Drawing Pie Chart in Symbian

[sunitha.m13]

Hi,
I want to show the percentage of the score as Pie Chart.
Can anyone help me in drawing pie chart in Symbian.
In some other thread, some one is telling Math::Sin() or Math::Cos() functions.
What is the relation of these functions with Pie chart ? How can I draw ?

[wizard_hu_]

Those other threads are right. Sine and cosine are trigonometric functions (http://en.wikipedia.org/wiki/Trigonometric_functions), particularly useful for coordinate geometry. And you actually do need the resulting coordinates of geometric transformations.
In short: when you want x and y to traverse around a circle with radius r, you can use

x = r * cos (a)
y = r * sin (a)

where a is an angle, running from 0 to 2*pi (most computing environments expect you to provide angles in radians, http://en.wikipedia.org/wiki/Radian)
For expressing 100% as a full circle

a = p / 100 * 2 * pi = p * pi /50

can be used, where p is a percentage.

[sunitha.m13]

Those other threads are right. Sine and cosine are trigonometric functions (http://en.wikipedia.org/wiki/Trigonometric_functions), particularly useful for coordinate geometry. And you actually do need the resulting coordinates of geometric transformations.
In short: when you want x and y to traverse around a circle with radius r, you can use

x = r * cos (a)
y = r * sin (a)

where a is an angle, running from 0 to 2*pi (most computing environments expect you to provide angles in radians, http://en.wikipedia.org/wiki/Radian)
For expressing 100% as a full circle

a = p / 100 * 2 * pi = p * pi /50

can be used, where p is a percentage.

Thanks for the reply....

but its not displaying with respect to percentage given.
see my code:

TInt p = 50; // percentage
    TReal src  = (p * 360) / 100;
    RDebug::Print(_L("---> src = %f"), src);
    TInt r = 155;    
    TReal result;
    
    Math::Cos(result, src);
    TInt x = r * result;
    RDebug::Print(_L("result X = %d"), result);
    RDebug::Print(_L("x = %d"), x);
    
    Math::Sin (result, src);
    TInt y = r * result;
    RDebug::Print(_L("result Y = %d"), result);
    RDebug::Print(_L("y = %d"), y);

 // draw a pie slice centered in the rectangle
    gc.SetBrushStyle(CGraphicsContext::ESolidBrush);
    gc.SetBrushColor(KRgbRed);
    TRect ellipseRect=Rect(); // for arcs and ellipse
    ellipseRect.SetWidth(250);
    ellipseRect.SetHeight(250);
    ellipseRect.Shrink(10,10); // set size so inside the border rectangle
    
    //TRect rect;
    TPoint screenCenterPoint=ellipseRect.Center(); // the center of the screen
    // set up a pair of construction points for arc and pie slice drawing
    TPoint constructionPoint1(210,125); // outside the construction ellipse
TPoint constructionPoint2(y,x); // inside the construction ellipse
    	TSize size(250,250);
		gc.DrawRoundRect(ellipseRect,size);
		//gc.DrawPie(ellipseRect,constructionPoint1,constructionPoint2);
		// draw the other portion of the elliptical disc
		gc.SetBrushColor(KRgbGreen);
		gc.DrawPie(ellipseRect,constructionPoint1,constructionPoint2);

[wizard_hu_]

see my code:

TInt p = 50; // percentage
    TReal src  = (p * 360) / 100;

I see it. Guess why I wrote "a = p / 100 * 2 * pi = p * pi /50".
Computing languages measure angles in radians ("RAD" mode on a scientific calculator), while your code does that in degrees ("DEG" mode).
2*pi (~6.2832) radians are 360 degrees, a full circle. Replace 360 with 2*pi (2*KPi in Symbian C++), and it will be better.

[sunitha.m13]

I see it. Guess why I wrote "a = p / 100 * 2 * pi = p * pi /50".
Computing languages measure angles in radians ("RAD" mode on a scientific calculator), while your code does that in degrees ("DEG" mode).
2*pi (~6.2832) radians are 360 degrees, a full circle. Replace 360 with 2*pi (2*KPi in Symbian C++), and it will be better.

I have changed 360 to 2*KPi, but still no change. Its not drawing correctly.
I guess I need to change the logic behind the constructionPoint1 & constructionPoint2

TPoint constructionPoint1(210,125); // outside the construction ellipse
TPoint constructionPoint2(x,y); // inside the construction ellipse
gc.DrawPie(ellipseRect,constructionPoint1,constructionPoint2);

[wizard_hu_]

Those points should be absolute coordinates, so add a

constructionPoint2+=screenCenterPoint;

, and it is going to get much better. After that try with various p-s (0, 25, 50, 75), and you will see that constructionPoint1 needs to be re-calculated, because it represents something else than 0% (25% or 75%, I have not checked exactly, but it is a quarter pie to one direction).

[sunitha.m13]

Yes...its drawing as expected but in reverse direction.
Can you tell me how to change the direction of drawing ?

I tried to give negative sign for the co-ordinates, but entire calculation goes wrong with that.

[tamhanna]

invert the angle

look at the angle from 0 to 360 degrees and then think what you have to add or subtract.