Drawing a line with RGA

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Article Metadata

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Tested with

Devices(s): Nokia N93, Nokia N95

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Compatibility

Platform(s): S60 3rd Edition

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Article

Created: stolik (26 Sep 2008)

Last edited: lpvalente (18 Sep 2012)

Overview

This snippet shows how to draw a line using the RGA API. RGA does not have a function for drawing lines.

Note: In order to use this code, you need to install the Open C plug-in.

Preconditions

This example relies on the RGA API ngi framework to draw a pixel (IGraphicsContext:: SetPixel()).

To run this snippet you need to create a project according to Using RGA with Carbide.c++ and create a simple application like this Simple RGA application. You can also modify the existing examples provided with Open C/C++ Plug-ins for S60 3rd Edition.

MMP file

The following capabilities and libraries are required:

CAPABILITY SwEvent

STATICLIBRARY libcrt0.lib
LIBRARY euser.lib
LIBRARY runtime.lib
LIBRARY libc.lib
LIBRARY libm.lib
LIBRARY libpthread.lib

Note: The snippet itself does not require any special capabilities, but due to the use of RGA API ngi framework, the resulting application requires SwEvent capability. (See also Open C/C++ DLL.)

Source file

#include <graphicscontext.h>    // ngi
#include "helper.h"        //examplefw
 
#include <math.h>
int CExamplePage::sgn (long a) 
    {
    if (a > 0) 
        return +1;
    else 
        if (a < 0) 
            return -1;
    else 
        return 0;
}
void CExamplePage::Line(IGraphicsContext& aGraphicsContext, 
                        int aX1, int aY1, int aX2, int aY2, int aColor) 
{
    long u,s,v,d1x,d1y,d2x,d2y,m,n;
    int i;
    u   = aX2-aX1;
    v   = aY2-aY1;
    d1x = sgn(u);
    d1y = sgn(v);
    d2x = sgn(u);
    d2y = 0;
    m   = abs(u);
    n   = abs(v);
    if (m<=n) 
        {
        d2x = 0;
        d2y = sgn(v);
        m   = abs(v);
        n   = abs(u);
        }
    s = (int)(m / 2);
    for (i=0;i<round(m);i++) 
        {
        aGraphicsContext.SetPixel(aColor, CPoint(aX1,aY1));
        s += n;
        if (s >= m) 
            {
            s -= m;
            aX1 += d1x;
            aY1 += d1y;
            }
        else 
            {
            aX1 += d2x;
            aY1 += d2y;
            }
}
    }

Postconditions

The function will draw a line from a start point to the end point with the provided color.

See also

• Grant Smith's line drawing algorithm