Documentation and comments on Jorge's patch.

3 files changed, 43 insertions, 1 deletions

diff --git a/devdoc/dw-miscellaneous.doc b/devdoc/dw-miscellaneous.doc
index 2828e539..dc282354 100644
--- a/devdoc/dw-miscellaneous.doc
+++ b/devdoc/dw-miscellaneous.doc
@@ -45,4 +45,37 @@ Extra space
 Should dw::core::Widget::calcExtraSpace be called from
 dw::core::Widget::getExtremes?
 
+
+Widget sizes
+============
+
+Relation between dw::core::Widget::markSizeChange and  dw::core::Widget::queueResize
+------------------------------------------------------------------------------------
+dw::oof::OOFFloatsMgr::markSizeChange (called from
+dw::Textblock::markSizeChange) calls dw::oof::OOFAwareWidget::updateReference,
+whose implementation dw::Textblock::updateReference calls
+dw::core::Widget::queueResize. This may result in a recursion,
+
+- for which it is not clear whether it ends in all cases (although endless cases
+  are not known yet), and
+- which nevertheless may take much time in cases where the number of calls
+  increases exponentially with the depth of the widget tree.
+
+The recent change in dw::Textblock::updateReference (`if (lines->size () > 0)`)
+seems to fix the performance problem, but the issue should be examined further,
+albeit with lower priority. Especially, it has to be determined, under which
+conditions it is allowed to (directly or indirectly) call
+dw::core::Widget::queueResize within an implementation of
+dw::core::Widget::markSizeChange.
+
+Here is the orginal test case (slow, when `if (lines->size () > 0)` is removed
+again):
+
+    (for i in $(seq 1 20); do echo '<div style="float:left"><div></div>'; done) > tmp.html; src/dillo tmp.html
+
+You may change the numner (20), or examine smaller cases with
+<a href="http://home.gna.org/rtfl/">RTFL</a>:
+
+    (for i in $(seq 1 3); do echo '<div style="float:left"><div></div>'; done) > tmp.html; src/dillo tmp.html | rtfl-objview -OM -A "*" -a resize -a resize.oofm
+
 */
diff --git a/dw/oofawarewidget.hh b/dw/oofawarewidget.hh
index e49cce14..8d18675e 100644
--- a/dw/oofawarewidget.hh
+++ b/dw/oofawarewidget.hh
@@ -249,7 +249,8 @@ public:
               core::DrawingContext *context);
 
    /**
-    * ...
+    * Update content in flow, down from `ref`. Uses e. g. when floats sizes have
+    * changed.
     */
    virtual void updateReference (int ref);
 
diff --git a/dw/textblock.cc b/dw/textblock.cc
index f851fd4e..dbf6e8e1 100644
--- a/dw/textblock.cc
+++ b/dw/textblock.cc
@@ -3034,6 +3034,14 @@ void Textblock::queueDrawRange (int index1, int index2)
 
 void Textblock::updateReference (int ref)
 {
+   // The condition "(lines->size () > 0)" prevents CPU hogging in some cases,
+   // see devdoc/dw-miscellaneous.doc, "Relation between
+   // dw::core::Widget::markSizeChange and dw::core::Widget::queueResize".
+   //
+   // This condition is safe, since an implementation of
+   // dw::oof::OOFAwareWidget::updateReference should only affect content in
+   // flow, not widgets out of flow, like floats.
+   
    if (lines->size () > 0)
       queueResize (ref, false);
 }