TAChart: Series icons
lazarus / 55-TAChart

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wp · 2011-06-18 19:41

@ask:
Could you please add a the following public method to
TBasicChartSeries? This method, DrawSeriesIcon, would enable
population of an TImageList with the icon of each series. The
imagelist could be used in further controls for series selection
(Listbox, Listview etc.).

This is my proposed code:
Code: [Select]procedure
TBasicChartSeries.DrawSeriesIcon(ADrawer:IChartDrawer; const
ARect:TRect);
var
  legItems : TChartLegendItems;
  i : integer;
begin
  legItems := TChartLegendItems.Create;
  try
    GetLegendItemsBasic(legItems);
    for i:=0 to legItems.Count-1 do
      (legItems[i] as TLegendItem).Draw(ADrawer, ARect);
  finally
    legItems.Free;
  end;
end; 

For those interested, this would be the code to populate the imagelist
with the series icons:
Code: [Select]procedure PopulateSeriesImageList(AChart: TChart;
AImageList:TImageList);
var
  drawer: IChartDrawer;
  bmp : TBitmap;
  R : TRect;
  i : integer;
begin
  AImageList.Clear;
  bmp := TBitmap.Create;
  try
    bmp.Width := AImageList.Width;
    bmp.Height := AImageList.Height;
    R := Rect(0, 0, bmp.Width, bmp.Height);
    bmp.Canvas.Brush.Color := clWindow;
    drawer := TCanvasDrawer.Create(bmp.Canvas);
    for i:=0 to AChart.SeriesCount-1 do
    begin
      bmp.Canvas.FillRect(R);
      AChart.Series[i].DrawSeriesIcon(drawer, R);
      AImageList.Add(bmp, nil);
    end;
  finally
    bmp.Free;
  end;
end;

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Ask · 2011-06-22 14:17

Sorry for delayed reply -- missed your post.
The method you propose is not quite correct, since there is no
guarantee
that there is exactly one legend item per series.
Instead, I have implemented TChart.GetLegendItems function
(and TChartLegend.MeasureItem helper in case you need to estimate item
size).
Also, I have added combobox with legend items to the legend demo since
r31335

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wp · 2011-06-22 14:43

Thank you - this helps a lot.

Quote...there is no guarantee that there is exactly one legend item
per series.I'm a bit confused: how can this be? How can I create two
legend entries for the same series? If I'd want to plot the same data
twice my understanding was to use a datasource attached to both
series.

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Ask · 2011-06-22 16:37

Quote from: wp on June 22, 2011, 04:43:21 pmHow can I create two
legend entries for the same series?

Currently -- by either setting Legend.Multiplicity to lmPoint or using
user-drawn legend,
both of which are demonstrated in legend demo. I plan to add other
multiplicity values --
for example, an item per stack level in stacked series.

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wp · 2011-06-23 10:06

Thanks again. I am impressed by the complexity of TAChart.

Maybe I am wrong, but there seems to be a weakness of legenditems
being independent of series: how can I get the icon of a series which
is inactive and therefore not displayed in the legend? One reason for
wanting to do this could be using the series icons in a
TCheckedListbox for quickly turning on and off of series, such as
Delphi's TChartListbox. Of course, I could temporarily turn on all
series, extract the icon of the hidden series and then turn the
inactive series back off again. But this seems to be a bit cumbersome.
Wouldn't it be better to have the LegendItems as a member of
TBasicSeries?

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wp · 2011-06-24 12:12

Please ignore my previous post - after looking into the sources in
more detail I found out that the LegendItems are defined by the
series, just as I though it should be.

But the issue with the inactive series still is still existing. Could
you add a parameter "AllSeries:boolean=false" to the new method
TChart.GetLegendItems in order to be able to include all series in the
legend items list?

Code: [Select]function TChart.GetLegendItems(AllSeries:boolean=false):
TChartLegendItems;
var
  i: Integer;
begin
  Result := TChartLegendItems.Create;
  try
    for i := 0 to SeriesCount - 1 do
      with Series[i] do
        if (Active and GetShowInLegend)
           or AllSeries // new
        then
          GetLegendItemsBasic(Result);
  except
    FreeAndNil(Result);
    raise;
  end;
end;

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Ask · 2011-06-24 13:42

Heh, I have almost added this parameter first time -- then decided to
wait for feedback.
Turns out my plan was correct ;-)

Added in r31359.
I have credited you in the commit message as "Werner",
since this is how you signed some of you messages.
If you want different name, please let me know.

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wp · 2011-06-24 13:46

Thank you

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wp · 2011-07-04 10:09

Hi, beginning to implement a TChartListbox (a TCheckListbox descendant
for turning on and off of series) I got stuck since I do not know the
series to which a LegendItem belongs.

Code: [Select]procedure TChartListbox.Populate;
var
  i : integer;
begin
  try
    FreeAndNil(FLegendItems);
    Items.BeginUpdate;
    Items.Clear;
    if (FChart <> nil) then begin
      FLegendItems := FChart.GetLegendItems(true);
      for i:=0 to FLegendItems.Count-1 do begin
        Items.AddObject(FLegendItems[i].Text, FLegendItems[i]);
        //Checked[i] := FLegendItems[i].Series.Visible;
        // not possible, since TLegendItem forgot the series where it
came from
      end;
    end;
  finally
    Items.EndUpdate;
  end;
end;

Could you add a series field to the definition of TLegendItem? Or is
there another way to get the series which belongs to a given
LegendItem?

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Ask · 2011-07-04 12:01

QuoteCould you add a series field to the definition of TLegendItem?
Added Owner field in r31557. It is of the base type, since otherwise
a circular reference would be introduced.

However, with multiple items per legend, TChartListBox would look
strange.
I have implemented TCustomChartSeries.GetSingleLegendItem in r31556.

If you are planning to submit TChartListBox for inclusion, please
consider the possibility
of using it in design-time series editor.

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wp · 2011-07-05 10:32

Thank you.

Now I have to assign the series to the new owner property. Is this the
correct place?

Code: [Select]procedure TCustomChartSeries.GetLegendItemsBasic(AItems:
TChartLegendItems);
var
  i, oldCount: Integer;
begin
  oldCount := AItems.Count;
  if Assigned(Legend.OnDraw) then
    for i := 0 to Legend.UserItemsCount - 1 do
      AItems.Add(TLegendI]"]>BlockedserDrawn.Create(i, Legend.OnDraw,
Title))
  else
    GetLegendItems(AItems);
  for i := oldCount to AItems.Count - 1 do begin
    AItems[i].Owner := self;              // <---  new
    Legend.InitItem(AItems[i], i - oldCount, FChart.Legend);
  end;
end;

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Ask · 2011-07-05 14:14

I do not quite understand. Does it not work already?

Also, since you can now get a single item from series, you can write a
loop
over series, like you wanted at the beginning.

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wp · 2011-07-05 16:09

Thank you once more - I did not understand why you introduced the
GetSingleLegendItem because you had discussed multiple legend items
before. This is working now. However, there's another issue with
notification - but I'll open a separate thread for that.

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wp · 2011-07-05 19:11

Going back to your answer of July 04: yes - I'd like to donate the
component once it is finished. There are some issues left, though.

Anyway: why should the component be used in the design-time series
editor? It is just a supplementary component, e.g. like the
TChartLegendPanel.

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Ask · 2011-07-06 05:00

QuoteAnyway: why should the component be used in the design-time
series editor?
It is not a requirement, of course, but I think it would be logical.
See, for example, documentation for similar Delphi/TeeChart component:
http://www.berneda.com/TeeChart6Docs/TCHARTLISTBOX.html

Note that I am NOT asking you to modify series editor,
just to consider it and design your API with this possibility in mind.