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Diffstat (limited to 'doc/dw-size-request-pos.doc')
| -rw-r--r-- | doc/dw-size-request-pos.doc | 61 |
1 files changed, 60 insertions, 1 deletions
diff --git a/doc/dw-size-request-pos.doc b/doc/dw-size-request-pos.doc index e50f341c..93c84bb3 100644 --- a/doc/dw-size-request-pos.doc +++ b/doc/dw-size-request-pos.doc @@ -10,6 +10,65 @@ Motivation ========== As described in \ref dw-out-of-flow (*The sizeRequest/sizeAllocate -problem*), ... +problem*), the principle that the size of a widget depends only on the +sizes of its children causes some problems with floats; the current +solution is a frequent correction by calling +dw::core::Widget::queueResize. In this document, an alternative +approach is presented. + + +General Idea +============ + +A widget size may depend on the position relative to an anchestor +widget. If a widget wants to get the size of a child widget, it should + +1. call the new method **dw::core::Widget::sizeRequestReference**, + which returns NULL, when the child's size does not depend on the + position, or a widget relative to which the child's position must + be calculated; +2. call dw::core::Widget::sizeRequest with the position relative to + this widget. + +The position passed to dw::core::Widget::sizeRequest must be the +position at which this child will be allocated. + +There are situations where the parent widget is unable to determine +this position before the size is known. An example: a textblock widget +cannot determine the position of an inline widget (like an image, or +an inline block) before the line is finished; on the other hand, +finishing the line depends on knowing the sizes of the inline widgets. + +This may result in a conflict, when the size of an inline widgets +depends on the position. Fortunately, this is not the case in dillo: +the only widget whose size depends on the position is dw::Textblock +(the size will depend on the position within its floats container); but +an inline blocks constitute its own floats container, so that there is +no dependance on a position within another widget. + +Generally, this case should be handled by providing a fallback +strategy. (TODO: How does this look like? The widget is forced to +calculate its size independant of the position?) + +Resizing +-------- + +Currently, the size of a widget has to be recalculated, when + +1. it has called dw::core::Widget::queueResize, or +2. the size of a child widget has to be recalculated. + +Since for this new approach, the size does not only depend on the size +of the children, the second condition must be modified. However, +regarding changes of the position is not sufficient. Consider this +example, where a float size changes as soon as the image is loaded: + +\image html dw-size-request-pos-01.png + +The second paragraph ("A longer paragraph" ...) stays at the same +position, both absolute and relative to the float container, but has +to be rewrapped because of the float. + +(TODO: A detailed design is yet to de developed.) */
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