/// <summary>
/// The CallbackProc. Called by the shell to inform of key property page events.
/// </summary>
/// <param name="hWnd">The h WND.</param>
/// <param name="uMsg">The u MSG.</param>
/// <param name="ppsp">The PPSP.</param>
/// <returns></returns>
private uint CallbackProc(IntPtr hWnd, PSPCB uMsg, ref PROPSHEETPAGE ppsp)
{
switch (uMsg)
{
case PSPCB.PSPCB_ADDREF:
// Increment the reference count.
referenceCount++;
break;
case PSPCB.PSPCB_RELEASE:
// Decrement the reference count.
referenceCount--;
// If we're down to zero references, cleanup.
if (referenceCount == 0)
{
Cleanup();
}
break;
case PSPCB.PSPCB_CREATE:
// Allow the sheet to be created.
return(1);
}
return(0);
}
/// <summary>
/// The CallbackProc. Called by the shell to inform of key property page events.
/// </summary>
/// <param name="hWnd">The h WND.</param>
/// <param name="uMsg">The u MSG.</param>
/// <param name="ppsp">The PPSP.</param>
/// <returns></returns>
private uint CallbackProc(IntPtr hWnd, PSPCB uMsg, ref PROPSHEETPAGE ppsp)
{
switch (uMsg)
{
case PSPCB.PSPCB_ADDREF:
break;
case PSPCB.PSPCB_RELEASE:
break;
case PSPCB.PSPCB_CREATE:
// Allow the sheet to be created.
return(1);
}
return(0);
}
/// <summary>
/// The CallbackProc. Called by the shell to inform of key property page events.
/// </summary>
/// <param name="hWnd">The h WND.</param>
/// <param name="uMsg">The u MSG.</param>
/// <param name="ppsp">The PPSP.</param>
/// <returns></returns>
private uint CallbackProc(IntPtr hWnd, PSPCB uMsg, ref PROPSHEETPAGE ppsp)
{
// Important: The docs at: https://docs.microsoft.com/en-us/windows/desktop/shell/how-to-register-and-implement-a-property-sheet-handler-for-a-file-type
// Imply we *must* set PSP_USEPARENTREF and give access to the parent reference count, to avoid the server being
// unloaded while the property sheet is still visible. It is damn near impossible to do this as
// the IUnknown of the IShellPropSheetExt is managed by the runtime. Instead, when the internal
// reference count increases, we will manually increment the COM server ref count, then release
// it when our property sheet tells us we are done. This *appears* to have resolved the lifetime
// issues. The theory is that we are using the lifecycle hooks below to manage our IShellPropSheetExt
// server ref count and ensure that the shell will not unload it while the property sheet is in use.
switch (uMsg)
{
case PSPCB.PSPCB_ADDREF:
{
// Increment the internal reference count.
Log($"Add Internal Ref {referenceCount} -> {referenceCount + 1}");
referenceCount++;
// At this point, increment the IPropSheetShellExt interface reference count, so that the
// shell doesn't try and release the server before we are done.
var pUnk = Marshal.GetIUnknownForObject(Parent); // i.e. IShellPropSheetExt
var newCount = Marshal.AddRef(pUnk);
Log($"IShellPropSheetExt: Add Ref {newCount - 1} -> {newCount}");
break;
}
case PSPCB.PSPCB_RELEASE:
{
Log($"Release Internal Ref {referenceCount} -> {referenceCount - 1}");
// Decrement the internal reference count.
referenceCount--;
// If we're down to zero references, cleanup.
if (referenceCount == 0)
{
// The Target is a child of the host window handle, and that is child of the sheet.
// So these windows will be destroyed as part of the normal lifecycle. It's important
// we *don't* destroy them here or they could be destroyed twice. This is the place
// however to free up other resources which might be used by the page.
try
{
Target?.OnRelease();
}
catch (Exception exception)
{
LogError("An exception occured releasing the property page", exception);
}
}
// Balance out the AddRef all from PSPCB_ADDREF by releasing now.
var pUnk = Marshal.GetIUnknownForObject(Parent); // i.e. IShellPropSheetExt
var newCount = Marshal.Release(pUnk);
Log($"IShellPropSheetExt: Release {newCount + 1} -> {newCount}");
break;
}
case PSPCB.PSPCB_CREATE:
Log($"Create Callback");
// Allow the sheet to be created.
return(1);
}
return(0);
}
/// <summary>
/// The CallbackProc. Called by the shell to inform of key property page events.
/// </summary>
/// <param name="hWnd">The h WND.</param>
/// <param name="uMsg">The u MSG.</param>
/// <param name="ppsp">The PPSP.</param>
/// <returns></returns>
private uint CallbackProc(IntPtr hWnd, PSPCB uMsg, ref PROPSHEETPAGE ppsp)
{
switch (uMsg)
{
case PSPCB.PSPCB_ADDREF:
// Increment the reference count.
referenceCount++;
break;
case PSPCB.PSPCB_RELEASE:
// Decrement the reference count.
referenceCount--;
// If we're down to zero references, cleanup.
if (referenceCount == 0)
Cleanup();
break;
case PSPCB.PSPCB_CREATE:
// Allow the sheet to be created.
return 1;
}
return 0;
}
/// <summary>
/// The CallbackProc. Called by the shell to inform of key property page events.
/// </summary>
/// <param name="hWnd">The h WND.</param>
/// <param name="uMsg">The u MSG.</param>
/// <param name="ppsp">The PPSP.</param>
/// <returns></returns>
private uint CallbackProc(IntPtr hWnd, PSPCB uMsg, ref PROPSHEETPAGE ppsp)
{
switch (uMsg)
{
case PSPCB.PSPCB_ADDREF:
break;
case PSPCB.PSPCB_RELEASE:
break;
case PSPCB.PSPCB_CREATE:
// Allow the sheet to be created.
return 1;
}
return 0;
}
