In article <6E64952A914E43E6B743E3CBCDF54ADA(a)gmail.com&gt;, Hoà V. Dinh <dinh.viet.hoa(a)gmail.com&gt; wrote: The first thing to do is to define the byte code for the properties you want to add. See docs/Bytecode: http://source.netsurf-browser.org/libcss.git/tree/docs/Bytecode Then there's two parts to adding support for a property. You need the code to parse the property into bytecode, in src/parse/, and the code to handle selection (cascade, computed value calculation, etc of the property), in src/select/. Here are some examples: Adding new properties to the parser: http://source.netsurf-browser.org/libcss.git/commit/?id=32ed7d0984f0dd872... Adding new shorthand properties to the parser: http://source.netsurf-browser.org/libcss.git/commit/?id=bd8ef0f5e2ec383b5... Note that the shorthand properties just set the values for other properties, so they don't have their own bytecode. Adding new properties to the selection engine: http://source.netsurf-browser.org/libcss.git/commit/?id=89ef7a8acf13143ac... You need to know and understand the spec. Note that the overflow-x and -y properties are still at an early draft stage. Also, the overflow property has to change from an actual property to a shorthand property that sets the values for both overflow-x and -y. Sure. It's easier to follow once you come up with the byte code. Taking the overflow one as an example: overflow:CSS_PROP_OVERFLOW IDENT:( INHERIT: VISIBLE:0,OVERFLOW_VISIBLE HIDDEN:0,OVERFLOW_HIDDEN SCROLL:0,OVERFLOW_SCROLL AUTO:0,OVERFLOW_AUTO IDENT:) "overflow" is the property, which is used for the file/function name of the generated parser. "CSS_PROP_OVERFLOW" is the css_properties_e enum value from include/libcss/properties.h Note enum the value is the number of the bytecode for the property. Then in the brackets, you have INHERIT: because the property may be inherited. And then a list of the other values the property may take. So VISIBLE:0,OVERFLOW_VISIBLE means if the value matches the VISIBLE string defined in parser/propstrings.{c|h}, then set the property to the enum value OVERFLOW_VISIBLE which is in src/bytecode/opcodes.h. That opcodes enum is set up according to the bytecode design in docs/Bytecode. The 0 is for the flags, a part of the bytecode. That's always 0. Anyway, given the state of the spec, especially ISSUE 1, I'd be tempted not to add supprt for the paged-* and fragments values at this stage. So in that case, you just need to rename the overflow property handler to overflow-x, add an overflow-y which behaves the same, add a parser for the shorthand overflow property, and update the selection code to handle the two overflow-x and overflow-y properties instead of overflow. -- Michael Drake (tlsa) http://www.netsurf-browser.org/