From 7278ed20159f95550b5bd0468e2be453320f0359 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Herv=C3=A9=20Poussineau?= <hpoussin@reactos.org>
Date: Wed, 28 Sep 2022 18:26:44 +0200
Subject: [PATCH] [WIN32SS] Change LDEVOBJ_bProbeAndCaptureDevmode to account
 for not provided fields when searching an exact mode

This fixes mode change if an application requests (for example) 640x480x32, without providing display frequency.
---
 win32ss/gdi/eng/ldevobj.c | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/win32ss/gdi/eng/ldevobj.c b/win32ss/gdi/eng/ldevobj.c
index 6408c20648f..803cbd37fe1 100644
--- a/win32ss/gdi/eng/ldevobj.c
+++ b/win32ss/gdi/eng/ldevobj.c
@@ -804,9 +804,9 @@ LDEVOBJ_bProbeAndCaptureDevmode(
     if (!bResult)
         return FALSE;
 
-    if (bSearchClosestMode)
+    if (LDEVOBJ_bGetClosestMode(pGraphicsDevice, &dmSearch, &pdmSelected))
     {
-        if (LDEVOBJ_bGetClosestMode(pGraphicsDevice, &dmSearch, &pdmSelected))
+        if (bSearchClosestMode)
         {
             /* Ok, found a closest mode. Update search */
             dmSearch.dmBitsPerPel = pdmSelected->dmBitsPerPel;
@@ -814,6 +814,29 @@ LDEVOBJ_bProbeAndCaptureDevmode(
             dmSearch.dmPelsHeight = pdmSelected->dmPelsHeight;
             dmSearch.dmDisplayFrequency = pdmSelected->dmDisplayFrequency;
         }
+        else
+        {
+            /* Only update not provided fields */
+            _SEH2_TRY
+            {
+                if (!(RequestedMode->dmFields & DM_BITSPERPEL) || RequestedMode->dmBitsPerPel == 0)
+                    dmSearch.dmBitsPerPel = pdmSelected->dmBitsPerPel;
+                if (!(RequestedMode->dmFields & DM_PELSWIDTH) || RequestedMode->dmPelsWidth == 0)
+                    dmSearch.dmPelsWidth = pdmSelected->dmPelsWidth;
+                if (!(RequestedMode->dmFields & DM_PELSHEIGHT) || RequestedMode->dmPelsHeight == 0)
+                    dmSearch.dmPelsHeight = pdmSelected->dmPelsHeight;
+                if (!(RequestedMode->dmFields & DM_DISPLAYFREQUENCY) || RequestedMode->dmDisplayFrequency == 0)
+                    dmSearch.dmDisplayFrequency = pdmSelected->dmDisplayFrequency;
+            }
+            _SEH2_EXCEPT(EXCEPTION_EXECUTE_HANDLER)
+            {
+                bResult = FALSE;
+            }
+            _SEH2_END;
+
+            if (!bResult)
+                return FALSE;
+        }
     }
 
     /* Now, search the exact mode to return to caller */