Impl horizontal scroll

1 files changed, 32 insertions, 9 deletions

diff --git a/vdp.cpp b/vdp.cpp
index 735ec13..395237f 100644
--- a/vdp.cpp
+++ b/vdp.cpp
@@ -61,6 +61,14 @@
     ((reg) = ((reg) & ~SCROLLB_ADDR_MASK) \
                 | (((uint16_t)(v) >> SCROLLB_ADDR_SHIFT) & SCROLLB_ADDR_MASK))
 
+#define HSCROLL_TABLE_ADDR_MASK (0x3f)
+#define HSCROLL_TABLE_ADDR_SHIFT (10)
+#define HSCROLL_TABLE_ADDR_GET(reg) \
+    ((((uint16_t)(reg)) & (HSCROLL_TABLE_ADDR_MASK)) << HSCROLL_TABLE_ADDR_SHIFT)
+#define HSCROLL_TABLE_ADDR_SET(reg, v) \
+    ((reg) = ((reg) & ~HSCROLL_TABLE_ADDR_MASK) \
+                | (((uint16_t)(v) >> HSCROLL_TABLE_ADDR_SHIFT) & HSCROLL_TABLE_ADDR_MASK))
+
 // 0: V32 CELL, 1: V64 CELL, 2: Prohibited, 3: V128 CELL
 #define SCROLLSIZE_VCELL_MASK (3)
 #define SCROLLSIZE_VCELL_SHIFT (4)
@@ -219,12 +227,18 @@ void VDP::renderScrollBLine(const size_t line_index, const size_t hcell_count)
         if (cx * kCellWidthPixels >= kRenderWidth) {
             break;
         }
-        const uint16_t cell_id = GetU16BE(
+        const uint16_t sprite_id = GetU16BE(
                 _vram + scroll_addr + (cy * hcell_count + cx) * sizeof(uint16_t));
         const uint32_t val = GetU32BE(
-                _vram + (cell_id * kCellHeightPixels + y) * (kCellWidthPixels / kPixelsPerByte));
+                _vram + (sprite_id * kCellHeightPixels + y) * (kCellWidthPixels / kPixelsPerByte));
+        const size_t hscroll_table_addr_reg =
+            _reg[static_cast<size_t>(RegID::kHScrollTableAddress)];
+        const size_t hscroll_table_addr = HSCROLL_TABLE_ADDR_GET(hscroll_table_addr_reg);
+        const size_t hscroll = GetU16BE(_vram + hscroll_table_addr + sizeof(uint16_t) * 1) & 0x3ff;
         for (size_t x = 0; x < kCellWidthPixels; x++) {
-            if (cx * kCellWidthPixels + x >= kRenderWidth) {
+            const size_t render_offset_x = (cx * kCellWidthPixels + x + hscroll) %
+                (hcell_count * kCellWidthPixels);
+            if (render_offset_x >= kRenderWidth) {
                 continue;
             }
             const size_t color_index = (val >> ((kCellWidthPixels - 1 - x) * 4)) & 0xf;
@@ -240,7 +254,7 @@ void VDP::renderScrollBLine(const size_t line_index, const size_t hcell_count)
             const uint16_t cram_color = GetU16BE(_cram + color_index * sizeof(uint16_t));
             const uint32_t color = RenderColorFromCRAM(cram_color);
             const size_t render_offset =
-                ((cy * kCellHeightPixels + y) * kRenderWidth) + cx * kCellWidthPixels + x;
+                ((cy * kCellHeightPixels + y) * kRenderWidth) + render_offset_x;
             _rendered_buffer[render_offset] = color;
         }
     }
@@ -256,12 +270,18 @@ void VDP::renderScrollALine(const size_t line_index, const size_t hcell_count)
         if (cx * kCellWidthPixels >= kRenderWidth) {
             break;
         }
-        const uint16_t cell_id = GetU16BE(
+        const uint16_t sprite_id = GetU16BE(
                 _vram + scroll_addr + (cy * hcell_count + cx) * sizeof(uint16_t));
         const uint32_t val = GetU32BE(
-                _vram + (cell_id * kCellHeightPixels + y) * (kCellWidthPixels / kPixelsPerByte));
+                _vram + (sprite_id * kCellHeightPixels + y) * (kCellWidthPixels / kPixelsPerByte));
+        const size_t hscroll_table_addr_reg =
+            _reg[static_cast<size_t>(RegID::kHScrollTableAddress)];
+        const size_t hscroll_table_addr = HSCROLL_TABLE_ADDR_GET(hscroll_table_addr_reg);
+        const size_t hscroll = GetU16BE(_vram + hscroll_table_addr + sizeof(uint16_t) * 0) & 0x3ff;
         for (size_t x = 0; x < kCellWidthPixels; x++) {
-            if (cx * kCellWidthPixels + x >= kRenderWidth) {
+            const size_t render_offset_x = (cx * kCellWidthPixels + x + hscroll) %
+                (hcell_count * kCellWidthPixels);
+            if (render_offset_x >= kRenderWidth) {
                 continue;
             }
             const size_t color_index = (val >> ((kCellWidthPixels - 1 - x) * 4)) & 0xf;
@@ -277,7 +297,7 @@ void VDP::renderScrollALine(const size_t line_index, const size_t hcell_count)
             const uint16_t cram_color = GetU16BE(_cram + color_index * sizeof(uint16_t));
             const uint32_t color = RenderColorFromCRAM(cram_color);
             const size_t render_offset =
-                ((cy * kCellHeightPixels + y) * kRenderWidth) + cx * kCellWidthPixels + x;
+                ((cy * kCellHeightPixels + y) * kRenderWidth) + render_offset_x;
             _rendered_buffer[render_offset] = color;
         }
     }
@@ -290,7 +310,10 @@ bool VDP::Scanline()
         return true;
     }
     const uint16_t lines_per_screen = _status.pal_mode ? kLinesPerScreenPAL : kLinesPerScreenNTSC;
-    memset(_rendered_buffer + kRenderWidth * _lines_counter, 0, kRenderWidth);
+    memset(
+            _rendered_buffer + kRenderWidth * _lines_counter,
+            0,
+            kRenderWidth * sizeof(*_rendered_buffer));
     if (_lines_counter >= (int)kRenderHeight) {
         // just render palette
         for (size_t i = 0; i < kRenderWidth; i++) {