Add isStroked overload for IGeometryContext

[emmauss]

What does the pull request do?

Adds an IGeomtryContextEx interface, with a LineTo method that allow disabling stroke on a line.

What is the current behavior?

What is the updated/expected behavior with this PR?

How was the solution implemented (if it's not obvious)?

Checklist

• Added unit tests (if possible)?
• Added XML documentation to any related classes?
• Consider submitting a PR to https://github.com/AvaloniaUI/Documentation with user documentation

Breaking changes

Obsoletions / Deprecations

Fixed issues

[avaloniaui-team]

You can test this PR using the following package version. 11.0.999-cibuild0038648-beta. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[robloo]

"hasStroke", "drawStroke" or "includeStroke" might be better names for the parameter. I do prefer "Is" when naming bool; however, "stroked" isn't a standard word. "isStroked" has good symmetry with "isFilled" though... so just ideas.

[emmauss]

The name was taken from wpf's, but if there's better wording for it, I could change it.

[robloo]

Ah ok, if naming is coming over from WPF its fine and I don't have concerns other than noted below (line should always have a stroke I think).

[robloo]

Fundamentally, I'm not sure I understand this PR. In WPF, lines have no Fill -- they are only stroke. Therefore, having an isStroked parameter may be a mistake in API and missing something fundamental.

Since a line has no area, the Path object's Fill is not specified; instead the Stroke and StrokeThickness properties are used.

https://learn.microsoft.com/en-us/dotnet/desktop/wpf/graphics-multimedia/how-to-create-a-line-using-a-linegeometry?view=netframeworkdesktop-4.8

Setting the Fill element for a line has no effect, because a line has no interior.

https://learn.microsoft.com/en-us/dotnet/desktop/wpf/graphics-multimedia/how-to-draw-a-line?view=netframeworkdesktop-4.8

Additionally, Skia doesn't have line fill either.

Path contains three Contours: Line, Circle, and Quad. Line is stroked but not filled. Circle is stroked and filled; Circle stroke forms a loop. Quad is stroked and filled, but since it is not closed, Quad does not stroke a loop.

https://skia.org/docs/user/api/skpath_overview/

[avaloniaui-team]

You can test this PR using the following package version. 11.0.999-cibuild0038653-beta. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[kekekeks]

In WPF individual parts of the path can be skipped from being filled or stroked. You can ask BeginFigure to not fill the next figure or ask LineTo to not stroke the next path segment.
So it can essentially have two different paths in one geometry instance.
e. g.

            var geo = new StreamGeometry();
            using (var c = geo.Open())
            {
                c.BeginFigure(new Point(10,10), false, true);
                c.LineTo(new Point(20,10), true, true);
                c.LineTo(new Point(20, 20), true, true);
                c.BeginFigure(new Point(40,10), true, true);
                c.LineTo(new Point(50, 10), true, true);
                c.LineTo(new Point(50, 20), false, true);
                c.Close();
            }
            

            var drawing = new GeometryDrawing(Brushes.Blue, new Pen(Brushes.Red, 1), geo);
            Content = new Image
            {
                Source = new DrawingImage(drawing)
            };

results in:

We implement that by maintaining two separate SKPath instances per geometry if paths are actually different.

[robloo]

@kekekeks Thanks for the explanation. I understand now and especially since this follows WPF I have no concerns.

[jmacato]

Closing this PR temporarily due to inactivity. Please ping me if this needs to be reopened.

[robloo]

Hi @jmacato I mentioned this last time but etiquette is to comment on the PR asking for status and blockers before closing. Just closing suddenly is very bad practice.

Some PRs are blocked for reasons other than the initial author too I believe.

[timunie]

@robloo I somehow agree for some of the closed PRs. But a PR opened by a team member can be discussed internally. And @emmauss could re-open it on his own.

[robloo]

@timunie Yes, sorry, I don't mean for this PR specifically. It was just the last notification I received so commented here.

They are general comments that perhaps are best left somewhere else. Apologies as I do know you discuss these internally as well.