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| author | Sebastian Geerken <devnull@localhost> | 2015-06-01 22:00:10 +0200 |
|---|---|---|
| committer | Sebastian Geerken <devnull@localhost> | 2015-06-01 22:00:10 +0200 |
| commit | 1463c3936ce6a57352590b901c9dbd6bc2f2086d (patch) | |
| tree | 3e7983b72fe63770fd2870b57683afd9421a36bd /devdoc/dw-out-of-flow-floats.doc | |
| parent | eb7ee4703ced8a02404eb0ebfa5b771fc5e916d5 (diff) | |
Split up user and developer documentation.
Diffstat (limited to 'devdoc/dw-out-of-flow-floats.doc')
| -rw-r--r-- | devdoc/dw-out-of-flow-floats.doc | 121 |
1 files changed, 121 insertions, 0 deletions
diff --git a/devdoc/dw-out-of-flow-floats.doc b/devdoc/dw-out-of-flow-floats.doc new file mode 100644 index 00000000..53c6b220 --- /dev/null +++ b/devdoc/dw-out-of-flow-floats.doc @@ -0,0 +1,121 @@ +/** \page dw-out-of-flow-floats Handling Elements Out Of Flow: Floats + +(Note: Bases on work at <http://flpsed.org/hgweb/dillo_grows>, I plan +to split the documentation on elements out of flow into different +parts: general part, floats, positioned elements. In this document, +informations about floats are collected.) + + +GB lists and CB lists +===================== + +Floats generated by a block which is not yet allocated are initially +put into a list related to the *generator*: + +- dw::OutOfFlowMgr::TBInfo::leftFloatsGB or +- dw::OutOfFlowMgr::TBInfo::rightFloatsGB. + +These lists are also called GB lists. + +Floats of allocated generators are put into lists related to the +*container* (called CB lists): + +- dw::OutOfFlowMgr::leftFloatsCB or +- dw::OutOfFlowMgr::rightFloatsCB. + +As soon as the container is allocated, all floats are moved from the +GB lists to the CB lists (dw::OutOfFlowMgr::sizeAllocateStart → +dw::OutOfFlowMgr::moveFromGBToCB). + +Here, it is important to preserve the *generation order* (for reasons, +see below: *Sorting floats*), i. e. the order in which floats have +been added (dw::OutOfFlowMgr::addWidgetOOF). This may become a bit +more complicated in a case like this: + + <head> + <style> + \#fl-1, \#fl-2, \#fl-3 { float: right } + </style> + </head> + <body> + <div id="bl-1"> + <div id="fl-1">float 1</div> + <div id="bl-2"> + <div id="fl-2">float 2</div> + </div> + <div id="fl-3">float 3</div> + </div> + </body> + +The floats are generated in this order: + +- \#fl-1 (generated by \#bl-1), +- \#fl-2 (generated by \#bl-2), +- \#fl-3 (generated by \#bl-1). + +Since the floats must be moved into the CB list in this order, it +becomes clear that the floats from one GB list cannot be moved at +once. For this reason, each float is assigned a "mark", which is +different from the last one as soon as the generator is *before* the +generator of the float added before. In the example above, there are +three generators: body, \#bl-1, and \#bl-2 (in this order), and floats +are assigned these marks: + +- \#fl-1: 0, +- \#fl-2: also 0, +- \#fl-3 is assigned 1, since its generator (\#bl-1) lies before the + last generator (\#bl-2). + +dw::OutOfFlowMgr::moveFromGBToCB will then iterate over all marks, so +that the generation order is preserved. + + +Sorting floats +============== + +Floats are sorted, to make binary search possible, in these lists: + +- for each generator: dw::OutOfFlowMgr::TBInfo::leftFloatsGB and + dw::OutOfFlowMgr::TBInfo::rightFloatsGB; +- for the container: dw::OutOfFlowMgr::leftFloatsCB and + dw::OutOfFlowMgr::rightFloatsCB. + +The other two lists, dw::OutOfFlowMgr::leftFloatsAll and +dw::OutOfFlowMgr::rightFloatsAll are not sorted at all. + +New floats are always added to the end of either list; this order is +called *generation order*. See also above: *GB lists and CB lists*. + +On the other hand, there are different sorting criteria, implemented +by different comparators, so that different kinds of keys may be used +for searching. These sorting criteria are equivalent to the generation +order. + +dw::OutOfFlowMgr::Float::CompareSideSpanningIndex compares +*sideSpanningIndex* (used to compare floats to those on the respective +other side); if you look at the definition +(dw::OutOfFlowMgr::addWidgetOOF) it becomes clear that this order is +equivalent to the generation order. + +dw::OutOfFlowMgr::Float::CompareGBAndExtIndex compares *externalIndex* +for floats with same generators, otherwise: (i) if one generator (T1) +is a direct anchestor of the other generator (T2), the child of T1, +which is an anchestor of, or identical to, T2 is compared to the float +generated by T1, using *externalIndex*, as in this example: + + T1 -+-> child --> ... -> T2 -> Float + `-> Float + +Otherwise, the two blocks are compared, according to their position in +dw::OutOfFlowMgr::tbInfos: + + common anchestor -+-> ... --> T1 -> Float + `-> ... --> T2 -> Float + +This is equivalent to the generation order, as long it is ensured that +*externalIndex* reflects the generation order within a generating +block, for both floats and child blocks. + +dw::OutOfFlowMgr::Float::ComparePosition ... + +*/ |