From 39b2e69540046d669d6f9e72a3e9e72d0c99b36b Mon Sep 17 00:00:00 2001
From: FunkyFr3sh <cc.red.alert.1@googlemail.com>
Date: Mon, 16 Dec 2024 21:33:05 +0100
Subject: [PATCH] make sure we don't update the palette twice

---
 inc/ddpalette.h    |  2 ++
 src/ddpalette.c    | 14 ++++++++++++++
 src/winapi_hooks.c |  2 +-
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/inc/ddpalette.h b/inc/ddpalette.h
index 5f6d112..e780b5a 100644
--- a/inc/ddpalette.h
+++ b/inc/ddpalette.h
@@ -7,6 +7,8 @@
 #include "IDirectDrawPalette.h"
 #include "dd.h"
 
+#define DDPCAPS_REFRESH_CHANGED_ONLY (1 << 31)
+
 HRESULT ddp_GetEntries(IDirectDrawPaletteImpl* This, DWORD dwFlags, DWORD dwBase, DWORD dwNumEntries, LPPALETTEENTRY lpEntries);
 HRESULT ddp_SetEntries(IDirectDrawPaletteImpl* This, DWORD dwFlags, DWORD dwStartingEntry, DWORD dwCount, LPPALETTEENTRY lpEntries);
 HRESULT dd_CreatePalette(DWORD dwFlags, LPPALETTEENTRY lpDDColorArray, IDirectDrawPaletteImpl** lpDDPalette, IUnknown FAR* unkOuter);
diff --git a/src/ddpalette.c b/src/ddpalette.c
index af18231..46af3a1 100644
--- a/src/ddpalette.c
+++ b/src/ddpalette.c
@@ -5,6 +5,7 @@
 #include "ddsurface.h"
 #include "IDirectDrawPalette.h"
 #include "debug.h"
+#include "crc32.h"
 
 
 HRESULT ddp_GetEntries(
@@ -38,6 +39,13 @@ HRESULT ddp_SetEntries(
     if (!lpEntries)
         return DDERR_INVALIDPARAMS;
 
+    unsigned long crc32 = 0;
+
+    if ((dwFlags & DDPCAPS_REFRESH_CHANGED_ONLY))
+    {
+        crc32 = Crc32_ComputeBuf(0, This->data_rgb, sizeof(This->data_rgb));
+    }
+
     for (int i = dwStartingEntry, x = 0; i < dwStartingEntry + dwCount && i < 256; i++, x++)
     {
         This->data_bgr[i] = (lpEntries[x].peBlue << 16) | (lpEntries[x].peGreen << 8) | lpEntries[x].peRed;
@@ -64,6 +72,12 @@ HRESULT ddp_SetEntries(
         This->data_rgb[255].rgbReserved = 0;
     }
 
+    if (crc32 && crc32 == Crc32_ComputeBuf(0, This->data_rgb, sizeof(This->data_rgb)))
+    {
+        // do not set palette_updated BOOL if nothing changed
+        return DD_OK;
+    }
+
     if (g_ddraw.ref && g_ddraw.primary && g_ddraw.primary->palette == This && g_ddraw.render.run)
     {
         InterlockedExchange(&g_ddraw.render.palette_updated, TRUE);
diff --git a/src/winapi_hooks.c b/src/winapi_hooks.c
index e06e6f1..4bcfa3c 100644
--- a/src/winapi_hooks.c
+++ b/src/winapi_hooks.c
@@ -1460,7 +1460,7 @@ UINT WINAPI fake_RealizePalette(HDC hdc)
 
             ddp_SetEntries(
                 g_ddraw.primary->palette, 
-                0, 
+                DDPCAPS_REFRESH_CHANGED_ONLY,
                 0, 
                 g_ddraw.primary->selected_pal_count,
                 g_ddraw.primary->selected_pal);