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| author | Sebastian Geerken <devnull@localhost> | 2015-06-03 22:40:07 +0200 |
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| committer | Sebastian Geerken <devnull@localhost> | 2015-06-03 22:40:07 +0200 |
| commit | 0a565f9b2bfc084a3292ad0c3db85e76cc8dc060 (patch) | |
| tree | ae743c7a37bfde4293c142e4a6d32648526b7776 /doc/dw-interrupted-drawing.doc | |
| parent | da88ede8c401449729ae9c4b78f4c9914d81fa09 (diff) | |
Moved dev docs to devdoc.
Diffstat (limited to 'doc/dw-interrupted-drawing.doc')
| -rw-r--r-- | doc/dw-interrupted-drawing.doc | 121 |
1 files changed, 0 insertions, 121 deletions
diff --git a/doc/dw-interrupted-drawing.doc b/doc/dw-interrupted-drawing.doc deleted file mode 100644 index c7037666..00000000 --- a/doc/dw-interrupted-drawing.doc +++ /dev/null @@ -1,121 +0,0 @@ -/** \page dw-interrupted-drawing Interrupted drawing - -Describing the problem -====================== - -Without interrupting drawing (which is described below), a widget can -define the order in which its parts (background, non-widget content, -child widgets, etc.) are drawn, but it must be drawn as a whole. There -are situations when this is not possible. - -Consider the following simple HTML document: - - <head> - <style> - #sc-1 { position: relative; z-index: 1; background: #ffe0e0; } - #fl-1 { float: right; background: #b0ffb0; } - #sc-2 { position: relative; z-index: 1; background: #f0f0ff; } - </style> - </head> - <body> - <div id="sc-1"> - <div id="fl-1"> - Float, line 1/3<br/> - Float, line 2/3<br/> - Float, line 3/3 - </div> - Stacking Context 1 - <div id="sc-2">Stacking Context 2</div> - </div> - </body> - -The rendering will look like this: - -\image html dw-interrupted-drawing-1.png - -Note the missing "Float, line 2/3" of element #fl-1, which is covered -by element #sc-2. - -As described in \ref dw-out-of-flow, it has to be distinguished -between the *container* hierarchy (equivalent to the hierarchy of -dw::core::Widget.) and the the *generator* hierarchy. In the following -diagram, the former is represented by solid lines, the latter by -dotted lines: - -\dot -digraph G { - node [shape=rect, fontname=Helvetica, fontsize=10]; - edge [arrowhead="vee"]; - - "#sc-1" [fillcolor="#ffe0e0", style="filled"]; - "#fl-1" [fillcolor="#b0ffb0", style="filled"]; - "#sc-2" [fillcolor="#f0f0ff", style="filled"]; - - "body" -> "#sc-1"; - "body" -> "#fl-1"; - { rank=same; "#sc-1" -> "#fl-1" [style=dotted]; } - "#sc-1" -> "#sc-2"; -} -\enddot - - -The drawing order of the four elements (represented by widgets) is: - -- body, -- #sc-1, -- #fl-1, -- #sc-2. - -Since - -1. #sc-2 is a child of #sc-1, but -2. #fl-1 is a child of the body, and -3. a widget can only draw its descendants (not neccessary children, - but drawing siblings is not allowed), - -#sc-1 cannot be drawn as a whole; instead drawing is **interrupted** -by #fl-1. This means: - -1. the background and text of #sc-1 is drawn; -2. drawing of #sc-1 is **interrupted** by #fl-1 (see below for details), -3. drawing of #sc-1 is **continued**, by drawing #sc-2. - -The exact control flow is described in this sequence diagram: - -\image html dw-interrupted-drawing-2.png - - -When is drawing interrupted? -============================ - -A widget out of flow is regarded as part of the stacking context (see -\ref dw-stacking-context) of its *generator* (in the example above: -#fl-1 is part of the stacking context stablished by #sc-1, not the one -established by body). For this reason, a widget out of flow must, in -some cases, drawn while the *gerator* is drawn, as an -interruption. The exact rule: - -A widget out of flow must be drawn as an interruption (while the -*generator* is drawn) if the stacking context of the generator (to -which this widget belongs) is in front of the stacking context of the -container (the parent widget). - -See dw::oof::OOFAwareWidget::doesWidgetOOFInterruptDrawing. - - -How does interruption of drawing work? -====================================== - -When a widget detects that an other widget should be drawn as -interruption (see above), it calls dw::core::Widget::drawInterruption, -which - -1. draws the widget within another "context" (area and reference - widget); for this the original drawing area - (dw::core::DrawingContext::getToplevelArea) is used. -2. Using dw::core::DrawingContext::addWidgetDrawnAsInterruption, and - checking later with - dw::core::DrawingContext::hasWidgetBeenDrawnAsInterruption prevents - these widgets from being drawn twice. - -*/ |