From 8b2df35475443ebfede42e52a608c0a175efb543 Mon Sep 17 00:00:00 2001
From: Ry <ryanst755@gmail.com>
Date: Sat, 16 Apr 2022 16:13:16 -0700
Subject: [PATCH] fox32rom: Add draw_pixel routines

---
 background.asm | 19 +++++++++++++++++++
 draw_pixel.asm | 32 ++++++++++++++++++++++++++++++++
 fox32rom.def   | 15 +++++++++------
 main.asm       |  4 ++++
 overlay.asm    | 25 +++++++++++++++++++++++++
 5 files changed, 89 insertions(+), 6 deletions(-)
 create mode 100644 draw_pixel.asm

diff --git a/background.asm b/background.asm
index 129a089..aac0fae 100644
--- a/background.asm
+++ b/background.asm
@@ -22,6 +22,25 @@ fill_background_loop:
     pop r1
     ret
 
+; draw a pixel to the background
+; inputs:
+; r0: X coordinate
+; r1: Y coordinate
+; r2: color
+; outputs:
+; none
+draw_pixel_to_background:
+    push r5
+    push r6
+
+    mov r3, BACKGROUND_FRAMEBUFFER
+    mov r4, 640
+    call draw_pixel_generic
+
+    pop r6
+    pop r5
+    ret
+
 ; draw a filled rectangle to the background
 ; inputs:
 ; r0: X coordinate of top-left
diff --git a/draw_pixel.asm b/draw_pixel.asm
new file mode 100644
index 0000000..3536caf
--- /dev/null
+++ b/draw_pixel.asm
@@ -0,0 +1,32 @@
+; generic pixel drawing routines
+
+; draw a pixel to a framebuffer
+; inputs:
+; r0: X coordinate
+; r1: Y coordinate
+; r2: color
+; r3: pointer to framebuffer
+; r4: framebuffer width (pixels)
+; outputs:
+; none
+draw_pixel_generic:
+    push r0
+    push r1
+    push r3
+    push r4
+
+    ; calculate pointer to the framebuffer
+    mul r4, 4                ; 4 bytes per pixel
+    mul r1, r4               ; y * width * 4
+    mul r0, 4                ; x * 4
+    add r0, r1               ; y * width * 4 + (x * 4)
+    add r3, r0
+    mov r0, r3               ; r0: pointer to framebuffer
+
+    mov [r0], r2
+
+    pop r4
+    pop r3
+    pop r1
+    pop r0
+    ret
diff --git a/fox32rom.def b/fox32rom.def
index f982669..a03aba5 100644
--- a/fox32rom.def
+++ b/fox32rom.def
@@ -15,7 +15,8 @@ draw_format_str_generic:                  jmp [0xF0041004]
 draw_decimal_generic:                     jmp [0xF0041008]
 draw_hex_generic:                         jmp [0xF004100C]
 draw_font_tile_generic:                   jmp [0xF0041010]
-draw_filled_rectangle_generic:            jmp [0xF0041014]
+draw_pixel_generic:                       jmp [0xF0041014]
+draw_filled_rectangle_generic:            jmp [0xF0041018]
 
 ; background jump table entries
 fill_background:                          jmp [0xF0042000]
@@ -24,7 +25,8 @@ draw_format_str_to_background:            jmp [0xF0042008]
 draw_decimal_to_background:               jmp [0xF004200C]
 draw_hex_to_background:                   jmp [0xF0042010]
 draw_font_tile_to_background:             jmp [0xF0042014]
-draw_filled_rectangle_to_background:      jmp [0xF0042018]
+draw_pixel_to_background:                 jmp [0xF0042018]
+draw_filled_rectangle_to_background:      jmp [0xF004201C]
 
 ; overlay jump table entries
 fill_overlay:                             jmp [0xF0043000]
@@ -33,10 +35,11 @@ draw_format_str_to_overlay:               jmp [0xF0043008]
 draw_decimal_to_overlay:                  jmp [0xF004300C]
 draw_hex_to_overlay:                      jmp [0xF0043010]
 draw_font_tile_to_overlay:                jmp [0xF0043014]
-draw_filled_rectangle_to_overlay:         jmp [0xF0043018]
-find_overlay_covering_position:           jmp [0xF004301C]
-check_if_overlay_covers_position:         jmp [0xF0043020]
-check_if_enabled_overlay_covers_position: jmp [0xF0043024]
+draw_pixel_to_overlay:                    jmp [0xF0043018]
+draw_filled_rectangle_to_overlay:         jmp [0xF004301C]
+find_overlay_covering_position:           jmp [0xF0043020]
+check_if_overlay_covers_position:         jmp [0xF0043024]
+check_if_enabled_overlay_covers_position: jmp [0xF0043028]
 
 ; menu bar jump table entries
 enable_menu_bar:                          jmp [0xF0044000]
diff --git a/main.asm b/main.asm
index 7651b99..8691434 100644
--- a/main.asm
+++ b/main.asm
@@ -132,6 +132,7 @@ get_rom_version:
     #include "boot.asm"
     #include "debug.asm"
     #include "disk.asm"
+    #include "draw_pixel.asm"
     #include "draw_rectangle.asm"
     #include "draw_text.asm"
     #include "event.asm"
@@ -165,6 +166,7 @@ get_rom_version:
     data.32 draw_format_str_generic
     data.32 draw_decimal_generic
     data.32 draw_font_tile_generic
+    data.32 draw_pixel_generic
     data.32 draw_filled_rectangle_generic
 
     ; background jump table
@@ -174,6 +176,7 @@ get_rom_version:
     data.32 draw_format_str_to_background
     data.32 draw_decimal_to_background
     data.32 draw_font_tile_to_background
+    data.32 draw_pixel_to_background
     data.32 draw_filled_rectangle_to_background
 
     ; overlay jump table
@@ -183,6 +186,7 @@ get_rom_version:
     data.32 draw_format_str_to_overlay
     data.32 draw_decimal_to_overlay
     data.32 draw_font_tile_to_overlay
+    data.32 draw_pixel_to_overlay
     data.32 draw_filled_rectangle_to_overlay
     data.32 find_overlay_covering_position
     data.32 check_if_overlay_covers_position
diff --git a/overlay.asm b/overlay.asm
index c5c4875..6b26f7b 100644
--- a/overlay.asm
+++ b/overlay.asm
@@ -33,6 +33,31 @@ fill_overlay_loop:
     pop r1
     ret
 
+; draw a pixel to an overlay
+; inputs:
+; r0: X coordinate
+; r1: Y coordinate
+; r2: color
+; r3: overlay number
+; outputs:
+; none
+draw_pixel_to_overlay:
+    push r3
+    push r4
+
+    mov r4, r3
+    or r4, 0x80000100        ; bitwise or the overlay number with the command to get the overlay size
+    or r3, 0x80000200        ; bitwise or the overlay number with the command to get the framebuffer pointer
+    in r3, r3                ; r3: overlay framebuffer poiner
+    in r4, r4
+    and r4, 0x0000FFFF       ; r4: overlay width
+
+    call draw_pixel_generic
+
+    pop r4
+    pop r3
+    ret
+
 ; draw a filled rectangle to an overlay
 ; inputs:
 ; r0: X coordinate of top-left