Clarify the difference between packed layers and stacking contexts #824

mrobinson · 2017-02-02T06:49:20Z

Eventually scroll layers will create packed layers as well, so this will
help to keep things clear. This shouldn't change behavior, because
currently packed layer ids will always be equal to the stacking context
ids of their owners.

This change is

mrobinson · 2017-02-02T07:28:25Z

@glennw r?

bors-servo · 2017-02-02T09:10:44Z

☔ The latest upstream changes (presumably #802) made this pull request unmergeable. Please resolve the merge conflicts.

kvark · 2017-02-02T14:28:44Z

currently packed layer ids will always be equal to the stacking context
ids of their owners

Let's hope all of the are called sc_index so that we don't miss any ;)

kvark

Looks pretty straightforward and clean in terms of implementation.
For the future, I'd like to remove those xf_rect.as_ref().unwrap() calls and revise the coordinate system names.

kvark · 2017-02-02T14:45:14Z

webrender/src/frame.rs

-                                   &[]);
+        context.builder.push_stacking_context(layer_rect,
+                                              &ClipRegion::simple(&layer_rect),
+                                              LayerToScrollTransform::identity(),


Not directly related to this PR, but is it correct to still call it LayerToScrollTransform?
AFAIK, the SC's/items are attached to their reference frames, but the transformation we pass here is relative to the parent stacking context (not necessarily the scroll layer).

@kvark, I think you are right. The naming of this is off now. There is a chance that in the future StackingContexts won't have transforms at all. It depends if we decide to make all coordinates relative to reference frames or not.

Yep, I'd say let's not have the transformations in there. Since they only affect the initial placement of items, we should use it and forget about them, only keeping the reference frames in our sight.

mrobinson · 2017-02-02T15:49:31Z

@kvark, thanks for looking at this. I've pushed a new rebased version with a few other minor naming changes and a new use of Default::default().

kvark · 2017-02-02T18:58:24Z

webrender/src/tiling.rs

-impl Default for PackedStackingContext {
-    fn default() -> PackedStackingContext {
-        PackedStackingContext {
+impl Default for PackedLayer {


I believe the semantics of Default is misused here. It's not a "default" layer, it's an empty one. Default is applicable where you could drop it if you don't care, and it's going to somewhat work. This is not the case here.

Hrm. Okay. I'm happy to change it, but does that mean that the implementation of Default::default should change.

Since there was already impl Default for PackedStackingContext, this is not something that has to be done in your PR. But for the future I think we should remove the impl Default and just have the same thing as an fn empty() -> PackedLayer constructor. No implementation change needed.

mrobinson · 2017-02-03T06:37:21Z

The build failure seems to be

Could not open dynamic library `OsMesa`

glennw · 2017-02-03T06:42:47Z

I think the build failure should be resolved now (I reverted the commit that seems to cause that) - but travis might need a rebuild?

mrobinson · 2017-02-03T07:46:55Z

@bors-servo try

bors-servo · 2017-02-03T07:46:58Z

⌛ Trying commit e115f89 with merge 9df10a0...


        Auto merge of #824 - mrobinson:packed-layer-id, r=<try>

Clarify the difference between packed layers and stacking contexts Eventually scroll layers will create packed layers as well, so this will help to keep things clear. This shouldn't change behavior, because currently packed layer ids will always be equal to the stacking context ids of their owners.  --- This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/webrender/824)

bors-servo · 2017-02-03T08:47:47Z

☀️ Test successful - status-travis
State: approved= try=True


        Clarify the difference between packed layers and stacking contexts

Eventually scroll layers will create packed layers as well, so this will help to keep things clear. This shouldn't change behavior, because currently packed layer ids will always be equal to the stacking context ids of their owners.

mrobinson · 2017-02-03T10:46:13Z

This is related to #742, by the way.

mrobinson · 2017-02-03T10:46:23Z

@bors-servo r=kvark

bors-servo · 2017-02-03T10:46:24Z

📌 Commit fce5d7c has been approved by kvark

bors-servo · 2017-02-03T10:46:27Z

⌛ Testing commit fce5d7c with merge a63d0a2...


        Auto merge of #824 - mrobinson:packed-layer-id, r=kvark

Clarify the difference between packed layers and stacking contexts Eventually scroll layers will create packed layers as well, so this will help to keep things clear. This shouldn't change behavior, because currently packed layer ids will always be equal to the stacking context ids of their owners.  --- This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/webrender/824)

bors-servo · 2017-02-03T11:46:04Z

☀️ Test successful - status-travis
Approved by: kvark
Pushing a63d0a2 to master...

kvark approved these changes Feb 2, 2017

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mrobinson force-pushed the mrobinson:packed-layer-id branch from 8870224 to e115f89 Feb 2, 2017

kvark approved these changes Feb 2, 2017

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glennw closed this Feb 2, 2017

glennw reopened this Feb 2, 2017

mrobinson force-pushed the mrobinson:packed-layer-id branch from e115f89 to fce5d7c Feb 3, 2017

bors-servo merged commit fce5d7c into servo:master Feb 3, 2017
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mrobinson deleted the mrobinson:packed-layer-id branch Feb 3, 2017

servo / webrender

Clarify the difference between packed layers and stacking contexts #824

Clarify the difference between packed layers and stacking contexts #824

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edited by larsbergstrom