1069378 - Matrix4x4::TransformBounds should take a RectTyped rather than a Rect

Status: RESOLVED WONTFIX

(Core :: Graphics, defect)

Description

[Kartikaya Gupta (email:[e-mail])]

gfx::Rect is a typedef for gfx::RectTyped<UnknownUnits> which is something we should be trying to phase out, or use as little as possible. Matrix4x4::TransformBounds should accept any gfx::RectTyped<T> instead, to encourage use of typed units. I would have suggested it take a gfx::BaseRect except that can be derived with integer-based rects (e.g. gfx::IntRect) which presumably we don't want to allow transformation of without rounding considerations.

Comment 1

[Botond Ballo [:botond]]

Would the return type be a rect of the same type as the input? Matrices often transform rectangles from one coordinate space into another.

A related change I've been meaning to propose is to make a strongly-typed version of Matrix4x4, such as Matrix4x4Typed<SourceUnits, TargetUnits>. The TransformBounds method of this type could then take a RectTyped<SourceUnits> as input, and return a RectTyped<TargetUnits>.

Comment 2

[Botond Ballo [:botond]]

Also note that there is a non-member TransformTo function in UnitTransforms.h that's very convenient to use in such scenarios [1].

[1] http://mxr.mozilla.org/mozilla-central/source/layout/base/UnitTransforms.h?rev=4df5daa7ca34#80

Comment 3

[Kartikaya Gupta (email:[e-mail])]

(In reply to Botond Ballo [:botond] from comment #1)
> Would the return type be a rect of the same type as the input? Matrices
> often transform rectangles from one coordinate space into another.

That's a good point, maybe we shouldn't fix this and ensure the callers are doing their type conversions properly. A strongly-typed TransformBounds would be nice though.

Comment 4

[Botond Ballo [:botond]]

(In reply to Botond Ballo [:botond] from comment #1)
> A related change I've been meaning to propose is to make a strongly-typed
> version of Matrix4x4, such as Matrix4x4Typed<SourceUnits, TargetUnits>. The
> TransformBounds method of this type could then take a RectTyped<SourceUnits>
> as input, and return a RectTyped<TargetUnits>.

Filed bug 1069417 for this.

Comment 5

[Botond Ballo [:botond]]

Didn't mean to make that resolution change.