From cf439d5c63d80fa3672bdfb468ca8e64116aa6fe Mon Sep 17 00:00:00 2001
From: Ramez Ragaa <[EMAIL REDACTED]>
Date: Sat, 28 Dec 2024 18:02:52 +0200
Subject: [PATCH] Fix dib-to-bmp logic in SDL_windowsclipboard.c
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.
---
src/video/windows/SDL_windowsclipboard.c | 72 ++++++++----------------
1 file changed, 24 insertions(+), 48 deletions(-)
diff --git a/src/video/windows/SDL_windowsclipboard.c b/src/video/windows/SDL_windowsclipboard.c
index e62936bb9a4e2..dcb46bab597ba 100644
--- a/src/video/windows/SDL_windowsclipboard.c
+++ b/src/video/windows/SDL_windowsclipboard.c
@@ -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;
}