I'm trying to make an animation for my C# program. There's a space rocket that ascends 8 pixels vertically with a timer interval of 25ms. I've managed to make the animation but since the picturebox's background (I've used for the rocket) is set to transparent it flickers the form's background image everytime it moves. What can I do to prevent it?
The code I've used for timer tick :
pictureBox1.Top -= 8;
P.S: I've tried to change the picturebox with panel, slow downed the rocket and timer but nothing seemed to change.
Well i haven't tried it myself now.
There needs to be a render event which you can hook to and make manipulations to your UI which would render smoothly.
Control.Paint
Try something like these :
private void Form1_Load(object sender, System.EventArgs e)
{
pictureBox1.Paint += new System.Windows.Forms.PaintEventHandler(this.pictureBox1_Paint);
}
private void pictureBox1_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
{
pictureBox1.Top -= 8;
}
Again this isn't tested and i haven't developed any thing in winforms for ages.
But that's the direction you should go for to render things smoothly.
That double buffered thing mentioned above is also a factor in some cases.
but this is mainly the way to do it.
I am developing a windows 8 app and have to enable panning on the image through mouse.It is working on the Tablet but somehow I need to enable it from the mouse also.
And I am writing pointer wheel changed event for zooming the image but it is calling just once.
This is my code for Zooming
private void MyScrollView_PointerWheelChanged(object sender, PointerRoutedEventArgs e)
{
MyScrollView.ChangeView(MyScrollView.HorizontalOffset + 40, MyScrollView.VerticalOffset + 20, MyScrollView.ZoomFactor + 0.1f);
}
Any help would be grateful to me.
I encountered the same problem while trying to do the same thing. Your code will work as long as the Scrollviewer is not handling scroll event internally.
To explain more closely:
When all of the content of the Scrollviewer is visible (ie no need to scroll), the Scrollviewer will not handle any scroll event internally and the event will fire and you handle it in your code.
If, however, there is content that is larger than the visible area of the Scrollviewer, the scrollbars will show up. At this point the Scrollviewer will handle scroll event (so that when you scroll, you move the scrollbar). This is the expected behaviour, as it is in web browsers and other applications with content that's larger than the viewport or visible area. The event will no longer fire and your handler will not run because the internal logic stops the event from ever reaching your code.
You can capture the event by setting e.Handled to true like so:
private void MyScrollView_PointerWheelChanged(object sender, PointerRoutedEventArgs e)
{
e.Handled = true; // Tell the event system that the event has been handled and it should not execute any more handlers.
MyScrollView.ChangeView(MyScrollView.HorizontalOffset + 40, MyScrollView.VerticalOffset + 20, MyScrollView.ZoomFactor + 0.1f);
}
But I found it to be a bad experience. The zooming is not cenetered on the pointer and moves the content in a way that's confusing and jarring. I found no good way to override this.
As a last point, I want to mention that there's built in zoom functionality in the Scrollviewer by using Ctrl+Scroll. Works nicely and it's the same shortcut used in browsers.
I'm creating a large number of texts in WPF using DrawText and then adding them to a single Canvas.
I need to redraw the screen in each MouseWheel event and I realized that the performance is a bit slow, so I measured the time the objects are created and it was less than 1 milliseconds!
So what could be the problem? A long time ago I guess I read somewhere that it actually is the Rendering that takes the time, not creating and adding the visuals.
Here is the code I'm using to create the text objects, I've only included the essential parts:
public class ColumnIdsInPlan : UIElement
{
private readonly VisualCollection _visuals;
public ColumnIdsInPlan(BaseWorkspace space)
{
_visuals = new VisualCollection(this);
foreach (var column in Building.ModelColumnsInTheElevation)
{
var drawingVisual = new DrawingVisual();
using (var dc = drawingVisual.RenderOpen())
{
var text = "C" + Convert.ToString(column.GroupId);
var ft = new FormattedText(text, cultureinfo, flowdirection,
typeface, columntextsize, columntextcolor,
null, TextFormattingMode.Display)
{
TextAlignment = TextAlignment.Left
};
// Apply Transforms
var st = new ScaleTransform(1 / scale, 1 / scale, x, space.FlipYAxis(y));
dc.PushTransform(st);
// Draw Text
dc.DrawText(ft, space.FlipYAxis(x, y));
}
_visuals.Add(drawingVisual);
}
}
protected override Visual GetVisualChild(int index)
{
return _visuals[index];
}
protected override int VisualChildrenCount
{
get
{
return _visuals.Count;
}
}
}
And this code is run each time the MouseWheel event is fired:
var columnsGroupIds = new ColumnIdsInPlan(this);
MyCanvas.Children.Clear();
FixedLayer.Children.Add(columnsGroupIds);
What could be the culprit?
I'm also having trouble while panning:
private void Workspace_MouseMove(object sender, MouseEventArgs e)
{
MousePos.Current = e.GetPosition(Window);
if (!Window.IsMouseCaptured) return;
var tt = GetTranslateTransform(Window);
var v = Start - e.GetPosition(this);
tt.X = Origin.X - v.X;
tt.Y = Origin.Y - v.Y;
}
I'm currently dealing with what is likely the same issue and I've discovered something quite unexpected. I'm rendering to a WriteableBitmap and allowing the user to scroll (zoom) and pan to change what is rendered. The movement seemed choppy for both the zooming and panning, so I naturally figured the rendering was taking too long. After some instrumentation, I verified that I'm rendering at 30-60 fps. There is no increase in render time regardless of how the user is zooming or panning, so the choppiness must be coming from somewhere else.
I looked instead at the OnMouseMove event handler. While the WriteableBitmap updates 30-60 times per second, the MouseMove event is only fired 1-2 times per second. If I decrease the size of the WriteableBitmap, the MouseMove event fires more often and the pan operation appears smoother. So the choppiness is actually a result of the MouseMove event being choppy, not the rendering (e.g. the WriteableBitmap is rendering 7-10 frames that look the same, a MouseMove event fires, then the WriteableBitmap renders 7-10 frames of the newly panned image, etc).
I tried keeping track of the pan operation by polling the mouse position every time the WriteableBitmap updates using Mouse.GetPosition(this). That had the same result, however, because the returned mouse position would be the same for 7-10 frames before changing to a new value.
I then tried polling the mouse position using the PInvoke service GetCursorPos like in this SO answer eg:
[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool GetCursorPos(out POINT lpPoint);
[StructLayout(LayoutKind.Sequential)]
public struct POINT
{
public int X;
public int Y;
public POINT(int x, int y)
{
this.X = x;
this.Y = y;
}
}
and this actually did the trick. GetCursorPos returns a new position each time it is called (when the mouse is moving), so each frame is rendered at a slightly different position while the user is panning. The same sort of choppiness seems to be affecting the MouseWheel event, and I have no idea how to work around that one.
So, while all of the above advice about efficiently maintaining your visual tree is good practice, I suspect that your performance issues may be a result of something interfering with the mouse event frequency. In my case, it appears that for some reason the rendering is causing the Mouse events to update and fire much slower than usual. I'll update this if I find a true solution rather than this partial work-around.
Edit: Ok, I dug into this a little more and I think I now understand what is going on. I'll explain with more detailed code samples:
I am rendering to my bitmap on a per-frame basis by registering to handle the CompositionTarget.Rendering event as described in this MSDN article. Basically, it means that every time the UI is rendered my code will be called so I can update my bitmap. This is essentially equivalent to the rendering that you are doing, it's just that your rendering code gets called behind the scenes depending on how you've set up your visual elements and my rendering code is where I can see it. I override the OnMouseMove event to update some variable depending on the position of the mouse.
public class MainWindow : Window
{
private System.Windows.Point _mousePos;
public Window()
{
InitializeComponent();
CompositionTarget.Rendering += CompositionTarget_Rendering;
}
private void CompositionTarget_Rendering(object sender, EventArgs e)
{
// Update my WriteableBitmap here using the _mousePos variable
}
protected override void OnMouseMove(MouseEventArgs e)
{
_mousePos = e.GetPosition(this);
base.OnMouseMove(e);
}
}
The problem is that, as the rendering takes more time, the MouseMove event (and all mouse events, really) gets called much less frequently. When the rendering code takes 15ms, the MouseMove event gets called every few ms. When the rendering code takes 30ms, the MouseMove event gets called every few hundred milliseconds. My theory on why this happens is that the rendering is happening on the same thread where the WPF mouse system updates its values and fires mouse events. The WPF loop on this thread must have some conditional logic where if the rendering takes too long during one frame it skips doing the mouse updates. The problem arises when my rendering code takes "too long" on every single frame. Then, instead of the interface appearing to slow down a little bit because the rendering is taking 15 extra ms per frame, the interface stutters greatly because that extra 15ms of render time introduces hundreds of milliseconds of lag between mouse updates.
The PInvoke workaround I mentioned before essentially bypasses the WPF mouse input system. Every time the rendering happens it goes straight to the source, so starving the WPF mouse input system no longer prevents my bitmap from updating correctly.
public class MainWindow : Window
{
private System.Windows.Point _mousePos;
public Window()
{
InitializeComponent();
CompositionTarget.Rendering += CompositionTarget_Rendering;
}
private void CompositionTarget_Rendering(object sender, EventArgs e)
{
POINT screenSpacePoint;
GetCursorPos(out screenSpacePoint);
// note that screenSpacePoint is in screen-space pixel coordinates,
// not the same WPF Units you get from the MouseMove event.
// You may want to convert to WPF units when using GetCursorPos.
_mousePos = new System.Windows.Point(screenSpacePoint.X,
screenSpacePoint.Y);
// Update my WriteableBitmap here using the _mousePos variable
}
[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool GetCursorPos(out POINT lpPoint);
[StructLayout(LayoutKind.Sequential)]
public struct POINT
{
public int X;
public int Y;
public POINT(int x, int y)
{
this.X = x;
this.Y = y;
}
}
}
This approach didn't fix the rest of my mouse events (MouseDown, MouseWheel, etc), however, and I wasn't keen on taking this PInvoke approach for all of my mouse input, so I decided I better just stop starving the WPF mouse input system. What I ended up doing was only updating the WriteableBitmap when it really needed to be updated. It only needs to be updated when some mouse input has affected it. So the result is that I receive mouse input one frame, update the bitmap on the next frame but do not receive more mouse input on the same frame because the update takes a few milliseconds too long, and then the next frame I'll receive more mouse input because the bitmap didn't need to be updated again. This produces a much more linear (and reasonable) performance degradation as my rendering time increases because the variable length frame times just sort of average out.
public class MainWindow : Window
{
private System.Windows.Point _mousePos;
private bool _bitmapNeedsUpdate;
public Window()
{
InitializeComponent();
CompositionTarget.Rendering += CompositionTarget_Rendering;
}
private void CompositionTarget_Rendering(object sender, EventArgs e)
{
if (!_bitmapNeedsUpdate) return;
_bitmapNeedsUpdate = false;
// Update my WriteableBitmap here using the _mousePos variable
}
protected override void OnMouseMove(MouseEventArgs e)
{
_mousePos = e.GetPosition(this);
_bitmapNeedsUpdate = true;
base.OnMouseMove(e);
}
}
Translating this same knowledge to your own particular situation: for your complex geometries that lead to performance issues I would try some type of caching. For example, if the geometries themselves never change or if they don't change often, try rendering them to a RenderTargetBitmap and then add the RenderTargetBitmap to your visual tree instead of adding the geometries themselves. That way, when WPF is performing it's rendering path, all it needs to do is blit those bitmaps rather than reconstruct the pixel data from the raw geometric data.
#Vahid: the WPF system is using [retained graphics]. What you eventually should do, is devise a system where you only send "what has changed compared to previous frame" - nothing more, nothing less, you should not be creating new objects at all. It's not about "creating objects takes zero seconds", it's about how it affects rendering and the time. It's about letting the WPF do it's job using caching.
Sending new objects to the GPU for rendering=slow. Sending only updates to the GPU which tells what objects moved=fast.
Also, it's possible to create Visuals in an arbitrary thread to improve the performance (Multithreaded UI: HostVisual - Dwayne Need). That all said, if your project is pretty complex in 3D wise - there's good chance that WPF won't just cut it. Using DirectX.. directly, is much, much, more performant!
Some of the articles I suggest you to read & understand:
[Writing More Efficient ItemsControls -
Charles Petzold] - understand the process how one achieves better drawing rate in WPF.
As for why your UI is lagging, Dan answer seems to be spot on. If you are trying to render more than WPF can handle, the input system will suffer.
The likely culprit is the fact that you are clearing out and rebuilding your visual tree on each wheel event. According to your own post, that tree includes a "large number" of text elements. For each event that comes in, each of those text elements must be recreated, reformatted, measured, and eventually rendered. That is not the way to accomplish simple text scaling.
Rather than setting a ScaleTransform on each FormattedText element, set one on the element containing the text. Depending on your needs, you can set a RenderTransform or LayoutTransform. Then, when you receive wheel events, adjust the Scale property accordingly. Don't rebuild the text on each event.
I would also do what other have recommended and bind an ItemsControl to the list of columns and generate the text that way. There is no reason you should need to do this by hand.
I have a SurfaceListBox that inside has a ScrollViewer. I have access to that ScrollViewer and I want to detect when the scrolling ends. Since it is a touch app and I can drag it, right now I'm detecting the PreviewTouchUp to do what I want, however, if I do a fast swipe, like you would do on a smartphone, because the content of the ScrollViewer is still dragging/scrolling, the PreviewTouchUp does not reflect the end of the scrolling, but is instead triggered before.
I have tried Manipulation events and several others on both the ScrollViewer and the SurfaceListBox. I have also tried ScrollViewer.PanningDeceleration and honestly, I don't see a difference. Basically, no luck so far.
So, how can I detect the end of the scrolling, even after the PreviewTouchUp in a ScrollViewer?
Can't you just handle the ScrollViewer.ScrollChanged event? From the linked page, it says that it...
Occurs when changes are detected to the scroll position, extent, or viewport size.
So you could just start a DispatcherTimer to wait for a short instant each time the event has been raised, eg. when it is scrolling. When the scrolling stops and the event stops being raised, then the Tick handler will be called and you can do whatever you like in it. Try something like this:
DispatcherTimer timer = new DispatcherTimer();
timer.Interval = new TimeSpan(0, 0, 0, 0, 250);
timer.Tick += Timer_Tick;
...
private void ScrollChanged(object sender, ScrollChangedEventArgs e)
{
if (timer.IsEnabled) timer.Stop();
timer.Start();
}
private void Timer_Tick(object sender, EventArgs e)
{
timer.Stop();
// Do what you want now that scrolling has stopped
}
Seems a bit messy but Sheridan's solution was the best way I could find to determine when a scrollviewer has stopped moving. I just tweaked the timer interval and, more importantly, put the "// Do what you want now that scrolling has stopped" between hittestvisible = false and then hittestvisible = true on the scrollviewer control.
i wonder how it works..
i have this code. it should paint pictures (Bitmap images ) on the form..constantly. but i dont know how often it is triggered. i need it to be triggered very often (at least every 1-2 seconds). i need it to send the parameters to another object that i have (Game game).. so game object will draw everything
public void Form1_Paint(object sender, EventArgs e)
{
//the animation has 4 cell to draw, so the arguments are passed to the game objects instructing it to which cells to draw.
using (Graphics g = this.CreateGraphics())
{
game.Draw(g, animationTimerCounter);
}
}
when is the event being fired?
A paint event is called when the form (or part of it) has to be redrawn, e.g. the form is moved, or another window has hidden a part of it etc.
You can force a Paint event by calling yourControl.Invalidate() method.
In your case you could use for example a Timer to force a Paint with the desired frequency (e.g. every 1-2 seconds).
Paint is basically triggered as required, events that trigger paint can be examples such as (there are others):
A form that was in front is moved
You form resizes
your form is restored
Is this XNA? it kinda looks like it is a similar effect. XNA is a good framework for what it looks like you're trying to do.
If you need your form to paint, you can invalidate it or tell it to paint.
The Paint event is raised when the control is redrawn. Control.Paint Event in MSDN