GC in Sciter’s Script

Excellent article by Ken Fox outlining architecture of different Garbage Collection strategies.

Sciter’s script uses “Copying Collector”. Its work is visualized as:

Copying GC at work

And DOM (tree of objects without cycles) is using Reference Counting that reflects in external native DOM API by pair of SciterUseElement and SciterUnUseElement (a.k.a. AddRef/Release).

Sciter for AngularJS practitioners. Directives.

Directives in AngularJS

From AngularJS documentation :

At a high level, directives are markers on a DOM element (such as an attribute, element name, comment or CSS class) that tell AngularJS’s HTML compiler ($compile) to attach a specified behavior to that DOM element (e.g. via event listeners), or even to transform the DOM element and its children.

And here is a typical AngularJS directive implementation:

app.directive('myCustomer', function() {
  return {
    template: 'Name: {{name}} Address: {{address}}', // content
    scope: { name:"", address:"" },  // internal data model
    link: function(scope, elem, attrs) { // initialization 
      elem.bind('click', function() { ... });
      elem.bind('dblclick', function() { ... });
    }
  };
});

It says that each <my-customer> element will have

  • Name: ... Address: ... content;
  • click and dblclick event handlers.

In Sciter

Behaviors

Declarative code-to-element binding in Sciter is made by CSS. Sciter’s prototype property is used for that purpose:

my-customer {
  prototype: MyCustomer url(my-customer.tis);
  display: block;
  ...
}

In plain text: all <my-customer> elements are rendered as block element and will have class MyCustomer assigned to them.  The class will be loaded from my-customer.tis file (if it was not loaded before):

class MyCustomer : Element 
{
  function attached() // called when element gets this class - "link" in terms of Angular 
  {
     // content initialization: 
     this.$content(Name: <output.name/> Address: <output.address/>);
  }
  // event handlers:
  event click { ... /* 'this' here is the element*/ }
  event dblclick { ... }
}

As the code is assigned by CSS then you can use full power of CSS selectors to assign code classes to elements.

Aspects

Another option to bind code with elements is to use so called aspects. Aspect here is just a script function that gets executed when its selector matched the element first time:

[collapsible] { aspect: Collapsible url(my-aspects.tis); }
[collapsible]:collapsed > :last-child { display:none; } // last child is invisible when collapsed

And Collapsible here is a simple function that handles click event and triggers :collapsed state flag switch:

function Collapsible() { 
  this << event click {
     if( this.state.collapsed ) this.state.expanded = true;
     else this.state.collapsed = true;    
  }
}

Having such aspect defined we can define collapsible element:

<div collapsible>
  click here to see content
  <p>Content</p>
</div>

So if you have multiple collapsible sections in your design then just add “collapsible” attribute to them.

New blocknote.net application is getting its shape.

My Blocknote.net editor is getting new shape.

BN is an editor “for the rest of us on the Net” – simple WYSIWYG editor producing clean HTML that is ready to be embedded into blogs, emails, etc.

It is an editor for “Internet writers” people who produce content and so need humanistic tool rather than plain text editor with cryptic HTML or even Markdown.

BN2

Some editing tasks are easy to do in source code though. So BN supports source code view with transparent selection – text selected in WYSIWYG will be selected in source and vice versa:

BN2

Sciter technology survey

Ramon, author of Omni/OmniCode from MI Software, is making a survey about how people are using Sciter technology.

In return he is promising to provide licenses of his products to those who participated in survey.

Survey: goo.gl/forms/BKGHVjTGBTEIVMl02

More info is on misoftware.rs site.

Hope you can participate and help him to get that information.

+plus and +formation, what’s the difference?

+plus

+plus is the way to define and support mapping between DOM tree and data tree rooted at some object or namespace. So if you have these two declarations, markup:

<style>@import url(plus.css)</style>
<section model="person">
    <label>First</label> <input(name.first)>
    <label>Second</label> <input(name.last)>
    <label>Age</label> <input|integer(age)>
</section>

and script

namespace person {
  var name = { first: "Albert", last:"Einshtein" };
  var age = 53;
}

then the +plus will establish live two-way mapping (binding)  between DOM elements above and the data structure.

When the user changes value of input(name.first) field  (short form of <input name="name.first"> in Sciter) the following happens:

  1. Sciter generates “change” DOM event;
  2. +plus handles that event and
  3. updates value of person.name.first in data namespace.

And when data gets changed by some other code like

person.name.first = "Some other name";

then pretty much similar flow occurs:

  1. Sciter determines that filed first  has changed on observable object.
  2. Sciter calls attached function-observer – each object/array inside bound namespace has an observer function attached to it.
  3. And that function-observer updates bound DOM element.

As you see, in order binding to work both-ways, each data node (object, array) in bound namespace has to have corresponding observer attached to it.

+formation

The main difference from the above is that the +formation does not require separate data structure.  The formation is a data structure by itself naturally mapped to markup structure.

This markup:

<section(person)>
    <label>First</label> <input(name.first)>
    <label>Second</label> <input(name.last)>
    <label>Age</label> <input|integer(age)>
</section

gets mapped by formation() function to the [formation] tree structure:

And code can access that tree directly as:

var root = formation( self );
// setting whole formation:
root.person.value = {
   name : {
     first: "Albert",
     last: "Einshtein"
   },
   age:69
 };

// or setting particular field in the formation:
root.person.name.first.value = "Some other name";

Note: root.person.name.first is a direct reference to <input> DOM element thus .value is required.

The formation is a data structure derived from actual DOM tree (its projection)  and so you can use normal DOM events to be notified when some data changes by the user:

root.person.name.first.on("change", function() {...}) // or
self.on("change", "section[name=person]", function() {...}) // any change in person fields.

Resume

Essentially +plus and +formation are aimed to the same task – update UI from code and update/notify code about some changes in UI.

  • +plus
    • pros: Allows to bind arbitrary data structure to arbitrary DOM tree.
    • cons: Can be memory and CPU consuming on large data and DOM trees.
  • +formation
    • pros: Fast and not CPU consuming.  Yet allows to access “fields of interest” by using dot notation (“paths in formation”):  root.person.name.first.state.disabled = true;
    • cons: data structure you get (the formation tree) is bound with DOM structure. So when you change DOM structure then  formation paths in code may change.

Better use of style @set’s

In next version (4.0.0.2 and above) I am changing the way of how @set’s are applied in user’s style sheet.

Style sets will be applied before any other rules in the same style sheet.

So if you have

@set MySet {
  :root { color:red; width:*; }
}

myelement { style-set: MySet; }

And later define

myelement#test {
  color:blue;
}

then <myelement id=test>...</myelement> element will have blue color.

So you can think of style sets as definition of default styles. Ordinary CSS rules are applied on top of them allowing to style concrete elements.

Starting Sciter v.4.*.*.* series

Major changes:

SDK will include versions of Sciter with Skia graphics backend.

On Windows sciter is compiled as different DLLs having the same name sciter.dll locating in following folders:

  • bin/32/sciter.dll \
  • bin/64/sciter.dll – Direct2D and GDI+ backends as before
  • bin/skia32/sciter.dll \
  • bin/skia64/sciter.dll – Direct2D and Skia/OpenGL backends.

On MacOS sciter will include as CoreGraphics as Skia/OpenGL backends switchable by SciterSetOption() function.

On Linux I will have separate sciter.so that will not use GTK at all . Instead it will expose SciterProcX function similar to SciterProcND. Basic purpose: to use Sciter with SDL, GLFW and the like environments.

On the road to better documentation

Sciter documentation, how to say in polite manner, is not convenient. I know.

So looking for ideas of making it better.

Problem is that I need documentation for at least of two types of media: for Sciter’s help browser and for the web. While I can use HTML it is not always use the same files. Standard CSS is not at Sciter’s level yet.

For example I missed things like flow:row(dt,dd), simply no such things in conventional CSS. <dl/dt/dd> lists are barely usable without proper styling. To achieve flow:row(dt,dd) layout on the web it need to render it as a table, sigh.

So it is clear that documentation shall use some other format and be assembled from it for particular use. One of obvious choices is to use Markdown for that. So I need markdown parser in Sciter that supports hierarchical constructs like <li><pre>… I’ve managed to implement such a parser in 250 lines of code. Just in case, original Perl parser written by John Gruber is about 1400 lines of highly cryptic Perl code. In Sciter I am using generators/yield that allowed to simplify the whole thing.

This is how test-bed looks that far:

And speaking about software documentation in general.

I’d appreciate any examples of good examples of software documentation. But not from Microsoft or Apple please – they are barely readable.

Optimising ‘+=’ and ‘+’ operators for strings.

This simple code:

var s = "";
for(var i = 0; i < 50000; ++i) {
  s += "*";
}

code used to run in Sciter in 874ms.

After implementing simple and obvious optimization it runs now in just 4ms.

String concatenation was implemented as simple string allocation of size(r) = size(s1) + size(s2) and memcpy of s1 and s2 into that new string r.

Memory allocation in script is cheap - just increment memory pointer by size of requested memory chunk and you are done. So in theory that naïve strcat shall be lightning fast. But it is definitely not. There is a hidden cost of GC cycles - at the moment of concatenation r,s1 and s2 shall be present in memory.

So "0123456789" + "A" needs memory for 10 + 1 + 11 = 22 characters. And on each iteration that number increases - the VM is busy cleaning garbage most of the time.

So when someone from C# and Java crowds is saying you that memory allocation is cheap take it with a grain of salt.