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diff --git a/old/dw/html/dw-interrupted-drawing.html b/old/dw/html/dw-interrupted-drawing.html new file mode 100644 index 0000000..c9aeb3c --- /dev/null +++ b/old/dw/html/dw-interrupted-drawing.html @@ -0,0 +1,115 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml"> +<head> +<meta http-equiv="Content-Type" content="text/xhtml;charset=UTF-8"/> +<meta http-equiv="X-UA-Compatible" content="IE=9"/> +<meta name="generator" content="Doxygen 1.8.8"/> +<title>Dillo: Interrupted drawing</title> +<link href="tabs.css" rel="stylesheet" type="text/css"/> +<script type="text/javascript" src="https://www.dillo.org/dw/html/jquery.js"></script> +<script type="text/javascript" src="dynsections.js"></script> +<link href="doxygen.css" rel="stylesheet" type="text/css" /> +</head> +<body> +<div id="top"><!-- do not remove this div, it is closed by doxygen! --> +<div id="titlearea"> +<table cellspacing="0" cellpadding="0"> + <tbody> + <tr style="height: 56px;"> + <td style="padding-left: 0.5em;"> + <div id="projectname">Dillo + </div> + </td> + </tr> + </tbody> +</table> +</div> +<!-- end header part --> +<!-- Generated by Doxygen 1.8.8 --> + <div id="navrow1" class="tabs"> + <ul class="tablist"> + <li><a href="index.html"><span>Main Page</span></a></li> + <li class="current"><a href="pages.html"><span>Related Pages</span></a></li> + <li><a href="namespaces.html"><span>Namespaces</span></a></li> + <li><a href="annotated.html"><span>Classes</span></a></li> + <li><a href="files.html"><span>Files</span></a></li> + </ul> + </div> +</div><!-- top --> +<div class="header"> + <div class="headertitle"> +<div class="title">Interrupted drawing </div> </div> +</div><!--header--> +<div class="contents"> +<div class="textblock"><h1>Describing the problem </h1> +<p>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.</p> +<p>Consider the following simple HTML document: </p><pre class="fragment"><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> +</pre><p>The rendering will look like this:</p> +<div class="image"> +<img src="dw-interrupted-drawing-1.png" alt="dw-interrupted-drawing-1.png"/> +</div> +<p>Note the missing "Float, line 2/3" of element #fl-1, which is covered by element #sc-2.</p> +<p>As described in <a class="el" href="dw-out-of-flow.html">Handling Elements Out Of Flow</a>, it has to be distinguished between the <em>container</em> hierarchy (equivalent to the hierarchy of <a class="el" href="classdw_1_1core_1_1Widget.html" title="The base class of all dillo widgets. ">dw::core::Widget</a>.) and the the <em>generator</em> hierarchy. In the following diagram, the former is represented by solid lines, the latter by dotted lines:</p> +<div align="center"> +<img src="dot_inline_dotgraph_3.png" alt="dot_inline_dotgraph_3.png" border="0" usemap="#dot_inline_dotgraph_3.map"/> +<map name="dot_inline_dotgraph_3.map" id="dot_inline_dotgraph_3.map"></map> +</div> +<p>The drawing order of the four elements (represented by widgets) is:</p> +<ul> +<li>body,</li> +<li>#sc-1,</li> +<li>#fl-1,</li> +<li>#sc-2.</li> +</ul> +<p>Since</p> +<ol type="1"> +<li>#sc-2 is a child of #sc-1, but</li> +<li>#fl-1 is a child of the body, and</li> +<li>a widget can only draw its descendants (not neccessary children, but drawing siblings is not allowed),</li> +</ol> +<p>#sc-1 cannot be drawn as a whole; instead drawing is <b>interrupted</b> by #fl-1. This means:</p> +<ol type="1"> +<li>the background and text of #sc-1 is drawn;</li> +<li>drawing of #sc-1 is <b>interrupted</b> by #fl-1 (see below for details),</li> +<li>drawing of #sc-1 is <b>continued</b>, by drawing #sc-2.</li> +</ol> +<p>The exact control flow is described in this sequence diagram:</p> +<div class="image"> +<img src="dw-interrupted-drawing-2.png" alt="dw-interrupted-drawing-2.png"/> +</div> +<h1>When is drawing interrupted? </h1> +<p>A widget out of flow is regarded as part of the stacking context (see <a class="el" href="dw-stacking-context.html">Handling stacking contexts</a>) of its <em>generator</em> (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 <em>gerator</em> is drawn, as an interruption. The exact rule:</p> +<p>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).</p> +<p>See <a class="el" href="classdw_1_1oof_1_1OOFAwareWidget.html#a71c15f48f27369ba42e21aa1ae738e9f">dw::oof::OOFAwareWidget::doesWidgetOOFInterruptDrawing</a>.</p> +<h1>How does interruption of drawing work? </h1> +<p>When a widget detects that an other widget should be drawn as interruption (see above), it calls <a class="el" href="classdw_1_1core_1_1Widget.html#aaebe553117db0b7ba2cb0243d06311df">dw::core::Widget::drawInterruption</a>, which</p> +<ol type="1"> +<li>draws the widget within another "context" (area and reference widget); for this the original drawing area (<a class="el" href="classdw_1_1core_1_1DrawingContext.html#a290ae2431e7edf6dacb1daf021cea72f">dw::core::DrawingContext::getToplevelArea</a>) is used.</li> +<li>Using dw::core::DrawingContext::addWidgetDrawnAsInterruption, and checking later with dw::core::DrawingContext::hasWidgetBeenDrawnAsInterruption prevents these widgets from being drawn twice. </li> +</ol> +</div></div><!-- contents --> +<!-- start footer part --> +<hr class="footer"/><address class="footer"><small> +Generated on Sat May 28 2016 11:47:43 for Dillo by  <a href="http://www.doxygen.org/index.html"> +<img class="footer" src="doxygen.png" alt="doxygen"/> +</a> 1.8.8 +</small></address> +</body> +</html> |