Add Render event and workaround

Hi,

Today I was trying to resize the plot to a specific size. The reason is that we need to align the actual plot without axes to a specific size. Unfortunately the sizes cannot be specified (only for the whole control).

I tried to get an event when the plot is being drawn (because I need the PlotArea to have valid values), but there are no events on the PlotModel class.

Below is a workaround which works great:

public static class OxyPlotExtensions
{
    private class RenderAnnotation : Annotation
    {
        public event EventHandler<EventArgs> Rendered;

        public override void Render(IRenderContext rc, PlotModel model)
        {
            base.Render(rc, model);

            Rendered.SafeInvoke(this);
        }
    }

    public static void AddRenderHandler(this PlotModel plotModel, EventHandler<EventArgs> handler)
    {
        Argument.IsNotNull(() => plotModel);
        Argument.IsNotNull(() => handler);

        var renderAnnotation = EnsureRenderAnnotation(plotModel);
        renderAnnotation.Rendered += handler;
    }

    public static void RemoveRenderHandler(this PlotModel plotModel, EventHandler<EventArgs> handler)
    {
        Argument.IsNotNull(() => plotModel);
        Argument.IsNotNull(() => handler);

        var renderAnnotation = EnsureRenderAnnotation(plotModel);
        renderAnnotation.Rendered -= handler;
    }

    private static RenderAnnotation EnsureRenderAnnotation(PlotModel plotModel)
    {
        var annotation = plotModel.Annotations.FirstOrDefault(x => x is RenderAnnotation);
        if (annotation == null)
        {
            annotation = new RenderAnnotation();
            plotModel.Annotations.Add(annotation);
        }

        return (RenderAnnotation)annotation;
    }
}

Maybe you can add the Render event to the PlotModel so everyone can do something when the plot is being rendered?

Rendering does belong to the control not to the model.

I fully agree. But then why is there a PlotArea on the model? And although the render itself is not part of the model, it would be very nice if I could at least be notified when the model is being rendered by the control.

Did you try setting the Width, Height, AutoAdjustPlotMargins and PlotMargins of the Plot control? If you do this, I think the size of the plot should be fixed.
It is easy to add Rendering/Rendered events to the PlotModel, but I would like to avoid it if it is not really needed.
The PlotModel was meant to be the abstraction of the plot view - so it contains both the "plot area" and all the transforms that are related to the size of the view. See also https://oxyplot.codeplex.com/workitem/10133 which is related to this.

What I did was to use the Padding of the PlotModel to make sure that the plotarea itself always has a fixed size. Below is the code that allows a developer to make the width of the PlotArea (thus the plot itself can be larger) exactly the size of RealPlotWidth.

private void UpdatePlotArea(int dispatchCounter = 0)
{
    if (!plot.IsVisible)
    {
        return;
    }

    var plotWidth = plot.ActualWidth;
    if (plotWidth == 0d)
    {
        return;
    }

    var plotModel = plot.Model;
    if (plotModel == null)
    {
        return;
    }

    if (plotModel.PlotArea.Width == 0d)
    {
        if (dispatchCounter < 5)
        {
            Dispatcher.BeginInvoke(() => UpdatePlotArea(dispatchCounter + 1));
        }
        return;
    }

    // Magic constants we need to fix the left and right margins of Oxyplot
    const int RightPadding = 5;
    const int DefaultOxyplotPadding = 8;

    var axisWidth = plotModel.PlotArea.Left - plotModel.PlotAndAxisArea.Left + DefaultOxyplotPadding;

    var leftPadding = plot.ActualWidth - RealPlotWidth - axisWidth - DefaultOxyplotPadding;
    if (leftPadding < 50)
    {
        // Exit, issue with redrawing
        return;
    }

    var padding = new OxyThickness(leftPadding, 0, RightPadding + DefaultOxyplotPadding, 0);
    if (AreEqualOxyThickness(padding, plotModel.Padding))
    {
        return;
    }

    plotModel.Padding = padding;
    plotModel.InvalidatePlot(false);
}

private static bool AreEqualOxyThickness(OxyThickness oxyThickness1, OxyThickness oxyThickness2)
{
    if (oxyThickness1.Left != oxyThickness2.Left)
    {
        return false;
    }

    if (oxyThickness1.Top != oxyThickness2.Top)
    {
        return false;
    }

    if (oxyThickness1.Right != oxyThickness2.Right)
    {
        return false;
    }

    if (oxyThickness1.Bottom != oxyThickness2.Bottom)
    {
        return false;
    }

    return true;
}

objo wrote:

Did you try setting the Width, Height, AutoAdjustPlotMargins and PlotMargins of the Plot control? If you do this, I think the size of the plot should be fixed.
It is easy to add Rendering/Rendered events to the PlotModel, but I would like to avoid it if it is not really needed.
The PlotModel was meant to be the abstraction of the plot view - so it contains both the "plot area" and all the transforms that are related to the size of the view. See also https://oxyplot.codeplex.com/workitem/10133 which is related to this.

Is is possible to fix the width of the x-axis?
For example a plot will display a line series with data that can vary fro 0 to 1000000.
Let's assume we fix the plot width. If the data is within the range 0-10 then the x-axis width will have a certain value. However if we load data in the range between 10000 -100000 then the x-axis width will shrink to accommodate the extra digits displayed on the Y-axis.
It gets even worse if we enable the Y-axis title. (the x-axis shrinks even more.)

In other words rather than fixing the plot width, we need a way of fixing the x-axis width and allow the plot width to move dynamically. Ideally it would be great to anchor the origin of the x-axis as well.

If this is not possible, then having a "rendered" event would allow us to do all the calculations manually to ensure the x-axis has the correct width and location.