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Q: Custom painting and the clipping rectangle problem

User (Legacy)

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Being quite new to custom painting inside Chart FX Client

Server I would like to ask you what to do to avoid the not

wanted clipping.

The attached CFXtrend2.zip contains full working example

(see the information below). When drawing lines over the

bars, the result looks fine -- see the attached bars.png

picture. However, when gallery type is changed to LINES,

then the green line is painted correctly only when you

resize the window or so -- see the attached lines.png

picture that was obtained when dragging the marker

of the third point of the yellow serie.

The painting code can be found inside CCfxEvents::Fire_PostPaint()


Thanks for your kindness, time, and experience,


P.S. I did post the earlier version of this example

recently. It displays the following explanatory text inside

message box when started:


This example demonstrates customization of the Chart FX

painting. The code simulates drawing of the trend line with

respect to series for values of each point (demo with 3

series and 3 points). The example shows 3 ways of

determining coordinations of the end point of the lines. You

can see the difference when you change the gallery to the

lines instead of the bars. Try also to drag the top of the

joined bars. Try to resize the chart area or the main


The first (red) approach uses coordinations of the top of

bars of the first and the last series of the first point.

The second (blue) approach determines width of the area for

one point and draw 3 lines with coordinations independent on

values of the series (for the second point).

The third (green) approach determines the x coordination of

the line points with respect to the chosen gallery type of

the first and of the last series. When BARs are used, it

should behave the same way as the red case. When LINES are

used, the x's are determined as in the blue case. You can

observe some problem when using LINES and dragging the 3rd

point markers.

This example detects PostPaint events through the ICfxEvents

interface. See SoftwareFX Knowledge Base "Q1381010. Handling

events in Chart FX DLL" for details. The code is not

necessarily pretty, nor extremely efficient. It is rather

quick hack with reasonable style ;)

The example uses Cfx4032.dll via #import (VC++ 6.0). It uses

only ATL::CWindowImpl<> methods and the Win32 GDI functions

(which was one of the goals) in a very simple way. No MFC is

used. If you are not familiar with ATL, you will probably be

able to rewrite the code using GDI functions only.



P.S.: Feel free to use the code as an example, or for

whatever purpose.



Petr Prikryl (prikrylp at skil dot cz)

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The Dragging feature refreshes only the part of the screen that has changed.

Because your custom painting goes beyond this area, only part of your line

is drawn in the new position while the other remains unchanged.

The solution: Refresh the whole chart when you receive a LButtonUp event.



Software FX, Inc.

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"SoftwareFX Support" wrote...

> [...] The solution: Refresh the whole chart when you receive a LButtonUp


Thanks! This works quite fine. The updated sample is attached.

Just being curious, is it possible to avoid the "blink" when the chart is


When not using Refresh() and when the Refresh() is not needed, the

window content behaves more smoothly.




Petr Prikryl (prikrylp at skil dot cz)


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