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Creating a Widget
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The Basics in Creating a Useful Widget
by Brad Wardell

Creating widgets with DesktopX 3 is, relatively speaking, a snap. Today I'm going to walk you through how to create a widget. It's actually going to be a pretty complicated one (for me anyway) but it will hopefully show you the ropes on how to create fully featured widget.

The widget I want to create is one I've been looking for for a long while - A disk space meter that lets the user configure which drive they are monitoring.

Step 1: Load up the DesktopX development environment.

Welcome menu -Select Create 

Click on the last option (Create) on the DesktopX Standard "Welcome" screen.

Once you had loaded it, you will be greeted with this dialog:

Builder 

At this point, depending on your skill-level you're going to either want to import an existing widget (which is what I'm going to do because I need to have a sample in front of me) or you'll jump right in to making the widget.

Step 2: Import existing widget or create one from scratch.

Since my widget is going to be getting the amount of disk space available from a particular drive, I will want to look at a similar widget that gets the amount of free memory available. There is a sample included with DesktopX 3 that does this. So I'm going to click on the "Import a widget" button.

If I had wanted to create from scratch, I would have clicked on the "Desktop" tab in the builder dialog and chosen "New" object and started from scratch.

Memory Meter 

The widget in question is called the WM-Memory_meter widget. All it does is display the amount of free memory. It's very simple. But the reason I need it is that I don't personally know how to get system information like this via VB Script or JavaScript.

So now I'm going to right-click on it and choose "Edit Script".

Step 3: Write your script.

'Let's allocate the object globally, so we don't waste time allocating it on each call
Dim objWMIService

Sub Object_OnScriptEnter
    object.settimer 123, 5000
    Set objWMIService = GetObject("winmgmts:\\.\root\cimv2")
    Object_OnTimer123
End Sub

'Let's clean it, as a good practice
Sub Object_OnScriptExit
    Set objWMIService = nothing
End Sub

Sub Object_OnTimer123
    Dim colItems
    Set colItems = objWMIService.ExecQuery("Select AvailableMBytes from Win32_PerfFormattedData_PerfOS_Memory",,48)
    For Each objItem In colItems
        Object.text = "Available memory: " & objItem.AvailableMBytes & " MB"
        'we just really need one result here, so we exit
        Exit Sub
    Next  
End Sub

So there's the whole thing. When it starts, it created a timer called "123" that gets called every 5,000ms (5 seconds). He's accessing the WMI stuff (which I'm not that familiar with). And on the Timer, he's grabbing specific stuff from the WMI object.

So okay, how do I use this to get % of disk space available. My answer: Google. I am going to look for "Win32_PerfFormattedData_PerfOS_Memory" in Google and see what other goodies are available. And I found this page. And boy are there a lot of different things you can display. But I find the one I want: "Win32_PerfFormattedData_PerfDisk_LogicalDisk".

But there's a bit more I need. The memory thingy in the example doesn't have to grab from a particular drive. I need a way to get the disk space free on a particular drive. That leads me back to Google where I start trying in searches to with my newly found term with drive letters and such. I find this page. It doesn't have what I have but you may find it useful for other things. I eventually make it to this page here. And then I find this gold mine! Holy cow, there are so many things I could make with this one page. Okay, one thing at a time..

I make this change in code:

Sub Object_OnTimer123
    Dim colItems
    Set colItems = objWMIService.ExecQuery("Select * from Win32_PerfFormattedData_PerfDisk_LogicalDisk where Name = 'C:'",,48)
    For Each objItem In colItems
        Object.text = "Available space: " & objItem.FreeMegabytes & " MB"
        Exit Sub
    Next
End Sub

But there's a whole bunch of things I could have instead of .FreeMegabytes. That page has tons of things (including free space). If I want to display the percentage of free space available, I'd use PercentFreeSpace instead of FreeMegabytes.

It took a bit to figure out that I simply had to plugin 'C:' as the name of the drive in the query. But once I figured that out I was ready for the next step.

Step 4: The Preferences Dialog

What sets this widget apart from others is that you can set which drive you're monitoring the disk space for. To do that, I will need to build a preferences dialog. So I look in the "DX Scripting Guide" that comes with DesktopX and chapter 8 is "Widget Preferences".

There is only one simple rule with creating preferences -- they have to be the very first thing you do in your script or else they won't be created. All I want to do is create a simple combo box where the user selects the drive letter.

Therefore: I need to add these lines right after the Object_OnScriptEnter:

Sub Object_OnScriptEnter
    Widget.AddPreference "Combolist1"
    Widget.Preference("Combolist1").Type = "ComboList"
    Widget.Preference("Combolist1").AddValue "C:"
    Widget.Preference("Combolist1").AddValue "D:"
    Widget.Preference("Combolist1").AddValue "E:"
    Widget.Preference("Combolist1").AddValue "F:"
    Widget.Preference("Combolist1").AddValue "G:"
    Widget.Preference("Combolist1").DefaultValue = "C:"
    Widget.Preference("Combolist1").Caption = "Available Drives"
    Widget.Preference("Combolist1").Description = "Disk Drives"

    object.settimer 123, 5000
    Set objWMIService = GetObject("winmgmts:\\.\root\cimv2")
End Sub

The current value of the combo box is known as Widget.Preference("Combolist1").value. So I go back to that other function where I had hard coded 'C:' and change it to:

Set colItems = objWMIService.ExecQuery("Select * from Win32_PerfFormattedData_PerfDisk_LogicalDisk where Name = '" & Widget.Preference("Combolist1").Value &"'",,48)


The other thing we will want to add is to have it recheck when the user closes the preferences dialog (after changing the drive letter). This is from the docs.

Sub Widget_OnPreferencesChange
    Object_OnTimer123
End Sub

At this point on our screen we have:

Avail memory 

Step 5: Export the object as a widget.

Now it's time to export it as a widget. To do that, right click on it and choose "Export".

Export 

If you have DesktopX Pro, you can export this as a "gadget" which turns it into a stand-alone program you can send to anyone.

And here we go:

Widget 

My widget is ready to go.

Here is the full source code:

'Let's allocate the object globally, so we don't waste time allocating it on each call
Dim objWMIService
Dim szDrive

Sub Object_OnScriptEnter
    Widget.AddPreference "Combolist1"
    Widget.Preference("Combolist1").Type = "ComboList"
    Widget.Preference("Combolist1").AddValue "C:"
    Widget.Preference("Combolist1").AddValue "D:"
    Widget.Preference("Combolist1").AddValue "E:"
    Widget.Preference("Combolist1").AddValue "F:"
    Widget.Preference("Combolist1").AddValue "G:"
    Widget.Preference("Combolist1").DefaultValue = "C:"
    Widget.Preference("Combolist1").Caption = "Available Drives"
    Widget.Preference("Combolist1").Description = "Disk Drives"
    'If I wasn't so lame I'd write something that would go through the list of drives available and make sure only available drives are here but I'm too lazy for that.
    object.settimer 123,5000
    Set objWMIService = GetObject("winmgmts:\\.\root\cimv2")

End Sub


Sub Object_OnScriptExit
    Set objWMIService = nothing
End Sub

Sub Widget_OnPreferencesChange
    Object_OnTimer123
End Sub

Sub Object_OnTimer123
    Dim colItems
    Set colItems = objWMIService.ExecQuery("Select * from Win32_PerfFormattedData_PerfDisk_LogicalDisk where Name = '" & Widget.Preference("Combolist1").Value &"'",,48)
    For Each objItem In colItems
        Object.text = "Available memory: " & objItem.FreeMegabytes & " MB"
        'we just really need one result here, so we exit
        Exit Sub
    Next
End Sub

Some Other Notes

A few observations worth noting. DesktopX isn't cross-platform. On a widget enabling program such as this, this should be considered a feature not a limitation. Because DesktopX is designed exclusively for Microsoft Windows (or 98% of the market) it is able to support all kinds of things that a cross platform program would not. For instance, this example relied on the WMI Service of Windows. There are tons of things of this nature that are specific to Windows that can be created that wouldn't be practical if it were cross-platform since different platforms have different features and limitations.

You can learn more about DesktopX 3. It comes in 3 forms: DesktopX Client (a run-time to make use of objects, widgets, and desktops). DesktopX Standard which is what would be the least you'd need for this example (and comes with Stardock's mega OS enhancement suite, Object Desktop), or DesktopX Pro which allows you to export these widgets as "gadgets" that can be sent to anyone whether they have DesktopX or not.


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