Turns out that I partially misunderstood the use of Path2D in
GraphicsContext. I had been using appendSVGPath for nearly everything and
within a single beginPath/closePath. Under those circumstances
converting GraphicsContext.path from Path2D to Path (using code from
Shape.createFromGeomShape(Path2D p)) gives you a relatively simple path
that can be used as a simplified version of what is rendered in the
Canvas. It can be used as a very "degraded" version of what was placed in
the canvas and is way faster than other solutions.
However, it would only apply to the last beginPath/closePath and it does
not include any of the other path methods in GraphicsContext. Path IS used
by those methods but is empty after a call to e.g. fillRect. That's
unfortunate... If path did retain everything, I'd continue to push for a
"getPath" method on GraphicsContext. I'll have to stick with my current
implementations.
As for the performance of Canvas vs. the Scene, I'm also speaking from
experience. But I'm referring to highly dynamic applications. If you have
an app with lots of objects (and lots dynamic behavior such as motion of
all types, animation, and color) Canvas will be many times more performant
than the Scene graph. I think Gerrit Grunwald's TileFX is a good example
(more complex usage of Canvas than most but still not even close to the
level of dynamic behavior that I'm referring to).
On Fri, May 8, 2020 at 7:13 PM Michael Paus <m...@jugs.org> wrote:
> I think I know quite a bit about JavaFX graphics and I do not generally
> agree with your statements.
> Especially the statement that the Canvas is so much superior is a myth
> from the old days of Java 8
> where there were a few performance bugs in the scene graph handling. But
> that's a long time ago.
> (I even gave a workshop on this at the JavaLand conference some time ago.)
> Maybe you could present
> a few more details about your use-case and not so much about the technique
> that you think is the
> best fit for it. Maybe even some demo code somewhere. I am always
> interested in a discussion about
> graphics as long as it is supported by facts. Neither the scene graph nor
> the canvas is a silver bullet.
> It always depends on your use-case.
> Michael
>
> Am 09.05.20 um 00:18 schrieb jfx user2:
>
> From the JavaDoc "Canvas is an image that can be drawn on using a set of
> graphics commands provided by a GraphicsContext." This a bit of a
> misnomer. While canvas can be used to draw in image (actually
> GraphicsContext not canvas itself), the image based methods of
> GraphicsContext are far outweighed by the "vector" or path based methods.
> The GraphicsContext gives you the ability to freely create dynamic graphics
> without the constraints of the Scene Graph. It can be highly performant
> and scalable if done properly. The Scene Graph will not perform like the
> GraphicsContext. If you haven't worked with highly dynamic graphics, you
> might not have encountered any issues. The Scene Graph works ok up to a
> certain number of objects and it is not good at adding and removing objects
> often. GraphicsContext does not have the same restrictions. It can
> involve more work but the end result will scale far beyond what you can do
> in a Scene Graph... I think this is already widely accepted.
>
> The proposed method on the GraphicsContext simply returns what is already
> there. It would convert the already stored Path2D to a Path. Why reinvent
> what is already present and only private? This in turn CAN be used in the
> Scene Graph but it can also be used as a container to draw back onto the
> GraphicsContext. You see, a Path that is calculated once and then used
> repeatedly to draw in the GraphicsContext (possibly even transformed) is
> better than sub-optimally calculating that Path on every pass through the
> GraphicsContext or storing it as an image or Shape (those were some of my
> workarounds).
>
> Anyway, I'm requesting that a private API be used to create a new public
> method. This is really no different than existing public methods that use
> private APIs. I'm not asking to expose private APIs (not in this request
> :o). There isn't even much code. It's reusing what's already there.
>
> Ask Gerrit Grunwald about his experience with the Scene Graph vs
> Canvas/GraphicsContext.
>
>
> On Fri, May 8, 2020 at 4:27 PM Michael Paus <m...@jugs.org> wrote:
>
>> Hi,
>> I have to say that your requirements sound a little bit strange to me,
>> but maybe you can make it clearer what your real use-case behind them is.
>> What I do not understand is why you are using the canvas at all.
>> Conceptually the canvas is for direct mode rendering into an image. The
>> fact that
>> this is handled a little bit different internally is an implementation
>> detail, you should not rely on. Why don't you use the scene graph which
>> seems
>> to provide many of the aspects that you need? I admit that there are a
>> few hidden gems internally that I would also like to be made public
>> (e.g. the flattening path iterator) but I definitely see these things
>> more in the scene graph context but not for Canvas.
>> Just my two €ent.
>> Michael
>>
>> Am 08.05.20 um 22:08 schrieb jfx user2:
>> > No... given a Shape, create a Path that represents the outline of that
>> shape. If I had a Path I wouldn’t be requesting the new methods.
>> >
>> > One of the workarounds for getting a Path from a GraphicsContext is to
>> keep track of it as I’m drawing... however, this is overhead in the gc call
>> that can become very expensive when you have a lot of gcs or if your gc is
>> doing a lot of work. The path is already there in Path2D along with a
>> method to convert it to a public Path. There’s no need for an expensive
>> custom workaround. All that’s required is a method on the GraphicsContext
>> that returns a Path. The same is true for getting a Path from a Shape.
>> >
>> > Please note that this behavior is desirable for highly optimized use of
>> GraphicsContext and Shapes where you need “outlines” of things in vector
>> format. The private api is unnecessarily hiding this information.
>> >
>> >> On May 8, 2020, at 3:38 PM, Philip Race <philip.r...@oracle.com>
>> wrote:
>> >>
>> >> The current path is defined by the application - you - and yet you
>> don't know what it is ?
>> >> You do say
>> >>> I have other workarounds where I have to maintain a path as I’m
>> drawing in the canvas
>> >> Why can't you do that ? No internal API digging.
>> >>
>> >> -phil
>> >>
>> >>> On 5/8/20, 12:02 PM, jfx user2 wrote:
>> >>> Ok, then please consider the GraphicsContext request that I’ve made.
>> It simply enables you to get the Path from the context without exposing com
>> classes at all. I have other workarounds where I have to maintain a path
>> as I’m drawing in the canvas or I have to do hit testing on a non vector
>> image to determine the path but these are way more expensive than simply
>> creating a Path object from the Path2D that is already in the
>> GraphicContext. That path can be used in drag and drop scenarios, fast
>> secondary rendering under heavy gc use, edge tracing, and the list goes on.
>> >>>
>> >>> The same is true for the Shape class. I’d like to request that the
>> following be added to Shape:
>> >>> public Path getPath() {
>> >>> return Shape.createFromGeomShape(getTransformedArea());
>> >>> }
>> >>>
>> >>> That’s it. The underlying methods are there but the public api
>> doesn’t expose them. This gives you a vector outline of the Shape as
>> Path.l on demand, not stored.
>> >>>
>> >>> There are expensive workarounds for performing these tasks and I
>> spent a long time trying... until I discovers the private apis already had
>> the capability but simply did. It expose it.
>> >>>
>> >>> I’d these are not supported, I’ll have to stick with reflection,
>> bytebuddy, or forking - non of which will be easily maintained or portable.
>> >>>
>> >>> Ps I will post additional concerns over time. The next one likely
>> has to do with the mismatch between javafx canvas (gc) and other canvases
>> such as svg, html2. I think there is private api that would help in this
>> case.
>> >>>
>> >>>>> On May 8, 2020, at 2:41 PM, Kevin Rushforth<
>> kevin.rushfo...@oracle.com> wrote:
>> >>>> Since Canvas is an immediate mode graphics API, I presume you are
>> interested in the most recent drawing primitive? (we don't keep the
>> composite shape for all drawing primitives -- that would be both too
>> expensive and not really appropriate). How would you expect current
>> rendering attributes (e.g., transforms) to affect the results? These are
>> all questions that need to be addressed.
>> >>>>
>> >>>> As for the bigger picture, we intentionally have a separate render
>> graph with "peers" for each node, although some of the duplication of
>> classes is historical (we used to have a looser decoupling before Prism
>> became the only backend). Unless there is a compelling need, we are
>> unlikely to consider changing this in the general case, but perhaps could
>> look at specific cases if it made sense. This is a separate issue, though,
>> from public API and the two shouldn't be conflated.
>> >>>>
>> >>>> Btw, JavaFX has been fully open-sourced since 2013, although the
>> design of Prism predates that.
>> >>>>
>> >>>> -- Kevin
>> >>>>
>> >>>>
>> >>>>> On 5/8/2020 10:43 AM, jfx user2 wrote:
>> >>>>> Kevin, go easy please :0). There is a need.
>> >>>>>
>> >>>>> Access to the outline of the path in the canvas is great for edge
>> following, node attachment points, animating around the non-rectangular
>> border of what’s actually displayed, etc.
>> >>>>>
>> >>>>> The other request that I haven’t posted yet is to do the same for
>> Shape. I’ve tested both of these enhancements and it works as desired.
>> I’ll post the second request soon.
>> >>>>>
>> >>>>> But back to the bigger picture. The requests that I’m making are
>> only additions to return a path from javafx not com. But there are other
>> cases where geometry and convenience methods in com would be beneficial to
>> the public api. It also seems odd that there are two layers to begin
>> with... parallel apis often result in too much object creation or cpu
>> overhead translating between them. I’ll be more specific about these cases
>> over time. Part of my intention is to spark a discussion about the design
>> since previously this was relatively closed source.
>> >>>>>
>> >>>>>>> On May 8, 2020, at 1:12 PM, Kevin Rushforth<
>> kevin.rushfo...@oracle.com> wrote:
>> >>>>>> While there is no plan to "open up" more of com.sun.javafx (and
>> that isn't really the right way to look at it), if you have a proposed
>> enhancement to the existing public javafx.* classes we could discuss it.
>> >>>>>>
>> >>>>>> As for your specific example, can you say more about what your use
>> case is? The GraphicsContext object is a drawing context for a Canvas node,
>> so it is not a natural place to put an API that computes or returns a path.
>> I get the sense that you are looking at the existing internal
>> implementation classes and saying "how can I get access to some information
>> that might be useful to my application" rather than describing what your
>> application is trying to do. Once we understand what you are trying to do,
>> we can discuss whether the need is general enough to propose adding to the
>> public API of JavaFX and what form such a new API might take.
>> >>>>>>
>> >>>>>> -- Kevin
>> >>>>>>
>> >>>>>>
>> >>>>>>> On 5/8/2020 9:35 AM, jfx user2 wrote:
>> >>>>>>> I am aware of this and that’s why I am asking. There are useful
>> private features in com.sun.javafx and I explained one of them in my
>> message. I have an additional related example but the larger question is
>> if there is a plan to open more of com.sun.javafx to the public api,
>> documentation surrounding this, or possibly a complete replacement?
>> >>>>>>>
>> >>>>>>> Please consider the example I provided as a feature request.
>> >>>>>>>
>> >>>>>>>>> On May 8, 2020, at 9:39 AM, Kevin Rushforth<
>> kevin.rushfo...@oracle.com> wrote:
>> >>>>>>>> Only javafx.* packages are part of the public API. Anything
>> else, including com.sun.javafx.*, is internal implementation details that
>> an application should never call.
>> >>>>>>>>
>> >>>>>>>> -- Kevin
>> >>>>>>>>
>> >>>>>>>>
>> >>>>>>>>> On 5/8/2020 12:38 AM, jfx user2 wrote:
>> >>>>>>>>> Is there documentation around the packages (com.sun.javafx vs
>> javafx) used
>> >>>>>>>>> in JavaFX?
>> >>>>>>>>>
>> >>>>>>>>> For example, why is there a com.sun.javafx.geom that isn't
>> fully mirrored
>> >>>>>>>>> in the javafx.scene.shape package? Why are there missing
>> features from
>> >>>>>>>>> Graphics2D?
>> >>>>>>>>>
>> >>>>>>>>> I have a specific example that prompted the question:
>> >>>>>>>>>
>> >>>>>>>>> Consider the following classes:
>> >>>>>>>>>
>> >>>>>>>>> javafx.scene.shape.Shape
>> >>>>>>>>> private static Path
>> >>>>>>>>> createFromGeomShape(com.sunjavafx.geom.Shape geomShape)
>> >>>>>>>>>
>> >>>>>>>>> javafx.scene.canvas.GraphicsContext
>> >>>>>>>>> Path2D path;
>> >>>>>>>>>
>> >>>>>>>>> I want to write a line as follows:
>> >>>>>>>>> Path path = Path.createFromGeomShape(gc.path);
>> >>>>>>>>> b/c I want to inexpensively get the outline of the
>> GraphicsContext.
>> >>>>>>>>>
>> >>>>>>>>> However:
>> >>>>>>>>> We can't access Path2D b/c it's in com.sun.javafx.geom which
>> isn't exported
>> >>>>>>>>> by the module.
>> >>>>>>>>> We can't access Path.createFromGeomShape b/c it's private.
>> >>>>>>>>> We can't access path in GraphicsContext b/c it's default and
>> doesn't have
>> >>>>>>>>> an accessor.
>> >>>>>>>>>
>> >>>>>>>>> A possible solution is to add a new method:
>> >>>>>>>>> javafx.scene.canvas.GraphicsContext
>> >>>>>>>>> public Path getPath() {
>> >>>>>>>>> //implementation copied from
>> >>>>>>>>> javafx.scene.shape.Shape.createFromGeomShape but use gc.path as
>> the path
>> >>>>>>>>> }
>> >>>>>>>>>
>> >>>>>>>>> That would solve my immediate problem but raises the
>> question... why is
>> >>>>>>>>> com.sun.javafx hidden? What's the architectural reason? Is
>> there any work
>> >>>>>>>>> in progress that will impact this design?
>> >>>>>>>>>
>> >>>>>>>>> PS my example is actually very important. I currently use
>> reflection and
>> >>>>>>>>> module opens in the build to get the path but if the getPath
>> method could
>> >>>>>>>>> be added to GraphicsContext, that would be great. For
>> performance, it
>> >>>>>>>>> would be even better to get the PathIterator directly instead of
>> >>>>>>>>> translating into a javafx..Path but that is related to the
>> bigger question.
>>
>>
>>
>
