diff --git a/src/ppu.rs b/src/ppu.rs
index 74a549ed86ec545f0122ffcf6ba698454c0a9ef5..17057e43f73475aa8e70a7bed5e491df2a63920d 100644
--- a/src/ppu.rs
+++ b/src/ppu.rs
@@ -2,6 +2,7 @@ use core::fmt;
use std::{
borrow::BorrowMut,
cell::RefCell,
+ cmp::max,
fmt::{Display, Formatter},
rc::Rc,
};
@@ -24,6 +25,8 @@ pub const RGB_SIZE: usize = 3;
pub const RGBA_SIZE: usize = 4;
pub const TILE_WIDTH: usize = 8;
pub const TILE_HEIGHT: usize = 8;
+pub const TILE_WIDTH_I: usize = 7;
+pub const TILE_HEIGHT_I: usize = 7;
pub const TILE_DOUBLE_HEIGHT: usize = 16;
pub const TILE_COUNT_DMG: usize = 384;
@@ -124,8 +127,8 @@ impl Tile {
}
pub fn get_flipped(&self, x: usize, y: usize, xflip: bool, yflip: bool) -> u8 {
- let x: usize = if xflip { 7 - x } else { x };
- let y = if yflip { 7 - y } else { y };
+ let x: usize = if xflip { TILE_WIDTH_I - x } else { x };
+ let y = if yflip { TILE_HEIGHT_I - y } else { y };
self.buffer[y * TILE_WIDTH + x]
}
@@ -988,7 +991,7 @@ impl Ppu {
let mut mask;
for x in 0..TILE_WIDTH {
- mask = 1 << (7 - x);
+ mask = 1 << (TILE_WIDTH_I - x);
#[allow(clippy::bool_to_int_with_if)]
tile.set(
x,
@@ -1159,60 +1162,64 @@ impl Ppu {
let y = (ld as usize + scy as usize) & 0x07;
let mut x = (scx & 0x07) as usize;
- for index in 0..DISPLAY_WIDTH {
- // in case the current pixel to be drawn for the line
- // is visible within the window draws it an increments
- // the X coordinate of the tile
- if index as i16 >= wx as i16 - 7 {
- // obtains the current pixel data from the tile and
- // re-maps it according to the current palette
- let pixel = tile.get_flipped(x, y, xflip, yflip);
- let color = &palette[pixel as usize];
-
- // updates the pixel in the color buffer, which stores
- // the raw pixel color information (unmapped)
- self.color_buffer[color_offset] = pixel;
-
- // set the color pixel in the frame buffer
- self.frame_buffer[frame_offset] = color[0];
- self.frame_buffer[frame_offset + 1] = color[1];
- self.frame_buffer[frame_offset + 2] = color[2];
-
- // increments the current tile X position in drawing
- x += 1;
-
- // in case the end of tile width has been reached then
- // a new tile must be retrieved for rendering
- if x == TILE_WIDTH {
- // resets the tile X position to the base value
- // as a new tile is going to be drawn
- x = 0;
-
- // calculates the new line tile offset making sure that
- // the maximum of 32 is not overflown
- line_offset = (line_offset + 1) % 32;
-
- // calculates the tile index and makes sure the value
- // takes into consideration the bg tile value
- tile_index = self.vram[map_offset + row_offset + line_offset] as usize;
- if !self.bg_tile && tile_index < 128 {
- tile_index += 256;
- }
-
- // in case the current mode is CGB and the DMG compatibility
- // flag is not set then a series of tile values must be
- // updated according to the tile attributes field
- if self.gb_mode == GameBoyMode::Cgb && !self.dmg_compat {
- tile_attr = &bg_map_attrs[row_offset + line_offset];
- palette = &self.palettes_color_bg[tile_attr.palette as usize];
- xflip = tile_attr.xflip;
- yflip = tile_attr.yflip;
- tile_index += tile_attr.vram_bank as usize * TILE_COUNT_DMG;
- }
+ // calculates the initial tile X position in drawing, doing this
+ // allows us to position the background map properly in the display
+ let initial_index = max(wx as i16 - 7, 0) as usize;
+ color_offset += initial_index;
+ frame_offset += initial_index * RGB_SIZE;
+
+ // iterates over all the pixels in the current line of the display
+ // to draw the background map, note that the initial index is used
+ // to skip the drawing of the tiles that are not visible (WX)
+ for _ in initial_index..DISPLAY_WIDTH {
+ // obtains the current pixel data from the tile and
+ // re-maps it according to the current palette
+ let pixel = tile.get_flipped(x, y, xflip, yflip);
+ let color = &palette[pixel as usize];
+
+ // updates the pixel in the color buffer, which stores
+ // the raw pixel color information (unmapped)
+ self.color_buffer[color_offset] = pixel;
+
+ // set the color pixel in the frame buffer
+ self.frame_buffer[frame_offset] = color[0];
+ self.frame_buffer[frame_offset + 1] = color[1];
+ self.frame_buffer[frame_offset + 2] = color[2];
+
+ // increments the current tile X position in drawing
+ x += 1;
+
+ // in case the end of tile width has been reached then
+ // a new tile must be retrieved for rendering
+ if x == TILE_WIDTH {
+ // resets the tile X position to the base value
+ // as a new tile is going to be drawn
+ x = 0;
+
+ // calculates the new line tile offset making sure that
+ // the maximum of 32 is not overflown
+ line_offset = (line_offset + 1) % 32;
+
+ // calculates the tile index and makes sure the value
+ // takes into consideration the bg tile value
+ tile_index = self.vram[map_offset + row_offset + line_offset] as usize;
+ if !self.bg_tile && tile_index < 128 {
+ tile_index += 256;
+ }
- // obtains the reference to the new tile in drawing
- tile = &self.tiles[tile_index];
+ // in case the current mode is CGB and the DMG compatibility
+ // flag is not set then a series of tile values must be
+ // updated according to the tile attributes field
+ if self.gb_mode == GameBoyMode::Cgb && !self.dmg_compat {
+ tile_attr = &bg_map_attrs[row_offset + line_offset];
+ palette = &self.palettes_color_bg[tile_attr.palette as usize];
+ xflip = tile_attr.xflip;
+ yflip = tile_attr.yflip;
+ tile_index += tile_attr.vram_bank as usize * TILE_COUNT_DMG;
}
+
+ // obtains the reference to the new tile in drawing
+ tile = &self.tiles[tile_index];
}
// increments the color offset by one, representing
@@ -1368,7 +1375,11 @@ impl Ppu {
let has_priority =
index_buffer[x as usize] == -256 || obj.x < index_buffer[x as usize];
- let pixel = tile_row[if obj.xflip { 7 - tile_x } else { tile_x }];
+ let pixel = tile_row[if obj.xflip {
+ TILE_WIDTH_I - tile_x
+ } else {
+ tile_x
+ }];
if is_visible && has_priority && pixel != 0 {
// marks the current pixel in iteration as "owned"
// by the object with the defined X base position,