[SOLVED]BeginUpdate and EndUpdate for TChart
lazarus / 55-TAChart

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jwdietrich · 2011-09-24 07:46

In order to speed up the drawing of a large time series with TChart, I
would like to use a function similar to BeginUpdate / EndUpdate for
grids. Unfortunately, I can't find corresponding methods in the TChart
class.

How can I instruct TChart to wait for XY-pairs being filled before
beginning with the drawing?

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Ask · 2011-09-24 10:03

You can either use DisableRedrawing/EnableRedrawing for entire chart
or
Source.BeginUpdate/EndUpdate for specific source.

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wp · 2011-09-24 14:38

Does this mechanism also temporarily stop updating extent and axis
labels?

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Ask · 2011-09-24 15:29

Currently TAChart does not support partial redrawing,
so it is either repainted fully, with all labels, or not at all.

As for the cached extent of the list source, it is updated if
you use SetXXX methods, but is not updated if you assign values
directly
to X and Y fields of chart items.

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jwdietrich · 2011-09-25 08:22

Quote from: Ask on September 24, 2011, 12:03:38 pmYou can either use
DisableRedrawing/EnableRedrawing for entire chart or
Source.BeginUpdate/EndUpdate for specific source.

At least with my Lazarus version (0.9.30) DisableRedrawing and
EnableRedrawing are not supported. Source.BeginUpdateEndUpdate,
however, works and dramatically speeds up execution time.

Thank you for your hints.