From ec0dbeca6bac5252a717a811c46c049f98290cfe Mon Sep 17 00:00:00 2001
From: FunkyFr3sh <cc.red.alert.1@googlemail.com>
Date: Fri, 26 Jul 2024 08:29:43 +0200
Subject: [PATCH] add workaround for flickering (black frames) during zoom

---
 inc/dd.h          | 1 +
 src/ddsurface.c   | 3 +++
 src/dllmain.c     | 1 +
 src/render_d3d9.c | 3 +++
 src/render_ogl.c  | 3 +++
 5 files changed, 11 insertions(+)

diff --git a/inc/dd.h b/inc/dd.h
index bce317a..31708ff 100644
--- a/inc/dd.h
+++ b/inc/dd.h
@@ -168,6 +168,7 @@ typedef struct CNCDDRAW
 
     struct
     {
+        LONG frame_skip;
         BOOL enabled;
     } zoom;
 } CNCDDRAW;
diff --git a/src/ddsurface.c b/src/ddsurface.c
index 2f6a873..83e05b6 100644
--- a/src/ddsurface.c
+++ b/src/ddsurface.c
@@ -418,6 +418,9 @@ HRESULT dds_Blt(
 
     if ((This->caps & DDSCAPS_PRIMARYSURFACE) && g_ddraw.ref && g_ddraw.render.run)
     {
+        if (!(dwFlags & DDBLT_COLORFILL))
+            InterlockedExchange(&g_ddraw.zoom.frame_skip, 0);
+
         InterlockedExchange(&g_ddraw.render.surface_updated, TRUE);
 
         if (!(This->flags & DDSD_BACKBUFFERCOUNT) || This->last_flip_tick + FLIP_REDRAW_TIMEOUT < timeGetTime())
diff --git a/src/dllmain.c b/src/dllmain.c
index b75c335..3dee497 100644
--- a/src/dllmain.c
+++ b/src/dllmain.c
@@ -152,6 +152,7 @@ void DDEnableZoom()
     TRACE("%s [%p]\n", __FUNCTION__, _ReturnAddress());
 
     g_ddraw.zoom.enabled = TRUE;
+    InterlockedExchange(&g_ddraw.zoom.frame_skip, 20);
 }
 
 BOOL DDIsWindowed()
diff --git a/src/render_d3d9.c b/src/render_d3d9.c
index 9109f96..876618d 100644
--- a/src/render_d3d9.c
+++ b/src/render_d3d9.c
@@ -552,6 +552,9 @@ DWORD WINAPI d3d9_render_main(void)
         (g_config.minfps < 0 || WaitForSingleObject(g_ddraw.render.sem, timeout) != WAIT_FAILED) &&
         g_ddraw.render.run)
     {
+        if (InterlockedDecrement(&g_ddraw.zoom.frame_skip) > 0)
+            continue;
+
 #if _DEBUG
         dbg_draw_frame_info_start();
 #endif
diff --git a/src/render_ogl.c b/src/render_ogl.c
index d1c7df2..fa4c9d1 100644
--- a/src/render_ogl.c
+++ b/src/render_ogl.c
@@ -887,6 +887,9 @@ static void ogl_render()
         (g_config.minfps < 0 || WaitForSingleObject(g_ddraw.render.sem, timeout) != WAIT_FAILED) &&
         g_ddraw.render.run)
     {
+        if (InterlockedDecrement(&g_ddraw.zoom.frame_skip) > 0)
+            continue;
+
 #if _DEBUG
         dbg_draw_frame_info_start();
 #endif