NewModelViewArchitecture
Homepage for the WIP Model-View architecture for CEGUI widgets!
Contents
Introduction
The new architecture aims to unify the underlying implementation of several widgets so that they will use a common base model provider. This will involve a lot of ABI and API breakage.
Proposed architecture
TODO - decide on another concepts than row/column
ModelIndex
Identifies uniquely items in the model.
Properties:
- row : size_t
- column : size_t
- parent : ModelIndex
- modelData : void * (protected)
Methods:
- isValid
Since ModelIndex will be friend with the ViewModel, only the VM will be able to use the model data and thus prevent View(s) to use it by mistake.
ViewModel
The model for the view, that provides data like items count to the view. This is implemented by the developers that want to use this new architecture.
Structure-related methods:
- rowCount(modelIndex)
- columnCount(modelIndex)
- makeIndex(row, column, parentModelIndex)
- getParentIndex(modelIndex)
Data-provider methods:
- getItemDisplayString(modelIndex)
- getItemDisplayImage(modelIndex)
Events:
- Rows/ColumnsAdded - start, count
- Rows/ColumnsRemoved - start, count
- Rows/ColumnsDataChanged - start, count
ModelIndex Invalidation
Views might (read: will) store indices for a faster rendering or operations on the view. But these indices might become invalid if:
- the underlying model instance changes (i.e.: model is set to another instance)
- Solution: Just invalidate the memorized indices
- an index from the "middle" is removed
- Solution1: Create persistent model indices, like Qt does.
- Con: too much management required, prone to errors.
- Solution2: Query the model for validity
- isValid will be moved to the ViewModel
- Solution3: Other?
- Solution1: Create persistent model indices, like Qt does.
Affected widgets
Changed (to the new architecture) widgets
- ComboBox + ComboDropList -> ComboView
- Tree -> TreeView
- ListBox -> ListView
New widgets
- GridView
- ListBoxWidget (combines model & view together for simple usage cases)
Removed/deprecated widgets
- MultiColumnList (replaced by GridView)
- ItemListbox (duplicated by ListBox)
To decide
- ItemListBase
- It's used in other places like: MenuBase and ScrolledItemListBase
- Remove the other usages as well?