A good friend recently sent me a number of resources related to hooking common dialog controls. I’ve been interested in common dialog hooking for PhotoDemon, as it would allow me to add support for image previewing right in the dialog itself. This isn’t as necessary in modern versions of Windows (7 in particular includes a number of GDI+ improvements, making Explorer very robust with standard formats), but it can be helpful for unsupported formats like RAW photographs.
Unfortunately, several days of research have shown that it is not possible to hook a Vista or Windows 7 style dialog and maintain the modern layout. Let me explain with pictures:
The common dialog above comes directly from PhotoDemon’s current common dialog implementation. This is the native common dialog control on Vista and 7. I very much like it. As a comparison, here is the same dialog in Windows XP:
I strongly prefer the Vista/7-style dialog, particularly the breadcrumb nav and the persistent folder tree on the left.
Unfortunately, it is impossible to hook the Vista/7 dialog and maintain the native Vista/7 appearance. If you attempt to hook it, Windows will ALWAYS drop back to a previous generation common dialog. Here are some images to demonstrate, using a basic image preview hook:
Note that the image above uses an older version of the OPENFILENAME struct, namely (this is its declaration in VB):
Private Type OPENFILENAME lStructSize As Long hwndOwner As Long hInstance As Long lpstrFilter As String lpstrCustomFilter As String nMaxCustFilter As Long nFilterIndex As Long lpstrFile As String nMaxFile As Long lpstrFileTitle As String nMaxFileTitle As Long lpstrInitialDir As String lpstrTitle As String Flags As Long nFileOffset As Integer nFileExtension As Integer lpstrDefExt As String lCustData As Long lpfnHook As Long lpTemplateName As String End Type
If you modify the struct to its newest version (as described here), you can slightly improve the dialog to look like this:
That is the best you can get if you want to hook a common dialog in Vista or 7.
Reasons for this have been speculated on by more qualified individuals than I. Over at stackoverflow, David H explains:
The reason for this is that MS completely re-organised the file dialogs for Vista. Hooks are used to extend a file dialog by supplying a resource file. This gives the customiser too much power. They can all too easily modify standard elements of the dialog and indeed many apps did so. The reorganisation of the dialogs would have broken many apps that used hooks. Those would have tried to manipulate elements of the dialog that were not there, or were implemented differently. Legacy versions of the dialogs remain for such apps to “get their hooks into”.
You are correct that it is impossible to get the new look when you use a hook. Instead you need to use the IFileDialogCustomize interface to customise the dialog. This is less powerful but does result in appearance and behaviour that is more consistent with the standard part of the dialog.
(More information is available here for those who are interested.)
Unfortunately, I am not aware of any way to access the iFileDialogCustomize interface in classic VB. If someone knows how, I’d love to hear it.
The take home message of all this is – if you work in classic VB and you want to hook a common dialog, you need to be content with an XP-style dialog. There is currently no way to maintain a Vista/7 style dialog while hooking.
For this reason, I’m going to stick with the stock common dialog control in PhotoDemon. I may look at a dedicated “browse” window in the future, which would allow for full image previewing, but I’m afraid such a feature is not on the roadmap for the next few versions.
All hooking-related screenshots were created using Carles PV’s iBMP project, which made it very easy to modify various hooking parameters and test the output. Thanks, Carles!