kcalcdisplay.cpp

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/*
Copyright (C) 2001 - 2013 Evan Teran
                          evan.teran@gmail.com

Copyright (C) 1996 - 2000 Bernd Johannes Wuebben
                          wuebben@kde.org

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of 
the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "kcalcdisplay.h"

#include <QClipboard>
#include <QMouseEvent>
#include <QPainter>
#include <QStyle>
#include <QStyleOption>
#include <QTimer>

#include <kglobal.h>
#include <klocale.h>
#include <knotification.h>

#include "kcalc_core.h"
#include "kcalc_settings.h"

#include "kcalcdisplay.moc"

//------------------------------------------------------------------------------
// Name: KCalcDisplay
// Desc: constructor
//------------------------------------------------------------------------------
KCalcDisplay::KCalcDisplay(QWidget *parent) : QFrame(parent), beep_(false), 
        groupdigits_(true), twoscomplement_(true), button_(0), lit_(false),
        num_base_(NB_DECIMAL), precision_(9), fixed_precision_(-1), display_amount_(0), 
        history_index_(0), selection_timer_(new QTimer(this)) {
        
    setFocusPolicy(Qt::StrongFocus);

    setSizePolicy(QSizePolicy(QSizePolicy::Expanding, QSizePolicy::Fixed));

    setBackgroundRole(QPalette::Base);
    setForegroundRole(QPalette::Text);
    setFrameStyle(QFrame::StyledPanel | QFrame::Sunken);   // set in kalc.ui

    KNumber::setDefaultFloatOutput(true);
    KNumber::setDefaultFractionalInput(true);

    connect(this, SIGNAL(clicked()), this, SLOT(slotDisplaySelected()));
    connect(selection_timer_, SIGNAL(timeout()), this, SLOT(slotSelectionTimedOut()));

    sendEvent(EventReset);
}

//------------------------------------------------------------------------------
// Name: ~KCalcDisplay
// Desc: destructor
//------------------------------------------------------------------------------
KCalcDisplay::~KCalcDisplay() {
}

//------------------------------------------------------------------------------
// Name: changeSettings
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::changeSettings() {
    QPalette pal = palette();

    pal.setColor(QPalette::Text, KCalcSettings::foreColor());
    pal.setColor(QPalette::Base, KCalcSettings::backColor());

    setPalette(pal);

    setFont(KCalcSettings::displayFont());

    setPrecision(KCalcSettings::precision());

    if (!KCalcSettings::fixed()) {
        setFixedPrecision(-1);
    } else {
        setFixedPrecision(KCalcSettings::fixedPrecision());
    }

    setBeep(KCalcSettings::beep());
    setGroupDigits(KCalcSettings::groupDigits());
    setTwosComplement(KCalcSettings::twosComplement());
    setBinaryGrouping(KCalcSettings::binaryGrouping());
    setOctalGrouping(KCalcSettings::octalGrouping());
    setHexadecimalGrouping(KCalcSettings::hexadecimalGrouping());
    updateDisplay();
}

//------------------------------------------------------------------------------
// Name: 
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::updateFromCore(const CalcEngine &core, bool store_result_in_history) {

    bool tmp_error;
    const KNumber &output = core.lastOutput(tmp_error);
    
    if (tmp_error) {
        sendEvent(EventError);
    }
    
    if (setAmount(output) && store_result_in_history && (output != KNumber::Zero)) {
        // add this latest value to our history
        history_list_.insert(history_list_.begin(), output);
        history_index_ = 0;
    }
}

//------------------------------------------------------------------------------
// Name: enterDigit
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::enterDigit(int data) {

    switch (data) {
    case 0: newCharacter(QLatin1Char('0')); break;
    case 1: newCharacter(QLatin1Char('1')); break;
    case 2: newCharacter(QLatin1Char('2')); break;
    case 3: newCharacter(QLatin1Char('3')); break;
    case 4: newCharacter(QLatin1Char('4')); break;
    case 5: newCharacter(QLatin1Char('5')); break;
    case 6: newCharacter(QLatin1Char('6')); break;
    case 7: newCharacter(QLatin1Char('7')); break;
    case 8: newCharacter(QLatin1Char('8')); break;
    case 9: newCharacter(QLatin1Char('9')); break;
    case 0xa: newCharacter(QLatin1Char('A')); break;
    case 0xb: newCharacter(QLatin1Char('B')); break;
    case 0xc: newCharacter(QLatin1Char('C')); break;
    case 0xd: newCharacter(QLatin1Char('D')); break;
    case 0xe: newCharacter(QLatin1Char('E')); break;
    case 0xf: newCharacter(QLatin1Char('F')); break;
    default:
        Q_ASSERT(0);
        break;
    }
}

//------------------------------------------------------------------------------
// Name: slotHistoryForward
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::slotHistoryForward() {

    if (history_list_.empty()) {
        return;
    }

    if (history_index_ <= 0) {
        return;
    }

    history_index_--;
    setAmount(history_list_[history_index_]);
}

//------------------------------------------------------------------------------
// Name: slotHistoryBack
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::slotHistoryBack() {

    if (history_list_.empty()) {
        return;
    }

    if (history_index_ >= history_list_.size()) {
        return;
    }

    setAmount(history_list_[history_index_]);
    history_index_++;
}

//------------------------------------------------------------------------------
// Name: sendEvent
// Desc: 
//------------------------------------------------------------------------------
bool KCalcDisplay::sendEvent(Event event) {

    switch (event) {
    case EventClear:
    case EventReset:
        display_amount_ = KNumber::Zero;
        str_int_ = QLatin1String("0");
        str_int_exp_.clear();

        eestate_ = false;
        period_ = false;
        neg_sign_ = false;

        updateDisplay();

        return true;
    
    case EventChangeSign:
        return changeSign();
    
    case EventError:
        updateDisplay();
        return true;
        
    default:
        return false;
    }
}

//------------------------------------------------------------------------------
// Name: slotCut
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::slotCut() {

    slotCopy();
    sendEvent(EventReset);
}

//------------------------------------------------------------------------------
// Name: slotCopy
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::slotCopy() {

    QString txt = text_;

    switch(num_base_) {
    case NB_HEX:
        txt.prepend(QLatin1String("0x"));
        txt.remove(QLatin1Char(' '));
        break;
    case NB_BINARY:
        txt.prepend(QLatin1String("0b"));
        txt.remove(QLatin1Char(' '));
        break;
    case NB_OCTAL:
        txt.prepend(QLatin1String("0"));
        txt.remove(QLatin1Char(' '));
        break;
    case NB_DECIMAL:
        break;
    }

    (QApplication::clipboard())->setText(txt, QClipboard::Clipboard);
    (QApplication::clipboard())->setText(txt, QClipboard::Selection);
}

//------------------------------------------------------------------------------
// Name: slotPaste
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::slotPaste(bool bClipboard) {

    QString tmp_str = (QApplication::clipboard())->text(bClipboard ? QClipboard::Clipboard : QClipboard::Selection);

    if (tmp_str.isNull()) {
        if (beep_) {
            KNotification::beep();
        }
        return;
    }

    NumBase tmp_num_base = num_base_;

    // fix up string
    tmp_str = tmp_str.trimmed();
    
    if (groupdigits_) {
        tmp_str.remove(KGlobal::locale()->thousandsSeparator());
    }
    
    tmp_str = tmp_str.toLower();

    // determine base
    if (tmp_str.startsWith(QLatin1String("0x"))) {
        tmp_num_base = NB_HEX;
        tmp_str.remove(0, 2);
    } else if (tmp_str.startsWith(QLatin1String("0b"))) {
        tmp_num_base = NB_BINARY;
        tmp_str.remove(0, 2);
    } else if (tmp_str.startsWith(QLatin1String("0"))) {
        // we don't want this to trigger on "0.xxxxxx" cases
        if(tmp_str.length() < 2 || QString(tmp_str[1]) != KNumber::decimalSeparator()) {
            tmp_num_base = NB_OCTAL;
            tmp_str.remove(0, 1);
        }
    }

    if (tmp_num_base != NB_DECIMAL) {
        bool was_ok;
        const qint64 tmp_result = tmp_str.toULongLong(&was_ok, tmp_num_base);

        if (!was_ok) {
            setAmount(KNumber::NaN);
            if (beep_) {
                KNotification::beep();
            }
            return;
        }
        setAmount(KNumber(tmp_result));
    } else {
        setAmount(KNumber(tmp_str));
        if (beep_ && display_amount_ == KNumber::NaN) {
            KNotification::beep();
        }
    }
}

//------------------------------------------------------------------------------
// Name: slotDisplaySelected
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::slotDisplaySelected() {

    if (button_ == Qt::LeftButton) {
        if (lit_) {
            slotCopy();
            selection_timer_->start(100);
        } else {
            selection_timer_->stop();
        }

        invertColors();
    } else {
        slotPaste(false);   // Selection
    }
}

//------------------------------------------------------------------------------
// Name: slotSelectionTimedOut
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::slotSelectionTimedOut() {

    lit_ = false;
    invertColors();
    selection_timer_->stop();
}

//------------------------------------------------------------------------------
// Name: invertColors
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::invertColors() {

    QPalette tmp_palette = palette();
    tmp_palette.setColor(QPalette::Base, palette().color(QPalette::Text));
    tmp_palette.setColor(QPalette::Text, palette().color(QPalette::Base));
    setPalette(tmp_palette);
}

//------------------------------------------------------------------------------
// Name: mousePressEvent
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::mousePressEvent(QMouseEvent *e) {

    if (e->button() == Qt::LeftButton) {
        lit_ = !lit_;
        button_ = Qt::LeftButton;
    } else {
        button_ = Qt::MidButton;
    }

    emit clicked();
}

//------------------------------------------------------------------------------
// Name: setPrecision
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::setPrecision(int precision) {

    precision_ = precision;
}

//------------------------------------------------------------------------------
// Name: setFixedPrecision
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::setFixedPrecision(int precision) {

    if (fixed_precision_ > precision_) {
        fixed_precision_ = -1;
    } else {
        fixed_precision_ = precision;
    }
}

//------------------------------------------------------------------------------
// Name: setBeep
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::setBeep(bool flag) {
    beep_ = flag;
}

//------------------------------------------------------------------------------
// Name: setGroupDigits
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::setGroupDigits(bool flag) {
    groupdigits_ = flag;
}

//------------------------------------------------------------------------------
// Name: setTwosComplement
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::setTwosComplement(bool flag) {
    twoscomplement_ = flag;
}

//------------------------------------------------------------------------------
// Name: setBinaryGrouping
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::setBinaryGrouping(int digits) {
    binaryGrouping_ = digits;
}

//------------------------------------------------------------------------------
// Name: setOctalGrouping
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::setOctalGrouping(int digits) {
    octalGrouping_ = digits;
}

//------------------------------------------------------------------------------
// Name: setHexadecimalGrouping
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::setHexadecimalGrouping(int digits) {
    hexadecimalGrouping_ = digits;
}

//------------------------------------------------------------------------------
// Name: getAmount
// Desc: 
//------------------------------------------------------------------------------
const KNumber &KCalcDisplay::getAmount() const {
    return display_amount_;
}

//------------------------------------------------------------------------------
// Name: setAmount
// Desc: 
//------------------------------------------------------------------------------
bool KCalcDisplay::setAmount(const KNumber &new_amount) {

    QString display_str;

    str_int_ = QLatin1String("0");
    str_int_exp_.clear();
    period_   = false;
    neg_sign_ = false;
    eestate_  = false;

    if ((num_base_ != NB_DECIMAL) && (new_amount.type() != KNumber::TYPE_ERROR)) {
        display_amount_ = new_amount.integerPart();
    
        if (twoscomplement_) {
            // treat number as 64-bit unsigned
            const quint64 tmp_workaround = display_amount_.toUint64();
            display_str = QString::number(tmp_workaround, num_base_).toUpper();
        } else {
            // QString::number treats non-decimal as unsigned
            qint64 tmp_workaround = display_amount_.toInt64();
            const bool neg = tmp_workaround < 0;
            if (neg) {
                tmp_workaround = qAbs(tmp_workaround);
            }
            
            display_str = QString::number(tmp_workaround, num_base_).toUpper();
            if (neg) {
                display_str.prepend(KGlobal::locale()->negativeSign());
            }
        }
    } else {
        // num_base_ == NB_DECIMAL || new_amount.type() == KNumber::TYPE_ERROR
        display_amount_ = new_amount;
        display_str = display_amount_.toQString(KCalcSettings::precision(), fixed_precision_);
    }

    setText(display_str);
    emit changedAmount(display_amount_);
    return true;
}

//------------------------------------------------------------------------------
// Name: setText
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::setText(const QString &string)
{
    // note that "C" locale is being used internally
    text_ = string;
    
    // don't mess with special numbers
    const bool special = (string.contains(QLatin1String("nan")) || string.contains(QLatin1String("inf")));
    
    // The decimal mode needs special treatment for two reasons, because: a) it uses KGlobal::locale() to get a localized 
    // format and b) it has possible numbers after the decimal place. Neither applies to Binary, Hexadecimal or Octal.
    
    if (groupdigits_ && !special){
        switch (num_base_) {
        case NB_DECIMAL:
            if (string.endsWith(QLatin1Char('.'))) {
                text_.chop(1);
                // Note: rounding happened already above!
                text_ = KGlobal::locale()->formatNumber(text_, false, 0);
                text_.append(KGlobal::locale()->decimalSymbol());
            } else {
                // Note: rounding happened already above!
                text_ = KGlobal::locale()->formatNumber(text_, false, 0);
            }
            break;
            
        case NB_BINARY:
            text_ = groupDigits(text_, binaryGrouping_);
            break;
        
        case NB_OCTAL:
            text_ = groupDigits(text_, octalGrouping_);
            break;
            
        case NB_HEX:
            text_ = groupDigits(text_, hexadecimalGrouping_);
            break;
        }
    } else if(special) {
#if 0
        // TODO: enable this code, it replaces the "inf" with an actual infinity
        //       symbol, but what should be put into the clip board when they copy?
        if(string.contains(QLatin1String("inf"))) {
            text_.replace("inf", QChar(0x221e));
        }
#endif
    }

    update();
    emit changedText(text_);
}

//------------------------------------------------------------------------------
// Name: groupDigits
// Desc: 
//------------------------------------------------------------------------------
QString KCalcDisplay::groupDigits(const QString &displayString, int numDigits) {

    QString tmpDisplayString;
    const int stringLength = displayString.length();

    for (int i = stringLength; i > 0 ; i--){
        if(i % numDigits == 0 && i != stringLength) {
            tmpDisplayString = tmpDisplayString + ' ';
        }

        tmpDisplayString = tmpDisplayString + displayString[stringLength - i];
    }

    return tmpDisplayString;
}

//------------------------------------------------------------------------------
// Name: text
// Desc: 
//------------------------------------------------------------------------------
QString KCalcDisplay::text() const {
    return text_;
}

//------------------------------------------------------------------------------
// Name: setBase
// Desc: change representation of display to new base (i.e. binary, decimal,
//       octal, hexadecimal). The amount being displayed is changed to this
//       base, but for now this amount can not be modified anymore (like
//       being set with "setAmount"). Return value is the new base.
//------------------------------------------------------------------------------
int KCalcDisplay::setBase(NumBase new_base) {

    switch (new_base) {
    case NB_HEX:
        num_base_ = NB_HEX;
        period_  = false;
        break;
    case NB_DECIMAL:
        num_base_ = NB_DECIMAL;
        break;
    case NB_OCTAL:
        num_base_ = NB_OCTAL;
        period_  = false;
        break;
    case NB_BINARY:
        num_base_ = NB_BINARY;
        period_  = false;
        break;
    default:
        Q_ASSERT(0);
    }

    // reset amount
    setAmount(display_amount_);
    return num_base_;
}

//------------------------------------------------------------------------------
// Name: setStatusText
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::setStatusText(int i, const QString &text) {

    if (i < NUM_STATUS_TEXT) {
        str_status_[i] = text;
    }
    
    update();
}

//------------------------------------------------------------------------------
// Name: updateDisplay
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::updateDisplay() {

    // Put sign in front.
    QString tmp_string;
    if (neg_sign_) {
        tmp_string = QLatin1Char('-') + str_int_;
    } else {
        tmp_string = str_int_;
    }

    bool ok;

    switch (num_base_) {
    case NB_BINARY:
        Q_ASSERT(!period_ && !eestate_);
        setText(tmp_string);
        display_amount_ = KNumber(str_int_.toULongLong(&ok, 2));
        if (neg_sign_) {
            display_amount_ = -display_amount_;
        }
        break;

    case NB_OCTAL:
        Q_ASSERT(!period_ && !eestate_);
        setText(tmp_string);
        display_amount_ = KNumber(str_int_.toULongLong(&ok, 8));
        if (neg_sign_) {
            display_amount_ = -display_amount_;
        }
        break;

    case NB_HEX:
        Q_ASSERT(!period_ && !eestate_);
        setText(tmp_string);
        display_amount_ = KNumber(str_int_.toULongLong(&ok, 16));
        if (neg_sign_) {
            display_amount_ = -display_amount_;
        }
        break;

    case NB_DECIMAL:
        if (!eestate_) {
            setText(tmp_string);
            display_amount_ = KNumber(tmp_string);
        } else {
            if (str_int_exp_.isNull()) {
                // add 'e0' to display but not to conversion
                display_amount_ = KNumber(tmp_string);
                setText(tmp_string + QLatin1String("e0"));
            } else {
                tmp_string +=  QLatin1Char('e') + str_int_exp_;
                setText(tmp_string);
                display_amount_ = KNumber(tmp_string);
            }
        }
        break;

    default:
        Q_ASSERT(0);
    }

    emit changedAmount(display_amount_);
}

//------------------------------------------------------------------------------
// Name: newCharacter
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::newCharacter(const QChar new_char) {

    // test if character is valid
    switch (new_char.toLatin1()) {
    case 'e':
        // EE can be set only once and in decimal mode
        if (num_base_ != NB_DECIMAL || eestate_) {
            if (beep_) {
                KNotification::beep();
            }
            return;
        }
        eestate_ = true;
        break;

    case 'F':
    case 'E':
    case 'D':
    case 'C':
    case 'B':
    case 'A':
        if (num_base_ == NB_DECIMAL) {
            if (beep_) {
                KNotification::beep();
            }
            return;
        }
        // no break
    case '9':
    case '8':
        if (num_base_ == NB_OCTAL) {
            if (beep_) {
                KNotification::beep();
            }
            return;
        }
        // no break
    case '7':
    case '6':
    case '5':
    case '4':
    case '3':
    case '2':
        if (num_base_ == NB_BINARY) {
            if (beep_) {
                KNotification::beep();
            }
            return;
        }
        // no break
    case '1':
    case '0':
        break;

    default:
        if(new_char == KGlobal::locale()->decimalSymbol()[0]) {
            // Period can be set only once and only in decimal
            // mode, also not in EE-mode
            if (num_base_ != NB_DECIMAL || period_ || eestate_) {
                if (beep_) {
                    KNotification::beep();
                }
                return;
            }
            period_ = true;
        } else {
            if (beep_) {
                KNotification::beep();
            }
            return;
        }
    }

    // change exponent or mantissa
    if (eestate_) {
        // ignore '.' before 'e'. turn e.g. '123.e' into '123e'
        if (new_char == QLatin1Char('e') && str_int_.endsWith(KGlobal::locale()->decimalSymbol())) {
            str_int_.chop(1);
            period_ = false;
        }

        // 'e' only starts ee_mode, leaves strings unchanged
        // do not add '0' if at start of exp
        if (new_char != QLatin1Char('e')  && !(str_int_exp_.isNull() && new_char == QLatin1Char('0'))) {
            str_int_exp_.append(new_char);
        }
    } else {
        // handle first character
        if (str_int_ == QLatin1String("0")) {
            switch (new_char.toLatin1()) {
            case 'e':
                // display "0e" not just "e"
                // "0e" does not make sense either, but...
                str_int_.append(new_char);
                break;
            default:
                if(new_char == KGlobal::locale()->decimalSymbol()[0]) {
                    // display "0." not just "."
                    str_int_.append(new_char);
                } else {
                    // no leading '0's
                    str_int_[0] = new_char;
                }
            }
        } else {
            str_int_.append(new_char);
        }
    }

    updateDisplay();
}

//------------------------------------------------------------------------------
// Name: deleteLastDigit
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::deleteLastDigit() {

    // Only partially implemented !!
    if (eestate_) {
        if (str_int_exp_.isNull()) {
            eestate_ = false;
        } else {
            const int length = str_int_exp_.length();
            if (length > 1) {
                str_int_exp_.chop(1);
            } else {
                str_int_exp_ = QLatin1String((const char *)0);
            }
        }
    } else {
        const int length = str_int_.length();
        if (length > 1) {
            if (str_int_[length-1] == KGlobal::locale()->decimalSymbol()[0]) {
                period_ = false;
            }
            str_int_.chop(1);
        } else {
            Q_ASSERT(!period_);
            str_int_[0] = QLatin1Char('0');
        }
    }

    updateDisplay();
}

//------------------------------------------------------------------------------
// Name: changeSign
// Desc: change Sign of display. Problem: Only possible here, when in input
//       mode. Otherwise return 'false' so that the kcalc_core can handle
//       things.
//------------------------------------------------------------------------------
bool KCalcDisplay::changeSign() {

    //stupid way, to see if in input_mode or display_mode
    if (str_int_ == QLatin1String("0")) {
        return false;
    }

    if (eestate_) {
        if (!str_int_exp_.isNull()) {
            if (str_int_exp_[0] != QLatin1Char('-')) {
                str_int_exp_.prepend(QLatin1Char('-'));
            } else {
                str_int_exp_.remove(QLatin1Char('-'));
            }
        }
    } else {
        neg_sign_ = !neg_sign_;
    }

    updateDisplay();
    return true;
}

//------------------------------------------------------------------------------
// Name: initStyleOption
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::initStyleOption(QStyleOptionFrame *option) const {

    if (!option) {
        return;
    }

    option->initFrom(this);
    option->state &= ~QStyle::State_HasFocus; // don't draw focus highlight

    if (frameShadow() == QFrame::Sunken) {
        option->state |= QStyle::State_Sunken;
    } else if (frameShadow() == QFrame::Raised) {
        option->state |= QStyle::State_Raised;
    }
    
    option->lineWidth = style()->pixelMetric(QStyle::PM_DefaultFrameWidth, option, this);
    option->midLineWidth = 0;
}

//------------------------------------------------------------------------------
// Name: paintEvent
// Desc: 
//------------------------------------------------------------------------------
void KCalcDisplay::paintEvent(QPaintEvent *) {

    QPainter painter(this);

    QStyleOptionFrame option;
    initStyleOption(&option);

    style()->drawPrimitive(QStyle::PE_PanelLineEdit, &option, &painter, this);

    // draw display text
    const int margin = style()->pixelMetric(QStyle::PM_DefaultFrameWidth, 0, 0);
    QRect cr = contentsRect();
    cr.adjust(margin*2, 0, -margin*2, 0);   // provide a margin
    
    const int align = QStyle::visualAlignment(layoutDirection(), Qt::AlignRight | Qt::AlignVCenter);
    painter.drawText(cr, align | Qt::TextSingleLine, text_);

    // draw the status texts using half of the normal
    // font size but not smaller than 7pt
    QFont fnt(font());
    fnt.setPointSize(qMax((fnt.pointSize() / 2), 7));
    painter.setFont(fnt);
    
    QFontMetrics fm(fnt);
    const uint w = fm.width(QLatin1String("________"));
    const uint h = fm.height();

    for (int n = 0; n < NUM_STATUS_TEXT; ++n) {
        painter.drawText(5 + n * w, h, str_status_[n]);
    }
}

//------------------------------------------------------------------------------
// Name: sizeHint
// Desc: 
//------------------------------------------------------------------------------
QSize KCalcDisplay::sizeHint() const {

    // basic size
    QSize sz = fontMetrics().size(Qt::TextSingleLine, text_);

    // expanded by half font height to make room for  the status texts
    QFont fnt(font());
    fnt.setPointSize(qMax((fnt.pointSize() / 2), 7));
    
    const QFontMetrics fm(fnt);
    sz.setHeight(sz.height() + fm.height());

    QStyleOptionFrame option;
    initStyleOption(&option);

    return (style()->sizeFromContents(QStyle::CT_LineEdit, &option, sz.expandedTo(QApplication::globalStrut()), this));
}