From 84c90c4665031bd7f2c6d12092f04837ea417c90 Mon Sep 17 00:00:00 2001
From: Colby <colby@taplaboratories.com.au>
Date: Mon, 1 Aug 2016 20:21:06 +1000
Subject: [PATCH] re-enable drawing sprites and windows

---
 lib/waterfoul/gpu.rb | 132 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 132 insertions(+)

diff --git a/lib/waterfoul/gpu.rb b/lib/waterfoul/gpu.rb
index 7a152ee..57c06c2 100644
--- a/lib/waterfoul/gpu.rb
+++ b/lib/waterfoul/gpu.rb
@@ -29,6 +29,7 @@ module Waterfoul
       @vblank_line = 0
       @auxillary_modeclock = 0
       @screen_enabled = true
+      @window_line = 0
     end
 
     def step(cycles = 1)
@@ -53,6 +54,7 @@ module Waterfoul
           @modeclock = 0
           @mode = 0
           @auxillary_modeclock = 0
+          @window_line = 0
           reset_current_line
           update_stat_mode
           compare_lylc
@@ -92,6 +94,7 @@ module Waterfoul
         @mode = V_BLANK_STATE
         @auxillary_modeclock = @modeclock
         @vblank = true
+        @window_line = 0
         Interrupt.request_interrupt(Interrupt::INTERRUPT_VBLANK)
       end
 
@@ -120,6 +123,8 @@ module Waterfoul
 
     def scanline
       render_bg
+      render_window
+      render_sprites
     end
 
     def update_stat_mode
@@ -128,6 +133,133 @@ module Waterfoul
       $mmu.write_byte 0xFF41, new_stat
     end
 
+    def render_window
+      line = current_line
+      line_width = line * Screen::SCREEN_WIDTH
+      # dont render if the window is outside the bounds of the screen or
+      # if the LCDC window enable bit flag is not set
+      return if @window_line > 143 || !IO::LCDControl.window_enabled?
+
+      window_pos_x = $mmu.read_byte(0xFF4B) - 7
+      window_pos_y = $mmu.read_byte(0xFF4A)
+
+      # don't render if the window is outside the bounds of the screen
+      return if window_pos_x > 159 || window_pos_y > 143 || window_pos_y > line
+
+      map_select = IO::LCDControl.window_map_select
+      tiles_select = IO::LCDControl.bg_tile_select
+
+      line_adjusted = @window_line
+      y_offset = (line_adjusted / 8) * 32
+      tile_line = line_adjusted % 8
+      tile_line_offset = tile_line * 2
+
+      0.upto(31) do |x|
+        tile = 0
+        if tiles == 0x8800
+          tile = signed_value $mmu.read_byte(map_select + y_offset + x)
+          tile += 128
+        else
+          tile = $mmu.read_byte map_select + y_offset + x
+        end
+
+        line_pixel_offset = x * 8
+        tile_select_offset = tile * 16
+        tile_address = tiles_select + tile_select_offset + tile_line_offset
+
+        byte_1 = $mmu.read_byte tile_address
+        byte_2 = $mmu.read_byte (tile_address + 1)
+
+        0.upto(7) do |pixelx|
+          buffer_addr = line_pixel_offset + pixelx + wx
+
+          next if buffer_addr < 0 || buffer_addr >= SCREEN_WIDTH
+
+          shift 0x1 << (7 - pixelx)
+
+          pixel = 0
+          if (byte_1 & shift == shift) && (byte_2 & shift == shift)
+            pixel = 3
+          elsif (byte_1 & shift == 0x0) && (byte_2 & shift == shift)
+            pixel = 1
+          elsif (byte_1 & shift == shift) && (byte_2 & shift == 0x0)
+            pixel = 2
+          elsif (byte_1 & shift == 0x0) && (byte_2 & shift == 0x00)
+            pixel = 0
+          end
+
+          position = line_width + buffer_addr
+          @framebuffer[position] = pixel
+        end
+      end
+      @window_line += 1
+    end
+
+    def render_sprites
+      line = current_line
+      line_width = line * Screen::SCREEN_WIDTH
+
+      return unless IO::LCDControl.obj_display
+
+      sprite_size = IO::LCDControl.obj_size
+
+      39.downto(0) do |sprite|
+        sprite_offset = sprite * 4
+
+        sprite_y = $mmu.read_byte(0xFE00 + sprite_offset) - 16
+        next if sprite_y > line || (sprite_y + sprite_size) <= line
+
+        sprite_x = $mmu.read_byte(0xFE00 + sprite_offset + 1) - 8
+        next if sprite_x < -7 || sprite_x >= SCREEN_WIDTH
+
+        sprite_tile_offset = ($mmu.read_byte(0xFE00 + sprite_offset + 2) & (sprite_size == 16 ? 0xFE : 0xFF)) * 16
+        sprite_flags = $mmu.read_byte(0xFE00 + sprite_offset + 3)
+        x_flip = sprite_flags & 0x20 == 0x20 ? true : false
+        y_flip = sprite_flags & 0x40 == 0x40 ? true : false
+        #above_bg = sprite_flags & 0x80 == 0x80 ? true : false
+
+        tiles = 0x8000
+        pixel_y = y_flip ? (sprite_size == 16 ? 15 : 7) - (line - sprite_y) : line - sprite_y
+
+        pixel_y_2 = 0
+        offset = 0
+
+        if sprite_size == 16 && (pixel_y >= 8)
+          pixel_y_2 = (pixel_y - 8) * 2
+          offset = 16
+        else
+          pixel_y_2 = pixel_y * 2
+        end
+
+        tile_address = tiles + sprite_tile_offset + pixel_y_2 + offset
+
+        byte_1 = $mmu.read_byte tile_address
+        byte_2 = $mmu.read_byte (tile_address + 1)
+
+        0.upto(7) do |pixelx|
+          shift = 0x1 << (x_flip ? pixelx : 7 - pixelx)
+          pixel = 0
+
+          if (byte_1 & shift == shift) && (byte_2 & shift == shift)
+            pixel = 3
+          elsif (byte_1 & shift == 0x0) && (byte_2 & shift == shift)
+            pixel = 1
+          elsif (byte_1 & shift == shift) && (byte_2 & shift == 0x0)
+            pixel = 2
+          elsif (byte_1 & shift == 0x0) && (byte_2 & shift == 0x00)
+            pixel = 0
+          end
+
+          buffer_x = sprite_x + pixelx
+          next if buffer_x < 0 || buffer_x >= Screen::SCREEN_WIDTH
+
+          position = line_width + buffer_x
+
+          @framebuffer[position] = pixel
+        end
+      end
+    end
+
     def render_bg
       line = current_line
       line_width = line * Screen::SCREEN_WIDTH