UI Button module

The ui button module extends ui base with button ui element.

Implementation note: vs3 overlaps/is duplicates of uiExt module and uwill overwrite each other. Therefore - on changes - changes have to be applied to both of them to maintain consistent outcome. It is duplicated in the ui checkbox so that ui extensions does not need to be loaded when not used. It saves memory / vars with simple UIs.

Enable ui base with uiBtn and create a button with callback on untouch:

var ui = require("ui")       // load ui base module
      .adx(require("uiBtn")) // add module into base and remove from cache

Create - specify - plain buttons

// flgs  clazz id   x  y  w  h b f  value object /. callback on 'untouch'
ui.c( 3,"btn","b1",10,20,50,30,4,7,"B_1"
                  ,function() { (LED1.read()) ? LED1.reset() : LED1.set() }
//                  fs t x y   label text

Creates, adds to ui, conditionally displays and returns an active(2), visible(1) =(3) button ("btn") with id "b01". Button is positioned at 10 @ 20 (left @ top, x @ y) and is sized 50 x 30 (width x height), has 4(red) / 7(white) border / fill colors, has value object string "B_1", has (arguments ignoring) callback that toggles red LED1, and is labeled "RED" on top of it in fontVector (size) 20, text (font) color 0 (black on white button fill color) and x / y-offset of 5 / 15 from left top corner of button's bounding box.

Colors are bit-coded with 3-bit color-depth according ui.clrs=[...] setup.

Callback cb is called on untouch with id, v, ui, e, t as arguments:

args[] sym   description
  0    id  : button id ("b1")
  1    v   : value object ("B_1" - can be any object)
  2    ui  : ui (THE ui object)
  3    e   : uiBtn element (btn 'object' (runtime data structure))
  4    t   : touch info x, y,...  (where last touched)
        { x : x coordinate
        , y : y coordinate
        , t : touched (truey) / untouched (falsey)
        , f : flags

For ui base, color, label, and callback details see (also) ui base module.

For detailed ui setup, including color depth and custom colors, connecting to display and touch screen, soft key board or buttons, see ui module and example material (in the ui.zip file and sources with comments). Take a look at the example that shows all ui elements on one single display - uiExampleAll.js - project file in the _sbx Espruino sandbox projects folder. Make it the Espruino Web IDE sandbox folder and run the ready-made examples on your Espruino board. Espruino forum has several entries about the modules and hardware. Search in (google) for: Espruino Forum allObjects touch screen display modular ui framework

No board or display with touch screen yet? No Problem: Open uiExample.html in uidev folder in Web browser to run the same example in the Cross Development / Emulation environment (where modules are developed and maintained).

Some more details

A button with border and fill colors equal to display background color (ui.bc) creates a tap-able area that is useful to make anything, such as a displayed image, to act like a button...

uiBtn can be changed within callback: for example in example above, the label can be changed to indicate whether tapping will turn the LED on or off. In order to make the ui framework redraw the button and make the label change visible, the callback has to return truey ('JS true'). The button / callback definition for label changing button looks like this:

// flgs clazz id   x  y  w  h  b f  value object /. callback on 'untouch'
                  ,function(id, v, ui, e, t) { // on untouch event
                     if (LED1.read()) {
                       e[11][4] = "RED on"; // label text
                     } else {
                       e[11][4] = "RED off"; // label text
                     return true; // truey forces button to be re-drawn
                  ,[20,0,5,15,"RED on"]);
//                  fs t x y   label text

The same callback shared by multiple uiBtns can produce button specific results when callback takes into account the each buttone's unique id or value (object) as passed to the callback as 2nd argument. Example code for label change above shows that callback parameters include the value object of the button (as well as the button element itself). This allows to use the same callback with different outcome based on button value object (or button's fill color). Multiple, different colored buttons can be used to light up an RGB LED (string) in the button's colors as defined by the value object (and/or fill a rectangle somewhere on the display with the same color as the button's color using one and the same callback to keep the code terse and save space (variables).

Note: The preferred touch event to invoke the callback is on untouch, because it has these advantages:

  • UI behavior is simple in sequence and behavior.
  • Enables cancel of touchdown: releasing / untouch AFTER 'moving / dragging the touch' out of the bounding box of the initially touched button (touched on touch down) will not invoke the untouch callback that otherwise would be the inevitable consequence on touchdown on the button.
  • Implementation of callback is simpler because it is time-wise less critical for delivering a UX behavior with timely, intuitive (visual) feedback to user and no delay on execution of the callback.

To use the (experimental) alternative callback called on all touch events, the 11th ([10]) argument value for the preferred callback 11in the constructor - ui.c(...); - has to be a falsey value best is undefined) and the 13th [12] has to be the callback function. The alternative callback is called with the same arguments as the preferred one. The touch event object t has 12 bit coded flags - t.f, for example for the untouch event 0b000000011001 or 25 - which describe the touch event in detail. For details see ui base module.

Using a synchronous implementation for callback on touch down may delay the visual feedback to the user about the accepted touch down when it takes noticeable time to complete. Therefore, the callback should invoke the heavy lifting code in a setTimeout(function(...){...},10,...); function as the last thing in the (otherwise 'empty') callback. The 10 millisecond timeout is a value to start with. If it is not working, find the best value empirically by working thru the application varying the value.

If the button has to change to give additional visual feedback to the user that the callback is in execution, then that change has to be coded BEFORE* the setTimeout() and the callback has to return truey in order to trigger the redrawing of the button in the ui base module. Changing the button again after completion of the heavy lifting of the callback, it has to happen as last thing IN the setTimeout(function(...){...; e[#]=...; ... _.d(e); },10,...); (with _ being the ui singleton (ui base module) object, passed as the 3rd argument to the callback).

To prevent additional touch down events on the button to prevent triggering the callback again before its completion, disabling of the button has to happen before setTimeout() as well with e[1]=e|1]|2-2;. Re-enabling as absolutely last item IN the setTimeout(){...; e[1]=|2; } code, even after the redraw (see above). A more radical approach is to control the touch listener if it supports the method touch.listen(false) (and the opposite, touch.listen(), which is the same as touch.listen(true)... or 0 and 1 for false and true argument values, respective). Doing latter though, you loose the ability to issue a cancel of a long running callback (which of course has to yield once in a while to the touch controller module using chained setTimeout()s until done.

Example of a button with both untouch and touchdown event callback:

// flgs clazz id   x  y  w  h  b f  value object
//                  fs t x y   label text
                  ,function(id,v,_,e,t){ console.log(id+" "+t.f); } );

If you use both callbacks and put 'the (heavy) work' of the touch down callback into a setTimeout(function(...){...},10,...);, you may consider to put 'the work' of both callbacks into a setTimeout(); (with equal timeout value) to ensure proper sequence (to prevent touchdown callback being triggered first...). Having 'the work' of the untouch in a setTimout();, it is recommended to implement button changes the same way as it has to be done in the touchdown callback by invoking the redraw in the callback with _.d(e); and let the callback return nothing (which is the same as falsey).

btn ui element constructor arguments (a[]) and runtime data structure (e[]) are:

arg runtime 'object' instance of 'clazz' button
a[]  e[]
 0   [0] f  - flags focus(4), active(2), visible(1)
 .    .         0bxx1 visible &1 visible
 .    .         0bx1x active  &2 active / senses touches vs read/display-only
 .    .         0b1xx focus   &4 focus by touch down, drag w/in bounding box
 1   [1] c  - clazz "btn"
 2   [2] i  - id eg "b01", short, at least 2..3 chars,  ui globally unique.
              Single letter ui element ids are 'reserved' (for keyboard(s)).
 3   [3] x  - x ((left ) of focus / touch bounding box)
 4   [4] y  - y ((top  ) of focus / touch bounding box)
 5       w  - width (of focus / touch box)
     [5] x2 - x ((right) of focus / touch bounding box: x - w + 1)
 6       h  - height (of focus / touch box,...
     [6] y2 - y ((bot  ) of focus / touch bounding box: y - h + 1)
 7   [7] bc - border color
 8   [8] fc - fill color
 9   [9] v  - value - any object, from simple string to number to
              complex { } object (returned when button pressed)
10  [10] cb - simple, preferred callback on untouch after touchdown
11  [11] l  - label (info), array with:
      l[0]  fs - font spec:s>0: fontVector (size); s<0: .fnts[-s] of loaded font
      l[1]  tc - (label) text color
      l[2]  x  - x offset from focus box x ( bounding box left )
      l[3]  y  - y offset from focus box y ( bounding box top  )
      l[4]  tx - label text to display (using .drawString())
      l[5]  fmt - opt. Formatter function(l[4],ui,l)
12  [12] ca - NON-preferred, experimental callback on any touch event

btn (button) ui element class properties - variables and methods - mixed into ui base:

exports = // "btn" (plain button) ui element ('clazz' name).
{ vs3: function(x,y,x2,y2,p,q) { // return vertices for btn like shapes ('round' corners)
    // 12 'round corners' (4x3) defined by 0, p and q insetting combinations for x and y
    return [ x,y+q,   x+p,y+p,   x+q,y, x2-q,y, x2-p,y+p, x2,y+q,
            x2,y2-q, x2-p,y2-p, x2-q,y2, x+q,y2, x+p,y2-p, x,y2-q]; }
// ...
// ... private variables and methods
// ...


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