Lazarus
Home
Help
TinyPortal
Search
Login
Register
Lazarus
»
Forum
»
Programming
»
Graphics and Multimedia
»
TAChart
(Moderator:
Ask
) »
clicking a chart, get x-axis value
Free Pascal
Website
Downloads
Wiki
Documentation
Bugtracker
Mailing List
Lazarus
Website
Downloads (Laz+FPC)
Packages (OPM)
FAQ
Wiki
Documentation (RTL/FCL/LCL)
Bugtracker
CCR Bugs
IRC channel
GIT
Mailing List
Other languages
Foundation
Website
Useful Wiki Links
Project Roadmap
Getting the Source
Screenshots
How to use the forum
About donations (wiki)
Bookstore
Computer Math and Games in Pascal
(preview)
Lazarus Handbook
Search
Advanced search
Recent
what to do if my target M...
by
nickysn
[
Today
at 04:16:02 pm]
Parameter passing odditie...
by
KodeZwerg
[
Today
at 04:15:23 pm]
trunk compiler bug for mi...
by
nickysn
[
Today
at 04:03:44 pm]
Offical launch of the 1 B...
by
BeniBela
[
Today
at 03:52:05 pm]
compiler error in unit
by
paule32
[
Today
at 03:49:50 pm]
Xcode Command Line Tools ...
by
Martin_fr
[
Today
at 03:45:26 pm]
Compile/Convert Delphi pr...
by
Joseph
[
Today
at 02:43:45 pm]
how to tweek fpmake to co...
by
Key-Real
[
Today
at 02:33:27 pm]
Can function be used for ...
by
VisualLab
[
Today
at 02:15:30 pm]
Multithreading - synchron...
by
mika
[
Today
at 01:48:51 pm]
A fairly simple sound sol...
by
KodeZwerg
[
Today
at 01:48:26 pm]
May be useful to somebody
by
KodeZwerg
[
Today
at 12:38:22 pm]
match automatic highlight...
by
Чебурашка
[
Today
at 11:35:14 am]
Tchart with dual numbers ...
by
wp
[
Today
at 10:48:18 am]
Generics - correct syntax
by
VisualLab
[
Today
at 10:23:16 am]
add new targets to make
by
Key-Real
[
Today
at 09:38:23 am]
Debugger crashes with App...
by
Martin_fr
[
Today
at 09:29:46 am]
Copyrights Q
by
BrassGear
[
Today
at 09:13:14 am]
[SOLVED] how to build the...
by
Key-Real
[
Today
at 09:12:33 am]
Quirky windows
by
tetrastes
[
Today
at 08:59:06 am]
How can I draw a rectangl...
by
Handoko
[
Today
at 07:30:55 am]
Draw a line in the Scroll...
by
Handoko
[
Today
at 07:27:54 am]
web development using pas...
by
Nate897
[
Today
at 02:04:05 am]
questionable function def...
by
440bx
[
Today
at 01:35:28 am]
Why isn't TTIRadioGroup's...
by
jamie
[
Today
at 12:13:45 am]
« previous
next »
Print
Pages: [
1
]
Author
Topic: clicking a chart, get x-axis value (Read 4380 times)
mtanner
Sr. Member
Posts: 287
clicking a chart, get x-axis value
«
on:
September 12, 2017, 12:26:23 pm »
What is the easiest way of allowing the user to click on a chart and getting the x-axis position for the point clicked. The clicked point may not coincide with a data point for ay of the series displayed.
Logged
wp
Hero Member
Posts: 11923
Re: clicking a chart, get x-axis value
«
Reply #1 on:
September 12, 2017, 12:58:06 pm »
Use the DatapointClickTool:
http://wiki.lazarus.freepascal.org/TAChart_Tutorial:_Chart_Tools#Using_a_TDataPointClickTool
If the click should be evaluated also if no datapoint is hit you can use the ordinary OnClick, or OnMouseDown event of the chart. Use Chart.ImageToGraph to convert the pixel coordinates to graph coordinates:
Code: Text
[Select]
[+]
[-]
procedure TForm1.Chart1Click(Sender: TObject);
var
P: TDoublePoint;
begin
P := Chart1.ImageToGraph(Chart1.ScreenToClient(Mouse.CursorPos));
Statusbar1.SimpleText := Format('X=%.2f, Y=%.2f', [P.X, P.Y]);
end;
But note that this works only if you did not use ChartTransformations. In this case you must decide which axes will be used, then call axis.GetTransform.GraphToAxis to further convert the chart's graph coordinates to the units displayed on the axis. Here with the example of the x axis:
Code: Text
[Select]
[+]
[-]
procedure TForm1.Chart1Click(Sender: TObject);
var
P: TDoublePoint;
x: Double;
begin
P := Chart1.ImageToGraph(Chart1.ScreenToClient(Mouse.CursorPos));
x := Chart1.BottomAxis.GetTransform.GraphToAxis(P.X);
StatusBar.SimpleText := Format('X = %.2f', [x]);
end;
Logged
mtanner
Sr. Member
Posts: 287
Re: clicking a chart, get x-axis value
«
Reply #2 on:
September 13, 2017, 08:59:38 am »
Thanks, that works fine. I don't use transformations, so the simple approach does what I need.
Logged
Print
Pages: [
1
]
« previous
next »
Lazarus
»
Forum
»
Programming
»
Graphics and Multimedia
»
TAChart
(Moderator:
Ask
) »
clicking a chart, get x-axis value
TinyPortal
© 2005-2018