Accelerator/Search support for combobox items

Submitted by Luca Bruno

Link to original bug (#567141)

Description

Hello, I'd like to suggest a new feature for GtkComboBox, which is included in other toolkits and also browsers. For long combo lists it's often boring to scroll the whole list before getting to an item. If items had accelerators or a kind of search, the user could use the keyboard to select the item. I said "accelerator" but it's mandatory to use the first letters of the item, underlines would confuse the user.

Other information: Suggested behavior:

1. When the user starts typing some keys the matching items in the combobox must be selected.
2. Pressing multiple keys is supported within a keyboard timeout (e.g. 1 second between each key) to improve the search pattern then select a more specific item.
3. API will expose a property for specifying which column of the model is going to be used for the search, though the cell renderer must be textual and visible to the user.

Version: 3.91.x