Canvas is actually a bit special and 'shortcuts' some of the layout routines that happen with every other panel. It's confusing and I've opened bugs on this in the past (caused us quite a bit of grief when we were implementing custom shapes in Blend), but the code is the way it is to maintain a very high level of performance for this specific layout control.
Alternatively Grid rather than Canvas should work for you. If you really are doing a fully custom positioning and sizing that you may want that raw performance that comes from Canvas, for many cases I don't see a need to go this far though. -----Original Message----- From: ozsilverlight-boun...@ozsilverlight.com [mailto:ozsilverlight-boun...@ozsilverlight.com] On Behalf Of Scott Barnes Sent: Wednesday, September 15, 2010 1:35 AM To: ozSilverlight Subject: Re: Textblock SizeChanged Well u could change the size of he font and then invalidate the textblock which should trigger sizechanged event but it's a lil ghetto ;) -- Sent from my mini iPad nano (excuse my spilling and grammar as I have giant man like fingers and this device as small keys) On 15/09/2010, at 5:08 PM, Colin Savage <colin.sav...@readify.net> wrote: > The app is a WYSIWYG layout for arranging textblocks and barcodes and things > to print on a label, so I want to avoid adding content that is not going to > be printed to the xaml. Since the changing of the font size is initiated by > the user, I can access the ActualHeight after that and update the rest of the > UI manually. > > It seems that the event only fires if it has in some way changed the layout > of the container, but that is contrary to what the doco says. > > http://msdn.microsoft.com/en-us/library/system.windows.frameworkelemen > t.sizechanged(VS.95).aspx "SizeChanged is raised whenever the size > (either ActualHeight or ActualWidth) has changed on the object, and is raised > after the Measure and Arrange passes are complete (for more information about > these concepts, see Silverlight Layout System). If the position of the object > within a parent container changes, but not the size, SizeChanged is not > raised. " > > In this case the ActualHeight has changed, but it doesn't fire. I'll find a > workaround for it, I was just wondering if anyone knew the reason. > > Regards, > Colin Savage > > -----Original Message----- > From: ozsilverlight-boun...@ozsilverlight.com > [mailto:ozsilverlight-boun...@ozsilverlight.com] On Behalf Of Scott > Barnes > Sent: Wednesday, 15 September 2010 4:10 PM > To: ozSilverlight > Subject: Re: Textblock SizeChanged > > Steve's correct, Canvas doesn't really care how wide/high its children > are in regards to itself. Encapsulating the TextBlock inside a border > and using that as your Source of Truth should get you the results you > desire, but yeah you have a ghetto border now :) > > Not sure why FontSize doesn't trigger SizeChanged though? in theory > the ActualWidth/ActualHeight should still trigger this event but given > FontSize may act differently to other FrameworkElements given it uses > glyphs etc. > > > > Regards, > > Scott Barnes > > http://www.riagenic.com > > > > On Wed, Sep 15, 2010 at 3:46 PM, Stephen Price <step...@littlevoices.com> > wrote: >> Without trying anything in code, I'd be guessing that putting the >> textblock onto/into the canvas makes it behave differently than when >> its in the border. I've seen quite a lot of sizing things behave >> differently depending upon the parent container. >> >> Have you tried it in a grid instead of a canvas? It might work >> (guessing, have not tried it out) >> >> On Wed, Sep 15, 2010 at 11:23 AM, Colin Savage <colin.sav...@readify.net> >> wrote: >>> Before this list turns entirely into an ausdotnet trollfest, how >>> about a Silverlight question? >>> >>> >>> >>> Does anyone know why a textblock is not firing SizeChanged event >>> when the fontsize changes? >>> >>> >>> >>> Example: >>> >>> <Grid x:Name="LayoutRoot" Background="White"> >>> >>> <StackPanel> >>> >>> <Button Content="Resize" >>> >>> Name="button1" >>> >>> Click="button1_Click" /> >>> >>> <TextBlock Name="result" >>> >>> Text="Size goes here"/> >>> >>> <TextBlock Name="actual" >>> >>> Text="Actual goes here" /> >>> >>> </StackPanel> >>> >>> <Canvas Height="200" >>> >>> HorizontalAlignment="Left" >>> >>> Margin="57,92,0,0" >>> >>> Name="canvas1" >>> >>> VerticalAlignment="Top" >>> >>> Width="311"> >>> >>> <!--<Border Canvas.Top="10" >>> >>> Canvas.Left="10" >>> >>> BorderBrush="Green" BorderThickness="1">--> >>> >>> <TextBlock Canvas.Top="10" >>> >>> Canvas.Left="10" >>> >>> Name="textblock1" >>> >>> Width="180" >>> >>> Text="Some Text" /> >>> >>> <!--</Border>--> >>> >>> </Canvas> >>> >>> </Grid> >>> >>> >>> >>> public partial class MainPage : UserControl >>> >>> { >>> >>> public MainPage() >>> >>> { >>> >>> InitializeComponent(); >>> >>> >>> >>> textblock1.SizeChanged += textblock1_SizeChanged; >>> >>> } >>> >>> >>> >>> void textblock1_SizeChanged(object sender, >>> SizeChangedEventArgs e) >>> >>> { >>> >>> result.Text = e.NewSize.ToString(); >>> >>> } >>> >>> >>> >>> private void button1_Click(object sender, RoutedEventArgs e) >>> >>> { >>> >>> textblock1.FontSize += 1; >>> >>> >>> >>> actual.Text = textblock1.ActualHeight.ToString(); >>> >>> } >>> >>> } >>> >>> >>> >>> >>> >>> Note that if I increase the fontsize, the ActualHeight changes, but >>> the SizeChanged event doesn't. Uncomment the border around the >>> textblock and it does start firing. >>> >>> >>> >>> Regards, >>> >>> Colin Savage >>> >>> _______________________________________________ >>> ozsilverlight mailing list >>> ozsilverlight@ozsilverlight.com >>> http://prdlxvm0001.codify.net/mailman/listinfo/ozsilverlight >>> >>> >> _______________________________________________ >> ozsilverlight mailing list >> ozsilverlight@ozsilverlight.com >> http://prdlxvm0001.codify.net/mailman/listinfo/ozsilverlight >> > _______________________________________________ > ozsilverlight mailing list > ozsilverlight@ozsilverlight.com > http://prdlxvm0001.codify.net/mailman/listinfo/ozsilverlight > > > _______________________________________________ > ozsilverlight mailing list > ozsilverlight@ozsilverlight.com > http://prdlxvm0001.codify.net/mailman/listinfo/ozsilverlight _______________________________________________ ozsilverlight mailing list ozsilverlight@ozsilverlight.com http://prdlxvm0001.codify.net/mailman/listinfo/ozsilverlight _______________________________________________ ozsilverlight mailing list ozsilverlight@ozsilverlight.com http://prdlxvm0001.codify.net/mailman/listinfo/ozsilverlight
