The Wiert Corner – irregular stream of stuff

Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘QC’ Category

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Delphi – TCustomGrid.InvalidateCol and InvalidateRow bug that has been there since at least Delphi 4^H^H^H^H^H^H^H^H 2 and 1

Posted by jpluimers on 2010/01/12

I just re-reported this in in QC as 81060, but wanted to let you know that there is a bug in TCustomGrid.InvalidateCol and TCustomGrid.InvalidateRow which has been there since at least Delphi 4 Delphi 1 (InvalidateRow) and Delphi 2 (InvalidateCol) and still present in Delphi 2010.

Both methods will not invalidate the entire Row/Col but only the Left/Top most cells of that Row/Col.
So the invalidate the absolute rectangle in stead of the visible rectangle.

You will see this behaviour when you have a virtual grid that is larger than the actual grid on the screen, you scroll through that grid, and perform your own drawing.

Boths bugs are easy to fix, have been reported in QC as number 8472 before (and reported even before QC existed), but denied as ‘test case error’  in stead of being investigated further.
The earliest reference I could find on them is as number 531 in the Delphi Buglist, by Rune Moberg, long time and well respected Delphi developer and bikedude.

Some of the 3rd party grid vendors are also to blame: they seemed to have worked around it without pressing the Delphi team to solve the issue.
For instance, the infamous rxgrid, just invalidates all Rows within InvalidateCol. Now that is pure overkill, as my solution will show. Read the rest of this entry »

Posted in Delphi, Development, QC, Software Development | 2 Comments »

Delphi – for … in on enumerated data types

Posted by jpluimers on 2009/10/27

I like [Wayback/Archive] enumerated type a lot.
The allow you to perfectly describe what the members of such a type actually mean, much more readable than a bunch of integer constants!

Given an enumerated type like TTraphicLightColors

type
  TTraphicLightColors = (Red, Orange, Green);

I always wondered why  – since the for ... in statement was added to the [Wayback/Archive] structured statements part of the Delphi language – it is not possible to use a for … in statement like the this:

</span>
<pre>var
  TraphicLightColor: TTraphicLightColors;
begin
  try
    for TraphicLightColor in TraphicLightColor do
      ShowValueAsTraphicLightColor(Ord(Value));
    // [DCC Error] EnumerationEnumeratorDemoProcedures.dpr(63): E2430 for-in statement cannot operate on collection type 'TTraphicLightColors'
end;

Somehow, for ... in [Wayback/Archive]  expects a collection type.
A request for [WayBack/Archive] the for … in do on enumerated types compiler feature is in QC, but it is closed with reason “Won’t do”.

Back in Delphi 2007, I tried working around this by writing a type implementing the GetEnumerator pattern myself, but got [WayBack/Archive] Internal Errors when compiling anything but the most basic sample.

Until today, where I found how I could get that most basic sample to work!
It is an example on how you could implement this: it is research, so you decide if you find the result practical enough to use yourself.

Read the rest of this entry »

Posted in Conference Topics, Conferences, Delphi, Development, Event, F2084, QC, Software Development | 20 Comments »

Delphi – Frames as visual Components – changing your inheritance

Posted by jpluimers on 2009/07/22

Did you ever get this error message when creating TFrame descendants?
Message 

---------------------------
Error Reading Form
---------------------------
Error reading TDioptreFrame.ClientHeight: Property ClientHeight does not exist. Ignore the error and continue?
NOTE: Ignoring the error may cause components to be deleted or property values to be lost.
---------------------------
Ignore   Cancel   Ignore All
---------------------------

It is odd: TFrame descendants do not have a ClientHeight property!

If you press Cancel, then you get this error message.

Message 

---------------------------
Error
---------------------------
Error creating form: Error reading TDioptreFrame.ClientHeight: Property ClientHeight does not exist.
---------------------------
OK
---------------------------

I did, and here is a reason why it can happen.
Read the rest of this entry »

Posted in Component Development, Delphi, Development, Package Development, QC, Software Development | 15 Comments »

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