_UNDOCUMENTED CORNER_
edited by Andrew Schulman
written by Jeffrey M. Cogswell


Figure 1:

(a)

Palette:
   ilPaletteHead         Offs: 00
   ilphPal               Offs: 0C
   ilpUseCount           Offs: 0E
   ilphLDevice           Offs: 10
   ilpFlags              Offs: 12
   ilphMetaList          Offs: 14
Colors:
   peForeIndex           Offs: 00
   peCurIndex            Offs: 02
   pePrevIndex           Offs: 04
   peColor               Offs: 06
PalGlobal:
   phNumEntries          Offs: 00
   phCurRealTime         Offs: 02
   phColors              Offs: 04

(b)

Region:
   rgnHead               Offs: 00
   rgnSize               Offs: 0C
   rgnSCnt               Offs: 0E
   rgnMaxScan            Offs: 10
   rgnBBox               Offs: 12
   rgnScnList            Offs: 1A
Scans:
   scnPntCnt             Offs: 00
   scnPntTop             Offs: 02
   scnPntBottom          Offs: 04
   scnPntsX              Offs: 06
   scnPtCntToo           Offs: 0A

Figure 2

typedef struct tagPALETTEENTRY {
    BYTE  peRed;
    BYTE  peGreen;
    BYTE  peBlue;
    BYTE  peFlags;
    } PALETTEENTRY;
typedef struct tagLOGPALETTE
    WORD         palVersion;
    WORD         palNumEntries;
    PALETTEENTRY palPalEntry[1];
    } LOGPALETTE, FAR * LPLOGPALETTE;

Figure 3

(a)

typedef struct tagGDIOBJHDR {
    HANDLE  hNext;
    WORD    wMagic;
    DWORD   dwCount;
    WORD    wMetaList;
#ifdef DEBUG_31
    WORD    wSelCount;
    HANDLE  hOwner; 
#endif
    } GDIOBJHDR, FAR *LPGDIOBJHDR;

(b)

#include "toolhelp.h"
// ...
SYSTEMHEAPINFO shi;
LOCALENTRY le;
shi.dwSize = sizeof(shi);
SystemHeapInfo(&shi);
hGDI = shi.hGDISegment;
for (ok = LocalFirst(&le, hGDI); ok; ok = LocalNext(&le))
    if (le.wType == LT_GDI_PALETTE)
        printf ("%04x\n",le.hHandle);



Figure 4

//structures within global heap
typedef struct tagCOLORS {
   WORD peForeIndex;         //Apparantly used for Foreground palettes.
   WORD peCurIndex;          //Index into system palette.  This
                             //number tells us where this particular
                             //RGB value is mapped into the system palette.
   WORD pePrevIndex;         //Previous index.  Exact use unclear. 
   PALETTEENTRY peColor;     //RGB and flags -- see Figure 2
} COLORS;
typedef struct tagPALGLOBAL{
   WORD phNumEntries;        //number of entries
   WORD phCurRealTime;       //number of times realized
   COLORS phColors[1];       //actual RGB values
} PALGLOBAL;
//structure within GDI's local heap 
typedef struct tagNewPALETTEOBJ {
    GDIOBJHDR       ilPaletteHead;  //see Figure 3(a)
    HANDLE          ilphPal;        //handle pointing to global structure
    WORD            ilphUseCount;   //Number of times currently selected
    HANDLE          ilphLDevice;    //copied in from DC when selected
    WORD            ilpFlags;       //Used internally to RealizePalette ???
    WORD            ilphMetaList;   //Apparantly used in metafiles
} NewPALETTEOBJ;




Example 1: 


hLocal = LocalAlloc(LPTR, sizeof(LOGPALETTE) + NUMCOLORS * sizeof(PALETTEENTRY));
LogPal = (NPLOGPALETTE) LocalLock(hLocal);


Example 2: 

(a)

case WM_PAINT:
   hDC = BeginPaint(hWnd, &PtStr);
   oldpal = SelectPalette(hdc,hpal,FALSE);
   mapped = RealizePalette(hDC);


(b)

SelectPalette(hDC, hOldPal, FALSE); 
EndPaint(hWnd, &PtStr);


Example 3: 

shi.dwSize = sizeof(shi);
SystemHeapInfo(&shi);
GDIHeap = shi.hGDISegment;
GDIHeap &= 0xfffc;
GDIHeap |= 1;