the case is this one:
I have an image representing a schema, let's say a cross like the following
I need to include the image in a WPF UserControl and let the user click on each of the branches (red, green or blue...) and, according to the branch selected, do something different.
What would be the best way to solve this?
I tried with canvas but I don't find a way to trace correctly the background image with shapes (also because the real image is not so simple as the sample cross here)
thanks for any suggestion
It depends on the comlexity of shapes but it is not difficult to find the shape where mouse up event is fired by VisualTreeHelper.HitTest method.
Let's say there is a Canvas which has two Rectangles inside.
<Canvas Background="Transparent"
PreviewMouseUp="Canvas_PreviewMouseUp">
<Rectangle x:Name="Rect1" Canvas.Left="20" Canvas.Top="20"
Width="20" Height="20" Fill="Red"/>
<Rectangle x:Name="Rect2" Canvas.Left="80" Canvas.Top="80"
Width="20" Height="20" Fill="Green"/>
</Canvas>
Catching its PreviewMouseUp event, you can tell the Rectangle where that event is fired.
private void Canvas_PreviewMouseUp(object sender, MouseButtonEventArgs e)
{
var position = e.GetPosition((IInputElement)sender);
var result = VisualTreeHelper.HitTest((Visual)sender, position);
if (result.VisualHit is Rectangle rect)
{
Debug.WriteLine($"Hit {rect.Name}");
}
}
Related
I have a Canvas that contains a Rectangle. On that canvas, I bind a mousedown event to a command on the ViewModel. In that command, I am being passed the MouseEventArgs, but there the Target element is either the Canvas or the Rectangle. Where can I find in the MouseEventArgs the Canvas this event was fired from?
My code is more or less:
<Canvas Background="White">
<i:EventTrigger EventName="MouseLeftButtonDown">
<local:InteractiveCommand Command="{Binding CmdMouseLeftButtonDown}"/>
</i:EventTrigger>
<Rectangle Width="50" Height="50" />
</Canvas>
And in the ViewModel:
ICommand CmdMouseLeftButtonDown => new DelegateCommand<MouseEventArgs>(e =>
{
e.??? // <= Where do I find the Canvas here, whether I click on the Rectangle or Canvas?
}
Please do not answer with some hackish solution like e.MouseDevice.Target.Parent. This needs to work however complicated the element in the canvas is. It could contain another canvas for instance.
A view model is not supposed to have a reference to a UI element such as a Canvas or a Rectangle at all in the first place. This effectively breaks the MVVM pattern and that's why it makes no sense to pass the sender argument to the command.
You might as well get rid of the EventTrigger and invoke the command programmatically from the code-behind of the view:
<Canvas Background="White" MouseLeftButtonDown="Canvas_MouseLeftButtonDown">
<Rectangle Width="50" Height="50" Fill="Red" />
</Canvas>
private void Canvas_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
var yourViewModel vm = DataContext as YourClass;
vm.CmdMouseLeftButtonDown.Execute(sender as Canvas); //<-- pass the Canvas as a command argument or create a new command argument type that holds a reference to the Canvas
}
This is certainly not any worse than your current approach as far as the MVVM pattern is concerned. You are still invoking the very same command from the very same view and MVVM is not about eliminating code. It is about separation of concerns.
Your MouseEventArgs.Source will reference to the Canvas in any case but the MouseEventArgs.OriginalSource will referece to the Rectange if you have clicked on its area. It will be the control determined by pure hit testing.
Set <Canvas Background="Transparent" ... />
as answered in the following question by #Rob Fonseca-Ensor:
WPF: Canvas mouse events not firing on empty space
I'm implementing a templated control, which should work as virtual keyboard button - when you hold it, it displays a popup with additional options to choose.
I've implemented the popup more less in the following way:
<Grid>
<Border>Content</Border>
<Grid x:Name="gPopup" Visibility="Collapsed">
<StackPanel x:Name="spSubItems" Orientation="Horizontal" />
</Grid>
</Grid>
I show the popup by changing visibility to visible and setting negative margins for top and bottom. However, when I do that, and when the popup is actually larger than the control, the control is being resized to match its size - despite fact, that it is not inside:
How can I implement the popup, such that it won't expand the container it's on? And such that the container will still match size of its contents?
Edit: In response to comments and answers
I'm not sure if I'm understood correctly. Here's an image with explanation:
I'd like to keep the original container's size the same after showing the popup. I'm unsure how WrapPanel or DockPanel could help me with that.
The solution is simply to use Popup instead of positioned Grid.
Sample- Create a grid
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
<!-- Setting a Rectangle having transparent background which set the
Visibility of popup -->
<Rectangle Name="popupRect" Fill="#80000000" Visibility="Collapsed"/>
<!—Here in the above Code we are just filling the rectangle With the transparent BackGround -->
<!—Creating A Border -->
<Border Name="popupBorder" Background="{StaticResource PhoneChromeBrush}" BorderBrush="Red" BorderThickness="2"
HorizontalAlignment="Center" VerticalAlignment="Center" Visibility="Collapsed">
<!-- Creating A grid Inside the Border and Rectangle -->
</Grid>
Create event for which popup should appear(for both cancel and appear)-
private void cancelButton_Click(object sender, RoutedEventArgs e)
{
popupRect.Visibility = Visibility.Collapsed;
popupBorder.Visibility = Visibility.Collapsed;
}
private void popupButton_Click(object sender, RoutedEventArgs e)
{
popupRect.Visibility = Visibility.Visible;
popupBorder.Visibility = Visibility.Visible;
}
It will work, I guess.
Like spook says, put your gPopup Grid in a Popup element and show it by opening the popup. This won't affect the main visual tree.
The reason the embedded grid embiggens the border is that the outer grid has to expand to hold pGrid and the border expands to fill the outer grid.
I have a grid that contains an image.
<Grid Name="grid1">
<Image Name="image1" Stretch="None" Source="C:\Users\User\Desktop\image.jpg"/>
</Grid>
If the size of image was greater than the size of the grid, I want to scale it manually by render transform to fit the grid. I don't want to use Stretch="Fill" because I need the scale factor.
Is there any way to detect the situation that an UIElement goes out of view?
I need your help.
You could simply set the Stretch property to Uniform (or perhaps Fill) and calculate the scaling factor from the ActualWidth of the Image and the Width of the ImageSource, whenever you need it. The sample below does the calculation in a SizeChanged handler, but it could be anywhere else.
<Image Name="image1" Stretch="Uniform" Source="C:\Users\User\Desktop\image.jpg"
SizeChanged="ImageSizeChanged"/>
The calculation looks like this:
private void ImageSizeChanged(object sender, SizeChangedEventArgs e)
{
var scale = image1.ActualWidth / image1.Source.Width;
}
As Uniform is the default value of the Stretch property, you wouldn't have to set it at all.
I'm not sure why you would want to rescale your image manually when WPF can do it for you...
Instead of putting the image straight into the grid, use a Viewbox control:
<Grid Name="grid1">
<Viewbox>
<Image Name="image1" Stretch="None" Source="C:\Users\User\Desktop\image.jpg"/>
</Viewbox>
</Grid>
The Viewbox will automatically scale the picture to fit inside the grid...
If there is a way to send mouse click event by location programatically it would be great, but if theres another approach that can solve following problem this it is fine too.
In my situation I got a canvas taking up whole application size (covering it completely) and when user clicks it with mouse I want to hide it, and then pass through this mouse click (taking its location x & y from user) to anything that is under canvas (in my case canvas visibility goes to collapsed so controls under it can be seen now).
I am guessing it is impossible, cause certain features like run silverlight fullscreen can only be done in button click handler (correct me if im wrong here).
But is there a place where I can read about those security based limitations of silverlight UI ?
you have to add an click event handler to your canvas. In this handler you get the x and y positon of your click (via MouseButtonEventArgs) and then you can use the VisualTreeHelper to get your "hit elements".
Lets assume the following xaml:
<Grid x:Name="LayoutRoot" Background="White">
<Button Width="50" Height="50" VerticalAlignment="Top" HorizontalAlignment="Left"/>
<TextBox Text="MyText" Width="200" Height="100" VerticalAlignment="Top" HorizontalAlignment="Left"/>
<Canvas Background="Red" x:Name="MyCanvas" />
</Grid>
with the following code behind:
public MainPage()
{
InitializeComponent();
MyCanvas.AddHandler(MouseLeftButtonUpEvent, new MouseButtonEventHandler(handler), true);
}
void handler(object sender, MouseButtonEventArgs e)
{
var point = new Point(e.GetPosition(this).X, e.GetPosition(this).Y);
var elements = VisualTreeHelper.FindElementsInHostCoordinates(point, this);
foreach (var uiElement in elements)
{
if (uiElement is TextBox){
((TextBox) uiElement).Focus();
break;
}
if(uiElement is Button)
{
//do button stuff here
break;
}
}
MyCanvas.Visibility = Visibility.Collapsed;
MyCanvas.RemoveHandler(MouseLeftButtonUpEvent, new MouseButtonEventHandler(handler));
}
But: In this simple example, you get at about 20 hit elements. But they are sorted in the correct "z-Index". So you can iterate through it and the first interesting element for you is where you could break(Maybe you can do this with LINQ, too). So for me, I know that the first hit TextBox is what I want to focus.
Is this what you need?
BR,
TJ
I have a Canvas, to which I've added several thousand polygons.
I would like to be able to zoom in (which I'm doing via a ScaleTransform.
However I've been trying to use a Canvas.Clip as well to only draw a portion of the Canvas, but as soon as the ScaleTransform values are changed, the clipping stops working...
<Canvas Grid.Row="1" Margin="10" x:Name="cnvMain" Background="Transparent" >
<Canvas.Clip>
<RectangleGeometry x:Name="CanvasClip" Rect="0, 0, 300, 300"/>
</Canvas.Clip>
<Canvas.RenderTransform>
<ScaleTransform x:Name="CanvasScaleTransform" ScaleX="1" ScaleY="1"></ScaleTransform>
</Canvas.RenderTransform>
</Canvas>
And in my codebehind,
private void slScale_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
{
CanvasScaleTransform.ScaleX = slScale.Value;
CanvasScaleTransform.ScaleY = slScale.Value;
}
Am I doing anything obviously wrong?
The ScaleTransform (as all other transformations) is applied AFTER every other rendering. That means, first the cliprect is applied, then the scale transform. A solution would be to do the clipping one level higher, by putting another canvas around this one.
Put a border around your canvas and attach the clip region to the border rather than the canvas.