[dev-servo] Abstract-dimension geometry for CSS Writing Modes
In preparation for CSS Writing Modes and porting all of our layout code, I started adding geometry primitives in abstract dimensions. Permanent link as of this writing: https://github.com/SimonSapin/servo/compare/d6caf26 Link tracking the branch: https://github.com/SimonSapin/servo/compare/abstract-geometry Relevant spec: http://dev.w3.org/csswg/css-writing-modes/#abstract-box AbstractSize and AbstractPoint are equivalent to rust-geom’s Size2D and Point2D, but in flow-relative dimensions rather than physical. I’ll add AbstractSideOffsets and AbstractRect when we’re happy with the design. Like the physical ones, they are generic over the representation of a scalar, and so should be orthogonal to Matt’s work on typed units. The two flow-relative axis are I and B, short of inline-direction and block-direction. I put this in the util crate for now to avoid dealing with submodules, but it could be in rust-geom. This is largely based on Gecko’s WritingModes.h file: http://dxr.mozilla.org/mozilla-central/source/layout/generic/WritingModes.h The addition on points is: AbstractPoint + AbstractSize -> AbstractPoint rather than Point + Point -> Point I find this makes more sense (a size is just a vector, whereas a point is a vector from an implied origin), but I don’t know yet how this used in practice. The mapping between abstract and physical dimensions is determined by "the writing mode", which is based on the 'direction', 'writing-mode', and 'text-orientation' CSS properties. The fields of abstract structs are private, and all method take the writing mode as a parameter. On debug builds (i.e. without --cfg ndebug), the writing mode is also stored in the struct and asserted at each method call. (Non-debug builds make this storage zero-size and the checks no-ops.) This has apparently caught several bugs in Gecko. Unlike C++, Rust does not have method overloading so the accessors are much more verbose. `nscoord ISize(WritingMode aWritingMode) const` overloaded with `nscoord& ISize(WritingMode aWritingMode)` becomes `get_i_size(&self, mode: WritingMode) -> T` and `set_i_size(&mut self, mode: WritingMode, T)`. The setter could be replaced with `i_size_ref(&'a mut self, mode: WritingMode) -> &'a mut T`, but the getter would still be needed so that reading does not require `&mut`. Or perhaps we should have all three. Is there a better way to do accessors in Rust? -- Simon Sapin ___ dev-servo mailing list dev-servo@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-servo
Re: [dev-servo] Abstract-dimension geometry for CSS Writing Modes
On 5/26/14 2:44 PM, Simon Sapin wrote: Unlike C++, Rust does not have method overloading so the accessors are much more verbose. `nscoord ISize(WritingMode aWritingMode) const` overloaded with `nscoord& ISize(WritingMode aWritingMode)` becomes `get_i_size(&self, mode: WritingMode) -> T` and `set_i_size(&mut self, mode: WritingMode, T)`. The setter could be replaced with `i_size_ref(&'a mut self, mode: WritingMode) -> &'a mut T`, but the getter would still be needed so that reading does not require `&mut`. Or perhaps we should have all three. Is there a better way to do accessors in Rust? Do we need the `get_` prefix? That is, could it just be `.isize()`? (In general, I find that single-letter abbreviations read better when squished up next to the word they go with, without underscores. Just personal preference, I guess.) Patrick ___ dev-servo mailing list dev-servo@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-servo
Re: [dev-servo] Abstract-dimension geometry for CSS Writing Modes
On 5/26/14 2:52 PM, Patrick Walton wrote: (In general, I find that single-letter abbreviations read better when squished up next to the word they go with, without underscores. Just personal preference, I guess.) Compare e.g. "xrange" in Python versus a hypothetical "x_range". I think "xrange" reads nicer. Patrick ___ dev-servo mailing list dev-servo@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-servo
Re: [dev-servo] Abstract-dimension geometry for CSS Writing Modes
On 26/05/2014 22:52, Patrick Walton wrote: On 5/26/14 2:44 PM, Simon Sapin wrote: Unlike C++, Rust does not have method overloading so the accessors are much more verbose. `nscoord ISize(WritingMode aWritingMode) const` overloaded with `nscoord& ISize(WritingMode aWritingMode)` becomes `get_i_size(&self, mode: WritingMode) -> T` and `set_i_size(&mut self, mode: WritingMode, T)`. The setter could be replaced with `i_size_ref(&'a mut self, mode: WritingMode) -> &'a mut T`, but the getter would still be needed so that reading does not require `&mut`. Or perhaps we should have all three. Is there a better way to do accessors in Rust? Do we need the `get_` prefix? That is, could it just be `.isize()`? (In general, I find that single-letter abbreviations read better when squished up next to the word they go with, without underscores. Just personal preference, I guess.) I’m fine with that, but I’m more interested in the signature than the naming. That is, which of these (or others) to have, for each private field? fn(&self) -> T fn(&mut self, T) fn(&'a mut self) -> &'a mut T -- Simon Sapin ___ dev-servo mailing list dev-servo@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-servo
