Fixed the issue with smooth scrolling with negative offset.

Trinity-11 · May 27, 2022 · f3cd22a · f3cd22a
1 parent 08cff96
commit f3cd22a
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Showing 2 changed files with 7 additions and 8 deletions.
diff --git a/Main/Display/Gpu.cs b/Main/Display/Gpu.cs
@@ -647,6 +647,7 @@ private unsafe void DrawTiles(int* p, bool gammaCorrection, byte TextColumns, in
 
             int tileSize = (smallTiles ? 8 : 16);
             int strideLine = tileSize * 16;
+            byte scrollMask = (byte)(smallTiles ? 7 : 15);
 
             int tilemapWidth = VICKY.ReadWord(addrTileCtrlReg + 4) & 0x3FF;   // 10 bits
             //int tilemapHeight = VICKY.ReadWord(addrTileCtrlReg + 6) & 0x3FF;  // 10 bits
@@ -656,31 +657,29 @@ private unsafe void DrawTiles(int* p, bool gammaCorrection, byte TextColumns, in
             // direction is bit 15.
             int tilemapWindowX = VICKY.ReadWord(addrTileCtrlReg + 8);
             bool dirLeft = (tilemapWindowX & 0x8000) != 0;
+            byte scrollX = (byte)(((tilemapWindowX & scrollMask) * (dirLeft ? -1 : 1)) & scrollMask);
             if (smallTiles)
             {
-                tilemapWindowX = (((tilemapWindowX & 0x3FF0) >> 1) + tilemapWindowX & 7);
-                tilemapWindowX *= (dirLeft ? -1 : 1);
+                tilemapWindowX = ((tilemapWindowX & 0x3FF0) >> 1) + scrollX;
             }
             else
             {
-                tilemapWindowX &= (0x3FFF);
-                tilemapWindowX *= (dirLeft ? -1 : 1);
+                tilemapWindowX = (tilemapWindowX & 0x3FF0) + scrollX;
             }
             int tileXOffset = tilemapWindowX % tileSize;
 
             // the tilemapWindowY is 10 bits and the scrollY is the lower 4 bits.  The IDE combines them.
             // direction is bit 15.
             int tilemapWindowY = VICKY.ReadWord(addrTileCtrlReg + 10);
             bool dirUp = (tilemapWindowY & 0x8000) != 0;
+            byte scrollY = (byte)(((tilemapWindowY & scrollMask) * (dirUp ? -1 : 1)) & scrollMask);
             if (smallTiles)
             {
-                tilemapWindowY = (((tilemapWindowY & 0x3FF0) >> 1) + tilemapWindowY & 7);
-                tilemapWindowY *= (dirUp ? -1 : 1);
+                tilemapWindowY = ((tilemapWindowY & 0x3FF0) >> 1) + scrollY;
             }
             else
             {
-                tilemapWindowY &= 0x3FFF;
-                tilemapWindowY *= (dirUp ? -1 : 1);
+                tilemapWindowY = tilemapWindowY & 0x3FF0 + scrollY;
             }
 
             int tileRow = ( line + tilemapWindowY ) / tileSize;

diff --git a/bin/Release/FoenixIDE.exe b/bin/Release/FoenixIDE.exe