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Fix dib-to-bmp logic in SDL_windowsclipboard.c

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This addresses the issue #11762 by reading the biCompression field to
determine the correct size of the color table, and consequently the
correct bih_size value.
This commit is contained in:
Ramez Ragaa 2024-12-28 18:02:52 +02:00 • committed by Sam Lantinga
parent ec29d3fd66
commit cf439d5c63
1 changed files with 24 additions and 48 deletions
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72
src/video/windows/SDL_windowsclipboard.c
View file

@ -41,51 +41,6 @@
// Assume we can directly read and write BMP fields without byte swapping
SDL_COMPILE_TIME_ASSERT(verify_byte_order, SDL_BYTEORDER == SDL_LIL_ENDIAN);
static int WIN_GetPixelDataOffset(BITMAPINFOHEADER bih)
{
int offset = 0;
// biSize Specifies the number of bytes required by the structure
// We expect to always be 40 because it should be packed
if (40 == bih.biSize && 40 == sizeof(BITMAPINFOHEADER))
{
//
// biBitCount Specifies the number of bits per pixel.
// Might exist some bit masks *after* the header and *before* the pixel offset
// we're looking, but only if we have more than
// 8 bits per pixel, so we need to ajust for that
//
if (bih.biBitCount > 8)
{
// If bih.biCompression is RBG we should NOT offset more
if (bih.biCompression == BI_BITFIELDS)
{
offset += 3 * sizeof(RGBQUAD);
} else if (bih.biCompression == 6 /* BI_ALPHABITFIELDS */) {
// Not common, but still right
offset += 4 * sizeof(RGBQUAD);
}
}
}
//
// biClrUsed Specifies the number of color indices in the color table that are actually used by the bitmap.
// If this value is zero, the bitmap uses the maximum number of colors
// corresponding to the value of the biBitCount member for the compression mode specified by biCompression.
// If biClrUsed is nonzero and the biBitCount member is less than 16
// the biClrUsed member specifies the actual number of colors
//
if (bih.biClrUsed > 0) {
offset += bih.biClrUsed * sizeof(RGBQUAD);
} else {
if (bih.biBitCount < 16) {
offset = offset + (sizeof(RGBQUAD) << bih.biBitCount);
}
}
return bih.biSize + offset;
}
static BOOL WIN_OpenClipboard(SDL_VideoDevice *_this)
{
// Retry to open the clipboard in case another application has it open
@ -157,9 +112,30 @@ static void *WIN_ConvertDIBtoBMP(HANDLE hMem, size_t *size)
LPVOID dib = GlobalLock(hMem);
if (dib) {
BITMAPINFOHEADER *pbih = (BITMAPINFOHEADER *)dib;
size_t bih_size = pbih->biSize + pbih->biClrUsed * sizeof(RGBQUAD);
// https://learn.microsoft.com/en-us/windows/win32/api/wingdi/ns-wingdi-bitmapinfoheader#color-tables
size_t color_table_size;
switch (pbih->biCompression) {
case BI_RGB:
if (pbih->biBitCount <= 8) {
color_table_size = sizeof(RGBQUAD) * (pbih->biClrUsed == 0 ? 1 << pbih->biBitCount : pbih->biClrUsed);
} else {
color_table_size = 0;
}
break;
case BI_BITFIELDS:
color_table_size = 3 * sizeof(DWORD);
break;
case 6 /* BI_ALPHABITFIELDS */:
// https://learn.microsoft.com/en-us/previous-versions/windows/embedded/aa452885(v=msdn.10)
color_table_size = 4 * sizeof(DWORD);
break;
default: // FOURCC
color_table_size = sizeof(RGBQUAD) * pbih->biClrUsed;
}
size_t bih_size = pbih->biSize + color_table_size;
size_t dib_size = bih_size + pbih->biSizeImage;
int pixel_offset = WIN_GetPixelDataOffset(*pbih);
if (dib_size <= mem_size) {
size_t bmp_size = sizeof(BITMAPFILEHEADER) + mem_size;
bmp = SDL_malloc(bmp_size);
@ -169,7 +145,7 @@ static void *WIN_ConvertDIBtoBMP(HANDLE hMem, size_t *size)
pbfh->bfSize = (DWORD)bmp_size;
pbfh->bfReserved1 = 0;
pbfh->bfReserved2 = 0;
pbfh->bfOffBits = (DWORD)(sizeof(BITMAPFILEHEADER) + pixel_offset);
pbfh->bfOffBits = (DWORD)(sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + color_table_size);
SDL_memcpy((Uint8 *)bmp + sizeof(BITMAPFILEHEADER), dib, dib_size);
*size = bmp_size;
}