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More notes about sizer changes

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git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@28272 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
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Robin Dunn
2004-07-16 21:40:01 +00:00
parent a61c65b304
commit da2c76724f
4 changed files with 183 additions and 81 deletions
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wxPython/docs/MigrationGuide.html
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@@ -378,30 +378,97 @@ Insert, Prepend, and etc.) methods any longer. Just use Add and the
wrappers will figure out what to do. <strong>[Changed in 2.5.2.x]</strong>
AddWindow, AddSize, AddSpacer and etc. will now issue a
DeprecationWarning.</p>
<p><strong>[Changed in 2.5.2.x]</strong> wx.ADJUST_MINSIZE is now the default
behaviour for window items in sizers. This means that the item's
GetMinSize and/or GetBestSize will be called when calculating layout
and the return value from that will be used for the minimum size used
by the sizer. The wx.FIXED_MINSIZE flag was added that will cause the
sizer to use the old behaviour in that it will <em>not</em> call the window's
methods to determine the new best size, instead the minsize that the
window had when added to the sizer (or the size the window was created
with) will always be used.</p>
<p>Related to the above, when controls and some other window types are
created either the size passed to the constructor, or their &quot;best
size&quot; if an explicit size was not passed in, is set as the window's
minimal size. For non top-level windows that hasn't meant much in the
past, but now the sizers are sensitive to the window's minimal size.
The key point to understand here is that it is no longer the window's
size it has when added to the sizer that matters, but its minimal
size. So you might have some issues to iron out if you create a
control without a size and then set its size to something before
adding it to the sizer. Since it's minimal size is probably not the
size you set then the sizer will appear to be misbehaving. The fix is
to either set the size when calling the window's constructor, or to
reset the min size by calling SetSizeHints. You can call SetSizeHints
at anytime to change the minsize of a window, just call the sizer's
Layout method to redistribute the controls as needed.</p>
<p><strong>[Changed in 2.5.2.x]</strong> The Sizers have had some fundamental internal
changes in the 2.5.2.x release intended to make them do more of the
&quot;Right Thing&quot; but also be as backwards compatible as possible.
First a bit about how things used to work:</p>
<blockquote>
<ul class="simple">
<li>The size that a window had when Add()ed to the sizer was assumed
to be its minimal size, and that size would always be used by
default when calculating layout size and positions, and the
sizer itself would keep track of that minimal size.</li>
<li>If the window item was added with the <tt class="literal"><span class="pre">wx.ADJUST_MINSIZE</span></tt>
flag then when layout was calculated the item's <tt class="literal"><span class="pre">GetBestSize</span></tt>
would be used to reset the minimal size that the sizer used.</li>
</ul>
</blockquote>
<p>The main thrust of the new Sizer changes was to make behaviour like
<tt class="literal"><span class="pre">wx.ADJUST_MINSIZE</span></tt> be the default, and also to push the tracking of
the minimal size to the window itself (since it knows its own needs)
instead of having the sizer take care of it. Consequently these
changes were made:</p>
<blockquote>
<ul class="simple">
<li>The <tt class="literal"><span class="pre">wx.FIXED_MINSIZE</span></tt> flag was added to allow for the old
behaviour. When this flag is used the size a window has when
added to the sizer will be treated as its minimal size and it
will not be readjusted on each layout.</li>
<li>The min size stored in <tt class="literal"><span class="pre">wx.Window</span></tt> and settable with
<tt class="literal"><span class="pre">SetSizeHints</span></tt> or <tt class="literal"><span class="pre">SetMinSize</span></tt> will by default be used by
the sizer (if it was set) as the minimal size of the sizer item.
If the min size was not set (or was only partially set) then the
window's best size is fetched and it is used instead of (or
blended with) the min size. <tt class="literal"><span class="pre">wx.Window.GetBestFittingSize</span></tt>
was added to facilitate getting the size to be used by the
sizers.</li>
<li>The best size of a window is cached so it doesn't need to
recaculated on every layout. <tt class="literal"><span class="pre">wx.Window.InvalidateBestSize</span></tt>
was added and should be called (usually just internally in
control methods) whenever something is done that would make the
best size change.</li>
<li>All wxControls were changed to set the minsize to what is passed
to the constructor or Create method, and also to set the real
size of the control to the blending of the min size and best
size. <tt class="literal"><span class="pre">wx.Window.SetBestFittingSize</span></tt> was added to help with
this, although most controls don't need to call it directly
because it is called indirectly via the <tt class="literal"><span class="pre">SetInitialSize</span></tt>
called in the base classes.</li>
</ul>
</blockquote>
<p>At this time, the only situation known not to work the same as before
is the following:</p>
<pre class="literal-block">
win = SomeWidget(parent)
win.SetSize(SomeNonDefaultSize)
sizer.Add(win)
</pre>
<p>In this case the old code would have used the new size as the minimum,
but now the sizer will use the default size as the minimum rather than
the size set later. It is an easy fix though, just move the
specification of the size to the constructor (assuming that SomeWidget
will set its minsize there like the rest of the controls do) or call
<tt class="literal"><span class="pre">SetMinSize</span></tt> instead of <tt class="literal"><span class="pre">SetSize</span></tt>.</p>
<p>In order to fit well with this new scheme of things, all wxControls or
custom controls should do the following things. (Depending on how
they are used you may also want to do the same thing for non-control
custom windows.)</p>
<blockquote>
<ul>
<li><p class="first">Either override or inherit a meaningful <tt class="literal"><span class="pre">DoGetBestSize</span></tt> method
that calculates whatever size is &quot;best&quot; for the control. Once
that size is calculated then there should normally be a call to
<tt class="literal"><span class="pre">CacheBestSize</span></tt> to save it for later use, unless for some
reason you want the best size to be recalculated on every
layout.</p>
<p>Note: In order to successfully override <tt class="literal"><span class="pre">DoGetBestSize</span></tt> in
Python the class needs to be derived from <tt class="literal"><span class="pre">wx.PyWindow</span></tt>,
<tt class="literal"><span class="pre">wx.PyControl</span></tt>, or etc. If your class instead derives from
one of the standard wx classes then just be sure that the min
size gets explicitly set to what would have been the best size
and things should work properly in almost all situations.</p>
</li>
<li><p class="first">Any method that changes the attributes of the control such that
the best size will change should call <tt class="literal"><span class="pre">InvalidateBestSize</span></tt> so
it will be recalculated the next time it is needed.</p>
</li>
<li><p class="first">The control's constructor and/or Create method should ensure
that the minsize is set to the size passed in, and that the
control is sized to a blending of the min size and best size.
This can be done by calling <tt class="literal"><span class="pre">SetBestFittingSize</span></tt>.</p>
</li>
</ul>
</blockquote>
</div>
<div class="section" id="platforminfo">
<h1><a name="platforminfo">PlatformInfo</a></h1>