[Qt-embedded-interest] Custom Graphics Driver Without mmap()

[Bryce Salmi]

Qt-embedded-interest,
     I decided to create a new thread as opposed to keeping my previous double buffer thread alive since I am no longer using the double buffer driver.  I have tried to implement Tom Cooksey's suggestions to create a custom driver and one of my main obstacles is that my board (ARM) does not support mmap so I must work around that:

"I don't know to any simple examples you could use. I think actually
you just need to create a new driver which inherits QScreen. As you
can't get a pointer to your graphics memory, the driver will need a
"shadow" buffer instead (So it can read data for blend operations).
You can create a QImage for that in initDevice, and set the screen's
addr pointer to the image's bits(). Then you just need to re-implement
blit() to copy the blended data to your real framebuffer using an
ioctl or whatever.

Hope that helps?


Cheers,

Tom"

I have implemented what I could and created a space in memory for the buffer with QImage and I believe set the screens address pointer (QImage::data) to it.  The following code is my implementation .cpp sourcefile named vopuScreenDriver.cpp

*****
// vopuScreenDriver.cpp

bool vopuScreenDriver::connect(const QString &displaySpec)
{
// Screen info
 QScreen::lstep = 480;
 QScreen::dw = QScreen::w = 480;
 QScreen::dh = QScreen::h = 240;
 QScreen::d = 24;
 QScreen::size = QScreen::lstep * dh;
 QScreen::data = 0;

 setPixelFormat(QImage::Format_RGB888);

//dpi set to internet standard of 72 dpi
 const int dpi = 72;

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

}


bool vopuScreenDriver::initDevice()
{

  //should more be placed here?  seems like
  //svgalib specific stuff is used here
  //for debugging related info

  initColorMap();

  // create address to QImage memory
  int vopuBuffer = QImage::QImage(int 480, int 240, Format Format_RGB888);

  QScreen::data = vopuBuffer;
  QScreenCursor::initSoftwareCursor();
  return true;
}

void vopuScreenDriver::shutdownDevice();
{
  gl_freecontext(content);
  //vga_setmode(TEXT);
}

void vopuScreenDriver::disconnect()
{
}

void SvgalibScreen::blit(const QImage &img, const QPoint &topLeft, const QRegion &reg)
{
     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());
    }
}
*****

The stars (*****) indicate the start and finish of the code, it made more sense on the web based email I am using when I implemented them to separate the code from text.  I would really appreciate any information on fixing up this code and also how to use this driver (compile,etc) when I get it completed. 
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