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Touch gesture support #279

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emilk opened this issue Apr 7, 2021 · 1 comment · Fixed by #306
Closed

Touch gesture support #279

emilk opened this issue Apr 7, 2021 · 1 comment · Fixed by #306
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feature New feature or request web Related to running Egui on the web

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@emilk
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emilk commented Apr 7, 2021

It would be great if egui could support pinch-to-zoom, multi-finger swipes and other touch gestures. For a start, the most important place to support it is the web (i.e. in egui_web).

(NOTE: full multi-touch support, e.g. dragging two sliders at once, is a separate issue).

I suggest we start by adding touch events to egui::Event. Let's do something similar to winit:

enum Event {
    …
    Touch(TouchEvent),
}

pub struct TouchId(pub u64);

struct TouchEvent {
    id: TouchId,
    pos: Pos2,
    phase: TouchPhase,
}

pub enum TouchPhase {
    Started,
    Moved,
    Ended,
    Cancelled,
}

egui::InputState can then keep track of the touches in a HashMap<TouchId, Pos2> and detect gestures. For instance, if there is exactly two touches then it could measure zoom, translation and rotation to support manipulating 2D surfaces. An egui application would then just do something like self.zoom *= ui.input().zoom(); to update its zoom-state each frame.
@emilk emilk added feature New feature or request web Related to running Egui on the web labels Apr 7, 2021
@quadruple-output
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I plan to spend some time on it on the weekend 🚧

@quadruple-output quadruple-output mentioned this issue Apr 13, 2021
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@emilk emilk closed this as completed in #306 May 6, 2021
emilk added a commit that referenced this issue May 6, 2021
@quadruple-output @emilk
Basic multi touch support (issue #279) (#306)
03721db 
* translate touch events from glium to egui

Unfortunately, winit does not seem to create _Touch_ events for the touch pad
on my mac.  Only _TouchpadPressure_ events are sent.

Found some issues (like
[this](rust-windowing/winit#54)), but I am not sure
what they exactly mean:  Sometimes, touch events are mixed with
touch-to-pointer translation in the discussions.

* translate touch events from web_sys to egui

The are a few open topics:
- egui_web currently translates touch events into pointer events.
  I guess this should change, such that egui itself performs this kind of
  conversion.
- `pub fn egui_web::pos_from_touch_event` is a public function, but I
  would like to change the return type to an `Option`.  Shouldn't this
  function be private, anyway?

* introduce `TouchState` and `Gesture`

InputState.touch was introduced with type `TouchState`, just as
InputState.pointer is of type `Pointer`.

The TouchState internally relies on a collection of `Gesture`s.  This commit
provides the first rudimentary implementation of a Gesture, but has no
functionality, yet.

* add method InputState::zoom()

So far, the method always returns `None`, but it should work as soon as the
`Zoom` gesture is implemented.

* manage one `TouchState` per individual device

Although quite unlikely, it is still possible to connect more than one touch
device. (I have three touch pads connected to my MacBook in total, but
unfortunately `winit` sends touch events for none of them.)

We do not want to mix-up the touches from different devices.

* implement control loop for gesture detection

The basic idea is that each gesture can focus on detection logic and does not
have to care (too much) about managing touch state in general.

* streamline `Gesture` trait, simplifying impl's

* implement first version of Zoom gesture

* fix failing doctest

a simple `TODO` should be enough

* get rid of `Gesture`s

* Provide a Zoom/Rotate window in the demo app

For now, it works for two fingers only.  The third finger interrupts the
gesture.

Bugs:
- Pinching in the demo window also moves the window -> Pointer events must be
  ignored when touch is active
- Pinching also works when doing it outside the demo window -> it would be nice
  to return the touch info in the `Response` of the painter allocation

* fix comments and non-idiomatic code

* update touch state *each frame*

* change egui_demo to use *relative* touch data

* support more than two fingers

This commit includes an improved Demo Window for egui_demo, and a complete
re-write of the gesture detection.  The PR should be ready for review, soon.

* cleanup code and comments for review

* minor code simplifications

* oops – forgot the changelog

* resolve comment https://github.com/emilk/egui/pull/306/files/fee8ed83dbe715b5b70433faacfe74b59c99e4a4#r623226656

* accept suggestion #306 (comment)

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

* fix syntax error (dough!)

* remove `dbg!` (why didnt clippy see this?)

* apply suggested diffs from review

* fix conversion of physical location to Pos2

* remove redundanct type `TouchAverages`

* remove trailing space

* avoid initial translation jump in plot demo

* extend the demo so it shows off translation

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
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Basic multi touch support (issue #279)
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@emilk @quadruple-output