I have a WPF app with a canvas inside a ScrollViewer. On the canvas I have some rectangles that I drag along a timeline (left-right). This works fine with a mouse, but on a touch screen I get weird behavior if the canvas is wider than the main form. First, when you begin to drag the rectangle, the canvas pans until it has scrolled to the limit, then the rectangle starts to move. I doesn't do this when using a mouse.
Another strange this is that if I pan/drag the canvas (using touch) to the limit of the scrollviewer, the main form compresses by 20-50 pixels on the side opposite of the pan direction. It springs back to shape as soon as you stop dragging. What's going on here and how do I disable this?
It seems that this has to do with ManipulationBoundaryFeedback, but I don't understand exactly how...
EDIT:
So I was able to get a little further by setting the scrollviewer panningmode to PanningMode.None in the rectangle TouchDown handler and then setting it back to PanningMode.Both in the TouchUp handler. This solved the problem of the canvas panning to the limit before the rectangle would move.
Well, I finally got my app to work with touch. As I mentioned above, setting the PanningMode to None on the TouchDown event eliminated the problem with the ScrollViewer. Setting it back to Both in the TouchUp event re-enabled it. What this means is that I can't drag the rectangle past the point where the ScrollViewer would start panning, but in my case this was not a problem.
I also had some issues with the MouseLeftButtonDown event firing during the TouchMove event so I removed it during TouchDown
-= new MouseButtonEventHandler(drag_start)
and re-added it back during TouchUp to eliminate the glitchy behavior.
+= new MouseButtonEventHandler(drag_start)
Maybe this will help someone in the future...
Related
In WPF, I dont still get the last position when my cursor drag/drop out of canvas.
Please tell me the solution ?
You can get the last position with MouseMouve event. If you still want to get the MousePosition even the mouse is not on the canvas anymore, then you have to subscripe the MouseMove event from the parent control/window.
I am new to Silverlight and I am looking to create a StackPanel that scrolls by dragging it up or down, similarly to how PDF readers work. I did not know if there was anything built in or if I would have to create my own based on mouse down and up.
Hm, just catch MouseMove when LMB is down and change scrolling offset by horizontal difference between last and current points.
In a WPF application, how can you detect if the mouse pointer has stopped moving?
I have a canvas and there is a circle(Ellipse) inside. User can move the mouse over the circle. I want see if the mouse is moving over the circle or it has stopped moving? MouseEnter even of the Ellipse object won't help cos it would be fired even if the mouse is not stopped over the Ellipse.
Any ideas on how to achieve this?
Thanks in advance.
Regards,
Rukshan
Try to look at the ToolTipOpening event, you can use it as a marker of the mouse stopped on your element.
I have a WPF scrollViewer that I use for panning (MouseDown, MouseMove, MouseUp) and I would like to include an acceleration effect that incorporates inertia. So, if the mouse moves beyond a threshold speed and I release the mouse, it continues to pan but slows down as a function of the initial speed. Any ideas, thoughts or examples?
I've done basically this before and started by looking at ScrollViewer but in the end threw it away and used a Viewbox with a Canvas as the child for absolute positioning of content (I was supporting zoom aswel as scroll, it was basically DeepZoom without the scaled images for zooming so there was pixelation when zoomed right in). I wrote code for determining the gesture direction and the speed of the gesture from the mouse events and converted this to a scroll direction and speed and then animated the Canvas.Left and Canvas.Top properties of the scrollable content (which was in the Children collection of the Viewbox's child Canvas) with DoubleAnimation. It worked well, however there may be a better way...heres a thread suggesting hosting DeepZoom in WPF via a Frame control (although I wouldn't do it that way).
EDIT: Basically the ScrollViewer was just too restricting. Even if you get into the ControlTemplate and get references to the ScrollBars directly, it is the position of the Thumb of these scrollbars that you would need to animate and I'm pretty sure this is what I found I couldn't do (it was almost 3 years ago :)
I'm trying to modify the default graph viewer of the Graph# library because its user interface is awful (just try dragging a node outside of the boundaries, you'll see!)
The basic setup is this: there is a GraphCanvas control (inherited from Panel) which has children of Vertex and Edge control types. What I want to achieve is:
GraphCanvas has scroll bars if the contents do not fit in the screen;
GraphCanvas can also be scrolled by "dragging" it (just click on an empty space and drag);
GraphCanvas can be zoomed in and out (via CTRL+mouse wheel);
Vertices can be dragged around. If a vertex is dragged outside the current boundaries of GraphCanvas, the boundaries are increased. The scroll bars should reflect this, however the current viewport should not scroll away while the vertex is being dragged . The same goes if dragging a vertex reduces the boundaries of GraphCanvas - it should stay the same size until the drag operation is finished and resize only then. Automatically scrolling the viewport during a drag operation is awfully confusing and easily introduces dragging errors. See the original implementation if you want to know what I mean.
Although I've got a fair bit of experience with .NET, I'm still a complete beginner in WPF. My current attempt is (in the measure/arrange layout phase) to give each vertext the XY coordinate it desires (even if negative) and implement zooming/scrolling by handling mouse events on the GraphCanvas and modifying the RenderTransform property. Dragging just changes the XY coordinates on the specific vertex (probably triggering the re-layout of the whole thing which would be nice to avoid too). Scrollbars are implemented by placing the GraphCanvas inside a ScrollViewer and implementing IScrollInfo on the GraphCanvas.
Unfortunately there seems to be a problem: I can get mouse events on the GraphCanvas itself only if it has a background at the point. That would be OK, I want a white background anyway, but in the negative coordinates of the GraphCanvas it does not draw the background - and thus does not respond to mouse events.
I'm also wondering if I'm doing the Right Thing by allowing all my child controls (vertices and edges) to go into negative coordinates. How would you implement this?
Added: To clarify about the background problem check out the following screenshot:
(source: valts.21.lv)
What you see here is a simple Windows Forms form with a WPF Host control on it. That has a ScrollViewer in it, and the ScrollViewer has the GraphCanvas in it. The GraphCanvas contains 4 vertices and 6 edges.
The GraphCanvas is stretched to fill the ScrollViewer. But since some of the vertices are at negative coordinates, it has a RenderTransform applied which simply shifts everything to the right (TranslateTransform). It also has a white background brush.
Note the gray area on the left. That's still a part of the GraphCanvas, but the background brush somehow doesn't exted there. Also, if I left-click there with my mouse (not on a node, but on the gray area), I do NOT get an event. If I left-click on the white area, I get all events just fine.
Call CaptureMouse on canvas.mouseDown and ReleaseMouseCapture on mouse up. Also, if you set your canvas background to transparent it will still be hit testable
You can attach a 'Draggable' behavior to each element.