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/** \page dw-images-and-backgrounds Images and Backgrounds in Dw
<h2>General</h2>
Representation of the image data is delegated to dw::core::Imgbuf, see
there for details. Drawing is delegated to dw::core::View
(dw::core::View::drawImgbuf).
Since dw::core::Imgbuf provides memory management based on reference
counting, there may be an 1-to-n relation from image renderers (image
widgets or backgrounds, see below) and dw::core::Imgbuf. Since
dw::core::Imgbuf does not know about renderers, but just provides
rendering functionality, the caller must (typically after calling
dw::core::Imgbuf::copyRow) notify all renderers connected to the
buffer.
<h2>Images</h2>
This is the simplest renderer, displaying an image. For each row to be
drawn,
<ol>
<li> first dw::core::Imgbuf::copyRow, and then
<li> for each dw::Image, dw::Image::drawRow must be called, with the same
argument (no scaling is necessary).
</ol>
dw::Image automatically scales the dw::core::Imgbuf, the root buffer
should be passed to dw::Image::setBuffer.
\see dw::Image for more details.
<h2>Future Extensions</h2>
(This is not implemented yet.) Rendering itself (image widgets and
background) will be abstracted, by a new interface
dw::core::ImageRenderer. In the current code for image decoding, this
interface will replace references to dw::Image, which implements
dw::core::ImageRenderer, in most cases.
<h2>Backgrounds</h2>
(This is based on future extensions described above.) Since background
are style resources, they are associated with
dw::core::style::Style. For backgrounds, another level is needed,
because of the 1-to-n relation from dw::core::style::Style to
dw::core::Widget:
\dot
digraph G {
node [shape=record, fontname=Helvetica, fontsize=10];
edge [arrowhead="open", arrowtail="none", labelfontname=Helvetica,
labelfontsize=10, color="#404040", labelfontcolor="#000080"];
fontname=Helvetica; fontsize=10;
"background renderer (as a part of style)" -> "image buffer" [headlabel="*",
taillabel="1"];
"widget (or a part of it)" -> "background renderer (as a part of style)"
[headlabel="*", taillabel="1"];
}
\enddot
Unlike dw::Image, dw::core::style::BgRenderer is not associated with a
certain rectangle on the canvas. Instead, widgets, or parts of widgets
take this role. This is generally represented by an implementation of
the interface dw::core::style::BgAllocation, which is implemented by
dw::core::Widget, but also by all parts of widget implementation,
which may have an own background image.
The following diagram gives a total overview:
\dot
digraph G {
node [shape=record, fontname=Helvetica, fontsize=10];
edge [arrowhead="open", arrowtail="none", labelfontname=Helvetica,
labelfontsize=10, color="#404040", labelfontcolor="#000080"];
fontname=Helvetica; fontsize=10;
"DICache Entry";
subgraph cluster_dw_images {
style="dashed"; color="#000080"; fontname=Helvetica; fontsize=10;
label="Dw Images";
ImageRenderer [URL="\ref dw::core::ImageRenderer", color="#ff8080"];
Imgbuf [URL="\ref dw::core::Imgbuf", color="#ff8080"];
}
subgraph cluster_widgets {
style="dashed"; color="#000080"; fontname=Helvetica; fontsize=10;
label="Widgets";
Widget [URL="\ref dw::core::Widget", color="#a0a0a0"];
Textblock [URL="\ref dw::Textblock"];
"Textblock::Word" [URL="\ref dw::Textblock::Word"];
Table [URL="\ref dw::Table"];
"Table::Row" [URL="\ref dw::Table::Row"];
Image [URL="\ref dw::Image"];
}
subgraph cluster_style {
style="dashed"; color="#000080"; fontname=Helvetica; fontsize=10;
label="dw::core::style";
Style [URL="\ref dw::core::style::Style"];
BgRenderer [URL="\ref dw::core::style::BgRenderer"];
BgAllocation [URL="\ref dw::core::style::BgAllocation", color="#ff8080"];
}
"DICache Entry" -> ImageRenderer [headlabel="*", taillabel="1"];
"DICache Entry" -> Imgbuf [headlabel="1", taillabel="1"];
BgRenderer -> Imgbuf [headlabel="1", taillabel="*"];
BgRenderer -> BgAllocation [headlabel="*", taillabel="1"];
ImageRenderer -> BgRenderer [arrowhead="none", arrowtail="empty",
style="dashed"];
ImageRenderer -> Image [arrowhead="none", arrowtail="empty",
style="dashed"];
Style -> BgRenderer [headlabel="0..1", taillabel="1"];
Widget -> Textblock [arrowhead="none", arrowtail="empty"];
Textblock -> "Textblock::Word" [headlabel="*", taillabel="1"];
Widget -> Table [arrowhead="none", arrowtail="empty"];
Table -> "Table::Row" [headlabel="*", taillabel="1"];
Widget -> Image [arrowhead="none", arrowtail="empty"];
BgAllocation -> Widget [arrowhead="none", arrowtail="empty",
style="dashed"];
BgAllocation -> "Textblock::Word" [arrowhead="none", arrowtail="empty",
style="dashed"];
BgAllocation -> "Table::Row" [arrowhead="none", arrowtail="empty",
style="dashed"];
}
\enddot
<center>[\ref uml-legend "legend"]</center>
<h2>Integration into dillo</h2>
\todo Add some references.
*/
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