I have created a usercontrol that is essentially a text editor (using Graphics.Drawstring in OnPaint).
I have set AutoScroll = true, and AutoScrollMinSize values appropriately. Everything is working how it should...
EXCEPT, i would like the control to scroll itself WHILST I am currently scrolling (i.e. click and drag the scroll bar... and whilst it is being dragged the control should be scrolling the entire time). At the moment it only scrolls when the scroll bar is released (mouse up).
I have tried implementing _Scroll and invalidating the control, but that just makes it flicker uncontrollably.
I cannot find any examples online for this, due to it being difficult to describe!
Can anyone point me in the right direction please?
Control.Invalidate() will make something flicker badly. I faced this problem drawing cross-hairs over a mouse position on a PictureBox drawing a line chart before. The trick is to use (and I cant remember which one is best to come first)
Control.Update();
Control.Refresh();
in the Scroll event. Depending on what else you are drawing in the Control and how you are drawing it this may be better for you. Also this is tested on PictureBox, Control may be another matter.
Related
I am trying to do something a little bit specific, and I can't seem to find if it is even possible. So I thought I would lay down the question here.
What I'm looking for is a way to change the anchor point of the scrollviewer from the top to the bottom (however you look at it). I'll explain what I mean.
By default when the control contained in your scrollviewer gets taller, so will your vertical scrollbar scollableheight.
But what happens is, the vertical scrollbar will stay at the same scrolloffset from the top, while what I want is that the vertical scrollbar keeps it's position relative to the bottom. The reason I want this behaviour is because I am creating a list that the user can expand more of by scrolling to the top. but then when I add the new items it looks like the scrollviewer scrolls up to the newly added items. (although it is actually the content the is pushed down) So if the scrollviewer would have the vertical scrollbar anchored to the bottom, the visible part of the content would stays at the same position to the user because the distance from that part to the bottom didn't change.
I hope you can understand what I'm trying to do.
I allready found one way of doing this, but it is not the desired option to me.
Option 1) Apply a Scaletransform of -1 in the Y-axis to the scrollviewer to flip it upside down. Then apply another ScaleTransform of -1 in the Y-axis to the content of the scrollviewer to make the content right side up.
But the problem with this technique is that for one, when you scroll using your mousewheel the scrollviewer scrolls inverted as normal. And second, I'm using 2 scaletransformations just to change the behaviour of the scrollviewer, and not even for eye candy. So that seems a bit excessive to me.
Option 2) anyone?
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.
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.
I currently have a Silverlight canvas that exceeds the viewable area of the screen (I'm letting the users drag the viewable areas around to navigate). I'm trying to display a modal popup that always shows up in the middle of the viewable area, and I can't seem to find any property that tells me what currently is on the screen. Basically if the user has panned down to the bottom and clicks something that causes a modal popup to appear it is stuck at the far top of the screen.
Any ideas anyone?
Thanks
~Steve
I don't think this is possible since the visibility isn't being surfaced. Perhaps with some fun JavaScript to figure out where the panning is?
Quite true. I wound up creating a holding canvas, making that full screen, and putting everything else as a child canvas within that. The modal popup now comes up in the holding canvas.
Gabriel Guimarães one works good.
App.Current.Host.Content.ActualHeight(and ActualWidth) does bring the browser size inside. Good for calculating position. And of course you can use LayoutUpdated on your main control to double check the sizes and resize stuff if need be.
I am developing a form in .NET Compact Framework, which hosts a variable number of controls. Every control should have the same width as the form. When there are only a few controls, no vertical scrollbar appears. When there are more controls than they can fit in one form, a vertical scrollbar appears. The width of the controls should then be modified, so that no horizontal scrollbar appears.
What is the best way to achieve this? I am interested in a solution that will work in all platforms/screen sizes and that can support screen orientation changes.
If I get this right, at one point, both a vertical and horizontal scrollbar appear, and you want only the vertical scrollbar? Doesn't setting the Anchor of each control to "Top|Left|Right" solve this problem automatically?
If every control is to be the same width as the form, why not just Dock every control to Top (or Bottom)? It'll take care of the resizing for you then. It might not look very attractive however, so I suggest adding in some empty Panels (docked the same way) to be used as vertical spacers.
I did some quick testing, and it seems, when you add controls, the panel raises the resize event when the added control tiggers the scollbars to go visible. The annoying part is here that the resize event is triggered a couple of times during startup :(
But knowing the compact framework, this might be your best shot at handling this.
Normally on the full framework you could if the DisplayRectangle is bigger than the size of the panel, but no such thing exists on the cf.
Hope this is of some help, I'll see if I can find anything more in the morning.