Improving the GrabAPicture Application (Part 3)

The second feature described in the in the Improving the GrabAPicture Application (Part 1) post is to make it possible to use the Windows 7 extended wallpaper settings. It might seem like a simple task at first, but remember that the GrabAPicture application must continue to work on older systems that don’t have the required settings. Consequently, this feature requires that you not only add the new functionality, but that you also make it possible to detect the operating system and act accordingly. When the user has Windows 7 installed, the GrabAPicture application needs to allow and react to two new settings (my book, Professional Windows 7 Development Guide, explains these and other Windows 7-specific features in greater detail):

• Fit: The graphic is resized to fit within the confines of the display, without modifying its aspect ration (as stretch will do).
  
• Fill: The graphic is resized to completely fill the confines of the display, even if this means chopping off part of the graphic, without modifying its aspect ratio.
  

Modifying frmMain

There are a number of techniques you can use to implement features that are operating system version specific. The best way is to customize the handling of the feature so that users who have older, less capable, versions of the operating system don’t even realize the feature exists, which is the approach taken with this example. The first step in accomplishing this goal is to modify the interface so that the extra options are added with Windows 7 and above, but not with older versions. The new frmMain interface looks like this:

In order to achieve this update, you perform these steps:

1. Change the frmMain.Size property to 328, 317.
2. Change the cbRemote.Location property to 8, 256.
3. Change the cbLocal.Location property to 8, 224.
4. Change the GroupBox1.Size property to 192, 148.
5. Add a new RadioButton control with the following property values:
   • (Name) = rbFit
   • Location = 16, 96
   • Modifiers = Friend
   • Size = 104, 24
   • TabIndex = 9
   • Text = &Fit
6. Add a new RadioButton control with the following property values:
   • (Name) = rbFill
   • Location = 16, 120
   • Modifiers = Friend
   • Size = 104, 24
   • TabIndex = 10
   • Text = Fi&ll
7. Change the cbRemote.TabIndex property to 11.
8. Change the cbLocal.TabIndex property to 12.
   

However, you still need to maintain the ability to use the old interface. This means making it possible to hide the two new controls and changing settings for four existing controls back to the old state when working with an older operation system. These four settings are:

• 
  frmMain.Size = 328, 269
• 
  GroupBox1.Size = 192,100
• 
  cbLocal.Location = 8, 176
• 
  cbRemote.Location = 8, 208

With this in mind, you must modify the frmMain_Load() method by adding some code to the beginning of the method. This code checks the operating system version and then makes changes as shown here to return the application appearance to its original condition (you originally saw this code in the Exploring the GrabAPicture Application (Part 10) post).

When GrabAPicture runs, it displays the appearance that best matches the host operating system. It’s important to disable the rbFill and rbFit controls so that the user can’t access them accidentally. In addition, you make them invisible so that the user can’t see them either. Notice that the If statement relies on an Or condition because either value could trigger the code. For example, Vista is version 6.0, so it would trigger the code because the Version.Minor value is 0.

Modifying frmAddEdit

The changes you make to frmMain also apply to frmAddEdit. However, this form is less complex, so the changes are less extensive. Follow this procedure to make the changes to the form.

1. Change the frmAddEdit.Size property to 300, 316.
2. Change the grpStyleSelect.Size property to 192, 148.
3. Add a new RadioButton control with the following property values:
   • (Name) = rbFit
   • Location = 16, 96
   • Modifiers = Friend
   • Size = 104, 24
   • TabIndex = 3
   • Text = &Fit
4. Add a new RadioButton control with the following property values:
   • (Name) = rbFill
   • Location = 16, 120
   • Modifiers = Friend
   • Size = 104, 24
   • TabIndex = 10
   • Text = Fi&ll

At this point, frmAddEdit should look like this:

You’ll need to add code to the frmAddEdit_Load() method to change the user interface back to it simpler form when the user has an older version of Windows. As before, add the following code to the beginning of the method (you originally saw this code in the Exploring the GrabAPicture Application (Part 12) post).

As before, the code checks the OS version and makes a decision about whether it can use the new features. If not, the form is configured to allow for the older wallpaper setup.

This is a good stopping point for this week. Next week you’ll see how to finish this particular update. You’ll need to modify the underlying code to allow use of the new settings. However, there are a few surprises in this area—things you have to discover by looking at the registry. In the meantime, let me know if you have any questions about this part of the change at John@JohnMuellerBooks.com. You can see the next post in this series at Improving the GrabAPicture Application (Part 4).