Backport adjusting cursorToX for trailing spaces from Qt 5

This is a backport of d07982b104de5dc2b54bef09c071500ce22cf539
from Qt 5 which fixes cursorToX() in some cases, e.g. when
a line filled with spaces is ended by a soft line break.

Task-number: QTBUG-27354
Change-Id: Ia88873aeb3c0620044fefe24fc6bb1310e3aa339
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Andrew den Exter <andrew.den.exter@qinetic.com.au>

3 files changed, 450 insertions, 15 deletions

diff --git a/src/gui/text/qtextengine.cpp b/src/gui/text/qtextengine.cpp
index b368fd9..319829d 100644
--- a/src/gui/text/qtextengine.cpp
+++ b/src/gui/text/qtextengine.cpp
@@ -2826,13 +2826,7 @@ QFixed QTextEngine::leadingSpaceWidth(const QScriptLine &line)
         || !isRightToLeft())
         return QFixed();
 
-    int pos = line.length;
-    const HB_CharAttributes *attributes = this->attributes();
-    if (!attributes)
-        return QFixed();
-    while (pos > 0 && attributes[line.from + pos - 1].whiteSpace)
-        --pos;
-    return width(line.from + pos, line.length - pos);
+    return width(line.from + line.length, line.trailingSpaces);
 }
 
 QFixed QTextEngine::alignLine(const QScriptLine &line)
@@ -2842,14 +2836,12 @@ QFixed QTextEngine::alignLine(const QScriptLine &line)
     // if width is QFIXED_MAX that means we used setNumColumns() and that implicitly makes this line left aligned.
     if (!line.justified && line.width != QFIXED_MAX) {
         int align = option.alignment();
-        if (align & Qt::AlignLeft)
-            x -= leadingSpaceWidth(line);
         if (align & Qt::AlignJustify && isRightToLeft())
             align = Qt::AlignRight;
         if (align & Qt::AlignRight)
-            x = line.width - (line.textAdvance + leadingSpaceWidth(line));
+            x = line.width - (line.textAdvance);
         else if (align & Qt::AlignHCenter)
-            x = (line.width - line.textAdvance)/2 - leadingSpaceWidth(line);
+            x = (line.width - line.textAdvance)/2;
     }
     return x;
 }
diff --git a/src/gui/text/qtextlayout.cpp b/src/gui/text/qtextlayout.cpp
index 4b26eb5..bb216e9 100644
--- a/src/gui/text/qtextlayout.cpp
+++ b/src/gui/text/qtextlayout.cpp
@@ -2498,13 +2498,14 @@ qreal QTextLine::cursorToX(int *cursorPos, Edge edge) const
     bool lastLine = i >= eng->lines.size() - 1;
 
     QFixed x = line.x;
-    x += eng->alignLine(line);
+    x += eng->alignLine(line) - eng->leadingSpaceWidth(line);
 
     if (!i && !eng->layoutData->items.size()) {
         *cursorPos = 0;
         return x.toReal();
     }
 
+    int lineEnd = line.from + line.length + line.trailingSpaces;
     int pos = *cursorPos;
     int itm;
     const HB_CharAttributes *attributes = eng->attributes();
@@ -2512,9 +2513,9 @@ qreal QTextLine::cursorToX(int *cursorPos, Edge edge) const
         *cursorPos = 0;
         return x.toReal();
     }
-    while (pos < line.from + line.length && !attributes[pos].charStop)
+    while (pos < lineEnd && !attributes[pos].charStop)
         pos++;
-    if (pos == line.from + (int)line.length) {
+    if (pos == lineEnd) {
         // end of line ensure we have the last item on the line
         itm = eng->findItem(pos-1);
     }
@@ -2546,7 +2547,6 @@ qreal QTextLine::cursorToX(int *cursorPos, Edge edge) const
 
     bool reverse = eng->layoutData->items[itm].analysis.bidiLevel % 2;
 
-    int lineEnd = line.from + line.length;
 
     // add the items left of the cursor
 
@@ -2619,6 +2619,9 @@ qreal QTextLine::cursorToX(int *cursorPos, Edge edge) const
     if (eng->option.wrapMode() != QTextOption::NoWrap && x > line.x + line.width)
         x = line.x + line.width;
 
+    if (eng->option.wrapMode() != QTextOption::NoWrap && x < 0)
+        x = 0;
+
     *cursorPos = pos + si->position;
     return x.toReal();
 }
diff --git a/tests/auto/qtextlayout/tst_qtextlayout.cpp b/tests/auto/qtextlayout/tst_qtextlayout.cpp
index b55c244..17a5333 100644
--- a/tests/auto/qtextlayout/tst_qtextlayout.cpp
+++ b/tests/auto/qtextlayout/tst_qtextlayout.cpp
@@ -57,6 +57,10 @@
 
 #define TESTFONT_SIZE 12
 
+Q_DECLARE_METATYPE(QTextOption::WrapMode)
+Q_DECLARE_METATYPE(Qt::LayoutDirection)
+Q_DECLARE_METATYPE(Qt::AlignmentFlag)
+
 //TESTED_CLASS=
 //TESTED_FILES=
 
@@ -83,6 +87,12 @@ private slots:
     void noWrap();
     void cursorToXForInlineObjects();
     void cursorToXForSetColumns();
+    void cursorToXForTrailingSpaces_data();
+    void cursorToXForTrailingSpaces();
+    void horizontalAlignment_data();
+    void horizontalAlignment();
+    void horizontalAlignmentMultiline_data();
+    void horizontalAlignmentMultiline();
     void defaultWordSeparators_data();
     void defaultWordSeparators();
     void cursorMovementFromInvalidPositions();
@@ -525,6 +535,436 @@ void tst_QTextLayout::cursorToXForSetColumns()
     QCOMPARE(line.cursorToX(1), (qreal) TESTFONT_SIZE);
 }
 
+void tst_QTextLayout::cursorToXForTrailingSpaces_data()
+{
+    qreal width = TESTFONT_SIZE * 4;
+
+    QTest::addColumn<QTextOption::WrapMode>("wrapMode");
+    QTest::addColumn<Qt::LayoutDirection>("textDirection");
+    QTest::addColumn<Qt::AlignmentFlag>("alignment");
+    QTest::addColumn<qreal>("cursorAt0");
+    QTest::addColumn<qreal>("cursorAt4");
+    QTest::addColumn<qreal>("cursorAt6");
+
+    // Aligned left from start of visible characters.
+    QTest::newRow("ltr nowrap lalign")
+            << QTextOption::NoWrap
+            << Qt::LeftToRight
+            << Qt::AlignLeft
+            << qreal(0)
+            << width
+            << qreal(TESTFONT_SIZE * 6);
+
+    // Aligned left from start of visible characters.
+    QTest::newRow("ltr wrap lalign")
+            << QTextOption::WrapAnywhere
+            << Qt::LeftToRight
+            << Qt::AlignLeft
+            << qreal(0)
+            << width
+            << width;
+
+    // Aligned right from end of whitespace characters.
+    QTest::newRow("ltr nowrap ralign")
+            << QTextOption::NoWrap
+            << Qt::LeftToRight
+            << Qt::AlignRight
+            << qreal(TESTFONT_SIZE * -2)
+            << qreal(TESTFONT_SIZE *  2)
+            << width;
+
+    // Aligned right from end of visible characters.
+    QTest::newRow("ltr wrap ralign")
+            << QTextOption::WrapAnywhere
+            << Qt::LeftToRight
+            << Qt::AlignRight
+            << qreal(TESTFONT_SIZE)
+            << width
+            << width;
+
+    // Aligned center of all characters
+    QTest::newRow("ltr nowrap calign")
+            << QTextOption::NoWrap
+            << Qt::LeftToRight
+            << Qt::AlignHCenter
+            << qreal(TESTFONT_SIZE * -1)
+            << qreal(TESTFONT_SIZE *  3)
+            << qreal(TESTFONT_SIZE *  5);
+
+    // Aligned center of visible characters
+    QTest::newRow("ltr wrap calign")
+            << QTextOption::WrapAnywhere
+            << Qt::LeftToRight
+            << Qt::AlignHCenter
+            << qreal(TESTFONT_SIZE * 0.5)
+            << qreal(width)
+            << qreal(width);
+
+    // Aligned right from start of visible characters
+    QTest::newRow("rtl nowrap ralign")
+            << QTextOption::NoWrap
+            << Qt::RightToLeft
+            << Qt::AlignRight
+            << width
+            << qreal(0)
+            << qreal(TESTFONT_SIZE * -2);
+
+    // Aligned right from start of visible characters
+    QTest::newRow("rtl wrap ralign")
+            << QTextOption::WrapAnywhere
+            << Qt::RightToLeft
+            << Qt::AlignRight
+            << width
+            << qreal(0)
+            << qreal(0);
+
+    // Aligned left from end of whitespace characters
+    QTest::newRow("rtl nowrap lalign")
+            << QTextOption::NoWrap
+            << Qt::RightToLeft
+            << Qt::AlignLeft
+            << qreal(TESTFONT_SIZE * 6)
+            << qreal(TESTFONT_SIZE * 2)
+            << qreal(0);
+
+    // Aligned left from end of visible characters
+    QTest::newRow("rtl wrap lalign")
+            << QTextOption::WrapAnywhere
+            << Qt::RightToLeft
+            << Qt::AlignLeft
+            << qreal(TESTFONT_SIZE * 3)
+            << qreal(0)
+            << qreal(0);
+
+    // Aligned center of all characters
+    QTest::newRow("rtl nowrap calign")
+            << QTextOption::NoWrap
+            << Qt::RightToLeft
+            << Qt::AlignHCenter
+            << qreal(TESTFONT_SIZE *  5)
+            << qreal(TESTFONT_SIZE *  1)
+            << qreal(TESTFONT_SIZE * -1);
+
+    // Aligned center of visible characters
+    QTest::newRow("rtl wrap calign")
+            << QTextOption::WrapAnywhere
+            << Qt::RightToLeft
+            << Qt::AlignHCenter
+            << qreal(TESTFONT_SIZE * 3.5)
+            << qreal(0)
+            << qreal(0);
+}
+
+void tst_QTextLayout::cursorToXForTrailingSpaces()
+{
+    QFETCH(QTextOption::WrapMode, wrapMode);
+    QFETCH(Qt::LayoutDirection, textDirection);
+    QFETCH(Qt::AlignmentFlag, alignment);
+    QFETCH(qreal, cursorAt0);
+    QFETCH(qreal, cursorAt4);
+    QFETCH(qreal, cursorAt6);
+
+    QTextLayout layout("%^&   ", testFont);
+
+    QTextOption o = layout.textOption();
+    o.setTextDirection(textDirection);
+    o.setAlignment(alignment);
+    o.setWrapMode(wrapMode);
+    layout.setTextOption(o);
+
+    layout.beginLayout();
+    QTextLine line = layout.createLine();
+    line.setLineWidth(TESTFONT_SIZE * 4);
+    layout.endLayout();
+
+    QCOMPARE(line.cursorToX(0), cursorAt0);
+    QCOMPARE(line.cursorToX(4), cursorAt4);
+    QCOMPARE(line.cursorToX(6), cursorAt6);
+}
+
+void tst_QTextLayout::horizontalAlignment_data()
+{
+    qreal width = TESTFONT_SIZE * 4;
+
+    QTest::addColumn<QTextOption::WrapMode>("wrapMode");
+    QTest::addColumn<Qt::LayoutDirection>("textDirection");
+    QTest::addColumn<Qt::AlignmentFlag>("alignment");
+    QTest::addColumn<qreal>("naturalLeft");
+    QTest::addColumn<qreal>("naturalRight");
+
+    // Aligned left from start of visible characters.
+    QTest::newRow("ltr nowrap lalign")
+            << QTextOption::NoWrap
+            << Qt::LeftToRight
+            << Qt::AlignLeft
+            << qreal(0)
+            << qreal(TESTFONT_SIZE * 6);
+
+    // Aligned left from start of visible characters.
+    QTest::newRow("ltr wrap lalign")
+            << QTextOption::WrapAnywhere
+            << Qt::LeftToRight
+            << Qt::AlignLeft
+            << qreal(0)
+            << qreal(TESTFONT_SIZE * 3);
+
+    // Aligned right from end of whitespace characters.
+    QTest::newRow("ltr nowrap ralign")
+            << QTextOption::NoWrap
+            << Qt::LeftToRight
+            << Qt::AlignRight
+            << qreal(TESTFONT_SIZE *  - 2)
+            << width;
+
+    // Aligned right from end of visible characters.
+    QTest::newRow("ltr wrap ralign")
+            << QTextOption::WrapAnywhere
+            << Qt::LeftToRight
+            << Qt::AlignRight
+            << qreal(TESTFONT_SIZE)
+            << width;
+
+    // Aligned center of all characters
+    QTest::newRow("ltr nowrap calign")
+            << QTextOption::NoWrap
+            << Qt::LeftToRight
+            << Qt::AlignHCenter
+            << qreal(TESTFONT_SIZE * -1)
+            << qreal(TESTFONT_SIZE *  5);
+
+    // Aligned center of visible characters
+    QTest::newRow("ltr wrap calign")
+            << QTextOption::WrapAnywhere
+            << Qt::LeftToRight
+            << Qt::AlignHCenter
+            << qreal(TESTFONT_SIZE * 0.5)
+            << qreal(TESTFONT_SIZE * 3.5);
+
+    // Aligned right from start of visible characters
+    QTest::newRow("rtl nowrap ralign")
+            << QTextOption::NoWrap
+            << Qt::RightToLeft
+            << Qt::AlignRight
+            << qreal(TESTFONT_SIZE * -2)
+            << width;
+
+    // Aligned right from start of visible characters
+    QTest::newRow("rtl wrap ralign")
+            << QTextOption::WrapAnywhere
+            << Qt::RightToLeft
+            << Qt::AlignRight
+            << qreal(TESTFONT_SIZE * 1)
+            << width;
+
+    // Aligned left from end of whitespace characters
+    QTest::newRow("rtl nowrap lalign")
+            << QTextOption::NoWrap
+            << Qt::RightToLeft
+            << Qt::AlignLeft
+            << qreal(0)
+            << qreal(TESTFONT_SIZE * 6);
+
+    // Aligned left from end of visible characters
+    QTest::newRow("rtl wrap lalign")
+            << QTextOption::WrapAnywhere
+            << Qt::RightToLeft
+            << Qt::AlignLeft
+            << qreal(0)
+            << qreal(TESTFONT_SIZE * 3);
+
+    // Aligned center of all characters
+    QTest::newRow("rtl nowrap calign")
+            << QTextOption::NoWrap
+            << Qt::RightToLeft
+            << Qt::AlignHCenter
+            << qreal(TESTFONT_SIZE * -1)
+            << qreal(TESTFONT_SIZE *  5);
+
+    // Aligned center of visible characters
+    QTest::newRow("rtl wrap calign")
+            << QTextOption::WrapAnywhere
+            << Qt::RightToLeft
+            << Qt::AlignHCenter
+            << qreal(TESTFONT_SIZE * 0.5)
+            << qreal(TESTFONT_SIZE * 3.5);
+}
+
+void tst_QTextLayout::horizontalAlignment()
+{
+    QFETCH(QTextOption::WrapMode, wrapMode);
+    QFETCH(Qt::LayoutDirection, textDirection);
+    QFETCH(Qt::AlignmentFlag, alignment);
+    QFETCH(qreal, naturalLeft);
+    QFETCH(qreal, naturalRight);
+
+    QTextLayout layout("%^&   ", testFont);
+
+    QTextOption o = layout.textOption();
+    o.setTextDirection(textDirection);
+    o.setAlignment(alignment);
+    o.setWrapMode(wrapMode);
+    layout.setTextOption(o);
+
+    layout.beginLayout();
+    QTextLine line = layout.createLine();
+    line.setLineWidth(TESTFONT_SIZE * 4);
+    layout.endLayout();
+
+    QRectF naturalRect = line.naturalTextRect();
+    QCOMPARE(naturalRect.left(), naturalLeft);
+    QCOMPARE(naturalRect.right(), naturalRight);
+}
+
+
+void tst_QTextLayout::horizontalAlignmentMultiline_data()
+{
+    qreal width = TESTFONT_SIZE * 8;
+
+    const QString linebreakText = QLatin1String("^%$&") + QChar(0x2028) + QLatin1String("^%&*^$");
+    QString wrappingText("^%$&^%&*^$");
+    QString wrappingWhitespaceText("^%$&        ^%&*^$");
+
+    QTest::addColumn<QString>("text");
+    QTest::addColumn<Qt::LayoutDirection>("textDirection");
+    QTest::addColumn<Qt::AlignmentFlag>("alignment");
+    QTest::addColumn<qreal>("firstLeft");
+    QTest::addColumn<qreal>("firstRight");
+    QTest::addColumn<qreal>("lastLeft");
+    QTest::addColumn<qreal>("lastRight");
+
+    Qt::LayoutDirection textDirection[] = { Qt::LeftToRight, Qt::RightToLeft };
+    QByteArray textDirectionText [] = { "ltr ", "rtl " };
+    for (int i = 0; i < 2; ++i) {
+        // Aligned left from start of visible characters.
+        QTest::newRow(textDirectionText[i] + "linebreak lalign")
+                << linebreakText
+                << textDirection[i]
+                << Qt::AlignLeft
+                << qreal(0)
+                << qreal(TESTFONT_SIZE * 4)
+                << qreal(0)
+                << qreal(TESTFONT_SIZE * 6);
+
+        // Aligned left from start of visible characters.
+        QTest::newRow(textDirectionText[i] + "wrap-text lalign")
+                << wrappingText
+                << textDirection[i]
+                << Qt::AlignLeft
+                << qreal(0)
+                << width
+                << qreal(0)
+                << qreal(TESTFONT_SIZE * 2);
+
+        // Aligned left from start of visible characters.
+        QTest::newRow(textDirectionText[i] + "wrap-ws lalign")
+                << wrappingWhitespaceText
+                << textDirection[i]
+                << Qt::AlignLeft
+                << qreal(0)
+                << qreal(TESTFONT_SIZE * 4)
+                << qreal(0)
+                << qreal(TESTFONT_SIZE * 6);
+
+        // Aligned right from start of visible characters.
+        QTest::newRow(textDirectionText[i] + "linebreak ralign")
+                << linebreakText
+                << textDirection[i]
+                << Qt::AlignRight
+                << qreal(TESTFONT_SIZE * 4)
+                << width
+                << qreal(TESTFONT_SIZE * 2)
+                << width;
+
+        // Aligned right from start of visible characters.
+        QTest::newRow(textDirectionText[i] + "wrap-text ralign")
+                << wrappingText
+                << textDirection[i]
+                << Qt::AlignRight
+                << qreal(0)
+                << width
+                << qreal(TESTFONT_SIZE * 6)
+                << width;
+
+        // Aligned left from start of visible characters.
+        QTest::newRow(textDirectionText[i] + "wrap-ws ralign")
+                << wrappingWhitespaceText
+                << textDirection[i]
+                << Qt::AlignRight
+                << qreal(TESTFONT_SIZE * 4)
+                << width
+                << qreal(TESTFONT_SIZE * 2)
+                << width;
+
+        // Aligned center from start of visible characters.
+        QTest::newRow(textDirectionText[i] + "linebreak calign")
+                << linebreakText
+                << textDirection[i]
+                << Qt::AlignCenter
+                << qreal(TESTFONT_SIZE * 2)
+                << qreal(TESTFONT_SIZE * 6)
+                << qreal(TESTFONT_SIZE * 1)
+                << qreal(TESTFONT_SIZE * 7);
+
+        // Aligned center from start of visible characters.
+        QTest::newRow(textDirectionText[i] + "wrap-text calign")
+                << wrappingText
+                << textDirection[i]
+                << Qt::AlignCenter
+                << qreal(0)
+                << width
+                << qreal(TESTFONT_SIZE * 3)
+                << qreal(TESTFONT_SIZE * 5);
+
+        // Aligned center from start of visible characters.
+        QTest::newRow(textDirectionText[i] + "wrap-ws calign")
+                << wrappingWhitespaceText
+                << textDirection[i]
+                << Qt::AlignCenter
+                << qreal(TESTFONT_SIZE * 2)
+                << qreal(TESTFONT_SIZE * 6)
+                << qreal(TESTFONT_SIZE * 1)
+                << qreal(TESTFONT_SIZE * 7);
+    }
+}
+
+void tst_QTextLayout::horizontalAlignmentMultiline()
+{
+    QFETCH(QString, text);
+    QFETCH(Qt::LayoutDirection, textDirection);
+    QFETCH(Qt::AlignmentFlag, alignment);
+    QFETCH(qreal, firstLeft);
+    QFETCH(qreal, firstRight);
+    QFETCH(qreal, lastLeft);
+    QFETCH(qreal, lastRight);
+
+    QTextLayout layout(text, testFont);
+
+    QTextOption o = layout.textOption();
+    o.setTextDirection(textDirection);
+    o.setAlignment(alignment);
+    o.setWrapMode(QTextOption::WrapAnywhere);
+    layout.setTextOption(o);
+
+    layout.beginLayout();
+    QTextLine firstLine = layout.createLine();
+    QTextLine lastLine;
+    for (QTextLine line = firstLine; line.isValid(); line = layout.createLine()) {
+        line.setLineWidth(TESTFONT_SIZE * 8);
+        lastLine = line;
+    }
+    layout.endLayout();
+
+    qDebug() << firstLine.textLength() << firstLine.naturalTextRect() << lastLine.naturalTextRect();
+
+    QRectF rect = firstLine.naturalTextRect();
+    QCOMPARE(rect.left(), firstLeft);
+    QCOMPARE(rect.right(), firstRight);
+
+    rect = lastLine.naturalTextRect();
+    QCOMPARE(rect.left(), lastLeft);
+    QCOMPARE(rect.right(), lastRight);
+}
+
 void tst_QTextLayout::defaultWordSeparators_data()
 {
     QTest::addColumn<QString>("text");