Fix Hercules blend mode so that adjacent lit pixels are brighter again [

#5064]
joncampbell123 · Jun 27, 2024 · 95d543a · 95d543a
1 parent a66af3a
commit 95d543a
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Showing 4 changed files with 25 additions and 2 deletions.
diff --git a/CHANGELOG b/CHANGELOG
@@ -1,4 +1,7 @@
 Next:
+  - Hercules/MDA and InColor integration broke the Hercules blend mode
+    render, fix the render so that adjacent lit pixels are brighter
+    again. (joncampbell123).
   - Fix "VRD" debugger command bug that didn't properly render out the
     rest of the VGA display frame. (joncampbell123).
   - Fixed debugger mapper shortcut bug where entering the debugger

diff --git a/src/hardware/vga.cpp b/src/hardware/vga.cpp
@@ -342,6 +342,7 @@ void vsync_poll_debug_notify() {
         vga_3da_polled = true;
 }
 
+uint32_t HercBlend_2_Table[16];
 uint32_t CGA_2_Table[16];
 uint32_t CGA_4_Table[256];
 uint32_t CGA_4_HiRes_Table[256];
@@ -1216,6 +1217,22 @@ void VGA_Reset(Section*) {
         /* Generate tables */
         VGA_SetCGA2Table(0,1);
         VGA_SetCGA4Table(0,1,2,3);
+
+        if (machine == MCH_HERC || machine == MCH_MDA) {
+            /* alternate table for blend mode, expect mapping 0=black 1-7=gray 8=black 9-f=white
+             * for use with blend code that reads this table and sums the output with a delayed version of the same */
+            const uint8_t total[2] = {0x0,0x05}; /* blending will yield {0,5,10} which is sufficient to recreate the effect */
+            for (Bitu i=0;i<16u;i++) {
+                HercBlend_2_Table[i]=
+#ifdef WORDS_BIGENDIAN
+                    ((Bitu)total[(i >> 0u) & 1u] << 0u  ) | ((Bitu)total[(i >> 1u) & 1u] << 8u  ) |
+                    ((Bitu)total[(i >> 2u) & 1u] << 16u ) | ((Bitu)total[(i >> 3u) & 1u] << 24u );
+#else 
+                    ((Bitu)total[(i >> 3u) & 1u] << 0u  ) | ((Bitu)total[(i >> 2u) & 1u] << 8u  ) |
+                    ((Bitu)total[(i >> 1u) & 1u] << 16u ) | ((Bitu)total[(i >> 0u) & 1u] << 24u );
+#endif
+            }
+        }
     }
 
     Section_prop * section2=static_cast<Section_prop *>(control->GetSection("vsync"));

diff --git a/src/hardware/vga_draw.cpp b/src/hardware/vga_draw.cpp
@@ -473,6 +473,8 @@ static uint8_t * VGA_Draw_1BPP_Line(Bitu vidstart, Bitu line) {
 	return VGA_Draw_1BPP_Line_Common<MCH_CGA,uint8_t>(TempLine,vidstart,line);
 }
 
+extern uint32_t HercBlend_2_Table[16];
+
 static uint8_t * VGA_Draw_1BPP_Blend_Line(Bitu vidstart, Bitu line) {
     const uint8_t *base = vga.tandy.draw_base + ((line & vga.tandy.line_mask) << vga.tandy.line_shift);
     uint32_t *draw = (uint32_t *)TempLine;
@@ -481,8 +483,8 @@ static uint8_t * VGA_Draw_1BPP_Blend_Line(Bitu vidstart, Bitu line) {
         Bitu val1 = base[vidstart & (8 * 1024 -1)];
         Bitu val2 = (val1 >> 1) + carry;
         carry = (val1 & 1) << 7;
-        *draw++=CGA_2_Table[val1 >> 4] + CGA_2_Table[val2 >> 4];
-        *draw++=CGA_2_Table[val1 & 0xf] + CGA_2_Table[val2 & 0xf];
+        *draw++=HercBlend_2_Table[val1 >> 4] + HercBlend_2_Table[val2 >> 4];
+        *draw++=HercBlend_2_Table[val1 & 0xf] + HercBlend_2_Table[val2 & 0xf];
     }
     return TempLine;
 }

diff --git a/src/hardware/vga_other.cpp b/src/hardware/vga_other.cpp
@@ -1058,6 +1058,7 @@ void CycleMonoCGABright(bool pressed) {
 void HercBlend(bool pressed) {
 	if (!pressed) return;
 	vga.herc.blend = !vga.herc.blend;
+	LOG_MSG("Hercules blend %u",vga.herc.blend);
 	VGA_SetupDrawing(0);
 }