When using System.Windows.Forms.ShowDialog(IWin32Window), should I be able to pass in an IWin32Window representing any window handle and have it be modal with respect to that window?
As part of an Internet Explorer 7 extension I’m trying to open a window modal with respect to an Internet Explorer tab. It’s not the currently selected tab, but I can get the hwnd of the tab OK. However, when I pass this to ShowDialog my Form is shown, but it’s not modal with respect to anything: I can still do things in Internet Explorer, including in the tab that’s supposed to be the owner. My form is shown floating above the Internet Explorer windows and it stays on top, so it’s not like it’s just opened as a normal form, but it’s not correctly modal.
Using Spy++, I can find my form and it’s owner handle is correctly set.
Does this mean that something has gone wrong, or I’m doing something wrong? How do I make my form correctly modal?
FYI, I’m using this wrapper class to create an IWin32Window from a hwnd (thanks Ryan!):
/// <summary> /// Wrapper class so that we can return an IWin32Window given a hwnd /// </summary> public class WindowWrapper : System.Windows.Forms.IWin32Window { public WindowWrapper(IntPtr handle) { _hwnd = handle; } public IntPtr Handle { get { return _hwnd; } } private IntPtr _hwnd; } UPDATE: Using Internet Explorer 7 & .NET 2.0
UPDATE: Playing around some more with Spy++ and the handles it exposes, I find that if I use a different hwnd then I can make my window modal to the tab:
I was using the tab’s hwnd as suggested by the IWebBrowser2.HWND doc, which in Spy++ appears as class TabWindowClass. It has a child of class Shell DocObject View, which has a child of Internet_Explorer_Server. If I use the hwnd of the Internet Explorer_Server then it works correctly, for example, when I click with the mouse on other tabs, Internet Explorer reacts normally. When I click with the mouse on the tab of interest, it plays the windows d’oh sound and doesn’t do anything.
I don’t yet know how to programatically get the Internet_Explorer_Server hwnd, but it should be possible.
Also, for what it’s worth, while playing with other window handles I was generally able to make my form modal to other applications and dialogs. So I guess the answer to my question is ‘many but not all handles’… possibly it depends on the application?
UPDATE: Another side-note: The original reason I wanted to make my form modal to the tab instead of the whole window is that when opening a MessageBox from my form, passing the form as owner, the MessageBox would not always open on top of my form. If a new Internet Explorer tab had just been opened but wasn’t active then the MessageBox would be hidden and that tab would start flashing. However, since Internet Explorer was disabled with my form opened modal it wasn’t possible to switch to that tab, so Internet Explorer would be frozen. I thought that opening my form modal to the tab would solve this, but I’ve found another solution is to avoid using MessageBox: if I use a second form and ShowDialog(this) from my first form then the second form correctly opens to the front. So it seems that Form.ShowDialog() works better than MessageBox.Show() in some cases. More discussion in Problems with modal dialogs and messageboxes.
Your code is correct. The problem you are likely running into though is that IE has a threading model related to its tabs. I don’t know the exact details but the short version is that each tab can and likely is running on a different thread than other tabs.
The Modal’ness of a dialog is specific to the thread where the dialog is running. UI on other threads will be unaffected by a model dialog on another thread. It’s entirely possible you are able to access tabs which are running on a different thread for this reason.