pas2js designtime

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Designtime support for Pas2JS Components

The pas2jscomponents.lpk package that comes with lazarus installs design-time support for pas2js webwidgets and design-time editing of components.

Installed functionality

  • there is a new file type 'HTML Fragment', this is akin to a 'Form' or 'Frame'.
  • There are several components that allow you to interact with the HTML.
    • THTMLElementActionList
    • TBootstrapModal
    • TBootstrapToastWidget
    • TTemplateLoader
    • TSQLDBRestConnection
    • TSQLDBRestDataset
    • TDBBootstraptableWidget
    • TDBLoopTableWidget
    • TDBSelectWidget

The package also installs support for parsing HTML files and loading HTML id attributes from the html. Properties that need a HTML element ID, will display a dropdown with the discovered ID attributes.

HTML Fragment

The HTML fragment is the HTML equivalent of a form in a native LCL application. An application can contain multiple HTML fragments, which can be shown at the same time or separately.

You can add a new HTML fragment with the File-New dialog:


This will start a new form, which looks like a datamodule in the IDE.

After dropping some components on it, it will look for example like this in the designer:


The object inspector can be used to manipulate the properties, just as for a regular form.

   You must add -JRjs to the custom compiler options of your project to include the form data in the application.
   Additionally, the p2jsres unit must be added to the uses clause of your program, so the resource data can be loaded when the program is run.

The HTML for the fragment can be loaded in 3 ways:

  • Set the UseProjectHTMLFile property to True if you will only use the main html file of your project. No additional HTML will be loaded.
  • Set the TemplateName property to the name of a template to load.
  • Set the HTMLFilename property to the name of a HTML file to load. It will be loaded using the global template loader in unit rtl.TemplateLoader

The ParentID property determines under what HTML element in the main HTML page the HTML fragment will be loaded.

The following events exist:

  • OnAllowUnrender is called when you wish to show another HTML fragment instead of this one. It is equivalent to OnCloseQuery in an LCL form.
  • OnCreate Called when the fragment is created. note that the HTML is not yet available.
  • OnDestroy Called when the fragment is destroyed.
  • OnHTMLLoaded Called when the HTML fragment has been loaded from the server.
  • OnRendered Called when the HTML fragment has been inserted in the DOM.
  • OnUnRendered Called when the HTML fragment has been removed from the DOM.

Installed components

The pas2jscomponents package also installs some components.


The THTMLElementActionList component is similar to the Action list in design-time concept, but works differently at runtime: You can associate a THTMLElementAction with every element in the HTML fragment's HTML that has an ID, or you can use a CSS selector to let an action respresent a series of HTML Elements.

You don't need to create these actions manually. In the context menu there is an item "Create actions for HTML tags"


This menu will pop up a wizard that finds all elements for which no action exists yet, and proposes to create an action:


If you check the Use Data-Aware Actions checkbox, then DB-Aware actions will be used. These can be used as button actions (to navigate in the data, insert/post/delete etc. etc)

The action editor works similar to the LCL action list editor:


The main properties of an action are:

  • ElementID the ID of the element you want to control.
  • CSSSelector A css selector for thes element you want to control in case of multiple elements (e.g. to get all rows in a table use #tableid tr)
  • Events a set of events to listen for. When the event is triggered, the OnExecute event handler is executed.
  • CustomEvents a space separated list of HTML to listen for, for events that do not appear in **Events**
  • PreventDefault can be set to True to prevent the default HTML action from happening.
  • StopPropagation can be set to True to prevent the event from bubbling, i.e. propagating to parent elements.


A component (similar to the LCL Dialog components) to show a modal dialog using Bootstrap. (you need to include the various bootstrap files in your project HTML file)

The following properties exist:

  • ShowOnRender set to True if you wish to show the modal as soon as it is rendered (meaning, the HTML was generated).
  • BackDrop show a backdrop shadow over the rest of the HTML page.
  • KeyBoard Allow keyboard actions
  • Focus set focus to the modal.
  • Template the HTML for the modal.
  • TemplateName the name of a template in TempateLoader containing the modal HTML.
  • TemplateLoader a custom template loader. If not set, a global template loader is used.
  • References a collection of CSS Selectors which can be used to get a reference to elements in the modal. These can be used to retrieve entered values during the **OnHide** event handler..

The following events exist:

  • OnHide event triggered when the modal is hidden.


The TBootstrapToastWidget allow you to show a small Toast message.

It can show a toast embedded in the HTML file, or the HTML can be generated from the properties

  • Header a string with the HTML for the header tag.
  • SmallHeader a string with the HTML for the sub (smaller) header tag.
  • Body a string with the HTML for body of the modal.
  • HeaderImage an URL for the header image.
  • CloseButton set to True to add a close button to the dialog.
  • Contextual an enumerated which allows you to select one of the primary bootstrap color schemes.
  • HideDelay a number of milliseconds before the toast automatically disappears when AutoHide is True.
  • AutoHide set to True to let the toast disappear automatically after HideDelay milliseconds.
  • Animate set to True to animate showing and hiding of the modal.
  • MinWidth minimum width for the modal.
  • UnrenderOnHide if set to True the HTML of the toast will be removed from the DOM when the toast is hidden.

The following event exists:

  • OnHide triggered when the toast is hidden.


This component can be used to load HTML fragments (in fact, any file) when the webapplication is run.

When loaded, the templates are available in a named array Templates where the index is the name of a template. The list of templates to load can be specified in the PreloadTemplates property, a collection.

The following properties exist:

  • BaseURL all filenames for templates are relative to this URL.
  • CheckResources When loading a template, check if a resource with the same name as the template exists. If yes, load the template from the resource.
  • PreloadTemplates List of templates to load as soon as the component is loaded from the form file.

The following events exist:

  • OnLoad triggered when a template is loaded. The name of the loaded template is passed to the event handler.
  • OnLoadFail triggered when a template fails to load. The name of the loaded template is passed to the event handler.

Because the loading happens asynchronous, the following method is useful:

Procedure IfTemplate(const aName : String; aEvent : TTemplateNotifyEvent);

this method will check if template aName is loaded, and calls aEvent if it is. If it is not yet loaded, it will wait till the template is loaded and then call the event.

Additional templates can be loaded with the following 2 calls:

Procedure LoadTemplate(Const aName,aURL : String; aOnSuccess : TTemplateNotifyEvent = Nil; AOnFail : TTemplateErrorNotifyEvent= Nil);
Procedure LoadTemplates(Const Templates : Array of String; aOnSuccess : TTemplateNotifyEvent = Nil; AOnFail : TTemplateErrorNotifyEvent= nil);

These methods will load a template, even if it was already loaded before. In case of the array, there must be an even number of elements, the odd elements are template names and the even elements are corresponding filenames.