From b59650f997008d1368beec159e61ec03f53e0023 Mon Sep 17 00:00:00 2001
From: Dirk Hoffmann <dirk.hoffmann@me.com>
Date: Sat, 30 Dec 2023 12:14:44 +0100
Subject: [PATCH] Work on setHSTRT (#799)

---
 Emulator/Components/Denise/Denise.cpp         | 48 ++++++++++++++++++-
 Emulator/Components/Denise/DeniseRegs.cpp     |  2 +-
 .../xcdebugger/Breakpoints_v2.xcbkptlist      |  6 +--
 3 files changed, 50 insertions(+), 6 deletions(-)

diff --git a/Emulator/Components/Denise/Denise.cpp b/Emulator/Components/Denise/Denise.cpp
index b99fc58c4..13986569f 100644
--- a/Emulator/Components/Denise/Denise.cpp
+++ b/Emulator/Components/Denise/Denise.cpp
@@ -1005,7 +1005,7 @@ Denise::updateBorderColor()
 void
 Denise::drawBorder()
 {
-    /* The following cases need to be distinguished:
+    /* The following cases must be distinguished:
      *
      * (1) No border                1 --------------------
      *     flop && !off             0
@@ -1027,6 +1027,36 @@ Denise::drawBorder()
     bool on = hflopOnPrev != INT16_MAX;
     bool off = hflopOffPrev != INT16_MAX;
 
+    isize hblank = 4 * HBLANK_MIN;
+
+    // EXPERIMENTAL
+
+    if (on && off && hflopOnPrev > hflopOffPrev) {
+
+        if (!flop) {
+
+            trace(true, "ECS feature (!flop): %ld %ld\n", hflopOnPrev, hflopOffPrev);
+            // Draw left border
+            auto end = std::min(2 * hflopOnPrev - hblank, isize(HPIXELS + 1));
+            for (isize i = 0; i < end; i++) {
+                bBuffer[i] = iBuffer[i] = mBuffer[i] = borderColor;
+            }
+
+        } else {
+
+            trace(true, "ECS feature (flop): %ld %ld\n", hflopOnPrev, hflopOffPrev);
+
+            // Draw border in the middle
+            auto start = std::max(2 * hflopOffPrev - hblank, isize(0));
+            auto end = std::min(2 * hflopOnPrev - hblank, isize(HPIXELS + 1));
+            for (isize i = start; i < end; i++) {
+                bBuffer[i] = iBuffer[i] = mBuffer[i] = 0;
+            }
+        }
+        return;
+    }
+    
+
     if (!flop && !on) {
 
         // Draw blank line (2)
@@ -1260,7 +1290,21 @@ Denise::eolHandler()
     hflopOffPrev = hflopOff;
 
     // Update the horizontal DIW flipflop
-    hflop = (hflopOff != INT16_MAX) ? false : (hflopOn != INT16_MAX) ? true : hflop;
+    //
+    //   hflopOn  | hflopOff | hFlop
+    //   ----------------------------------------
+    //   in range | in range | hflopOn > hflopOff
+    //   in range | inf      | true
+    //   inf      | in range | false
+    //   inf      | inf      | hflop
+    //
+    // hflop = (hflopOff != INT16_MAX) ? false : (hflopOn != INT16_MAX) ? true : hflop;
+    if (hflopOn != INT16_MAX) {
+        hflop = (hflopOff != INT16_MAX) ? (hflopOn > hflopOff) : true;
+    } else {
+        hflop = (hflopOff != INT16_MAX) ? hflop : false;
+    }
+
     hflopOn = denise.hstrt;
     hflopOff = denise.hstop;
 }
diff --git a/Emulator/Components/Denise/DeniseRegs.cpp b/Emulator/Components/Denise/DeniseRegs.cpp
index bd020f239..4e73cfd51 100644
--- a/Emulator/Components/Denise/DeniseRegs.cpp
+++ b/Emulator/Components/Denise/DeniseRegs.cpp
@@ -58,7 +58,7 @@ void
 Denise::setHSTRT(isize val)
 {
     // Invalidate the coordinate if it is out of range
-    if (val < 2 || val > 0x1C7) {
+    if ((val < 2 || val > 0x1C7) && agnus.pos.v > 8) {
 
         trace(DIW_DEBUG, "setHSTRT: %ld is out of range\n", val);
         val = INT16_MAX;
diff --git a/vAmiga.xcodeproj/xcuserdata/hoff.xcuserdatad/xcdebugger/Breakpoints_v2.xcbkptlist b/vAmiga.xcodeproj/xcuserdata/hoff.xcuserdatad/xcdebugger/Breakpoints_v2.xcbkptlist
index ba11fc498..95333c575 100644
--- a/vAmiga.xcodeproj/xcuserdata/hoff.xcuserdatad/xcdebugger/Breakpoints_v2.xcbkptlist
+++ b/vAmiga.xcodeproj/xcuserdata/hoff.xcuserdatad/xcdebugger/Breakpoints_v2.xcbkptlist
@@ -80,7 +80,7 @@
          BreakpointExtensionID = "Xcode.Breakpoint.RuntimeIssueBreakpoint">
          <BreakpointContent
             uuid = "1C34E446-9F03-4ADF-999F-3C4F93560618"
-            shouldBeEnabled = "Yes"
+            shouldBeEnabled = "No"
             ignoreCount = "0"
             continueAfterRunningActions = "No"
             breakpointStackSelectionBehavior = "1"
@@ -108,7 +108,7 @@
          BreakpointExtensionID = "Xcode.Breakpoint.RuntimeIssueBreakpoint">
          <BreakpointContent
             uuid = "E2606246-83A4-48C5-BC45-5FA47C77CC7E"
-            shouldBeEnabled = "Yes"
+            shouldBeEnabled = "No"
             ignoreCount = "0"
             continueAfterRunningActions = "No"
             breakpointStackSelectionBehavior = "1"
@@ -179,7 +179,7 @@
          BreakpointExtensionID = "Xcode.Breakpoint.FileBreakpoint">
          <BreakpointContent
             uuid = "9F889B32-39C8-498F-AFC3-14E8073A26C8"
-            shouldBeEnabled = "Yes"
+            shouldBeEnabled = "No"
             ignoreCount = "0"
             continueAfterRunningActions = "No"
             filePath = "Emulator/Components/CPU/Moira/Moira.cpp"