I have this problem.
So I have a bunch of data that must be visualized on a canvas (say more than 5000 items). So I draw them as a bunch of vertical rectangles over a horizontal line, some thing like this:
---|--|||||---|---|||---||----|||||||--------
Now, because the canvas is small, I only draw a different amount of rectangles at different zoom level. So if I zoom in more, the line get longer, and more rectangles I can see.
Problem is every time I zoom in, I have to clear the whole canvas, and redaw everything with the new zoom scale. And it is really suck, the drawing is slow and scaling not really nice.
So I wondering is there a way I can achieve a faster drawing, and good zooming (like those vector graph, you can zoom in unlimited)??
Have you tried ScaleTransform Class?
<Canvas.RenderTransform>
<ScaleTransform ScaleX="2" ScaleY="2" />
</Canvas.RenderTransform>
See How to: Scale an Element too. For performance reasons:
Freeze your Freezables.
Update Rather than Replace a RenderTransform
You may be able to update a Transform rather than replacing it as the
value of a RenderTransform property. This is particularly true in
scenarios that involve animation. By updating an existing Transform,
you avoid initiating an unnecessary layout calculation.
Have you looked at the ZoomableCanvas? I haven't used it, but it looks like it's designed to do exactly what you want.
Related
I have this <Path> element in a xaml file. I would like to create a copy and flip it horizontally so that the shape will point in the other direction. The <Path> has a really long Data field so I was wondering if there was a way to flip one of the elements instead of just eyeballing the element and manually making it appear the same shape and size.
I looked into flipping the image programatically using RenderTransform and ScaleTransform, but I am afraid it might hinder the performance of the application especially during a window resize.
References: https://learn.microsoft.com/en-us/dotnet/framework/wpf/graphics-multimedia/transforms-overview
Is there a protocol or way I can translate the Path element's Data
field into its horizontally flipped opposite in a way that wonder hurt
the performance of the application?
If you want to mirror the shape you might want to try this:
<Path data= "...">
<Path.RenderTransform>
<ScaleTransform ScaleX="-1.0"/>
</Path.RenderTransform>
</Path>
This doesn't really hurt the performance, since all rendered elements are transformed at some point anyway.
So I realize that I am venturing outside of the intended use of a Canvas here and will likely have to come up with a more manual solution. However, not being overly experienced in WPF I was hoping that there may be some solution which would allow me to continue using a Canvas control and the features it gives you for free.
The issue revolves around a Canvas which is used to zoom in and out of an image and some number of child controls that belong to the Canvas. These child controls are to be placed at various positions on the image and, as such, the Canvas works nicely in that it handles all of the layout/positioning for me as I zoom in or out.
However, one drawback is that the Canvas scales these child controls up as I zoom into the image, causing them to become too large to be usable in practice. What I am looking for is a solution that allows me to zoom into an image that belongs to a canvas without also zooming up the size of the child controls, preferably handling the layout for me.
I have tried modifying the width and height of these child controls as the zoom factor increases or decreases, but there is a slight lag time and it all looks a bit 'jerky'.
If it comes down to it I will simply do all of the zooming/panning/layout myself, but I thought I would ask first just to make sure that I am not missing anything that would allow me to tell the Canvas to not scale the size of certain controls. Thanks in advance.
You can bind the children's RenderTransform to the inverse of the Canvas' transform, see my answer to this similar question on rotation.
This is more of a thought than an answer, but what if you set a transform on the element that you did not want scaled that was the opposite of the canvas itself. So for example, if the canvas had a scale transform of 2.0, set the element to have a scale transform of 0.5. You could probably accomplish this by binding the transform values together using a value converter.
You'll probably want to make sure the element has a render transform origin of 0.5,0.5 so that it scales from the center.
I want to implement a rather complex CurveEditor that has to support the usual requirements like:
freely scalable and moveable axis
different interpolation types per curve point (Linear, Cubic, Spline)
Tangents (joined and broken)
Selecting one or several points to edit (move, scale, delete) via Fence or Click
Only show handles and highlights for selected curve points
I don't want to manipulate actual WPF curves but an existing model with key/value/tangents sets and sample the precise shape of the curve from our implementation.
I already gathered some experience on implementing custom UserControls and Templates. But I want to make sure, I don't miss any apparent solution. I planned to have this general XAML-tree:
CurveEditor - Window holding all content
MainThumb : Enable dragging and scaling the editor range
XAxis : UserControl rending some scale on the left side
YAxis : UserControl rending some scale on the bottom
Curves : Canvas holding the curves
Curve : UserControl for a single curve
CurveName - Label of the curve
CurveLine - DrawingVisual that will render the actual curve by sampling the internal implementation of the spline function.
CurveEditPoints - Canvas that holds all edit points
CurveEditPoint - UserControl for a single edit point
LeftTangent - UserControl for the left tangent handle
LeftTangentThumb - For modifying the handle
RightTangent - UserControl for the right tangent handle
RightTangentThumb - For modifying the handle
CurvePointCenter - Visualisation of the actual point, select state and interpolation type.
CurvePointThumb - Thumb to select and drag point around
I know, this is quite a complex question and I am not asking for an actual implementation. I am interested in the following questions:
Can you recommend any tutorials or books that might help me (I already got Illustrated WPF, WPF Control Development Unleashed, and a couple of other)
Should minor elements like the Tangents be individual UserControls?
What container is best suited for hosting the individual "Curves", "EditPoints" and "Tangents". Right now, I use Canvas and Canvas.SetLeft/SetTop to position the children, but that feels "strange".
Should I use "Shapes" like Path or DrawingVisual-Classes to implement actual representation. Path is straight forward, but I am concerned about performance with hundreds of CurvePoints.
Should I use Transforms to rotate the tangents or is just fine to do some triangulation math in the code behind files?
Does the structure roughly make sense, or do you suggest a completely different approach?
you seem to have the right tools at hand, WPF Unleashed is excellent, but I guess you have that one already.
make individual UserControls in one of these cases:
you are using the same xaml all over the place (DRY)
you xaml file gets too big (get some components out)
you need to inherit from some class
this depends on how much codebehind you want.
you can, as you suggested in your comment, use an ItemsControl as a container for wherever you need selection between multiple items. so this could also be done on the level of Curves, not just on the level of points on the curve. Depending on how you want to handle drawing of the actual lines and curves you can even have an ItemsControl for those. (on a side note: you will not have virtualization out of the box though, as your items won't have a constant height)
Path is OK with hundreds of CurvePoints. If you have 10.000, I'd say you could get problems.
can't imagine how a transform should be used here, maybe inside an Adorner.
your structure looks good. you will be able to implement all of this. I will suggest though how I would do it:
first of all use MVVM.
CurveEditor
ListBox(Panel=Canvas)(ItemsSource=Curves)(ItemTemplate=CurveControl)
CurveControl
Canvas(Background=Transparent) <= I'm not sure if standard is white, but you don't want to overlap other Curves...
CurveName
ListBox(Panel=Canvas(Background=Transparent))(ItemsSource=CurveParts)
ListBox(Panel=Canvas(Background=Transparent))(ItemsSource=CurvePoints)(ItemTemplate=>EditPointControl)
EditPointControl
Canvas
Thumb(Template = Ellipse) (Name=CenterHandle) (with some Visualstates for Selection and hiding of Tangents)
Thumb(Template = Ellipse) (Name=LeftHandle)
Thumb(Template = Ellipse) (Name=RightHandle)
Line (Binding X/Y to Centerpoint and LeftHandlePoint)
Line (Binding X/Y to Centerpoint and RightHandlePoint)
I have stated to set ItemTemplate for the ListBox. You can however style the listbox however you want (I think the standard style includes a border, you might want to remove that or set bordersize=0) and set instead of ItemTemplate the ItemContainerStyle and bind to IsSelected so you have control over IsSelected from your ViewModel (look here for what I mean).
So the viewmodel looks like this:
- CurveEditorViewModel
- ObservableCollection<CurveViewModel> Curves
- CurveViewModel
- string Label
- (Point LabelPlacement)
- bool IsSelected
- ObservableCollection<CurvePointViewModel> CurvePoints
- ObservableCollection<CurvePartViewModel> CurveParts
- CurvePointViewModel
- Point Position
- bool IsSelected
- Point LeftHandle
- Point RightHandle
- CurvePartViewModel
- CurvePointViewModel StartPoint
- CurvePointViewModel EndPoint
- Path CurvePath
in here you can subscribe to CurvePointViewModel's PropertyChanged and recalculate the Path you're exposing.
I'd probably improve on it as I go but that'd be my first guess.
There are some details you might want to watch out for. eg: the style for the thumbs might be a visible circle in the middle and an invisible bigger one around that with background=transparent. that way you can have your visible circle small, but have the user use the tumb in an area around the small circle.
EDIT:
here is an Example for the Thumb:
<Thumb Width="8" Height="8" Cursor="Hand" Margin="-4">
<Thumb.Template>
<ControlTemplate TargetType="Thumb">
<Grid>
<Ellipse Fill="Transparent" Margin="-6"/>
<Ellipse Stroke="Red" StrokeThickness="2"/>
</Grid>
</ControlTemplate>
</Thumb.Template>
</Thumb>
as you want to position this at a specific point on a canvas setting the Margin to minus half the width and height will place the center of the circle on that point. Furthermore, having that inner ellipse with a transparent fill and Margin of -6 you will get a 6px bigger radius around the inner (smaller) circle where you can drag the thumb.
In Direct2D they recommend drawing similar things together, to avoid unnecessary GPU state changes. They also do some drawing operation reordering behind the scene just for that.
I have to draw a lot of rectangles which can have one of two colors. I'm thinking of doing the drawing in two passes, one for the rectangles with the first color and another for the ones with the other color.
Do you have any idea if this will improve the rendering speed? The speed I have right now is not that great. I draw into a DrawingContext obtained from a DrawingVisual.
I really don't know what effect grouping by brush will have, but there are some things you should check first:
Make sure all brushes, pens and other freezables are frozen.
Simplify your visual tree, try to reduce element count.
Try to reduce the number of elements that change every time you update your drawing.
Read: http://msdn.microsoft.com/en-us/magazine/dd483292.aspx
I'm currently creating a MSPaint-like WPF-application and struggling with the implementation of a snappable grid.
The painting of the grid is no problem with a VisualBrush and a Rectangle but the problem is that these lines are then purely for looks and can't be easily changed (for example highlighted when the snapping to a specific line triggered).
My other idea was to have a 2 Canvas solution where 1 Canvas is used for the elements and one Canvas (who is positioned above the other) contains all the grid lines. However I have the feeling that this would mean quite a performance hit.
Are there any other possible ways to implement this kind of functionality?
Efficiency considerations of a two-panel approach vs DrawingContext
I have good news for you: You are wrong about the significant performance hit. Your two-canvas idea is nearly optimal, even if you use individual objects for the grid lines. This is because WPF uses retained-mode rendering: When you create the canvas, everything on it is serialized into a compact structure at native level. This only changes when you change the grid lines in some way, such as changing the grid spacing. At all other times the performance will be indistinguishable from the very fastest possible managed-code methods.
A slight performance increase could be had by using DrawingContext as Nicholas describes.
A simpler and more efficient solution
Perhaps a better way then drawing individual lines on the grid canvas is to use two tiled visual brushes (one horizontal, one vertical) to draw all unhilighted lines, then use Rectangle(s) added in code-behind to hilight the line(s) you are snapping to.
The main advantage of this technique is that your grid can be effectively infinite, so there is no need to calculate the right number of grid lines to draw and then update this every time the window resizes or the zoom changes. You also only have three UIElements involved, plus one more for each grid line that is currently hilighted. It also seems cleaner to me than tracking collections of grid lines.
The reason you want to use two visual brushes is that drawing is more efficient: The brush drawing the vertical lines is stretched to a huge distance (eg double.MaxValue/2) in the vertical direction so the GPU gets only one drawing call per vertical line, the same for the horizontal. Doing a two-way tiling is much less efficient.
Adorner layer
Since you asked about alternatives, another possibility is to use Adorner and AdornerLayer with any of the solutions above rather than stacking your canvas using eg a Grid or containing Canvas. For a Paint-like application this is nice because the adorner layer can be above your graphic layer(s) yet the adorners can still attach to individual items that are being displayed.
You might consider drawing your grid using the DrawingContext inside of OnRender. Drawing this way does not introduce new UIElements into the visual tree, which helps to keep performance up. In some ways, it is similar to what you are currently doing with the VisualBrush, which also does not create new UI elements per copy.
However, since you will actually be individually drawing each line instead of copying the look of a single line, you'll be able to highlight the grid line(s) that participate in snapping without changing the colors of those that do not.
If you are going to go down this route, make sure to have a look into GuidelineSets for positioning your guide lines (more details here), since you'll probably want to have your guide lines snap to the device's pixels so that they draw sharply.