source: trunk/tools/designer/editor/yyindent.cpp

/**********************************************************************
** Copyright (C) 2005-2007 Trolltech ASA.  All rights reserved.
**
** This file is part of Qt Designer.
**
** This file may be distributed and/or modified under the terms of the
** GNU General Public License version 2 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.
**
** Licensees holding valid Qt Enterprise Edition or Qt Professional Edition
** licenses may use this file in accordance with the Qt Commercial License
** Agreement provided with the Software.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
** See http://www.trolltech.com/gpl/ for GPL licensing information.
** See http://www.trolltech.com/pricing.html or email sales@trolltech.com for
**   information about Qt Commercial License Agreements.
**
** Contact info@trolltech.com if any conditions of this licensing are
** not clear to you.
**
**********************************************************************/

/*
  This file is a self-contained interactive indenter for C++ and Qt
  Script.

  The general problem of indenting a C++ program is ill posed. On the
  one hand, an indenter has to analyze programs written in a
  free-form formal language that is best described in terms of
  tokens, not characters, not lines. On the other hand, indentation
  applies to lines and white space characters matter, and otherwise
  the programs to indent are formally invalid in general, as they are
  begin edited.

  The approach taken here works line by line. We receive a program
  consisting of N lines or more, and we want to compute the
  indentation appropriate for the Nth line. Lines beyond the Nth
  lines are of no concern to us, so for simplicity we pretend the
  program has exactly N lines and we call the Nth line the "bottom
  line". Typically, we have to indent the bottom line when it's still
  empty, so we concentrate our analysis on the N - 1 lines that
  precede.

  By inspecting the (N - 1)-th line, the (N - 2)-th line, ...
  backwards, we determine the kind of the bottom line and indent it
  accordingly.

    * The bottom line is a comment line. See
      bottomLineStartsInCComment() and
      indentWhenBottomLineStartsInCComment().
    * The bottom line is a continuation line. See isContinuationLine()
      and indentForContinuationLine().
    * The bottom line is a standalone line. See
      indentForStandaloneLine().

  Certain tokens that influence the indentation, notably braces, are
  looked for in the lines. This is done by simple string comparison,
  without a real tokenizer. Confusing constructs such as comments and
  string literals are removed beforehand.
*/

#include <qregexp.h>

/* qmake ignore Q_OBJECT */

/*
  The indenter avoids getting stuck in almost infinite loops by
  imposing arbitrary limits on the number of lines it analyzes when
  looking for a construct.

  For example, the indenter never considers more than BigRoof lines
  backwards when looking for the start of a C-style comment.
*/
static const int SmallRoof = 40;
static const int BigRoof = 400;

/*
  The indenter supports a few parameters:

    * ppHardwareTabSize is the size of a '\t' in your favorite editor.
    * ppIndentSize is the size of an indentation, or software tab
      size.
    * ppContinuationIndentSize is the extra indent for a continuation
      line, when there is nothing to align against on the previous
      line.
    * ppCommentOffset is the indentation within a C-style comment,
      when it cannot be picked up.
*/

static int ppHardwareTabSize = 8;
static int ppIndentSize = 4;
static int ppContinuationIndentSize = 8;

static const int ppCommentOffset = 2;

void setTabSize( int size )
{
    ppHardwareTabSize = size;
}

void setIndentSize( int size )
{
    ppIndentSize = size;
    ppContinuationIndentSize = 2 * size;
}

static QRegExp *literal = 0;
static QRegExp *label = 0;
static QRegExp *inlineCComment = 0;
static QRegExp *braceX = 0;
static QRegExp *iflikeKeyword = 0;

/*
  Returns the first non-space character in the string t, or
  QChar::null if the string is made only of white space.
*/
static QChar firstNonWhiteSpace( const QString& t )
{
    int i = 0;
    while ( i < (int) t.length() ) {
        if ( !t[i].isSpace() )
            return t[i];
        i++;
    }
    return QChar::null;
}

/*
  Returns TRUE if string t is made only of white space; otherwise
  returns FALSE.
*/
static bool isOnlyWhiteSpace( const QString& t )
{
    return firstNonWhiteSpace( t ).isNull();
}

/*
  Assuming string t is a line, returns the column number of a given
  index. Column numbers and index are identical for strings that don't
  contain '\t's.
*/
int columnForIndex( const QString& t, int index )
{
    int col = 0;
    if ( index > (int) t.length() )
        index = t.length();

    for ( int i = 0; i < index; i++ ) {
        if ( t[i] == QChar('\t') ) {
            col = ( (col / ppHardwareTabSize) + 1 ) * ppHardwareTabSize;
        } else {
            col++;
        }
    }
    return col;
}

/*
  Returns the indentation size of string t.
*/
int indentOfLine( const QString& t )
{
    return columnForIndex( t, t.find(firstNonWhiteSpace(t)) );
}

/*
  Replaces t[k] by ch, unless t[k] is '\t'. Tab characters are better
  left alone since they break the "index equals column" rule. No
  provisions are taken against '\n' or '\r', which shouldn't occur in
  t anyway.
*/
static inline void eraseChar( QString& t, int k, QChar ch )
{
    if ( t[k] != '\t' )
        t[k] = ch;
}

/*
  Removes some nefast constructs from a code line and returns the
  resulting line.
*/
static QString trimmedCodeLine( const QString& t )
{
    QString trimmed = t;
    int k;

    /*
      Replace character and string literals by X's, since they may
      contain confusing characters (such as '{' and ';'). "Hello!" is
      replaced by XXXXXXXX. The literals are rigourously of the same
      length before and after; otherwise, we would break alignment of
      continuation lines.
    */
    k = 0;
    while ( (k = trimmed.find(*literal, k)) != -1 ) {
        for ( int i = 0; i < literal->matchedLength(); i++ )
            eraseChar( trimmed, k + i, 'X' );
        k += literal->matchedLength();
    }

    /*
      Replace inline C-style comments by spaces. Other comments are
      handled elsewhere.
    */
    k = 0;
    while ( (k = trimmed.find(*inlineCComment, k)) != -1 ) {
        for ( int i = 0; i < inlineCComment->matchedLength(); i++ )
            eraseChar( trimmed, k + i, ' ' );
        k += inlineCComment->matchedLength();
    }

    /*
      Replace goto and switch labels by whitespace, but be careful
      with this case:

          foo1: bar1;
              bar2;
    */
    while ( trimmed.findRev(':') != -1 && trimmed.find(*label) != -1 ) {
        QString cap1 = label->cap( 1 );
        int pos1 = label->pos( 1 );
        int stop = cap1.length();

        if ( pos1 + stop < (int) trimmed.length() && ppIndentSize < stop )
            stop = ppIndentSize;

        int i = 0;
        while ( i < stop ) {
            eraseChar( trimmed, pos1 + i, ' ' );
            i++;
        }
        while ( i < (int) cap1.length() ) {
            eraseChar( trimmed, pos1 + i, ';' );
            i++;
        }
    }

    /*
      Remove C++-style comments.
    */
    k = trimmed.find( "//" );
    if ( k != -1 )
        trimmed.truncate( k );

    return trimmed;
}

/*
  Returns '(' if the last parenthesis is opening, ')' if it is
  closing, and QChar::null if there are no parentheses in t.
*/
static inline QChar lastParen( const QString& t )
{
    int i = t.length();
    while ( i > 0 ) {
        i--;
        if ( t[i] == QChar('(') || t[i] == QChar(')') )
            return t[i];
    }
    return QChar::null;
}

/*
  Returns TRUE if typedIn the same as okayCh or is null; otherwise
  returns FALSE.
*/
static inline bool okay( QChar typedIn, QChar okayCh )
{
    return typedIn == QChar::null || typedIn == okayCh;
}

/*
  The "linizer" is a group of functions and variables to iterate
  through the source code of the program to indent. The program is
  given as a list of strings, with the bottom line being the line to
  indent. The actual program might contain extra lines, but those are
  uninteresting and not passed over to us.
*/

struct LinizerState
{
    QString line;
    int braceDepth;
    bool leftBraceFollows;

    QStringList::ConstIterator iter;
    bool inCComment;
    bool pendingRightBrace;
};

static QStringList *yyProgram = 0;
static LinizerState *yyLinizerState = 0;

// shorthands
static const QString *yyLine = 0;
static const int *yyBraceDepth = 0;
static const bool *yyLeftBraceFollows = 0;

/*
  Saves and restores the state of the global linizer. This enables
  backtracking.
*/
#define YY_SAVE() \
        LinizerState savedState = *yyLinizerState
#define YY_RESTORE() \
        *yyLinizerState = savedState

/*
  Advances to the previous line in yyProgram and update yyLine
  accordingly. yyLine is cleaned from comments and other damageable
  constructs. Empty lines are skipped.
*/
static bool readLine()
{
    int k;

    yyLinizerState->leftBraceFollows =
            ( firstNonWhiteSpace(yyLinizerState->line) == QChar('{') );

    do {
        if ( yyLinizerState->iter == yyProgram->begin() ) {
            yyLinizerState->line = QString::null;
            return FALSE;
        }

        --yyLinizerState->iter;
        yyLinizerState->line = *yyLinizerState->iter;

        yyLinizerState->line = trimmedCodeLine( yyLinizerState->line );

        /*
          Remove C-style comments that span multiple lines. If the
          bottom line starts in a C-style comment, we are not aware
          of that and eventually yyLine will contain a slash-aster.

          Notice that both if's can be executed, since
          yyLinizerState->inCComment is potentially set to FALSE in
          the first if. The order of the if's is also important.
        */

        if ( yyLinizerState->inCComment ) {
            QString slashAster( "/*" );

            k = yyLinizerState->line.find( slashAster );
            if ( k == -1 ) {
                yyLinizerState->line = QString::null;
            } else {
                yyLinizerState->line.truncate( k );
                yyLinizerState->inCComment = FALSE;
            }
        }

        if ( !yyLinizerState->inCComment ) {
            QString asterSlash( "*/" );

            k = yyLinizerState->line.find( asterSlash );
            if ( k != -1 ) {
                for ( int i = 0; i < k + 2; i++ )
                    eraseChar( yyLinizerState->line, i, ' ' );
                yyLinizerState->inCComment = TRUE;
            }
        }

        /*
          Remove preprocessor directives.
        */
        k = 0;
        while ( k < (int) yyLinizerState->line.length() ) {
            QChar ch = yyLinizerState->line[k];
            if ( ch == QChar('#') ) {
                yyLinizerState->line = QString::null;
            } else if ( !ch.isSpace() ) {
                break;
            }
            k++;
        }

        /*
          Remove trailing spaces.
        */
        k = yyLinizerState->line.length();
        while ( k > 0 && yyLinizerState->line[k - 1].isSpace() )
            k--;
        yyLinizerState->line.truncate( k );

        /*
          '}' increment the brace depth and '{' decrements it and not
          the other way around, as we are parsing backwards.
        */
        yyLinizerState->braceDepth +=
                yyLinizerState->line.contains( '}' ) -
                yyLinizerState->line.contains( '{' );

        /*
          We use a dirty trick for

              } else ...

          We don't count the '}' yet, so that it's more or less
          equivalent to the friendly construct

              }
              else ...
        */
        if ( yyLinizerState->pendingRightBrace )
            yyLinizerState->braceDepth++;
        yyLinizerState->pendingRightBrace =
                ( yyLinizerState->line.find(*braceX) == 0 );
        if ( yyLinizerState->pendingRightBrace )
            yyLinizerState->braceDepth--;
    } while ( yyLinizerState->line.isEmpty() );

    return TRUE;
}

/*
  Resets the linizer to its initial state, with yyLine containing the
  line above the bottom line of the program.
*/
static void startLinizer()
{
    yyLinizerState->braceDepth = 0;
    yyLinizerState->inCComment = FALSE;
    yyLinizerState->pendingRightBrace = FALSE;

    yyLine = &yyLinizerState->line;
    yyBraceDepth = &yyLinizerState->braceDepth;
    yyLeftBraceFollows = &yyLinizerState->leftBraceFollows;

    yyLinizerState->iter = yyProgram->end();
    --yyLinizerState->iter;
    yyLinizerState->line = *yyLinizerState->iter;
    readLine();
}

/*
  Returns TRUE if the start of the bottom line of yyProgram (and
  potentially the whole line) is part of a C-style comment; otherwise
  returns FALSE.
*/
static bool bottomLineStartsInCComment()
{
    QString slashAster( "/*" );
    QString asterSlash( "*/" );

    /*
      We could use the linizer here, but that would slow us down
      terribly. We are better to trim only the code lines we need.
    */
    QStringList::ConstIterator p = yyProgram->end();
    --p; // skip bottom line

    for ( int i = 0; i < BigRoof; i++ ) {
        if ( p == yyProgram->begin() )
            return FALSE;
        --p;

        if ( (*p).find(slashAster) != -1 || (*p).find(asterSlash) != -1 ) {
            QString trimmed = trimmedCodeLine( *p );

            if ( trimmed.find(slashAster) != -1 ) {
                return TRUE;
            } else if ( trimmed.find(asterSlash) != -1 ) {
                return FALSE;
            }
        }
    }
    return FALSE;
}

/*
  Returns the recommended indent for the bottom line of yyProgram
  assuming that it starts in a C-style comment, a condition that is
  tested elsewhere.

  Essentially, we're trying to align against some text on the previous
  line.
*/
static int indentWhenBottomLineStartsInCComment()
{
    int k = yyLine->findRev( "/*" );
    if ( k == -1 ) {
        /*
          We found a normal text line in a comment. Align the
          bottom line with the text on this line.
        */
        return indentOfLine( *yyLine );
    } else {
        /*
          The C-style comment starts on this line. If there is
          text on the same line, align with it. Otherwise, align
          with the slash-aster plus a given offset.
        */
        int indent = columnForIndex( *yyLine, k );
        k += 2;
        while ( k < (int) yyLine->length() ) {
            if ( !(*yyLine)[k].isSpace() )
                return columnForIndex( *yyLine, k );
            k++;
        }
        return indent + ppCommentOffset;
    }
}

/*
  A function called match...() modifies the linizer state. If it
  returns TRUE, yyLine is the top line of the matched construct;
  otherwise, the linizer is left in an unknown state.

  A function called is...() keeps the linizer state intact.
*/

/*
  Returns TRUE if the current line (and upwards) forms a braceless
  control statement; otherwise returns FALSE.

  The first line of the following example is a "braceless control
  statement":

      if ( x )
          y;
*/
static bool matchBracelessControlStatement()
{
    int delimDepth = 0;

    if ( yyLine->endsWith("else") )
        return TRUE;

    if ( !yyLine->endsWith(")") )
        return FALSE;

    for ( int i = 0; i < SmallRoof; i++ ) {
        int j = yyLine->length();
        while ( j > 0 ) {
            j--;
            QChar ch = (*yyLine)[j];

            switch ( ch.unicode() ) {
            case ')':
                delimDepth++;
                break;
            case '(':
                delimDepth--;
                if ( delimDepth == 0 ) {
                    if ( yyLine->find(*iflikeKeyword) != -1 ) {
                        /*
                          We have

                              if ( x )
                                  y

                          "if ( x )" is not part of the statement
                          "y".
                        */
                        return TRUE;
                    }
                }
                if ( delimDepth == -1 ) {
                    /*
                      We have

                          if ( (1 +
                                2)

                      and not

                          if ( 1 +
                               2 )
                    */
                    return FALSE;
                }
                break;
            case '{':
            case '}':
            case ';':
                /*
                  We met a statement separator, but not where we
                  expected it. What follows is probably a weird
                  continuation line. Be careful with ';' in for,
                  though.
                */
                if ( ch != QChar(';') || delimDepth == 0 )
                    return FALSE;
            }
        }

        if ( !readLine() )
            break;
    }
    return FALSE;
}

/*
  Returns TRUE if yyLine is an unfinished line; otherwise returns
  FALSE.

  In many places we'll use the terms "standalone line", "unfinished
  line" and "continuation line". The meaning of these should be
  evident from this code example:

      a = b;    // standalone line
      c = d +   // unfinished line
          e +   // unfinished continuation line
          f +   // unfinished continuation line
          g;    // continuation line
*/
static bool isUnfinishedLine()
{
    bool unf = FALSE;

    YY_SAVE();

    if ( yyLine->isEmpty() )
        return FALSE;

    QChar lastCh = (*yyLine)[(int) yyLine->length() - 1];
    if ( QString("{};").find(lastCh) == -1 && !yyLine->endsWith("...") ) {
        /*
          It doesn't end with ';' or similar. If it's neither
          "Q_OBJECT" nor "if ( x )", it must be an unfinished line.
        */
        unf = ( yyLine->contains("Q_OBJECT") == 0 &&
                !matchBracelessControlStatement() );
    } else if ( lastCh == QChar(';') ) {
        if ( lastParen(*yyLine) == QChar('(') ) {
            /*
              Exception:

                  for ( int i = 1; i < 10;
            */
            unf = TRUE;
        } else if ( readLine() && yyLine->endsWith(";") &&
                    lastParen(*yyLine) == QChar('(') ) {
            /*
              Exception:

                  for ( int i = 1;
                        i < 10;
            */
            unf = TRUE;
        }
    }

    YY_RESTORE();
    return unf;
}

/*
  Returns TRUE if yyLine is a continuation line; otherwise returns
  FALSE.
*/
static bool isContinuationLine()
{
    bool cont = FALSE;

    YY_SAVE();
    if ( readLine() )
        cont = isUnfinishedLine();
    YY_RESTORE();
    return cont;
}

/*
  Returns the recommended indent for the bottom line of yyProgram,
  assuming it's a continuation line.

  We're trying to align the continuation line against some parenthesis
  or other bracked left opened on a previous line, or some interesting
  operator such as '='.
*/
static int indentForContinuationLine()
{
    int braceDepth = 0;
    int delimDepth = 0;

    bool leftBraceFollowed = *yyLeftBraceFollows;

    for ( int i = 0; i < SmallRoof; i++ ) {
        int hook = -1;

        int j = yyLine->length();
        while ( j > 0 && hook < 0 ) {
            j--;
            QChar ch = (*yyLine)[j];

            switch ( ch.unicode() ) {
            case ')':
            case ']':
                delimDepth++;
                break;
            case '}':
                braceDepth++;
                break;
            case '(':
            case '[':
                delimDepth--;
                /*
                  An unclosed delimiter is a good place to align at,
                  at least for some styles (including Trolltech's).
                */
                if ( delimDepth == -1 )
                    hook = j;
                break;
            case '{':
                braceDepth--;
                /*
                  A left brace followed by other stuff on the same
                  line is typically for an enum or an initializer.
                  Such a brace must be treated just like the other
                  delimiters.
                */
                if ( braceDepth == -1 ) {
                    if ( j < (int) yyLine->length() - 1 ) {
                        hook = j;
                    } else {
                        return 0; // shouldn't happen
                    }
                }
                break;
            case '=':
                /*
                  An equal sign is a very natural alignment hook
                  because it's usually the operator with the lowest
                  precedence in statements it appears in. Case in
                  point:

                      int x = 1 +
                              2;

                  However, we have to beware of constructs such as
                  default arguments and explicit enum constant
                  values:

                      void foo( int x = 0,
                                int y = 0 );

                  And not

                      void foo( int x = 0,
                                      int y = 0 );

                  These constructs are caracterized by a ',' at the
                  end of the unfinished lines or by unbalanced
                  parentheses.
                */
                if ( QString("!=<>").find((*yyLine)[j - 1]) == -1 &&
                     (*yyLine)[j + 1] != '=' ) {
                    if ( braceDepth == 0 && delimDepth == 0 &&
                         j < (int) yyLine->length() - 1 &&
                         !yyLine->endsWith(",") &&
                         (yyLine->contains('(') == yyLine->contains(')')) )
                        hook = j;
                }
            }
        }

        if ( hook >= 0 ) {
            /*
              Yes, we have a delimiter or an operator to align
              against! We don't really align against it, but rather
              against the following token, if any. In this example,
              the following token is "11":

                  int x = ( 11 +
                            2 );

              If there is no such token, we use a continuation indent:

                  static QRegExp foo( QString(
                          "foo foo foo foo foo foo foo foo foo") );
            */
            hook++;
            while ( hook < (int) yyLine->length() ) {
                if ( !(*yyLine)[hook].isSpace() )
                    return columnForIndex( *yyLine, hook );
                hook++;
            }
            return indentOfLine( *yyLine ) + ppContinuationIndentSize;
        }

        if ( braceDepth != 0 )
            break;

        /*
          The line's delimiters are balanced. It looks like a
          continuation line or something.
        */
        if ( delimDepth == 0 ) {
            if ( leftBraceFollowed ) {
                /*
                  We have

                      int main()
                      {

                  or

                      Bar::Bar()
                          : Foo( x )
                      {

                  The "{" should be flush left.
                */
                if ( !isContinuationLine() )
                    return indentOfLine( *yyLine );
            } else if ( isContinuationLine() || yyLine->endsWith(",") ) {
                /*
                  We have

                      x = a +
                          b +
                          c;

                  or

                      int t[] = {
                          1, 2, 3,
                          4, 5, 6

                  The "c;" should fall right under the "b +", and the
                  "4, 5, 6" right under the "1, 2, 3,".
                */
                return indentOfLine( *yyLine );
            } else {
                /*
                  We have

                      stream << 1 +
                              2;

                  We could, but we don't, try to analyze which
                  operator has precedence over which and so on, to
                  obtain the excellent result

                      stream << 1 +
                                2;

                  We do have a special trick above for the assignment
                  operator above, though.
                */
                return indentOfLine( *yyLine ) + ppContinuationIndentSize;
            }
        }

        if ( !readLine() )
            break;
    }
    return 0;
}

/*
  Returns the recommended indent for the bottom line of yyProgram if
  that line is standalone (or should be indented likewise).

  Indenting a standalone line is tricky, mostly because of braceless
  control statements. Grossly, we are looking backwards for a special
  line, a "hook line", that we can use as a starting point to indent,
  and then modify the indentation level according to the braces met
  along the way to that hook.

  Let's consider a few examples. In all cases, we want to indent the
  bottom line.

  Example 1:

      x = 1;
      y = 2;

  The hook line is "x = 1;". We met 0 opening braces and 0 closing
  braces. Therefore, "y = 2;" inherits the indent of "x = 1;".

  Example 2:

      if ( x ) {
          y;

  The hook line is "if ( x ) {". No matter what precedes it, "y;" has
  to be indented one level deeper than the hook line, since we met one
  opening brace along the way.

  Example 3:

      if ( a )
          while ( b ) {
              c;
          }
      d;

  To indent "d;" correctly, we have to go as far as the "if ( a )".
  Compare with

      if ( a ) {
          while ( b ) {
              c;
          }
          d;

  Still, we're striving to go back as little as possible to accomodate
  people with irregular indentation schemes. A hook line near at hand
  is much more reliable than a remote one.
*/
static int indentForStandaloneLine()
{
    for ( int i = 0; i < SmallRoof; i++ ) {
        if ( !*yyLeftBraceFollows ) {
            YY_SAVE();

            if ( matchBracelessControlStatement() ) {
                /*
                  The situation is this, and we want to indent "z;":

                      if ( x &&
                           y )
                          z;

                  yyLine is "if ( x &&".
                */
                return indentOfLine( *yyLine ) + ppIndentSize;
            }
            YY_RESTORE();
        }

        if ( yyLine->endsWith(";") || yyLine->contains('{') > 0 ) {
            /*
              The situation is possibly this, and we want to indent
              "z;":

                  while ( x )
                      y;
                  z;

              We return the indent of "while ( x )". In place of "y;",
              any arbitrarily complex compound statement can appear.
            */

            if ( *yyBraceDepth > 0 ) {
                do {
                    if ( !readLine() )
                        break;
                } while ( *yyBraceDepth > 0 );
            }

            LinizerState hookState;

            while ( isContinuationLine() )
                readLine();
            hookState = *yyLinizerState;

            readLine();
            if ( *yyBraceDepth <= 0 ) {
                do {
                    if ( !matchBracelessControlStatement() )
                        break;
                    hookState = *yyLinizerState;
                } while ( readLine() );
            }

            *yyLinizerState = hookState;

            while ( isContinuationLine() )
                readLine();

            /*
              Never trust lines containing only '{' or '}', as some
              people (Richard M. Stallman) format them weirdly.
            */
            if ( yyLine->stripWhiteSpace().length() > 1 )
                return indentOfLine( *yyLine ) - *yyBraceDepth * ppIndentSize;
        }

        if ( !readLine() )
            return -*yyBraceDepth * ppIndentSize;
    }
    return 0;
}

/*
  Constructs global variables used by the indenter.
*/
static void initializeIndenter()
{
    literal = new QRegExp( "([\"'])(?:\\\\.|[^\\\\])*\\1" );
    literal->setMinimal( TRUE );
    label = new QRegExp(
        "^\\s*((?:case\\b([^:]|::)+|[a-zA-Z_0-9]+)(?:\\s+slots)?:)(?!:)" );
    inlineCComment = new QRegExp( "/\\*.*\\*/" );
    inlineCComment->setMinimal( TRUE );
    braceX = new QRegExp( "^\\s*\\}\\s*(?:else|catch)\\b" );
    iflikeKeyword = new QRegExp( "\\b(?:catch|do|for|if|while)\\b" );

    yyLinizerState = new LinizerState;
}

/*
  Destroys global variables used by the indenter.
*/
static void terminateIndenter()
{
    delete literal;
    delete label;
    delete inlineCComment;
    delete braceX;
    delete iflikeKeyword;
    delete yyLinizerState;
}

/*
  Returns the recommended indent for the bottom line of program.
  Unless null, typedIn stores the character of yyProgram that
  triggered reindentation.

  This function works better if typedIn is set properly; it is
  slightly more conservative if typedIn is completely wild, and
  slighly more liberal if typedIn is always null. The user might be
  annoyed by the liberal behavior.
*/
int indentForBottomLine( const QStringList& program, QChar typedIn )
{
    if ( program.isEmpty() )
        return 0;

    initializeIndenter();

    yyProgram = new QStringList( program );
    startLinizer();

    const QString& bottomLine = program.last();
    QChar firstCh = firstNonWhiteSpace( bottomLine );
    int indent;

    if ( bottomLineStartsInCComment() ) {
        /*
          The bottom line starts in a C-style comment. Indent it
          smartly, unless the user has already played around with it,
          in which case it's better to leave her stuff alone.
        */
        if ( isOnlyWhiteSpace(bottomLine) ) {
            indent = indentWhenBottomLineStartsInCComment();
        } else {
            indent = indentOfLine( bottomLine );
        }
    } else if ( okay(typedIn, '#') && firstCh == QChar('#') ) {
        /*
          Preprocessor directives go flush left.
        */
        indent = 0;
    } else {
        if ( isUnfinishedLine() ) {
            indent = indentForContinuationLine();
        } else {
            indent = indentForStandaloneLine();
        }

        if ( okay(typedIn, '}') && firstCh == QChar('}') ) {
            /*
              A closing brace is one level more to the left than the
              code it follows.
            */
            indent -= ppIndentSize;
        } else if ( okay(typedIn, ':') ) {
            QRegExp caseLabel(
                "\\s*(?:case\\b(?:[^:]|::)+"
                "|(?:public|protected|private|signals|default)(?:\\s+slots)?\\s*"
                ")?:.*" );

            if ( caseLabel.exactMatch(bottomLine) ) {
                /*
                  Move a case label (or the ':' in front of a
                  constructor initialization list) one level to the
                  left, but only if the user did not play around with
                  it yet. Some users have exotic tastes in the
                  matter, and most users probably are not patient
                  enough to wait for the final ':' to format their
                  code properly.

                  We don't attempt the same for goto labels, as the
                  user is probably the middle of "foo::bar". (Who
                  uses goto, anyway?)
                */
                if ( indentOfLine(bottomLine) <= indent )
                    indent -= ppIndentSize;
                else
                    indent = indentOfLine( bottomLine );
            }
        }
    }
    delete yyProgram;
    terminateIndenter();
    return QMAX( 0, indent );
}

#ifdef Q_TEST_YYINDENT
/*
  Test driver.
*/

#include <qfile.h>
#include <qtextstream.h>

#include <errno.h>

static QString fileContents( const QString& fileName )
{
    QFile f( fileName );
    if ( !f.open(IO_ReadOnly) ) {
        qWarning( "yyindent error: Cannot open file '%s' for reading: %s",
                  fileName.latin1(), strerror(errno) );
        return QString::null;
    }

    QTextStream t( &f );
    QString contents = t.read();
    f.close();
    if ( contents.isEmpty() )
        qWarning( "yyindent error: File '%s' is empty", fileName.latin1() );
    return contents;
}

int main( int argc, char **argv )
{
    if ( argc != 2 ) {
        qWarning( "usage: yyindent file.cpp" );
        return 1;
    }

    QString code = fileContents( argv[1] );
    QStringList program = QStringList::split( '\n', code, TRUE );
    QStringList p;
    QString out;

    while ( !program.isEmpty() && program.last().stripWhiteSpace().isEmpty() )
        program.remove( program.fromLast() );

    QStringList::ConstIterator line = program.begin();
    while ( line != program.end() ) {
        p.push_back( *line );
        QChar typedIn = firstNonWhiteSpace( *line );
        if ( p.last().endsWith(":") )
            typedIn = ':';

        int indent = indentForBottomLine( p, typedIn );

        if ( !(*line).stripWhiteSpace().isEmpty() ) {
            for ( int j = 0; j < indent; j++ )
                out += " ";
            out += (*line).stripWhiteSpace();
        }
        out += "\n";
        ++line;
    }

    while ( out.endsWith("\n") )
        out.truncate( out.length() - 1 );

    printf( "%s\n", out.latin1() );
    return 0;
}
#endif