Re: [Pharo-users] Athens and ellipse drawing

[Juraj Kubelka]

El 14-04-2014, a las 8:21, Juraj Kubelka <juraj.kube...@gmail.com> escribió: Thank you Stef, the example helped me a lot to understand how to play with Athens.  The solution is not what I am looking for. If someone starts to play with alpha canal, s/he will get unexpected results. I have finally found an example in C language. It look like this: -=-=-=-=- cairo_set_line_width (cr, 0.1); cairo_save (cr); cairo_scale (cr, 1, 0.2); cairo_arc (cr, 1.5, 1.5, 1, 0, 2 * M_PI); cairo_restore (cr);         cairo_set_source_rgba (cr, 0, 1, 0, 0.50); cairo_stroke (cr); -=-=-=-=- <tips-ellipse.png> I do not know how to write the same instructions with Athens.  First, they draw one arc (cairo_arc (cr, 1.5, 1.5, 1, 0, 2 * M_PI);), I draw 4 arcs: -=-=-=-=- canvas createPath: [ :builder |  builder absolute; moveTo: 0 @ 0.5; ccwArcTo: 0.5 @ 0.0 angle: 90 degreesToRadians; ccwArcTo: 0.0 @ -0.5 angle: 90 degreesToRadians; ccwArcTo: -0.5 @ 0.0 angle: 90 degreesToRadians; ccwArcTo: 0 @ 0.5 angle: 90 degreesToRadians ]. -=-=-=-=- OK, now I can draw ellipse with just one arc: -=-=-=- canvas createPath: [ :builder |  builder absolute; moveTo: 0.5 @ 0;  arcCenterX: 0 centerY: 0 radius: 0.5 startAngle: 0 endAngle: Float twoPi -=-=-=- Why is this method in private protocol? Why I should not use it? Why I have to use “moveTo:”? In C-example they do not use it. But I have to, otherwise there is an extra line on the canvas: Well, I see in AthensCairoPathBuilder>>createPath:, there is call of "self moveToX: 0 Y: 0.”. If I remove it, I do not have to write “moveTo: 0.5@0”. So, I understand why I have to write it in my code. The question is what is the purpose of "self moveToX: 0 Y: 0.”? I guess it simplify some situations, am I right? Which one? There is actual Athens example: -=-=-=- AthensSceneView new scene: [ :can | | path | path := can createPath: [ :builder |  builder absolute; moveTo: 0.5 @ 0; arcCenterX: 0 centerY: 0 radius: 0.5 startAngle: 0 endAngle: Float twoPi ]. can pathTransform restoreAfter: [  can pathTransform scaleBy: 200 @ 50. (can setStrokePaint: Color red) width: 0.1. can drawShape:  path. ]. ] ; openInWindow -=-=-=- Thank you, Juraj Second, they set line width, before any other action (like cairo_save). I do: -=-=-=-=- canvas pathTransform scaleBy: 200 @ 50. (can setStrokePaint: Color red) width: 0.1. can drawShape:  path. -=-=-=-=- So, my result in Athens is like this: <Captura de pantalla 2014-04-14 a la(s) 8.18.38.png> Any idea? The example is explained here, C source code is here (by clicking on the image in the page). Thank you, Jura El 12-04-2014, a las 4:01, Pharo4Stef <pharo4s...@free.fr> escribió: AthensSceneView new scene: [ :can | | path | path := can createPath: [ :builder | builder absolute; moveTo: 0 @ 0.5; ccwArcTo: 0.5 @ 0.0 angle: 90 degreesToRadians; ccwArcTo: 0.0 @ -0.5 angle: 90 degreesToRadians; ccwArcTo: -0.5 @ 0.0 angle: 90 degreesToRadians; ccwArcTo: 0 @ 0.5 angle: 90 degreesToRadians ]. can pathTransform restoreAfter: [ can pathTransform scaleBy: 200 . can setPaint: Color red ; drawShape:  path. "(athensCanvas setStrokePaint: strokePaint) width: (self strokeWidth / self scale) asFloat." can drawShape:  path.]. can pathTransform restoreAfter: [ can pathTransform scaleBy: 190 . can setPaint: Color blue ; drawShape:  path. "(athensCanvas setStrokePaint: strokePaint) width: (self strokeWidth / self scale) asFloat." can drawShape:  path ] ] ; openInWindow <Screen Shot 2014-04-12 at 09.01.09.pdf>