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Gecko:Overview: Difference between revisions
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→Reflow: Update links and documentation about reflow roots
(→Layout: various terminology updates and clarifications.) |
(→Reflow: Update links and documentation about reflow roots) |
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The reflow generally starts from the root of the frame tree, though some other | The reflow generally starts from the root of the frame tree, though some other | ||
types of frame can act as reflow roots and start a reflow from them. | types of frame can act as "reflow roots" and start a reflow from them | ||
(nsTextControlFrame is one example; see the | |||
[https://searchfox.org/mozilla-central/search?q=symbol:E_%3CT_nsFrameState%3E_NS_FRAME_REFLOW_ROOT&redirect=true NS_FRAME_REFLOW_ROOT] frame state bit). | |||
Reflow roots must obey the invariant that a change inside one of their | Reflow roots must obey the invariant that a change inside one of their | ||
descendants never changes their rect or overflow areas (though currently | descendants never changes their rect or overflow areas (though currently | ||
| Line 537: | Line 539: | ||
To do this, we maintain two bits on frames: | To do this, we maintain two bits on frames: | ||
[ | [https://searchfox.org/mozilla-central/search?q=symbol:E_%3CT_nsFrameState%3E_NS_FRAME_IS_DIRTY&redirect=true NS_FRAME_IS_DIRTY] | ||
indicates that a frame and all of its descendants require reflow. | indicates that a frame and all of its descendants require reflow. | ||
[ | [https://searchfox.org/mozilla-central/search?q=symbol:E_%3CT_nsFrameState%3E_NS_FRAME_HAS_DIRTY_CHILDREN&redirect=true NS_FRAME_HAS_DIRTY_CHILDREN] | ||
indicates that a frame has a descendant that | indicates that a frame has a descendant that | ||
is dirty or has had a descendant removed (i.e., that it has a child that | is dirty or has had a descendant removed (i.e., that it has a child that | ||
has NS_FRAME_IS_DIRTY or NS_FRAME_HAS_DIRTY_CHILDREN or it had a child | has NS_FRAME_IS_DIRTY or NS_FRAME_HAS_DIRTY_CHILDREN or it had a child | ||
removed). These bits allow coalescing of multiple updates; this | removed). These bits allow coalescing of multiple updates; this | ||
coalescing is done in | coalescing is done in PresShell, which tracks the set of reflow roots | ||
that require reflow. The bits are set during calls to | that require reflow. The bits are set during calls to | ||
[https://searchfox.org/mozilla-central/search?q=PresShell%3A%3AFrameNeedsReflow&path= PresShell::FrameNeedsReflow] | |||
and are cleared during reflow. | |||
The layout algorithms used by many of the frame classes are those | The layout algorithms used by many of the frame classes are those | ||