When one of the line widget's properties changes, only update the
blend tool filter if the property has an effect on the result. In
particular, don't update the filter when only the selection
changes.
Separate the handling of changes to the FG/BG color from the gradient
dirty signal handling, so that the gradient editor doesn't purge the
history in response. Additionally, correctly respond to such changes
whenever the gradient has segments that depend on the FG/BG colors,
even if the dependency is introduced after the gradient is selected.
Move the tool undo functionality of the blend tool to the editor,
and add support for undoing gradient edit operations. Each undo
step that affects the gradient holds, in addition to the line
endpoint poisitions, a copy of the gradient at the beginning of the
operation, as well as necessary information to allow the selection
to "follow" undo. When undoing the operation, the saved gradient
is copied back to the active gradient.
To avoid all kinds of complex scenarios, when the active gradient
changes, or when the gradient is modified externally (e.g., by the
(old) gradient editor), all undo steps that affect the gradient are
deleted from the history, while those that affect only the endpoint
positions are kept.
To be used by the blend tool gradient editor to edit the gradient
endpoint/stop/midpoint properties corresponding to the selected
handle.
The GUI is currently empty; the following commits add its contents.
Add a boolean "modify active gradient" option to the blend tool.
when checked, the active gradient is modified in-place while edited.
When unchecked, the active gradient is copied to the internal
"custom" gradient upon editing, and the custom gradient becomes
subsequently active.
Show a hint when the option is checked, but the active gradient is
non-writable, and can't be edited directly.
This commit adds the new gimpblendtool-editor.[hc] files, which are
where the gradient-editing related functionality of the blend tool
is going to go.
