06 May 2003Stylable CGM XML Europe 2003, London Stylable CGM Dave Cruikshank The Boeing Company Lofton Henderson Henderson Consulting

06 May 2003Stylable CGM XML Europe 2003, London CGM Version 4 The CGM standard (ISO 8632:1999) –CGM V4 - Application Structuring Syntax to define application structures (APS) as graphical groups Syntax to associate attributes to APS Definition of Semantics accomplished through profiles

06 May 2003Stylable CGM XML Europe 2003, London WebCGM Functionality WebCGM developed by CGM Open in collaboration with W3C graphics experts WebCGM profile approved by W3C – 1999 WebCGM Release 2 published

06 May 2003Stylable CGM XML Europe 2003, London WebCGM Functionality Requirements –Navigation Graphical object to graphical object within a CGM file Graphical object to graphical object in another CGM file Graphical object to a text objet –Query Search for a graphical object based on an attribute –Data extraction Retrieve non-graphical metadata from a graphical object

06 May 2003Stylable CGM XML Europe 2003, London WebCGM Functionality IG requirements Navigation Query Extraction Graphical Format Capabilities Structuring -- hierarchical object tagging Non-graphical properties Object id/naming Begin APS... APS Attribute... Begin APS Body...graphics to draw object......and/or, nested ApS... End Application Structure CGMCapability

06 May 2003Stylable CGM XML Europe 2003, London WebCGM Functionality Semantics 4 APS types: grobject layer para subpara APS Attributes: Region LinkURI ViewContext LayerName LayerDescription ScreenTip Name Content

06 May 2003Stylable CGM XML Europe 2003, London WebCGM Structure Picture body layergrobject para grobject para subpara grobject para subpara

06 May 2003Stylable CGM XML Europe 2003, London Motivation for Stylability Interoperability among vendors demonstrated several times Proprietary DOM implementations being developed for external browser control

06 May 2003Stylable CGM XML Europe 2003, London Approach CGM has inherent style, but… –WebCGM profile says: While WebCGM is a binary file format and is not stylable, nevertheless WebCGM follows published W3C requirements for scalable graphics format where such are applicable –CSS2 says: CSS can be used with any structured document format … –WebCGM is a structured document format

06 May 2003Stylable CGM XML Europe 2003, London Approach Application of CSS2 to WebCGM much the way CSS1 was applied to legacy HTML Use of attribute selectors for specifying a style scheme to WebCGM

06 May 2003Stylable CGM XML Europe 2003, London Requirements Scope –Granularity of application Picture APS –Control of individual graphical primitives out of scope

06 May 2003Stylable CGM XML Europe 2003, London Requirements - color Functions –PictureScopeLineColor - RBG or relative scale –PictureScopeEdgeColor - RBG or relative scale –PictureScopeFillColor - RBG or relative scale –PictureScopeMarkerColor - RBG or relative scale –APSScopeLineColor - RBG or relative scale –APSScopeEdgeColor - RBG or relative scale –APSFillColor - RBG or relative scale –APSScopeMarkerColor - RBG or relative scale –PictureScopeRasterIntensity – relative scale –APSScopeRasterIntensity - relative scale

06 May 2003Stylable CGM XML Europe 2003, London Requirements - color

06 May 2003Stylable CGM XML Europe 2003, London Requirements - color

06 May 2003Stylable CGM XML Europe 2003, London Requirements – line/edge weight Functions –PictureScopeLineWeight – absolute mm or relative scale –PictureScopeEdgeWeight – absolute mm or relative scale –APSScopeLineWeight – absolute mm or relative scale –APSScopeEdgeWeight – absolute mm or relative scale

06 May 2003Stylable CGM XML Europe 2003, London Requirements – line/edge weight

06 May 2003Stylable CGM XML Europe 2003, London Requirements – line/edge weight

06 May 2003Stylable CGM XML Europe 2003, London Requirements – character height Functions –PictureScopeCharacterHeight – absolute mm or relative scale –APSScopeCharacterHeight – absolute mm or relative scale

06 May 2003Stylable CGM XML Europe 2003, London Requirements – character height

06 May 2003Stylable CGM XML Europe 2003, London Requirements – character height

06 May 2003Stylable CGM XML Europe 2003, London Requirements Caveats –Applying style using CSS2 deviates from the actual CGM attribute model Character height scaling does not exist Line weight scaling behaves differently –Undoing style requires special handling Remembering attributes of various primitives, or Re-interpreting a picture or APS

06 May 2003Stylable CGM XML Europe 2003, London Issues/Resolution Binary/clear text –CGM is binary format –Style sheet should be ASCII text APSScopelinecolor grobject#xyz {color: red} – turn the lines in grobject with an apsid of xyz to red –CGM Structured Data Record (SDR) An issue for the WebCGM DOM when we deal with multiple fields for attribute values of APS attributes

06 May 2003Stylable CGM XML Europe 2003, London Issues/Resolution WebCGM tree model –Pictures contain: APS elements (nested) contain: –Graphical primitives (leaf nodes) –Nodes at the APS level | | | Simplest with a tree with four kinds of element nodes

06 May 2003Stylable CGM XML Europe 2003, London Issues/Resolution Alignment with CSS –Possible to align element names with SVG CSS style sheet parsing might be reusable But not much else –Appropriate solution Borrow principles from CSS, including matching mechanisms Customize solution for WebCGM DOM requirements

06 May 2003Stylable CGM XML Europe 2003, London Issues/Resolution CSS selectors –Minimal selector pattern matching set * – matches any element (universal selector) grobject – matches any grobject APS (type selector) grobject#xyz – matches any grobject APS with an apsid of xyz –Attribute selectors grobject[name] – matches any grobject APS whose name attribute is set grobject[name=bolt] – matches any grobject APS whose name attribute is set to bolt

06 May 2003Stylable CGM XML Europe 2003, London Issues/Resolution WebCGM element names –For styling solution Elements selectors –picturelayer –grobjectpara –subpara Attrubute selectors –Linkuriname –screentipviewcontext –regioncontent –layerdescriptionlayername

06 May 2003Stylable CGM XML Europe 2003, London Issues/Resolution Style rules declaration –Attribute types deviate LineColour is a CGM attribute applying to individual line primitives PictureScopeLineColor would apply to all lines in a picture –Attribute values deviate LineColour specified in WebCGM as an index into a color table, or an RGB n-tuple, or an sRGB n-tuple PictureScopeLinecolor would have an RGB n-tuple, or a relative scale –Align with CSS data types (RBG, scale, mm)

06 May 2003Stylable CGM XML Europe 2003, London Issues/Resolution CSS inheritance model –Styling attributes should inherit Nested APS are affected by styling

06 May 2003Stylable CGM XML Europe 2003, London Issues/Resolution Cascading precedence –Opposite of CSS User agent supplied style overrides author style Specificity –CSS rules apply In clashes, most specific rules

06 May 2003Stylable CGM XML Europe 2003, London Issues/Resolution Processing model –Open questions How are styling rules communicated to the viewer? Is there some sort of rule-by-rule interface? Or, so you have to pass an entire style sheet at a time? How do you turn off a style sheet after it has been applied and return to author rules? (unapply rules) How the the styling interface relate to the DOM? (DOM will get and set all APSattr parameters)

06 May 2003Stylable CGM XML Europe 2003, London Conclusions Preliminary design completed ACSII text style sheet Align with principles from CSS Use a subset of CSS selectors Use CGM clear text APS types and attributes Apply CSS inheritance model Override CSS cascading Apply CSS specificity

06 May 2003Stylable CGM XML Europe 2003, London Next Steps Define processing model WebCGM DOM –Adopt appropriate DOM Core elements (level 1) –Adopt appropriate DOM Event elements (levels 2 & 3) –Integrate CSS solution

06 May 2003Stylable CGM XML Europe 2003, London ?