[Gimp-gui] Commiting tools changes

[thomas manni free fr]

Hi,

For all image map based tools (Colors Tools and Filters), committing the changes is always done by the same 
action: clicking the OK button at the bottom right corner of the dialog.
This is a consistent and intuitive behavior.

For all tools which create on-canvas controls and require a specific user action to commit the changes, 3 
actions are available :

- click on a specific canvas region (scissors select tool, crop tool, blend tool) 
- click on a specific button on the overlay dialog (all transform tools, foreground select tool)
- press Enter

Currently, only the "press Enter" action is common to all these tools. I suggest to make the "click on a 
specific button" action a bit more coherent.

- add an overlay/detachable dialog (even if the tool has no information or parameters widgets to display)
- provide a button with always the same label (like "Proceed" or "Apply")

In this way, whatever tool is selected, users have an additional consistent and intuitive way to commit the 
tool changes.
And when new such tools will arrive into Gimp, users will already know how to commit their changes, even if 
they do not know how the new tool work.


Thomas Manni