Fix highlighting of C/C++ line continuation backslashes

The backslash itself is not a token, so we must make sure to only format
the trailing whitespace characters as visual whitespace, instead of
everything trailing.

Broke in a92694596e

Task-number: QTCREATORBUG-987
Change-Id: I4e9e84d29513ea317d7e3bde6c6b4c43749cb649
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/cppeditor/cpphighlighter.cpp

@@ -214,7 +214,7 @@ void CppHighlighter::highlightBlock(const QString &text)
     // mark the trailing white spaces
     const int lastTokenEnd = tokens.last().utf16charsEnd();
     if (text.length() > lastTokenEnd)
-        setFormatWithSpaces(text, lastTokenEnd, text.length() - lastTokenEnd, formatForCategory(C_VISUAL_WHITESPACE));
+        formatSpaces(text, lastTokenEnd, text.length() - lastTokenEnd);
 
     if (!initialLexerState && lexerState && !tokens.isEmpty()) {
         const Token &lastToken = tokens.last();

src/plugins/texteditor/syntaxhighlighter.cpp

@@ -477,15 +477,15 @@ void SyntaxHighlighter::setFormat(int start, int count, const QFont &font)
     setFormat(start, count, format);
 }
 
-void SyntaxHighlighter::formatSpaces(const QString &text)
+void SyntaxHighlighter::formatSpaces(const QString &text, int start, int count)
 {
     Q_D(const SyntaxHighlighter);
-    int offset = 0;
+    int offset = start;
-    const int length = text.length();
+    const int end = std::min(start + count, text.length());
-    while (offset < length) {
+    while (offset < end) {
         if (text.at(offset).isSpace()) {
             int start = offset++;
-            while (offset < length && text.at(offset).isSpace())
+            while (offset < end && text.at(offset).isSpace())
                 ++offset;
             setFormat(start, offset - start, d->whitespaceFormat);
         } else {

src/plugins/texteditor/syntaxhighlighter.h

@@ -33,6 +33,7 @@
 #include <QTextLayout>
 
 #include <functional>
+#include <limits.h>
 
 QT_BEGIN_NAMESPACE
 class QTextDocument;
@@ -84,7 +85,7 @@ protected:
     void setFormat(int start, int count, const QFont &font);
     QTextCharFormat format(int pos) const;
 
-    void formatSpaces(const QString &text);
+    void formatSpaces(const QString &text, int start = 0, int count = INT_MAX);
     void setFormatWithSpaces(const QString &text, int start, int count,
                              const QTextCharFormat &format);