Re: [libreoffice-design] Re: ODF spec for hiding a shape or group

On 08/03/2016 09:36 AM, Taylor Jenkins wrote:
> *See comments inline.*
>
> *In ODF (LO 5.1), groups do have a z-index. When a group is created, it
> is created as a new shape and assigned a z index. The sub shapes are
> assigned new z indices starting from the lowest z index, in order of the
> shapes contained within the group, but referenced to the group shape.
> Think of a sub array within an array.*
> *The ODF Specification also defines a group element <draw:g> which has
> the attribute <draw:z-index>. Here is the reference: *
> *http://docs.oasis-open.org/office/v1.2/os/OpenDocument-v1.2-os-part1.html#element-draw_g *
> *
> *
> *All shapes with z indices greater than the lowest z index to be
> included in the group, but less than the highest z index of the shapes
> to be included in the group are reassigned indices, in the order they
> were before the grouping, beginning at the index of the lowest shape to
> be included in the group. The group is then assigned the next z index to
> follow. All remaining shapes with z indices higher than the index of the
> last shape to be included are then reassigned in order beginning with
> the first index following the group.*
> *
> *
> *For example take the following array of shapes: [a, b, c, d, e, f, g, h].*
> *Here is the result after grouping shapes b, d, and f: [a,c,e, [b, d,
> f], g, h].*
> *The group now has the index of 3, and the index for h changed from 7 to
> 5. The rendering order is now a, c, e, b, d, f, g, h.*

Thanks for the clarification as this simplifies everything.

> *While this is a good workaround, I don't know that it is entirely
> necessary. I think both layering schemes could easily be incorporated
> with a change in UI terminology and an LO specific layer feature that
> also manages z-index. Since the existing layers are essentially nothing
> more than visibility layers, I suggest renaming them as such in the UI,
> or perhaps V-Layers for short. The LO specific layers could be called
> Z-Layers. Unlike a V-Layer which only has attributes: draw:display,
> draw:name, and draw:protected, and does not change draw:z-index, a
> Z-Layer could have V-Layers as child elements, and also manage the
> draw:z-index of its child elements, simply by assigning the values of
> both attributes: draw:layer, and draw:z-index for each drawing object
> that is a child element. *
> *
> *
> *Each drawing object has the attributes <draw:layer> and <draw:z-index>. *
> *
> *
> *http://docs.oasis-open.org/office/v1.2/os/OpenDocument-v1.2-os-part1.html#element-draw_layer-set
> *
> *http://docs.oasis-open.org/office/v1.2/os/OpenDocument-v1.2-os-part1.html#attribute-draw_z-index
> *
> *
> *
> * Using your workaround example, I could import the first ODF structure
> like so:*
> *
> *
> *[Z-Layer] Default*
> *  [V-Layer] Mobile
>      [Object] iPhone (z-index: 1)
>      [Object] Nexus (z-index: 3)
>   [V-Layer] Tablet
>      [Object] iPad (z-index: 2)
> *
> *
> *
> *I could then add objects and layers, while maintaining and ODF readable
> document like so:*
> *
> *
> *
> [Z-Layer] Default
>   [V-Layer] Mobile
>      [Object] iPhone (z-index: 1)
>      [Object] Nexus (z-index: 3)
>   [V-Layer] Tablet
>      [Object] iPad (z-index: 2)
>      [Object] Galaxy Tab(z-index: 4)
>   [V-Layer] PC
>      [Object] Laptop (z-index: 5)
> [Z-Layer] New
>   [V-Layer] Data
>      [Object] Specs (z-index: 6)*
> *
> *
> *Since Z-Layers are LO specific, they are ignored by ODF, but since we
> structured it like this the resulting ODF document opened in another
> application would maintain the same structure and appearance, as shown
> below:*
> *
> *
> *
>   [V-Layer] Mobile
>      [Object] iPhone (z-index: 1)
>      [Object] Nexus (z-index: 3)
>   [V-Layer] Tablet
>      [Object] iPad (z-index: 2)
>      [Object] Galaxy Tab(z-index: 4)
>   [V-Layer] PC
>      [Object] Laptop (z-index: 5)
>   [V-Layer] Data
>      [Object] Specs (z-index: 6)
> *

Now with the clarity that groups have z-index, the Z-Layer concept isnt 
needed as groups can easily take its place, and V-Layer is actually an 
attribute of objects so shouldnt be placed above objects in a hierarchy.

[Group] Default (z-index: 8)
  [Object] iPhone (z-index: 7, layer: Mobile)
  [Object] iPad (z-index: 6, layer: Tablet)
  [Object] Nexus (z-index: 5, layer: Mobile)
  [Object] Galaxy Tab (z-index: 4, layer: Tablet)
  [Object] Laptop (z-index: 3, layer: PC)
[Group] New (z-index: 2)
  [Object] Specs (z-index: 1, layer: Data)

Note: i could be mistaken with the z-index numbering and the numbers go 
in the opposite direction. :D

> *<draw:opacity> isn't an attribute of layers or groups, but it appears
> that it can be used to modify the opacity of a layer or group, since
> layers and groups are graphical objects. Ref:
> http://docs.oasis-open.org/office/v1.2/os/OpenDocument-v1.2-os-part1.html#__RefHeading__1415788_253892949
> Even if by chance layers and groups can't be directly modified by
> <draw:opacity>, then it can be used to modify the list of elements
> contained therein.*

Seems i incorrectly gave the <draw:opacity> tag when i meant to give the 
draw:opacity attribute, which states "The draw:opacity attribute 
specifies the opacity for an image or graphic object. The defined value 
range for the draw:opacity attribute is 0% to 100%, where 0% is fully 
transparent and 100% is fully opaque." Its currently available in 
<style:graphic-properties>, <style:background-image> and 
<style:drawing-page-properties>.

http://docs.oasis-open.org/office/v1.2/os/OpenDocument-v1.2-os-part1.html#__RefHeading__1417180_253892949

So if draw:opacity is available in layer and groups, thats great.

> *I don't see why any application specific feature couldn't be structured
> such that they will still display properly in other applications, since
> the application specific features could still be using the ODF specified
> features to accomplish their task.*

Okay, as i was under the impression that application specific features 
wouldnt be part of the ODF spec.

Thanks again for the insight.

Yousuf

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