canvas not occupying full space in grid - silverlight

Question

I have a canvas in grid. On the mousemove event of canvas i am trying to translate the canvas. It works fine. However my canvas doesn't occupy the full space in the grid. What changes do i need to make in this program so that the canvas occupies the full space.
This is my xaml :-
<UserControl x:Class="SilverlightTestCanvasDemo.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="400">
<Grid x:Name="LayoutRoot" Background="White">
<Canvas x:Name="canvas" Margin="0" Background="Red">
<TextBlock Canvas.Left="84" TextWrapping="Wrap" Text="This is some text to test whether screen is moving" Canvas.Top="99" Height="84" Width="196" FontSize="18.667" FontFamily="Cambria"/>
</Canvas>
</Grid>
</UserControl>
This is the code :-
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
namespace SilverlightTestCanvasDemo
{
public partial class MainPage : UserControl
{
private bool _isDown = false;
private Point _lastPoint;
public MainPage()
{
InitializeComponent();
this.Loaded += MainPage_Loaded;
}
void MainPage_Loaded(object sender, RoutedEventArgs e)
{
canvas.MouseLeftButtonDown += canvas_MouseLeftButtonDown;
canvas.MouseLeftButtonUp += canvas_MouseLeftButtonUp;
canvas.MouseMove += canvas_MouseMove;
}
void canvas_MouseMove(object sender, System.Windows.Input.MouseEventArgs e)
{
if (_isDown)
{
Point point = e.GetPosition(canvas);
double deltaX = point.X - _lastPoint.X;
double deltaY = point.Y - _lastPoint.Y;
CompositeTransform transform = null;
if (!(canvas.RenderTransform is CompositeTransform))
{
transform = new CompositeTransform();
canvas.RenderTransform = transform;
}
else
{
transform = canvas.RenderTransform as CompositeTransform;
}
transform.TranslateX += deltaX;
transform.TranslateY += deltaY;
//canvas.Height += deltaY;
//canvas.Width += deltaX;
_lastPoint = e.GetPosition(canvas);
}
}
void canvas_MouseLeftButtonUp(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
_isDown = false;
}
void canvas_MouseLeftButtonDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
_isDown = true;
_lastPoint = e.GetPosition(canvas);
}
}
}
Thanks in advance :)

Answer 1

Try this:-
<Grid x:Name="LayoutRoot">
<Canvas x:Name="canvas" Margin="0" Background="AliceBlue">
<Canvas>
<TextBlock Canvas.Left="84" TextWrapping="Wrap" Text="This is some text to test whether screen is moving" Canvas.Top="99" Height="84" Width="196" FontSize="18.667" FontFamily="Cambria"/>
</Canvas>
</Canvas>
</Grid>
and tweak the mouse move code behind to this:-
void canvas_MouseMove(object sender, System.Windows.Input.MouseEventArgs e)
{
if (_isDown)
{
Point point = e.GetPosition(canvas);
double deltaX = point.X - _lastPoint.X;
double deltaY = point.Y - _lastPoint.Y;
CompositeTransform transform = null;
if (!(canvas.Children[0].RenderTransform is CompositeTransform))
{
transform = new CompositeTransform();
canvas.Children[0].RenderTransform = transform;
}
else
{
transform = canvas.Children[0].RenderTransform as CompositeTransform;
}
transform.TranslateX += deltaX;
transform.TranslateY += deltaY;
_lastPoint = e.GetPosition(canvas);
}
}
What's happening here is a second inner Canvas is being used as a caddy to hold the set of actual children. Now you need only transform this inner canvas to move all the content about.