From f1814d0c65dba73b36cfb3261de434f2fc0d495d Mon Sep 17 00:00:00 2001
From: Cacodemon345 <wahil1976@outlook.com>
Date: Sun, 24 Aug 2025 00:08:00 +0600
Subject: [PATCH] Fix MDA refresh rate

Also improve monochrome contrast menu option
---
 src/qt/qt_mainwindow.cpp | 5 ++++-
 src/video/vid_mda.c      | 4 ++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/qt/qt_mainwindow.cpp b/src/qt/qt_mainwindow.cpp
index b335b3480..3b8bee2f0 100644
--- a/src/qt/qt_mainwindow.cpp
+++ b/src/qt/qt_mainwindow.cpp
@@ -1985,9 +1985,12 @@ MainWindow::on_actionCGA_PCjr_Tandy_EGA_S_VGA_overscan_triggered()
 void
 MainWindow::on_actionChange_contrast_for_monochrome_display_triggered()
 {
+    startblit();
     vid_cga_contrast ^= 1;
-    cgapal_rebuild();
+    for (int i = 0; i < MONITORS_NUM; i++)
+        cgapal_rebuild_monitor(i);
     config_save();
+    endblit();
 }
 
 void
diff --git a/src/video/vid_mda.c b/src/video/vid_mda.c
index 1065df8a8..184ad7fdd 100644
--- a/src/video/vid_mda.c
+++ b/src/video/vid_mda.c
@@ -130,8 +130,8 @@ mda_recalctimings(mda_t *mda)
     double _dispontime;
     double _dispofftime;
     double disptime;
-    disptime     = (mda->crtc[MDA_CRTC_HTOTAL] + 1) << 1;
-    _dispontime  = (mda->crtc[MDA_CRTC_HDISP]) << 1;
+    disptime     = (mda->crtc[MDA_CRTC_HTOTAL] + 1);
+    _dispontime  = (mda->crtc[MDA_CRTC_HDISP]);
     _dispofftime = disptime - _dispontime;
     _dispontime *= MDACONST;
     _dispofftime *= MDACONST;