You are viewing a plain text version of this content. The canonical link for it is here.
Posted to fop-dev@xmlgraphics.apache.org by Vincent Hennebert <vi...@anyware-tech.com> on 2008/02/28 19:51:15 UTC
Percentages in background images
Hi,
I need some help regarding percentages. I’m currently trying to
implement the rendering of backgrounds from table-column elements. But
since the space represented by the border-separation property must be
filled with the background of the table, I can’t simply create block
areas for the columns (as well as rows, BTW) that would span the whole
table.
The solution I’ve come up with is to create an area for each table-cell
containing the background informations, and set it as a child of the
table area. So there would be an area for the column background, above
it an area for the row background, above it an area for the cell. Only
that latter would have paddings and borders settings.
If the backgrounds only have colours there’s no problem, and this works
well. But if they also have images I must ensure that the image is
placed correctly (see attached picture). If I take the following example
(let’s say each column has a width of 100pt):
<fo:table-row background-image="asf-logo.png"
background-repeat="no-repeat">
<fo:table-cell border="4pt solid red">
<fo:block>Cell 1.1</fo:block>
<fo:block>Cell 1.1</fo:block>
</fo:table-cell>
<fo:table-cell border="4pt solid red">
<fo:block>Cell 1.2</fo:block>
<fo:block>Cell 1.2</fo:block>
</fo:table-cell>
</fo:table-row>
For cell 1.2, the image must be additionally shifted to the left by
104pt to actually start on the left side of the table. Since it will be
cropped to the dimensions of the area, this gives the desired effect.
Now if percentages are used to place the background image, this all
becomes more complicated, since the width of the image must be
substracted from the table’s IPD. And apparently there’s no simple mean
to do that. I can no longer rely on the width of the area, like is
currently done in TraitSetter.addBackground, since the area will have
the IPD of the cell instead of the row. I’d have to replace width with
a call to context.getBaseLength, but I have no access to the FObj that
will be used as the base.
Any ideas? I hope I’m clear.
Thanks,
Vincent
--
Vincent Hennebert Anyware Technologies
http://people.apache.org/~vhennebert http://www.anyware-tech.com
Apache FOP Committer FOP Development/Consulting
Re: Percentages in background images
Posted by Vincent Hennebert <vi...@anyware-tech.com>.
Jeremias Maerki wrote:
> Wow, what complexity/effort for so little gain. I guess there's no way
It’s not complicated; no more than adding one area for the whole row.
And it needs to be done anyway! And that allows to address all issues at
the same time: border-separation filled with table background, as well
as background of row/column-spanning cells which must be taken from the
first spanned row/column. Only the placement of images is a bit tricky.
> around adding reference values to the area tree so you can redo the
> percentage calculations in the renderer without the FO tree percentage
> infrastructure. But that doesn't really feel right.
Well I don’t need to redo any percentage calculation. I just need the
table’s IPD when adding the row background. But it isn’t accessible in
the TraitSetter.addBackground method, which is LayoutManager-agnostic.
But I have a workaround in mind that I’ll try to implement.
> The only other possibility to me seems to investigate what we've talked
> about once or twice in the past: Going for a different style of area
> tree and use absolute coordinates instead of relative coordinates there.
AFAICT that won’t help to retrieve the ipd of the row (table).
> But switching just for covering this feature...I don't know. If this
> were investigated in the context of the new intermediate format it might
> suddenly make sense again but I haven't thought this through.
>
> So in the end, I don't have any really good ideas right now.
<snip/>
Vincent
--
Vincent Hennebert Anyware Technologies
http://people.apache.org/~vhennebert http://www.anyware-tech.com
Apache FOP Committer FOP Development/Consulting
Re: Percentages in background images
Posted by Jeremias Maerki <de...@jeremias-maerki.ch>.
Wow, what complexity/effort for so little gain. I guess there's no way
around adding reference values to the area tree so you can redo the
percentage calculations in the renderer without the FO tree percentage
infrastructure. But that doesn't really feel right.
The only other possibility to me seems to investigate what we've talked
about once or twice in the past: Going for a different style of area
tree and use absolute coordinates instead of relative coordinates there.
But switching just for covering this feature...I don't know. If this
were investigated in the context of the new intermediate format it might
suddenly make sense again but I haven't thought this through.
So in the end, I don't have any really good ideas right now.
On 28.02.2008 19:51:15 Vincent Hennebert wrote:
> Hi,
>
> I need some help regarding percentages. I’m currently trying to
> implement the rendering of backgrounds from table-column elements. But
> since the space represented by the border-separation property must be
> filled with the background of the table, I can’t simply create block
> areas for the columns (as well as rows, BTW) that would span the whole
> table.
>
> The solution I’ve come up with is to create an area for each table-cell
> containing the background informations, and set it as a child of the
> table area. So there would be an area for the column background, above
> it an area for the row background, above it an area for the cell. Only
> that latter would have paddings and borders settings.
>
> If the backgrounds only have colours there’s no problem, and this works
> well. But if they also have images I must ensure that the image is
> placed correctly (see attached picture). If I take the following example
> (let’s say each column has a width of 100pt):
> <fo:table-row background-image="asf-logo.png"
> background-repeat="no-repeat">
> <fo:table-cell border="4pt solid red">
> <fo:block>Cell 1.1</fo:block>
> <fo:block>Cell 1.1</fo:block>
> </fo:table-cell>
> <fo:table-cell border="4pt solid red">
> <fo:block>Cell 1.2</fo:block>
> <fo:block>Cell 1.2</fo:block>
> </fo:table-cell>
> </fo:table-row>
>
> For cell 1.2, the image must be additionally shifted to the left by
> 104pt to actually start on the left side of the table. Since it will be
> cropped to the dimensions of the area, this gives the desired effect.
>
> Now if percentages are used to place the background image, this all
> becomes more complicated, since the width of the image must be
> substracted from the table’s IPD. And apparently there’s no simple mean
> to do that. I can no longer rely on the width of the area, like is
> currently done in TraitSetter.addBackground, since the area will have
> the IPD of the cell instead of the row. I’d have to replace width with
> a call to context.getBaseLength, but I have no access to the FObj that
> will be used as the base.
>
> Any ideas? I hope I’m clear.
>
> Thanks,
> Vincent
>
>
> --
> Vincent Hennebert Anyware Technologies
> http://people.apache.org/~vhennebert http://www.anyware-tech.com
> Apache FOP Committer FOP Development/Consulting
Jeremias Maerki