Tighter association between tab and their member panels

[gdargaud]

If a panel is made part of a tab (InsertPanelAsTabPage) or if a panel handle is obtained from a tab (GetPanelHandleFromTabPage), there are some restrictions as to how you can use that panel. Some of those restrictions could be lifted if the panel knew which tab it belonged to.

I suggest the addition of the following (or similar) attributes:

GetPanelAttribute(Panel, ATTR_PANEL_PARENT_TAB_CTRL, &TabCtrl);

GetPanelAttribute(Panel, ATTR_PANEL_PARENT_TAB_INDEX, &TabIndex);

And of course you can already get the parent panel with:

GetPanelAttribute(Panel, ATTR_PANEL_PARENT, &ParentTab);

So, now that a panel knows the tab it belongs to, some obvious associations can be handled by the UIR library:

• Calling DiscardPanel should, internally, call DeleteTabPage instead of the current undefined and illogical behavior
• SetActivePanel should do a SetActiveTabPage instead of the current buggy behavior
• SetPanelAttribute(.., ATTR_DIMMED) should do a SetTabPageAttribute(..., ATTR_DIMMED)
• - etc...

This would allow the user to select at runtime if he wants a Multiple Panels application (MDI) or a Single Panel/Multiple Tab application (tabbed SDI) and almost no changes are necessary to the code.