Ignore HBSTRT/STOP changes if they are only temporary (less than 2/3 of total field)

diff --git a/custom.cpp b/custom.cpp
index f5a60b7c7ca76ca57a4039768367eed63606eaa5..fb31135b05d6e29f039ad37b0c8e58cb6726ef65 100644 (file)
--- a/custom.cpp
+++ b/custom.cpp
@@ -349,6 +349,7 @@ static uae_u16 beamcon0_saved;
 static uae_u16 bplcon0_saved, bplcon1_saved, bplcon2_saved;
 static uae_u16 bplcon3_saved, bplcon4_saved;
 static int varsync_changed, varsync_maybe_changed[2];
+static int varhblank_lines, varhblank_val[2];
 static uae_u16 vt_old, ht_old, hs_old, vs_old;
 uae_u16 vtotal, htotal;
 static int maxvpos_stored, maxhpos_stored;
@@ -8934,14 +8935,14 @@ static void varsync(int reg, bool resync, int oldval)
        if ((reg == 0x1cc || reg == 0x1ce) && (beamcon0 & BEAMCON0_VARVBEN)) {
                // check for >1 because of interlace modes
                if ((reg == 0x1cc && abs(vbstrt - oldval) > 1) || (reg == 0x1ce && abs(vbstop - oldval) > 1)) {
-                       // check VB and HB changes only if there are no many changes per frame
-                       varsync_maybe_changed[0]++;
+                       // check VB changes only if there are not many changes per frame
+                       varsync_maybe_changed[reg == 0x1cc ? 0 : 1]++;
                }
        }
        // HB
        if ((reg == 0x1c4 || reg == 0x1c6) && exthblank) {
-               // check VB and HB changes only if there are no many changes per frame
-               varsync_maybe_changed[1]++;
+               // only do resync if HB value has been valid at least 66% of field
+               varhblank_lines = (maxvpos / 3) * 2;
        }
 
        if (!resync) {
@@ -12234,7 +12235,7 @@ static void vsync_display_render(void)
 
 static void vsync_check_vsyncmode(void)
 {
-       if ((varsync_maybe_changed[0] >= 1 && varsync_maybe_changed[0] <= 4) || (varsync_maybe_changed[1] >= 1 && varsync_maybe_changed[1] <= 4)) {
+       if (varsync_maybe_changed[0] == 1 || varsync_maybe_changed[1] == 1 || varhblank_lines == -1) {
                init_hz_normal();
        } else if (varsync_changed == 1) {
                init_hz_normal();
@@ -12249,6 +12250,7 @@ static void vsync_check_vsyncmode(void)
        }
        varsync_maybe_changed[0] = 0;
        varsync_maybe_changed[1] = 0;
+       varhblank_lines = 0;
 }
 
 static void check_display_mode_change(void)
@@ -14047,6 +14049,17 @@ static void hsync_handler_post(bool onvsync)
                vb_check();
        }
 
+       if (varhblank_lines > 0) {
+               varhblank_lines--;
+               if (!varhblank_lines) {
+                       if (varhblank_val[0] != hbstrt || varhblank_val[1] != hbstop) {
+                               varhblank_lines = -1;
+                               varhblank_val[0] = hbstrt;
+                               varhblank_val[1] = hbstop;
+                       }
+               }
+       }
+
        decide_vline(0);
 
        int hp = REFRESH_FIRST_HPOS;