocument::fromPlainText( const QStringList &lines )
 // Note -- must start and end with spaces, so that a tab character within
 // a html or css tag doesn't mess things up. Instead, Qt will just silently
 // ignore html attributes it doesn't know about, like this replacement string
-#define TAB_REPLACEMENT_MARKER " ignore_me_i_am_a_tab "
+#define TAB_REPLACEMENT_MARKER "!ignore_me_i_am_a_tab!"
 
 QgsTextDocument QgsTextDocument::fromHtml( const QStringList &lines )
 {

tests/src/python/test_qgstextrenderer.py

@@ -3656,6 +3656,20 @@ def testDrawTabFixedSize(self):
             self.checkRender(format, "text_tab_fixed_size", text=["with\ttabs", "a\tb"])
         )
 
+    def testDrawTabsMultipleHtmlFixedSize(self):
+        format = QgsTextFormat()
+        format.setFont(getTestFont("bold"))
+        format.setSize(20)
+        format.setAllowHtmlFormatting(True)
+        format.setSizeUnit(QgsUnitTypes.RenderUnit.RenderPoints)
+        format.setTabStopDistance(20)
+        format.setTabStopDistanceUnit(Qgis.RenderUnit.Millimeters)
+        self.assertTrue(
+            self.checkRender(
+                format, "text_tab_multiple_html", text=["with\t\ttabs", "a\t\tb"]
+            )
+        )
+
     def testDrawTabPositionsFixedSize(self):
         format = QgsTextFormat()
         format.setFont(getTestFont("bold"))