Example 3: Application images

Introduction

This topic shows how to display application images in a gICAPI-based web component.

In this example, we will focus on the technique to display application images dynamically in gICAPI web component HTML content, by using the ui.Interface.filenameToURI() method.

This sample application can be used with any Genero front-end configuration (as a web application with the GAS, in direct (development) mode with GDC/GMA/GMI, or as a mobile app running on a device)

For gICAPI programming basics, see Example 2: Simple text input.

The complete code example with program and form file is available at the end of this topic.

HTML code description

The HTML source file starts with the typical HTML tags:

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html" charset="utf-8" />
<meta name='viewport' content='initial-scale=1.0, maximum-scale=1.0' />

The JavaScript code defines the onICHostReady() function, and the set_image() function, to be called with the webcomponent.call front call. The set_image() function sets the src attribute in the image element:

<script language="JavaScript">

var onICHostReady = function(version) {
    if ( version != 1.0 )
        alert('Invalid API version');
}

var set_image = function(ressource) {
    var ie = document.getElementsByName("myimage")[0];
    ie.src = ressource;
}

</script>

Close the HTML head element with the </head> ending tag:

</head>

The body of the HTML page contains two elements:

an h2 title,
the image element, identified by a name:

<body height="100%" width="100%">
    <h2>Testing application images in gICAPI Web Component</h2>
    <img name="myimage" />
  </body>
</html>

Application directory structure

In order to easily build and install on mobile devices, create the following directory structure:

top-dir
|
|-- fglprofile
|-- main.4gl
|-- main.42m
|-- myform.per
|-- myform.42f
|-- images                  (application image files)
|   |-- image01.jpg
|   |-- image02.jpg
|   |-- image03.jpg
|   ...
|-- webcomponents
|   |-- mywebcomp
|       |-- mywebcomp.html
|
|-- gmi
|   |-- iOS resources       (icons, etc)
|   ...
|-- gma
|   |-- Android resources   (icons, etc)
|   ...
|

For more details about building mobile apps from the command line, see Deploying mobile apps.

Providing image files

Copy some of your favorite images in the "images" directory.

The sample program will scan this directory to fill a combobox and let you choose the image to be displayed:

FUNCTION init_image_list(cb)
    DEFINE cb ui.ComboBox
    DEFINE h INTEGER,
           fn STRING
    LET h=os.Path.dirOpen(os.Path.join(base.Application.getProgramDir(),"images"))
    WHILE h > 0
        LET fn = os.Path.dirNext(h)
        IF fn IS NULL THEN EXIT WHILE END IF
        IF fn=="." OR fn==".." THEN CONTINUE WHILE END IF
        CALL cb.addItem(fn, fn)
    END WHILE
END FUNCTION

Note:

When deployed on a mobile device, the images directory will be part of the application program files. Thus to access the directory you need to add the base.Application.getProgramDir path. For more details, see Directory structure for GMA apps and Directory structure for GMI apps.

In the program code, the ON CHANGE image interaction block will perform a front call to set the image resource in the gICAPI web component:

  ON CHANGE image
     LET rec.uri = ui.Interface.filenameToURI(rec.image)
     CALL ui.Interface.frontCall("webcomponent","call",
                       ["formonly.wc","set_image",rec.uri],[])

FGLIMAGEPATH environment settings

In order to find image resources when not executing behind a GAS, you need to define the FGLIMAGEPATH environment variable as follows:

$ FGLIMAGEPATH=$PWD/images:.

For deployed mobile applications, the FGLIMAGEPATH environment variable must be set in the default fglprofile file, by using the $FGLAPPDIR place holder:

mobile.environment.FGLIMAGEPATH = "$FGLAPPDIR/images:."

For more details about FGLIMAGEPATH settings, see Providing the image resource.

Complete source code

File myform.per:

LAYOUT
GRID
{
Current image: [f1                   ]
Image URI:     [f2                   ]
[wc                                  ]
[                                    ]
[                                    ]
[                                    ]
[                                    ]
}
END
END

ATTRIBUTES
COMBOBOX f1 = FORMONLY.image,
     INITIALIZER = init_image_list;
EDIT f2 = FORMONLY.uri, SCROLL;
WEBCOMPONENT wc = FORMONLY.wc,
   COMPONENTTYPE="mywebcomp",
   STRETCH=BOTH;
END

File main.4gl:

IMPORT os

MAIN
    DEFINE rec RECORD
               image STRING,
               uri STRING,
               wc STRING
           END RECORD
    OPEN FORM f1 FROM "myform"
    DISPLAY FORM f1
    INPUT BY NAME rec.* WITHOUT DEFAULTS ATTRIBUTES(UNBUFFERED)
        ON CHANGE image
           LET rec.uri = ui.Interface.filenameToURI(rec.image)
           CALL ui.Interface.frontCall("webcomponent","call",
                             ["formonly.wc","set_image",rec.uri],[])
    END INPUT
END MAIN

FUNCTION init_image_list(cb)
    DEFINE cb ui.ComboBox
    DEFINE h INTEGER,
           fn STRING
    LET h=os.Path.dirOpen(os.Path.join(base.Application.getProgramDir(),"images"))
    WHILE h > 0
        LET fn = os.Path.dirNext(h)
        IF fn IS NULL THEN EXIT WHILE END IF
        IF fn=="." OR fn==".." THEN CONTINUE WHILE END IF
        CALL cb.addItem(fn, fn)
    END WHILE
END FUNCTION

File mywebcomp.html:

<!DOCTYPE html>
<html>
<head>
<title>Test</title>
<meta Http-Equiv="Cache-Control" Content="no-cache">
<meta Http-Equiv="Pragma" Content="no-cache">
<meta Http-Equiv="Expires" Content="0">
<script LANGUAGE="JavaScript">

var onICHostReady = function(version) {
    if ( version != 1.0 )
        alert('Invalid API version');
}

var set_image = function(ressource) {
    var ie = document.getElementsByName("myimage")[0];
    ie.src = ressource;
}

</script>
</head>
<body>
<h2>Testing application images in gICAPI Web Component</h2>
<img name="myimage" />
</body>
</html>