After researching http://bugs.freepascal.org/view.php?id=19887, I have found the following:
0) For context, here is TDbChartSource desctiption: http://wiki.lazarus.freepascal.org/TAChart_documentation#Database_source 1) My implementation of TDbСhartSource is incorrect, because during the chart drawing it accesses dataset directly from the TDataLink descendant. Apparently this causes infinite loop, because such accesses generate DataSetChanged events, which in turn invalidate the chart. Even DisableControls/EnableControls do not help, since EnableControls calls DataSetChanged (!). 2) Looking at the code in TDBGrid, it seems that the correct way is to use DataLink's ActiveRecord property. Unfortunately, in contrast to TDBGrid, TDbСhartSource needs to read the whole dataset. It seems that the only way to do this is to set BufferCount := RecordCount, i.e. buffer entire dataset in memory, which I do not like. So, my questions are: 1) Is there a way to totally disable DataSetChanged events in the dataset? 2) Alternatively, is there a mechanism to read entire dataset via TDataLink without fully buffering it? -- Alexander S. Klenin -- _______________________________________________ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
