gui_canvas

Returns or sets the GUI canvas data for the specified canvas.

Available in:

Apps (win)	Apps (char)	Reportwriter	RPC	Standalone PL
X

Syntax

string gui_canvas(canvas_name[,data_string])
string            canvas_name
string            data_string

Description

The canvas_name parameter is the name of the canvas object. In WPF, if data_string is not specified, then the data values of all the modifiable named obects in the canvas are returned in an XML string. data_string has four options:

<DATA object_name='value'>	`object_name` matches the object's name in the string that defines it in the canvas. Multiple `object_name='value'` pairs can be passed at one time.
<EXEC object_name='JavaScriptFncName parms'>	`object_name` is the name of a previously loaded HTML browser object. `JavaScriptFncName` is the name of a JavaScript function in `object_name`. `value` is a parameter to pass into the JavaScript function. Multiple `object_name='JavaScriptFncName parms'` pairs can be passed at one time.
<HTML object_name='value'>	`object_name` matches the object's name in the string that defines it in the canvas. `value` the HTML code to assign to `object_name`
URL	Fills the canvas with a web browser opened to the URL.

There are two ways to load the HTML/XAML canvas definition. The first is using dvApp to insert the definition which is then stored as part of the design however the WPF client expects XAML and will fail if HTML is found in the canvas. Thus if the goal is to have a shared WPF and HTML5 browser project, then it is better to leave the dvApp canvas object definition empty and dynamically load it using gui_canvas() at runtime. The gui_id() function returns the type of the client being used.

WPF

WPF applications use XAML to define the canvas. While any valid XAML may be used, only the following object types and values can be read or written by gui_canvas():

Control	Write	Read	Format
Button	Button name	N/A	Text
CheckBox	State	State	"": null, 0: unchecked, non-zero: checked
Image	URI	URI	URI.
ProgressBar	Progress	Progress	nn.nn, the value between the miminum (default 0) and maximum (default 100).
Slider	Position	Position	nn.nn, the value between the miminum (default 0) and maximum (default 10).
TextBlock	Content	N/A	Text
TextBox	Content	Content	Text
WebBrowser	URL	URL	URL.

HTML5 Browser

HTML5 browser applications use any well-formed HTML to define the canvas. gui_canvas() cannot return any values from HTML except via the EXEC method.

WPF examples

A canvas object named CV has the following definition in the gap file:

<StackPanel>
 <TextBlock Name="TITLE">A Sample Canvas</TextBlock>
 <Button Name="B1" Tag="A909">Press Me</Button>
 <Button Name="B2" Tag="A808">And me!</Button>
 <StackPanel Orientation="Horizontal">
  <TextBox Name="FNAME"/>
  <Separator/>
  <TextBox Name="LNAME"/>
  <Separator/>
  <CheckBox Name="CB"/>
  <Separator/>
  <ProgressBar Name="PB" Width="200"/>
 </StackPanel>
 <Slider Name="SL"/>
 <WebBrowser Name="WB" Width="580" Height="300" Source="http://www.trifox.com"/>
 <Image Name="IM" Width="100" Height="100" Source="run.png"/>
</StackPanel>

To set the FNAME, LNAME, and CB values, use

gui_canvas("CV","<DATA LNAME='Doe' FNAME='John' CB='1'/>");

and these values will appear in the respective canvas objects with the checkbox showing checked. To read the current values,

buf = gui_canvas("CV");

and buf will contain

<DATA LNAME='Doe' FNAME='John' CB='1'/>

HTML5 examples

A canvas object named CV has the following definition in the gap file:

<iframe id='WB1' src='http://www.trifox.com'></iframe>
<iframe id='WB2'></iframe>
<iframe id='WB3'></iframe>
<iframe id='WB4' src='http://www.aptean.com'></iframe>

To set the FNAME, LNAME, and CB values, use

gui_canvas("CV","<DATA WB2='http://www.expressen.se' WB3='http://www.oracle.com'>");

and these values will appear in the respective canvas browser objects. To read the current values,

buf = gui_canvas("CV");

and buf will contain

<DATA WB1='http://www.trifox.com' WB2='http://www.expressen.se'
WB3='http://www.oracle.com' WD4='http://www.aptean.com'/>

As a shortcut, if you want to simply fill the canvas with a URL, you can just send

gui_canvas("CV","http://www.trifox.com");

EXEC example

EXEC is used to execute JavaScript functions. This HTML creates a JavaScript function called WB_EXE and an iframe:

HL = list_open("80",0);
list_mod(HL,1,"<html><head>");
list_mod(HL,1,"<script type='text/javascript'>");
list_mod(HL,1,"var what = 'World';");
list_mod(HL,1,"function WB_EX(parmOne) {");
list_mod(HL,1,"alert(parmOne);");
list_mod(HL,1,"return(what); }");
list_mod(HL,1,"</script></head>");
list_mod(HL,1,"<iframe width='600' height='500'");
list_mod(HL,1," src='http://www.trifox.com'></iframe>");
list_mod(HL,1,"</html>");
list_view(HL,0);

gui_canvas("CV","<HTML WB='" ^^ xml(xml_esc,list2str(HL)) ^^ "'/>");

The xml() function is used to escape the special HTML characters. Once the string is loaded, execute the function:

LL = list_open("select name,id from staff",99);
list_file(LL,"clipboard!","j");

gui_canvas("CV","<EXEC WB='WB_EX "^^ xml(xml_esc,clipboard(cb_extract)) ^^ "'/>");

and get the return value:

buf = gui_canvas("CV");

and buf will contain

World