[V8i MDL C++] Getting a BSIColorDescr from an element colour

Question

I need to get a BSIColorDescr for a given element colour. If the element colour is 0-256 then this is trivial with mdlColorPal_getElemColorDescrByModelRef(), but of course MicroStation allows the symbology colour to be any RGB colour these days, and this function won't work with colours above 256. 
 To achieve 24-bit colours, it seems MicroStation uses some internal colour map that stores these RGB colours as required. For example, creating a new shade of mauve from the colour swatch might assign an element colour of 780. 
 Now I can easily get the RGB of this value using mdlColor_elementColorToRGB(); however I don't know how to get the corresponding BSIColorDescr from this RGB. There must be some hidden colour table that MicroStation keeps of all of these assigned colours (above 256) within the DGN file, but I can't see any such table exposed in the SDK. 
 Since the BSIColorDescr is opaque, I can't allocate one for myself on the fly as required, as these pointers usually refer back to a colour table. The colour table APIs all expect a 256 entry colour table, so I can't really use these, and I won't know in advance how many of these allocated colours are in use in any model, since this is also missing from the SDK. 
 So how do I get a persistent BSIColorDescr pointer for any arbitrary RGB colour used in a model? It really seems the SDK is sorely lacking in exposing this to the programmer. If I want to display one of these colours in a dialog, then I need a persistent BSIColorDescrP for every arbitrary colour defined beyond the attached colour table. 
 Cheers.

Brien Bastings · Accepted Answer

This isn't really my area, but it would seem like you could do the following: 
 BSIColorDescr* fgColor = nullptr;
 if (SUCCESS == mdlListCell_getIconColorOverrides(pCell, &fgColor, nullptr) && (nullptr != fgColor)) // <- I suspect this probably comes back with nullptr though...
 {
 RgbColorDef rgb;

rgb.red = 0x7f; rgb.green = 0x7f; rgb.blue = 0;
 mdlColorDescr_setByRgb(fgColor, &rgb, 0);
 } 
 Use the method below from DgnColorMap to get the element color information... 
 //! Get the color information from the supplied element color id. //! @param[out] colorDef IntColorDef for the supplied element color, can be used to get TBGR or RGB color values. //! @param[out] colorIndex The 0 to INDEX_Background index into the file's DgnColorMap. For rgb and book colors this is the closest match from when they were created. //! @param[out] isTrueColor True if supplied element color is a rgb or book color, false for color index. //! @param[out] bookName Color book name for the supplied element color (empty string for rgb and indexed colors). //! @param[out] colorName Color name from color book for the supplied element color (empty string for rgb and indexed colors). //! @param[in] elementColor The element color to extract the information for. //! @param[in] dgnFile The file for the supplied element color. //! @return SUCCESS if element color is a valid rgb, book, or DgnColorMap index. //! COLOR_BYLEVEL or COLOR_BYCELL will return ERROR. static DGNPLATFORM_EXPORT StatusInt ExtractElementColorInfo (IntColorDef* colorDef, UInt32* colorIndex, bool* isTrueColor, WStringP bookName, WStringP colorName, UInt32 elementColor, DgnFileR dgnFile); 
 Worst case scenario, include these locally (I don't think you'll need to call destroy, the list cell should take care of that). 
 MSCORE_EXPORT int mdlColorDescr_create (BSIColorDescr **newDescrPP); 
 MSCORE_EXPORT int mdlColorDescr_destroy (BSIColorDescr **colorDescrPP); 
 HTH