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# svgalibscreen.cpp Example File
qws/svgalib/svgalibscreen.cpp

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     #include "svgalibscreen.h"
     #include "svgalibsurface.h"

     #include <QVector>
     #include <QApplication>
     #include <QColor>
     #include <QWidget>

     #include <math.h>

     static int getModeDepth(vga_modeinfo *mode)
     {
         const int bits = int(log2(mode->colors));
         if (bits == 24 && mode->bytesperpixel == 4)
             return 32;
         return bits;
     }

     bool SvgalibScreen::connect(const QString &displaySpec)
     {
         int mode = vga_getdefaultmode();
         if (mode <= 0) {
             qCritical("SvgalibScreen::connect(): invalid vga mode");
             return false;
         }

         vga_modeinfo *modeinfo = vga_getmodeinfo(mode);

         QScreen::lstep = modeinfo->linewidth;
         QScreen::dw = QScreen::w = modeinfo->width;
         QScreen::dh = QScreen::h = modeinfo->height;
         QScreen::d = getModeDepth(modeinfo);
         QScreen::size = QScreen::lstep * dh;
         QScreen::data = 0;

         switch (depth()) {
         case 32:
             setPixelFormat(QImage::Format_ARGB32_Premultiplied);
             break;
         case 24:
             setPixelFormat(QImage::Format_RGB888);
             break;
         case 16:
             setPixelFormat(QImage::Format_RGB16);
             break;
         case 15:
             setPixelFormat(QImage::Format_RGB555);
             break;
         default:
             break;
         }

         const int dpi = 72;
         QScreen::physWidth = qRound(QScreen::dw * 25.4 / dpi);
         QScreen::physHeight = qRound(QScreen::dh * 25.4 / dpi);

         const QStringList args = displaySpec.split(QLatin1Char(':'),
                                                    QString::SkipEmptyParts);
         grayscale = args.contains(QLatin1String("grayscale"), Qt::CaseInsensitive);

         return true;
     }

     void SvgalibScreen::initColorMap()
     {
         const int numColors = vga_getcolors();
         if (numColors == 2 || numColors > 256) {
             screencols = 0;
             return; // not a palette based mode
         }

         if (numColors == 16) {
             if (grayscale) {
                 for (int i = 0; i < 256; ++i) {
                     const int c = i * 16 / 256;
                     vga_setpalette(i, c, c, c);
                 }
                 screencols = 256; // XXX: takes advantage of optimization in alloc()
             } else { // read in EGA palette
                 int r, g, b;
                 for (int i = 0; i < 16; ++i) {
                     vga_getpalette(i, &r, &g, &b);
                     screenclut[i] = qRgb(r, g, b);
                 }
                 screencols = 16;
             }

             return;
         }

         Q_ASSERT(numColors == 256);

         if (grayscale) {
             for (int i = 0; i < 256; ++i) {
                 const int c = i * 64 / 256;
                 vga_setpalette(i, c, c, c);
             }
         } else {
             int i = 0;

     #if 0
             // read in EGA palette
             while (i < 16) {
                 int r, g, b;
                 vga_getpalette(i, &r, &g, &b);
                 screenclut[i] = qRgb(r, g, b);
                 ++i;
             }
             screencols = 16;
     #endif

             // 6 * 6 * 6 color cube
             for (int r = 0; r < 6; ++r) {
                 for (int g = 0; g < 6; ++g) {
                     for (int b = 0; b < 6; ++b) {
                         vga_setpalette(i, r * 64/6, g * 64/6, b * 64/6);
                         screenclut[i] = qRgb(r * 256/6, g * 256/6, b * 256/6);
                         ++i;
                     }
                 }
             }
             screencols = i;

             while (i < 256) {
                 screenclut[i] = qRgb(0, 0, 0);
                 ++i;
             }
         }
     }

     bool SvgalibScreen::initDevice()
     {
         if (vga_init() != 0) {
             qCritical("SvgalibScreen::initDevice(): unable to initialize svgalib");
             return false;
         }

         int mode = vga_getdefaultmode();
         if (vga_setmode(mode) == -1) {
             qCritical("SvgalibScreen::initialize(): unable to set graphics mode");
             return false;
         }

         if (gl_setcontextvga(mode) != 0) {
             qCritical("SvgalibScreen::initDevice(): unable to set vga context");
             return false;
         }
         context = gl_allocatecontext();
         gl_getcontext(context);

         vga_modeinfo *modeinfo = vga_getmodeinfo(mode);
         if (modeinfo->flags & IS_LINEAR)
             QScreen::data = vga_getgraphmem();

         initColorMap();

         QScreenCursor::initSoftwareCursor();
         return true;
     }

     void SvgalibScreen::shutdownDevice()
     {
         gl_freecontext(context);
         vga_setmode(TEXT);
     }

     void SvgalibScreen::disconnect()
     {
     }

     void SvgalibScreen::solidFill(const QColor &color, const QRegion &reg)
     {
         int c;
         if (depth() == 4 || depth() == 8)
             c = alloc(color.red(), color.green(), color.blue());
         else
             c = gl_rgbcolor(color.red(), color.green(), color.blue());

         const QVector<QRect> rects = (reg & region()).rects();
         for (int i = 0; i < rects.size(); ++i) {
             const QRect r = rects.at(i);
             gl_fillbox(r.left(), r.top(), r.width(), r.height(), c);
         }
     }

     void SvgalibScreen::blit16To8(const QImage &image,
                                   const QPoint &topLeft, const QRegion &region)
     {
         const int imageStride = image.bytesPerLine() / 2;
         const QVector<QRect> rects = region.rects();

         for (int i = 0; i < rects.size(); ++i) {
             const QRect r = rects.at(i).translated(-topLeft);
             int y = r.y();
             const quint16 *s = reinterpret_cast<const quint16*>(image.scanLine(y));

             while (y <= r.bottom()) {
                 int x1 = r.x();
                 while (x1 <= r.right()) {
                     const quint16 c = s[x1];
                     int x2 = x1;
                     // find span length
                     while ((x2+1 < r.right()) && (s[x2+1] == c))
                         ++x2;
                     gl_hline(x1 + topLeft.x(), y + topLeft.y(), x2 + topLeft.x(),
                              qt_colorConvert<quint8, quint16>(c, 0));
                     x1 = x2 + 1;
                 }
                 s += imageStride;
                 ++y;
             }
         }
     }

     void SvgalibScreen::blit32To8(const QImage &image,
                                   const QPoint &topLeft, const QRegion &region)
     {
         const int imageStride = image.bytesPerLine() / 4;
         const QVector<QRect> rects = region.rects();

         for (int i = 0; i < rects.size(); ++i) {
             const QRect r = rects.at(i).translated(-topLeft);
             int y = r.y();
             const quint32 *s = reinterpret_cast<const quint32*>(image.scanLine(y));

             while (y <= r.bottom()) {
                 int x1 = r.x();
                 while (x1 <= r.right()) {
                     const quint32 c = s[x1];
                     int x2 = x1;
                     // find span length
                     while ((x2+1 < r.right()) && (s[x2+1] == c))
                         ++x2;
                     gl_hline(x1 + topLeft.x(), y + topLeft.y(), x2 + topLeft.x(),
                              qt_colorConvert<quint8, quint32>(c, 0));
                     x1 = x2 + 1;
                 }
                 s += imageStride;
                 ++y;
             }
         }
     }

     void SvgalibScreen::blit(const QImage &img, const QPoint &topLeft,
                              const QRegion &reg)
     {
         if (depth() == 8) {
             switch (img.format()) {
             case QImage::Format_RGB16:
                 blit16To8(img, topLeft, reg);
                 return;
             case QImage::Format_RGB32:
             case QImage::Format_ARGB32:
             case QImage::Format_ARGB32_Premultiplied:
                 blit32To8(img, topLeft, reg);
                 return;
             default:
                 break;
             }
         }

         if (img.format() != pixelFormat()) {
             if (base())
                 QScreen::blit(img, topLeft, reg);
             return;
         }

         const QVector<QRect> rects = (reg & region()).rects();

         for (int i = 0; i < rects.size(); ++i) {
             const QRect r = rects.at(i);
             gl_putboxpart(r.x(), r.y(), r.width(), r.height(),
                           img.width(), img.height(),
                           static_cast<void*>(const_cast<uchar*>(img.bits())),
                           r.x() - topLeft.x(), r.y() - topLeft.y());
         }
     }

     QWSWindowSurface* SvgalibScreen::createSurface(QWidget *widget) const
     {
         if (base()) {
             static int onScreenPaint = -1;
             if (onScreenPaint == -1)
                 onScreenPaint = qgetenv("QT_ONSCREEN_PAINT").toInt();

             if (onScreenPaint > 0 || widget->testAttribute(Qt::WA_PaintOnScreen))
                 return new SvgalibSurface(widget);
         }
         return QScreen::createSurface(widget);
     }

     QWSWindowSurface* SvgalibScreen::createSurface(const QString &key) const
     {
         if (key == QLatin1String("svgalib"))
             return new SvgalibSurface;
         return QScreen::createSurface(key);
     }