[Lazarus] TEdit appears empty when text is too long

[Denis Kozlov]

I have tested Windows API directly using DrawText, TextOut and 
ExtTextOut functions - they all suffer from this problem.

The problem is bound by the total width of the drawn text (not just the 
small visible portion), where beyond some point it breaks. There appears 
to be no feasible workaround. It may be possible to programmatically 
break apart long text and draw it in chunks, but that is ugly and only 
addresses the symptoms of an unstable problem within Windows platform.

Moving on now...

Denis


On 12/05/2017 00:10, Denis Kozlov wrote:
> Hi,
>
> Has anybody experienced this problem or might know what is going on here?
>
> At around 5K characters the content of TEdit suddenly appears 
> empty/blank (visually). The content is correct when retrieved 
> programmatically. If enough characters are removed (programmatically) 
> the content will show up again. Changing the font size changes this 
> limit, where the limit is lower for a larger font size.
>
> It is as if the issue is bound by the visual width of entire text 
> content, as opposed to just the small visible part.
>
> Tested on Windows 7:
> Lazarus 1.4.4 r49931 FPC 2.6.4 i386-win32-win32/win64
> Lazarus 1.6.4 r54278 FPC 3.0.2 i386-win32-win32/win64
> Lazarus 1.9.0 r54874 FPC 3.0.2 i386-win32-win32/win64
>
> Also tested with Delphi 7, where the limit appeared past 50K characters.
>
> Sample project is attached.
>
> I will appreciate any clues to what's going on here.
>
> Thanks,
> Denis