Develop Reference

Drawing multiple rectangles chokes my WPF app

I am working in my own editor for making WPF forms. My issue is that I am having the worst time selecting multiple controls (buttons, labels, etc) and dragging them smoothly across the main window. My application chokes when I try to drag, oh say, 20 selected buttons at the same time.
I found that the culprit is the fact that I am drawing multiple rectangles for each object as they are being dragged and this function is being called in the MouseMove event.
void ControlObjectControl_MouseMove(object sender, MouseEventArgs e)
{
if (newPosition != oldPosition)
{
DragSelection(newPosition);
}
}
private void DragSelection(Point newPosition)
{
foreach (FrameworkElement item in designer.SelectionService.CurrentSelection)
{
if (item is ObjectControl)
(item as ObjectControl).m_ParentControlObject.Position = new System.Drawing.Rectangle() { X = X, Y = Y, Width = (int)item.Width, Height = (int)item.Height };
//..There's code that calculates the item's position and dimensions
}
}
How do I make it to where it only draws the rectangle once and I am still able to see my selected object(s) move smoothly when I drag them?

I did something similar in my application except I used a TranslateTransform to move my elements. Each "frame" (every mouse move) that I was dragging, I got the position of the mouse and compared that to the previous position of the mouse. I would then set a new TranslateTransform X/Y values equal to the X/Y mouse position change and then would give that to the RenderTransform of each object I wanted to move. Something like:
void ControlObjectControl_MouseMove(object sender, MouseEventArgs e)
{
if (dragging)
{
// Get the change in Location
mouseLocation = Mouse.GetPosition();
Point deltaLocation = mouseLocation - previousLocation;
// Make a new transform
TranslateTransform transform = new TranslateTransform();
transform.X = deltaLocation.X;
transform.Y = deltaLocation.Y;
// Apply the transform
// foreach thing
thing.RenderTransform = transform;
// set previous location
previousLocation = mouseLocation;
}
}
Now your objects only get drawn once and only their positions get changed. Hope this helps

Move object in ViewportControl WP8

I'm using the ViewportControl to scroll around and zoom in and out of my Map. In this map I've got a green ellipse which I wish to move around. Previously I used a ScrollViewer where I set the manipulationMode of the ScrollViewer to control, and thus making it capable of moving my ellipse around. However I can't find a similar way for the ViewportControl. So is there a way to move my ellipse around?
The code I've got so far is:
The xaml part where I have my ViewportControl around my map
<ViewportControl x:Name="ViewPortTestTest" Bounds="0,0,1271,1381.5" Height="480" Width="800" Canvas.ZIndex="1" Grid.Row="1">
<ViewportControl.RenderTransform>
<CompositeTransform x:Name="myTransformTest"/>
</ViewportControl.RenderTransform>
<View:Map x:Name="ZoomableContent" >
<View:Map.RenderTransform>
<CompositeTransform x:Name="myTransform" />
<!-- ScaleX="{Binding Map.imageScale}" ScaleY="{Binding Map.imageScale}"/>-->
</View:Map.RenderTransform>
</View:Map>
</ViewportControl>
It is in the map where I add the ellipse. The viewModel where I manipulate my ellipse
public void ManStart(ManipulationStartedEventArgs e)
{
e.Handled = true;
ViewportControl VP = FindParentOfType<ViewportControl>(ChampViewModelSel);
}
}
public void ManDelta(ManipulationDeltaEventArgs e)
{
e.Handled = true;
Point fingerPosition = e.DeltaManipulation.Translation;
Temp.x = fingerPosition.X;
Temp.y = fingerPosition.Y;
}
}
Where Temp.x and Temp.y is the new position of the ellipse.

I think you could try to use TouchPanel from XNA and Touch.FrameReported event for this purpose. Probably Map and VieportControl handle the manipulation event so it won't fire with your code.
In my proposal Touch_FrameReported will be fired every time you touch the screen, so we have to check only for situations we need - here comes IsGestureAvailable and TouchAction. Simple code can look like this:
public MainPage()
{
InitializeComponent();
TouchPanel.EnabledGestures = GestureType.FreeDrag;
Touch.FrameReported += Touch_FrameReported;
}
private void Touch_FrameReported(object sender, TouchFrameEventArgs e)
{
if (TouchPanel.IsGestureAvailable) // check only dragging
{
// get point relative to Viewport
TouchPoint mainTouch = e.GetPrimaryTouchPoint(ViewPortTestTest);
// check if drag has completed (key up)
if (mainTouch.Action == TouchAction.Up)
{
Temp.x = mainTouch.Position.X;
Temp.y = mainTouch.Position.Y;
}
}
}
You can read more about Gestures here at MSDN and on this blog.
You can also check other GestureTypes and for example check if TouchAction.Down and user clicked on your Ellipse.
These methods give you many possibilities to read TouchPoints and their Actions so maybe it will help.
It took me a while to find a way how to disable Vieport. I've found a little 'hack' for that, it will be easier if your VieportControl was only horizontal or vertical (there is a lock property, but doesn't work for both). Here is this little 'hack' which should disable both horizontal and vertical scrolling:
Rect originalBounds = new Rect();
private void Touch_FrameReported(object sender, TouchFrameEventArgs e)
{
TouchPoint myTouchPoint = e.GetPrimaryTouchPoint(ViewPortTestTest);
// disable scrolling
if (myTouchPoint.Action == TouchAction.Down) // here probably some other statement like if user hit ellipse
{
originalBounds = ViewPortTestTest.Bounds;
ViewPortTestTest.Bounds = ViewPortTestTest.Viewport; // set current view as Bounds
}
// more logic
// enable once again
if (myTouchPoint.Action == TouchAction.Up)
ViewPortTestTest.Bounds = originalBounds;
}
When I want to disable scrolling - I set bounds of the VieportControl to the current view (and I remember original ones). When I want to enable scrolling - I bring back original bounds.
As I've tested it - it is working - of course it needs a little more logic in locking if statement, so that it won't lock every time you touch the screen.

Drag Ovalshape across form

So I have a bit of a problem with moving Ovalshapes around a form. The goal is to have a circle move within the bounds of two other circles, one placed inside the other and the moving circle essentially moving around them.
I am having trouble moving the circle with the mouse. Whenever I click and hold the circle, the circle moves to the coordinates of the location I clicked on the circle, such that if I click in the middle of an Ovalshape of size 10, it would set the circle's location to (5,5).
Here is what I have:
public partial class Form1 : Form
{
int smallRadius;
int largeRadius;
int movingRadius;
int distanceFromCenterToLocation;
bool mouseDown;
Point movingCenter;
Point returnPoint;
public Form1()
{
mouseDown = false;
InitializeComponent();
smallRadius = (ovalShape1.Right - ovalShape1.Left) / 2;
largeRadius = (ovalShape2.Right - ovalShape2.Left) / 2;
Point center = new Point(ovalShape1.Left + smallRadius, ovalShape1.Top + smallRadius);
ovalShape3.Height = largeRadius - smallRadius;
ovalShape3.Width = largeRadius - smallRadius;
movingRadius = (ovalShape3.Right - ovalShape3.Left) / 2;
ovalShape3.Location = new Point(center.X - (movingRadius), center.Y - largeRadius);
movingCenter = new Point(ovalShape3.Left + movingRadius, ovalShape3.Top + movingRadius);
distanceFromCenterToLocation = Convert.ToInt32(Math.Sqrt(Math.Pow(movingRadius, 2.0) + Math.Pow(movingRadius, 2.0)));
int middleRadius = center.X - movingCenter.X;
}
private void ovalShape3_MouseUp(object sender, MouseEventArgs e)
{
mouseDown = false;
}
private void ovalShape3_MouseDown(object sender, MouseEventArgs e)
{
mouseDown = true;
}
private void ovalShape3_MouseMove(object sender, MouseEventArgs e)
{
if (mouseDown)
{
ovalShape3.Location = e.Location;
}
}
}

For some reason OvalShape isn't derived from Control and doesn't behave like a control.
When a control receives a mouse event the Location property of the MouseEventArgs holds the coordinates relative to the upper-left corner of the form. Shapes however receive the coordinates relative to their own upper-left corner.
When a mouse button is pressed over a control it will capture the mouse so that subsequent events are sent to the same control until you release the button. Shapes only receive mouse events if the mouse is over the shape no matter if a mouse button is pressed. Once you move the mouse to the top or left the shape doesn't receive any mouse events. Therefore the shape doesn't follow the mouse and also the MouseUp event is not handled.
All shapes in a form are embedded in a single control of type ShapeContainer. This is created automatically when you add a shape to a form in the Visual Studio designer. To get the expected behavior you need to find that ShapeContainer (probably called shapeContainer1) and handle its mouse events instead:
public Form1()
{
InitializeComponent();
// do your initialization
...
// assign the events to the ShapeContainer
// don't forget to remove the handlers from ovalShape3 in the designer!!!
ShapeContainer container = ovalShape3.Parent;
container.MouseUp += ovalShape3_MouseUp;
container.MouseDown += ovalShape3_MouseDown;
container.MouseMove += ovalShape3_MouseMove;
}

TranslateTransform offsets element a bit too much after multiple transforms in Windows 8 store application

I have a draggable element in a StackPanel in a Windows 8 store app. My goal is simple: drag the item somewhere on the screen and immediately after the user stops dragging it the element should return to its original starting position.
I have the following code which is meant to accomplish this task:
private void grdCover_ManipulationCompleted(object sender, ManipulationCompletedRoutedEventArgs e)
{
Grid coverControl = sender as Grid;
double xOffset = -e.Cumulative.Translation.X;
double yOffset = -e.Cumulative.Translation.Y;
if (coverControl.RenderTransform is TranslateTransform)
{
TranslateTransform existingTransform = coverControl.RenderTransform as TranslateTransform;
existingTransform.X += xOffset;
existingTransform.Y += yOffset;
}
else
{
TranslateTransform transform = new TranslateTransform();
transform.X = xOffset;
transform.Y = yOffset;
coverControl.RenderTransform = transform;
}
}
The code sort of works. The screen looks like this upon application start:
The top element, which looks like a H is well aligned with the bottom element which looks like a U. When I first drag the H element it jumps back to its well aligned position, or at least any misalignment is so little that it's hardly perceivable to the naked eye. As I keep dragging and releasing the H element it gets more and more misaligned like this:
After 15-20 dragging moves the H element gets completely misplaced:
The problem might be due to some rounding error of the double values in the Point objects when they are translated into pixels, but that's only a wild guess. Also, on a high resolution device, such as my PC it takes more moves for the misalignment to become visible than on a lower resolution one, such as the Windows Simulator in Visual Studio.
Some other code that may be related to this issue:
I perform the dragging operation with the following code:
private void Grid_ManipulationDelta(object sender, ManipulationDeltaRoutedEventArgs e)
{
TranslateTransform translateTransform = (sender as Grid).RenderTransform as TranslateTransform;
translateTransform.X += e.Delta.Translation.X;
translateTransform.Y += e.Delta.Translation.Y;
}
I also have the following event handler in place to stop the element from moving too much on the screen after the user is done dragging the element:
private void grdCover_ManipulationInertiaStarting(object sender, ManipulationInertiaStartingRoutedEventArgs e)
{
e.TranslationBehavior.DesiredDeceleration = 10000000000000000;
e.Handled = true;
}
In case you're wondering I wanted to set the desired deceleration to Double.Max to block any further "sliding" movement on the screen but I got an exception saying it was out of bounds. So instead I chose this arbitrary large value.
I have no extra margins or padding on the layout root or the element to be moved or its container.
Any ideas are welcome.
Thanks, Andras

OK, I got it to work. The problem was that there was a slight mismatch between the Point coordinates in the following code bits:
TranslateTransform translateTransform = (sender as Grid).RenderTransform as TranslateTransform;
translateTransform.X += e.Delta.Translation.X;
translateTransform.Y += e.Delta.Translation.Y;
and
double xOffset = -e.Cumulative.Translation.X;
double yOffset = -e.Cumulative.Translation.Y;
The solution was to retrieve the value of
e.Delta.Translation.X
and
e.Delta.Translation.Y
and assign their values to the variables xOffset and yOffset. Retrieving the values of
e.Cumulative.Translation.X
and
e.Cumulative.Translation.Y
gave slightly different coordinates so the element kept jumping back to the wrong location.

Rotate graphic towards mouse in WPF (like an analog dial)

In WPF/C# how would I rotate a "graphic" to face the current mouse position?
Basically what I want is a "wheel" UI Control (like an analog volume dial). I want to be able to click and drag the dial and it will rotate to follow the mouse. Then when I release the mouse it will stop following (obviously!).
How would I create one of these? does one already exist somewhere?

I haven't seen any controls like this around (though it's been a while since I looked at all of the controls that WPF control vendors were offering), but it's relatively straightforward to create one.
All you'd have to do is create a custom control containing an Image (or XAML drawing) that you can rotate to follow the mouse. Then, bind a RotateTransform to an 'Angle' DependencyProperty on your custom control so that when 'angle' is updated, the image/drawing rotates to match:
<UserControl x:Class="VolumeControlLibrary.VolumeControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:VolumeControlLibrary"
Height="60" Width="60">
<Image Source="/VolumeControl;component/knob.png" RenderTransformOrigin="0.5,0.5" >
<Image.RenderTransform>
<RotateTransform Angle="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:VolumeControl}}, Path=Angle}"/>
</Image.RenderTransform>
</Image>
</UserControl>
Setting RenderTransformOrigin to "0.5, 0.5" ensures that the control rotates around its center, rather than rotating around the top left corner; we'll have to compensate for this in the angle calculation too.
In the code behind file for your control, add handlers for the mouse and the Angle DependencyProperty:
public partial class VolumeControl : UserControl
{
// Using a DependencyProperty backing store for Angle.
public static readonly DependencyProperty AngleProperty =
DependencyProperty.Register("Angle", typeof(double), typeof(VolumeControl), new UIPropertyMetadata(0.0));
public double Angle
{
get { return (double)GetValue(AngleProperty); }
set { SetValue(AngleProperty, value); }
}
public VolumeControl()
{
InitializeComponent();
this.MouseLeftButtonDown += new MouseButtonEventHandler(OnMouseLeftButtonDown);
this.MouseUp += new MouseButtonEventHandler(OnMouseUp);
this.MouseMove += new MouseEventHandler(OnMouseMove);
}
private void OnMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
Mouse.Capture(this);
}
private void OnMouseUp(object sender, MouseButtonEventArgs e)
{
Mouse.Capture(null);
}
private void OnMouseMove(object sender, MouseEventArgs e)
{
if (Mouse.Captured == this)
{
// Get the current mouse position relative to the volume control
Point currentLocation = Mouse.GetPosition(this);
// We want to rotate around the center of the knob, not the top corner
Point knobCenter = new Point(this.ActualHeight / 2, this.ActualWidth / 2);
// Calculate an angle
double radians = Math.Atan((currentLocation.Y - knobCenter.Y) /
(currentLocation.X - knobCenter.X));
this.Angle = radians * 180 / Math.PI;
// Apply a 180 degree shift when X is negative so that we can rotate
// all of the way around
if (currentLocation.X - knobCenter.X < 0)
{
this.Angle += 180;
}
}
}
}
Capturing the mouse ensures that your control will continue to get mouse updates even when the user mouses off of the control (until they let go of the click), and by getting the position of the mouse relative to the current element (the control), your calculation should always be the same regardless of where the control actually renders on screen.
In this example, when the mouse moves we calculate the angle between it and the center of the control, and then set this angle to the Angle DependencyProperty we created. Since the image we're displaying is bound to this angle property, WPF automatically applies the new value, which results in the knob rotating in combination with the mouse moving.
Using the control in your solution is easy; just add:
<local:VolumeControl />
You would bind to the Angle property on VolumeControl if you wanted to bind the value of the knob to something in your application; that value is currently in degrees, but could add an additional property to convert between an angle in degrees and a value that makes sense to you (say, a value from 0 - 10).

To add to that post, the angle between the mouse point and the object point is calculated like:
dot = currentLocation.X * objectPosition.X + currentLocation.Y * objectPosition.Y;
angle = Math.Acos(dot);

In my case i have dynamically created shapes which shall rotated toward mouse direction. To solve this I used a lightweight function. All I need is following:
The centerpoint of the current selected shape
The point from the last mouseover step
And the point from the current mouseover step
It is not necessary to use methods from the Math library. I calculate the angle which depends on the difference of the current mouse over point and the previous mouse over point and the position in relation o the center point. Finally I add the angle on the exisitng angle of the current object.
private void HandleLeftMouseDown(MouseButtonEventArgs eventargs)
{
//Calculate the center point of selected object
//...
//assuming Point1 is the top left point
var xCenter = (_selectedObject.Point2.X - _selectedObject.Point1.X) / 2 + _selectedObject.Point1.X
var yCenter = (_selectedObject.Point2.Y - _selectedObject.Point1.Y) / 2 + _selectedObject.Point1.Y
_selectedObjectCenterPoint = new Point((double) xCenter, (double) yCenter);
//init set of last mouse over step with the mouse click point
var clickPoint = eventargs.GetPosition(source);
_lastMouseOverPoint = new Point(clickPoint.X,clickPoint.Y);
}
private void HandleMouseMove(MouseEventArgs eventArgs)
{
Point pointMouseOver = eventArgs.GetPosition(_source);
//Get the difference to the last mouse over point
var xd = pointMouseOver.X - _lastMouseOverPoint.X;
var yd = pointMouseOver.Y - _lastMouseOverPoint.Y;
// the direction depends on the current mouse over position in relation to the center point of the shape
if (pointMouseOver.X < _selectedObjectCenterPoint.X)
yd *= -1;
if (pointMouseOver.Y > _selectedObjectCenterPoint.Y)
xd *= -1;
//add to the existing Angle
//not necessary to calculate the degree measure
_selectedObject.Angle += (xd + yd);
//save mouse over point
_lastMouseOverPoint = new Point(pointMouseOver.X, pointMouseOver.Y);
}