774133 - Make nsDisplayTransform take account of zooming for SVG transforms

Status: RESOLVED FIXED

(Core :: SVG, defect)

Description

[Jonathan Watt [:jwatt]]

nsDisplayTransform needs to take account of zooming in the translation components of SVG transforms.

Comment 1

[Jonathan Watt [:jwatt]]

Attachment: patch

Comment 2

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Comment on attachment 642451 [details] [diff] [review]
patch

Review of attachment 642451 [details] [diff] [review]:
-----------------------------------------------------------------

::: layout/base/nsDisplayList.cpp
@@ +2784,1 @@
>      result = gfx3DMatrix::From2D(svgTransform);

Don't we need to scale the whole transform here?

@@ +2791,5 @@
>    if (hasSVGTransforms && !transformFromSVGParent.IsIdentity()) {
> +    // Correct translation components for zoom:
> +    float devPixelsPerCSSPx = aFrame->PresContext()->CSSPixelsToDevPixels(1.0f);
> +    transformFromSVGParent.x0 *= devPixelsPerCSSPx;
> +    transformFromSVGParent.y0 *= devPixelsPerCSSPx;

Don't we need to scale the whole transform here?

Comment 3

[Matt Woodrow (:mattwoodrow)]

I don't think we need to, no. Only the 'translation' components of the matrix have units (CSS pixels in this case) and need to be converted, the rest are just scale factors and can't have their units converted.

We also shouldn't be converting to dev pixels here, we should instead convert into AppUnits, and then use the passed in aAppUnitsPerPixel to convert into the correct pixel type. Some of the callers to this function are using AppUnitsPerCSSPixel(), and converting to dev pixels will change this behaviour.

Comment 4

[Jonathan Watt [:jwatt]]

Attachment: patch

(In reply to Matt Woodrow (:mattwoodrow) from comment #3)
> We also shouldn't be converting to dev pixels here, we should instead
> convert into AppUnits, and then use the passed in aAppUnitsPerPixel to
> convert into the correct pixel type.

Good point.

Comment 5

[Jonathan Watt [:jwatt]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/4a0746d9a89f

Comment 6

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/4a0746d9a89f