Re: [Sketch-devel] conflicting styles

[Mark R. <mr...@st...>]

On Wed, Dec 12, 2001 at 09:17:18PM +0100, Bernhard Herzog wrote:
> 
> A property stack more or less guarantees that all the properties (of the
> base style) are there. There were some situations where that may not be
> true anymore but they're hopefully fixed now. See the file Doc/styles.

What exactly is the base style?  It seems there are three types of
properties: line, fill, font.  The base styles seem to derive from
'factory_defaults' which gets initialized with every known property,
even if not really appropriate for a given object.

I noticed also that text objects were obtaining their base style from
FactoryTextStyle().  Shouldn't they use DefaultTextProperties()
to construct their PropertyStacks instead?

> > The motivation for all this is to have the style dialogs respect 
> > conflicting style attributes for multiple object selections so as 
> > not to disturb them when other attributes are changed.
> 
> The dialogs usually only deal with the properties of one style. They
> don't really need the whole property stack (with the obvious exception
> of the dialog that displayd the entire property stack). So we could have
> an editor method that returns a style with only those properties that
> the currently selected objects or object parts have in common.
> 
> I'm not sure what that means for, say, the line dialog if the style
> returned by that method contains only the line color but not the line
> width. Should the line width be grayed out? Probably not, because you
> couldn't modify it then. So there'd have to be one way to indicate that
> a proprty can be set, but that current value is not the one take from
> the selected object. OTOH, that might be too much information for the
> user.
 
I've implemented it as follows.  When the panel's context_changed()
method is called, it passes a list of selected objects and a Property-
Stack (probably should be a Style) of common attributes to the
dialog widget.  The common attributes are compiled using a helper
function that should probably go in the Sketch.Graphics.properties
module. It uses a new PropertyStack method called get_properties()
that updates the stack's cache and returns the __dict__ (minus the
'stack' variable).

The dialogs get the appropriate style attributes using getattr
with a default of NO_ATTR (just a module-level string).  That way
'None' (e.g. no arrows) can be distinguished from 'missing' or
'conflicting'.  Widgets for NO_ATTR properties display differently
from usual widgets to visually indicate the lack of the style.
For example, the check box for 'underline' has three states: on,
off, absent.  Absent properties use a common color for consistency
(low saturation red as I have it now).  If Apply is pressed, only
non-NO_ATTR properties are set.  If the user changes a widget that
has a NO_ATTR property, is loses the NO_ATTR state and appears as
a normal widget.  

This was actually a lot easier to implement than it sounds.  A
simple mixin class makes it easy to add the 'absent' feature to
existing gtk widgets.  The result looks good IMHO, and I don't
think it will prove confusing to the user (in fact it seems
very intuitive).  It is really no different than the standard 
paradigm used throughout M$ office and many other apps.

Mark