rasChangeBackColor

void __stdcall rasChangeBackColor(IPGC CachePtr, uint32_t Value);
BOOL32 __stdcall rasSetOCGState(IPGC CachePtr, uint32_t Handle, BOOL32 Visible, BOOL32 SaveState);
void __stdcall rasSetOnPaintCallback(IPGC CachePtr, void* UserData, TOnUpdateWindow Callback);

procedure rasChangeBackColor(CachePtr: IPGC; Value: Cardinal); stdcall;
function rasSetOCGState(CachePtr: IPGC; Handle: Cardinal; Visible, SaveState: LongBool): LongBool; stdcall;
procedure rasSetOnPaintCallback(CachePtr: IPGC; const UserData: Pointer; Callback: TOnUpdateWindow); stdcall;

Purpose. Three real paint-configuration setters: the viewport background fill color, per-optional-content-group visibility (consumed by rasRenderTile's content-filtering above), and a host repaint callback (consumed by rasUpdate above).

Description. rasChangeBackColor stores C.BackColor, read by rasPaint's ViewerFillBG call. rasSetOCGState adds/removes Handle from C.HiddenOCG (a real TList<Cardinal>) based on Visible, and calls C.ClearRenderCache — invalidating any bitmaps cached before the visibility change so the next paint/tile render reflects it; SaveState is accepted but this chapter did not find it consulted (no persistent "saved OCG state" mechanism was located). rasSetOnPaintCallback stores Callback/UserData — per an inline comment, this was formerly a silent no-op that discarded the callback and is now genuinely invoked by rasUpdate.

Parameters.

Return value. rasSetOCGState: True if CachePtr resolves. rasChangeBackColor/rasSetOnPaintCallback: none.

C# (P/Invoke)

public static extern void rasChangeBackColor(IntPtr CachePtr, uint Value);