More shared touch/mouse handling over all platforms #2395
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That is really difficult. To find a least common level is hard. And sometimes the framework has even more possibilities. Perhaps we should first discuss, what the map need as basic events. Then check, what each platform provides and implement the connection between both. |
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When I look through the events we have, then only Down/Move/Up exists on each platform. And even for Move it isn't clear, if it is only a Down-Move or also a Hover (which doesn't exists on touch platforms). If you want to handle the events in the shared code, then you must make all the events (click/tap, double-click/tap and so on) by yourself in the shared code. Could be, that they not react like the native events. In the other way, you have to catch the events of the native platform in the native part of MapControl and connect them with the Mapsui function. I assume, that all possible reactions are already existing in Mapsui. And some of the events are provided by SkiaSharp. |
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@charlenni I am now in the phase where I am investigating the problem. Many options are open. By posting this issue I am also trying to explain the way I am thinking so that I can take others along in my thoughts. Perhaps the first thing I should have mentioned is the underlying goal, which is to have a code base which is easy to maintain. I want to spend less time fixing bugs and it should be easy to add new functionality. To make it easier to maintain I want to have less code, more shared code, consistent implementations and clear responsibilities.
The mapping of platform specific events to platform independent events is something we are already doing for the widgets. We are even using double click and the shift key modifier. It is, however, not implemented on all platforms and not working correctly om some platforms. For instance, in current main the 'Editing' 'Editing Add Line' sample works different for Avalonia and WPF. This is because some of the events listed above overlap. So, a DoubleTapped is triggered while there is also a PointerUp. So, since we are already doing this kind of mapping we need to clean it up and make sure that what we have is correct. btw, in analyzing this we should also have clear what the use cases are. One thing to note is that support for widgets and support for app builders are different categories.
This is the kind of thing I am investigating in this issue. I am looking in both directions, what do we need or want (the listing above is related to that), and what do the platforms provide (this is something I have not fully clear yet).
If a platform has some advanced functionality not supported by the others then I would like to stay away from it. App builders on that platform would still be able to listen to those events and I want to make it possible to get MapInfo through extension methods on that platform. So, now we pass MapInfo in our events, instead the users could request MapInfo without the platform specific event.
The listing above is what we are currently using on those platforms. I did not fully investigate what is supported on all platforms, but this is the kind of research that should be part of this issue. So far I just looked at what we are using. From what I saw yesterday it looked like all platforms had some support for DoubleTapped. This is one of the decisions to take. Perhaps our widgets should not have a double tap.
Yes, that is something that I wanted to make clear with the listing. I knew it was used in MAUI, but it seems it is only used in MAUI. Also, MAUI uses nothing but SkiaSharp events. When aligning things with other MapControls it would make sense to use MAUI events in MAUI. Then again, it is also an option to use SkiaSharp events everywhere, there would be more shared code. Since I have also seen some bugs in the SkiaSharp touch handling I doubt if this is the best solution. Perhaps we could even provide both, so SkiaSharp touch handling would be an alternative touch handler for all platforms. |
pauldendulk
changed the title
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Perhaps it would be also helpful to look what other map library provide. I always look, what Google Maps does, because that's what users expect. I assume, that Mapsui could handle all the things, that are possible and expected on all platforms. But each platform expects it in a slightly different way. So I'm not sure, if you could reduce the size of code used by platform and increase the shared part. The next thing is, that you should have an expert on each platform. When I look into the code of SkiaSharp I found, that with each new platform, the handling is reduced, because on the new platform hasn't some of the events. It seems, that platform independence has its own limitations. Much work for a suboptimal result. |
Yes, that is something I can not find enough time for. I worked with several in the past, but that was long ago. I've looked into Leaflet somewhat recently and that was very useful. We should do that more.
'Much work'? Much work is spending three long days stepping through unintelligible code to figure out why widget handling is not working. While I wrote the Blazor touch handling in three hours. This issue is all about less work. |
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I tried today to get a first overview over this problem. I found, that it will not be possible to make this easily. Perhaps it is easier to provide functions for things, that you would like to use with a map:
These actions are connected on the different platforms with different events
And then there are MapControls that are running on a keyboard/mouse or a touch platform. Would it be a good idea to implement for the different things you could do with a map functions in the shared MapControl and then select this functions by platform specific events?
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There are two kind of events we need to think about.
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Use more shared code in handling touch and mouse
Currently all platforms have different implementations, which are also very different in nature. What we are looking for is a way to map the platform specific events to a platform neutral event handler. Which events should that be? Do we deal with touch and mouse events separately, or can we use the pointer event (applies to both touch and mouse). How about pinch zoom? Are all version available on all platforms? To make a start I went through all MapControl to register the events that are currently used.
What is used right now?
We have nine different platforms. WinUI and Uno have shared code, so eight MapControls to go through.
Android
Avalonia
In Avalonia Pointer events are individual fingers or the mouse. We have to track the number of fingers
Blazor
Eto
iOS
MAUI
The touch events have all kinds of touch types.
We determine which events this triggers, even LongPress and DoubleTapped.
To calculate Fling the Mapsui.FlingTracker is used.
WinUI / Uno
WPF
To calculate Fling the Mapsui.FlingTracker is used
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