Commit a4f9eea8 authored by Emilio Cobos Álvarez's avatar Emilio Cobos Álvarez
Browse files

Bug 1488414 - Use decomposition to interpolate matched perspective transform operations. r=birtles 

Looks like this produces sensible results for interpolation with 0, though I'm
not really convinced about the results from, let's say, 1px to 2000px in the
attached test-case, I would've expected a linear interpolation from that to go
through normal length interpolation.

css-transforms-1 says:

  > Two transform functions with the same name and the same number of arguments
  > are interpolated numerically without a former conversion. The calculated
  > value will be of the same transform function type with the same number of
  > arguments.
  >
  > Special rules apply to <matrix()>.

Which is what we do... I was going to file a spec issue but turns out that it's
already addressed in css-transforms-2:

  https://drafts.csswg.org/css-transforms-2/#interpolation-of-transform-functions

Which says:

  > The transform functions <matrix()>, matrix3d() and perspective() get
  > converted into 4x4 matrices first and interpolated as defined in section
  > Interpolation of Matrices afterwards.

Differential Revision: https://phabricator.services.mozilla.com/D4942

--HG--
extra : moz-landing-system : lando
parent bce574c7

servo/components/style/properties/helpers/animated_properties.mako.rs

+21 −3
Original line number Diff line number Diff line
@@ -1296,9 +1296,27 @@ impl Animate for ComputedTransformOperation { 
                &TransformOperation::Perspective(ref fd),

                &TransformOperation::Perspective(ref td),

            ) => {

                Ok(TransformOperation::Perspective(

                    fd.animate(td, procedure)?

                ))

                use values::computed::CSSPixelLength;

                use values::generics::transform::create_perspective_matrix;



                // From https://drafts.csswg.org/css-transforms-2/#interpolation-of-transform-functions:

                //

                //    The transform functions matrix(), matrix3d() and

                //    perspective() get converted into 4x4 matrices first and

                //    interpolated as defined in section Interpolation of

                //    Matrices afterwards.

                //

                let from = create_perspective_matrix(fd.px());

                let to = create_perspective_matrix(td.px());



                let interpolated =

                    Matrix3D::from(from).animate(&Matrix3D::from(to), procedure)?;



                let decomposed = decompose_3d_matrix(interpolated)?;

                let perspective_z = decomposed.perspective.2;

                let used_value =

                    if perspective_z == 0. { 0. } else { -1. / perspective_z };

                Ok(TransformOperation::Perspective(CSSPixelLength::new(used_value)))

            },

            _ if self.is_translate() && other.is_translate() => {

                self.to_translate_3d().animate(&other.to_translate_3d(), procedure)

servo/components/style/values/computed/transform.rs

+1 −0
Original line number Diff line number Diff line
@@ -42,6 +42,7 @@ impl TransformOrigin { 


/// computed value of matrix3d()

pub type Matrix3D = generic::Matrix3D<Number>;



/// computed value of matrix()

pub type Matrix = generic::Matrix<Number>;