QTextLayout: fix maximumWidth() for a text containing line separator

When laying out, we need to increase layout's maximum width _only_
if the previous line was not explicitly wrapped by a line or paragraph
separator, or if the current line's width is greater than the
previously accumulated layout's maximum width.

Fixes: QTBUG-89557
Fixes: QTBUG-104986
Pick-to: 6.2 6.4
Change-Id: Ib7cc4b9dda8f20166dcbd5cfd3b56424bb33d14a
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

src/gui/text/qtextengine.cpp

@@ -2603,6 +2603,7 @@ QTextEngine::LayoutData::LayoutData()
     hasBidi = false;
     layoutState = LayoutEmpty;
     haveCharAttributes = false;
+    previousLineManuallyWrapped = false;
     logClustersPtr = nullptr;
     available_glyphs = 0;
 }
@@ -2637,6 +2638,7 @@ QTextEngine::LayoutData::LayoutData(const QString &str, void **stack_memory, int
     hasBidi = false;
     layoutState = LayoutEmpty;
     haveCharAttributes = false;
+    previousLineManuallyWrapped = false;
 }
 
 QTextEngine::LayoutData::~LayoutData()
@@ -2722,6 +2724,7 @@ void QTextEngine::freeMemory()
         layoutData->hasBidi = false;
         layoutData->layoutState = LayoutEmpty;
         layoutData->haveCharAttributes = false;
+        layoutData->previousLineManuallyWrapped = false;
         layoutData->items.clear();
     }
     if (specialData)

src/gui/text/qtextengine_p.h

@@ -385,6 +385,7 @@ public:
         uint layoutState : 2;
         uint memory_on_stack : 1;
         uint haveCharAttributes : 1;
+        uint previousLineManuallyWrapped : 1;
         QString string;
         bool reallocate(int totalGlyphs);
     };

src/gui/text/qtextlayout.cpp

@@ -1808,6 +1808,7 @@ void QTextLine::layout_helper(int maxGlyphs)
     lbh.logClusters = eng->layoutData->logClustersPtr;
     lbh.previousGlyph = 0;
 
+    bool manuallyWrapped = false;
     bool hasInlineObject = false;
     QFixed maxInlineObjectHeight = 0;
 
@@ -1883,6 +1884,7 @@ void QTextLine::layout_helper(int maxGlyphs)
                 lbh.calculateRightBearingForPreviousGlyph();
             }
             line += lbh.tmpData;
+            manuallyWrapped = true;
             goto found;
         } else if (current.analysis.flags == QScriptAnalysis::Object) {
             lbh.whiteSpaceOrObject = true;
@@ -2105,7 +2107,10 @@ found:
         eng->maxWidth = qMax(eng->maxWidth, line.textWidth);
     } else {
         eng->minWidth = qMax(eng->minWidth, lbh.minw);
-        eng->maxWidth += line.textWidth;
+        if (eng->layoutData->previousLineManuallyWrapped)
+            eng->maxWidth = qMax(eng->maxWidth, line.textWidth);
+        else
+            eng->maxWidth += line.textWidth;
     }
 
     if (line.textWidth > 0 && item < eng->layoutData->items.size())
@@ -2119,6 +2124,8 @@ found:
 
     line.justified = false;
     line.gridfitted = false;
+
+    eng->layoutData->previousLineManuallyWrapped = manuallyWrapped;
 }
 
 /*!

tests/auto/gui/text/qtextlayout/tst_qtextlayout.cpp

@@ -125,6 +125,7 @@ private slots:
     void softHyphens_data();
     void softHyphens();
     void min_maximumWidth();
+    void min_maximumWidthWithLineSeparator();
 
 private:
     QFont testFont;
@@ -2683,5 +2684,32 @@ void tst_QTextLayout::min_maximumWidth()
     }
 }
 
+void tst_QTextLayout::min_maximumWidthWithLineSeparator()
+{
+    QTextLayout referenceLayout("text", testFont);
+
+    QString multilineText("text\ntext\ntext");
+    multilineText.replace('\n', QChar::LineSeparator);
+    QTextLayout layout(multilineText, testFont);
+
+    for (int wrapMode = QTextOption::NoWrap; wrapMode <= QTextOption::WrapAtWordBoundaryOrAnywhere; ++wrapMode) {
+        QTextOption opt;
+        opt.setWrapMode((QTextOption::WrapMode)wrapMode);
+
+        referenceLayout.setTextOption(opt);
+        referenceLayout.beginLayout();
+        while (referenceLayout.createLine().isValid()) { }
+        referenceLayout.endLayout();
+
+        layout.setTextOption(opt);
+        layout.beginLayout();
+        while (layout.createLine().isValid()) { }
+        layout.endLayout();
+
+        QCOMPARE(layout.minimumWidth(), referenceLayout.minimumWidth());
+        QCOMPARE(layout.maximumWidth(), referenceLayout.maximumWidth());
+    }
+}
+
 QTEST_MAIN(tst_QTextLayout)
 #include "tst_qtextlayout.moc"