#648 TImageList constructors use TColor::Sys3dFace as mask color

[Vidar Hasfjord]

Constructors TImageList(const TBitmap&...) and TImageList (const TDib&...) use TColor::Sys3dFace as the mask color. This color is dynamic and system setting dependent, hence is a poor fixed choice, as it means the client will have to make sure the real mask color in the bitmap is mapped to TColor::Sys3dFace before constructing the TImageList.

Proposed resolution: Make the mask color a constructor parameter.

[Vidar Hasfjord]

This issue has been fixed in Owlet [r8841]. Consistent mask color semantics was implemented in [r8842] (TColor::Transparent now consistently means that the upper left pixel of the bitmap should be used for the mask color).