Xamarin.forms: [Bug] UWP NavigationPage.TitleView does not fill Header

[YZahringer]

Description

On UWP the TitleView does not take up all the available space. There is a margin at the bottom and left.

Steps to Reproduce

````xaml


BackgroundColor="Red"
HorizontalOptions="FillAndExpand"
VerticalOptions="FillAndExpand" />

<Grid BackgroundColor="Yellow">

</Grid>

````

Expected Behavior

Grid with BackgroundColor="Red" Fill Header without margins:

Actual Behavior

Grid has Left 10px and Bottom 8px Margin:

Live Visual Tree of Header:

It is the Border in TitleViewPresenter that takes width=10px and height=48px. This one should have Visibility=Collapsed.

Basic Information

• Version with issue: 4.3.0.991211
• IDE: 16.3.10
• Platform Target Frameworks:
  
  
  
  • UWP: 18362
  
  

[jfversluis]

Hm I wonder if this has some connection to what is going on in #5661

[YZahringer]

@jfversluis Thanks! This also fixes the left "Padding" on TitleView?

[jfversluis]

Hm that I don't think so, this focusses mostly on the bottom thing. But it should be in the same area

[jfversluis]

Confirmed this happening in the attached repro project.

Repro8602.zip

[WayaFlyfeather]

I've tried to look into this. It appears the implementation of the TitleView in UWP is such, that it co-exists with the TitleIcon and Title properties, and this is causing the problems.

This becomes more obvious if a Title is added to the repro @jfversluis provided:

Note how the "Title" intrudes on the TitleView.

The left padding is caused by these lines in the default PageControlStyle - where a grid with 3 columns are used: one for any icon, one for the title, and one for the TitleView. As the TextBlock for the Title includes a left padding of 10, this is always there.

I can fix this, but I need to be sure my understanding is correct: that if a TitleView is specified, this should take precedence, and neither the Icon ot the Title property should be shown; but if no TitleView is specified, the Icon and Title should be shown.

?

[YZahringer]

My temp workaround (hide TextBlock of Title in entire app):
````xaml

<x:Double x:Key="AppBarThemeCompactHeight">48</x:Double>
<x:Double x:Key="AppBarExpandButtonThemeWidth">0</x:Double>

``` In my opinion, the [Title TextBlock](https://github.com/xamarin/Xamarin.Forms/blob/f06cb1f652ca5feac719a20cac98c9a61fd461aa/Xamarin.Forms.Platform.UAP/PageControlStyle.xaml#L35) should be collapsed when noTitle` provided.