Add option for 8-colour mode

Some BIOSs initialize the VGA card by default into a mode where the high
bit of background nybble signals that the cell should blink. The simple
way to avoid this is by restricting the background colours to the range
0…7. However, since our mouse cursor is implemented by swapping the
foreground and the background colours, we also need to restrict the
foreground colours to the range 0…7.

Makefile

@@ -2,6 +2,8 @@ NASM = nasm
 PYTHON = python3
 QEMU = qemu-system-i386
 
+BUILDOPTS =
+
 .SUFFIXES:
 .SUFFIXES: .bin .asm .ans .wall
 
@@ -26,10 +28,10 @@ viewer.bin: ponydos.inc
 memory.bin: ponydos.inc
 
 .asm.bin:
-	$(NASM) -fbin -o $@ $<
+	$(NASM) -fbin $(BUILDOPTS) -o $@ $<
 
 .ans.wall:
-	$(PYTHON) process_wallpaper.py $@ $< 7 0 0 0
+	env BUILDOPTS='$(BUILDOPTS)' $(PYTHON) process_wallpaper.py $@ $< 7 0 0 0
 
 run: ponydos.img
 	$(QEMU) -drive file=$<,index=0,if=floppy,format=raw

README.md

@@ -20,6 +20,16 @@ run `make`. `make run` runs the floppy disk image `ponydos.img` with QEMU.
 By default, `qemu-system-i386` is invoked. If you want to use a different
 backend, use `make QEMU=<backend> run`.
 
+### Build options
+
+You can configure the build using build options passed to the build system using
+the `BUILDOPTS` variable, e.g. `make BUILDOPTS='-DBLINKY'`. It is advised to run
+`make clean` before changing the value of `BUILDOPTS`.
+
+* `-DBLINKY` builds an image which restricts the number of colours to 8. This is
+  for compatibility with BIOSs which use the highest bit of background colour to
+  signal that a cell should blink.
+
 ### How do I contribute?
 
 There is a model `hello.asm` file to demonstrate how best to use the
@@ -70,3 +80,7 @@ You don't.
 
 At the moment, PonyDOS is only offered as a live floppy disk image with no
 installation option, for your safety.
+
+#### How do I stop my entire desktop from blinking?
+
+Build with the [build option](#build-options) `-DBLINKY`.

hello.asm

@@ -2,6 +2,14 @@
 cpu 8086
 bits 16
 
+%ifdef BLINKY
+TITLEBAR_ATTRIBUTE equ 0x07
+WINDOW_ATTRIBUTE equ 0x70
+%else
+TITLEBAR_ATTRIBUTE equ 0x0f
+WINDOW_ATTRIBUTE equ 0xf0
+%endif
+
 WINDOW_STATUS_NORMAL equ 0
 WINDOW_STATUS_MOVE equ 1
 WINDOW_STATUS_RESIZE equ 2
@@ -498,12 +506,12 @@ render_window:
 	mov cx, [window_height]
 	mul cx
 	mov cx, ax
-	mov ax, 0xf000 ; Attribute is in the high byte
+	mov ax, WINDOW_ATTRIBUTE<<8 ; Attribute is in the high byte
 	rep stosw
 
 	; Set title bar to be white-on-black
 	mov di, window_data
-	mov ax, 0x0f00
+	mov ax, TITLEBAR_ATTRIBUTE<<8
 	mov cx, [window_width]
 	rep stosw
 

memory.asm

@@ -2,6 +2,14 @@
 cpu 8086
 bits 16
 
+%ifdef BLINKY
+TITLEBAR_ATTRIBUTE equ 0x07
+WINDOW_ATTRIBUTE equ 0x70
+%else
+TITLEBAR_ATTRIBUTE equ 0x0f
+WINDOW_ATTRIBUTE equ 0xf0
+%endif
+
 WINDOW_STATUS_NORMAL equ 0
 WINDOW_STATUS_MOVE equ 1
 
@@ -572,9 +580,9 @@ window_status db WINDOW_STATUS_NORMAL
 window_move_x_offset dw 0
 
 window_data:
-	db 'U', 0x0f, 's', 0x0f, 'a', 0x0f, 'g', 0x0f, 'e', 0x0f
+	db 'U', TITLEBAR_ATTRIBUTE, 's', TITLEBAR_ATTRIBUTE, 'a', TITLEBAR_ATTRIBUTE, 'g', TITLEBAR_ATTRIBUTE, 'e', TITLEBAR_ATTRIBUTE
-	times 10-5-1 db 0x00, 0x0f
+	times 10-5-1 db 0x00, TITLEBAR_ATTRIBUTE
-	db 'x', 0x0f
+	db 'x', TITLEBAR_ATTRIBUTE
-	db '0', 0xf0, '1', 0xf0, '2', 0xf0, '3', 0xf0, '4', 0xf0, '5'
+	db '0', WINDOW_ATTRIBUTE, '1', WINDOW_ATTRIBUTE, '2', WINDOW_ATTRIBUTE, '3', WINDOW_ATTRIBUTE, '4', WINDOW_ATTRIBUTE, '5'
-	db 0xf0, '6', 0xf0, '7', 0xf0, '8', 0xf0, '9', 0xf0
+	db WINDOW_ATTRIBUTE, '6', WINDOW_ATTRIBUTE, '7', WINDOW_ATTRIBUTE, '8', WINDOW_ATTRIBUTE, '9', WINDOW_ATTRIBUTE
-	.indicators: times 10 db 0x00, 0xf0
+	.indicators: times 10 db 0x00, WINDOW_ATTRIBUTE

process_wallpaper.py

@@ -1,3 +1,4 @@
+import os
 import sys
 
 from collections import namedtuple
@@ -14,6 +15,15 @@ if len(sys.argv) != 7:
 	print("Usage: {sys.argv[0]} outfile infile default_fgcolor default_bgcolor origin_x origin_y", file=sys.stderr)
 	sys.exit(1)
 
+blinky_vgamode = False
+if 'BUILDOPTS' in os.environ:
+	for opt in os.environ['BUILDOPTS'].split():
+		if opt == '-DBLINKY':
+			blinky_vgamode = True
+		else:
+			print(f"Error: Unrecognized build option {opt}", file=sys.stderr)
+			sys.exit(1)
+
 outfile = sys.argv[1]
 infile = sys.argv[2]
 
@@ -118,5 +128,14 @@ with open(outfile, 'wb') as f:
 	for y in range(HEIGHT):
 		for x in range(WIDTH):
 			fgcolor, bgcolor, bold = attributes[x][y]
+			fgcolor = fgcolor | (8 if bold else 0)
+			if blinky_vgamode:
+				# VGA mode can be set up so that the highest
+				# bit of the bg colour marks that the cell
+				# should blink instead of intensity
+				# Restrict the colours (including foreground
+				# to account for swapping of the two) to 0…7
+				fgcolor = fgcolor & 0x7
+				bgcolor = bgcolor & 0x7
 			char = chars[x][y]
-			f.write(bytes([char, (bgcolor<<4) | fgcolor | (8 if bold else 0)]))
+			f.write(bytes([char, (bgcolor<<4) | fgcolor]))

shell.asm

@@ -1,4 +1,16 @@
 %include "ponydos.inc"
+cpu 8086
+bits 16
+
+%ifdef BLINKY
+TITLEBAR_ATTRIBUTE equ 0x07
+WINDOW_ATTRIBUTE equ 0x70
+DISK_ATTRIBUTE equ 0x07
+%else
+TITLEBAR_ATTRIBUTE equ 0x0f
+WINDOW_ATTRIBUTE equ 0xf0
+DISK_ATTRIBUTE equ 0x0f
+%endif
 
 struc window
 	.next resw 1
@@ -637,7 +649,7 @@ launch:
 show_launch_error:
 	mov di, launch_error_dialog.filename
 	mov cx, FS_DIRENT_NAME_SIZE-1
-	mov ah, 0xf0
+	mov ah, WINDOW_ATTRIBUTE
 	.copy:
 		lodsb
 		test al, al
@@ -937,11 +949,11 @@ render_file_window:
 	mov es, ax
 	mov di, [si + window.data]
 	mov cx, [si + window.width]
-	mov ax, 0x0f00
+	mov ax, TITLEBAR_ATTRIBUTE<<8
 	rep stosw
 
 	mov cx, (ROWS-1)*COLUMNS
-	mov ax, 0xf000
+	mov ax, WINDOW_ATTRIBUTE<<8
 	rep stosw
 
 	mov di, [si + window.data]
@@ -1225,28 +1237,28 @@ viewer_file_name db 'viewer.bin', 0
 ; ------------------------------------------------------------------
 
 disk_icon:
-	db 0x00, 0x0f, 0x00, 0x0f, 0x00, 0x0f, 0x00, 0x0f, 0x00, 0x0f
+	db 0x00, DISK_ATTRIBUTE, 0x00, DISK_ATTRIBUTE, 0x00, DISK_ATTRIBUTE, 0x00, DISK_ATTRIBUTE, 0x00, DISK_ATTRIBUTE
-	db 0x00, 0x0f, 0x00, 0x0f, 0x09, 0x0f, 0x00, 0x0f, 0x00, 0x0f
+	db 0x00, DISK_ATTRIBUTE, 0x00, DISK_ATTRIBUTE, 0x09, DISK_ATTRIBUTE, 0x00, DISK_ATTRIBUTE, 0x00, DISK_ATTRIBUTE
-	db 0x00, 0x0f, 0x00, 0x0f, '|', 0x0f, 0x00, 0x0f, 0x00, 0x0f
+	db 0x00, DISK_ATTRIBUTE, 0x00, DISK_ATTRIBUTE, '|', DISK_ATTRIBUTE, 0x00, DISK_ATTRIBUTE, 0x00, DISK_ATTRIBUTE
 
 oom_error_dialog:
-	db 'E', 0x0f, 'r', 0x0f, 'r', 0x0f, 'o', 0x0f, 'r', 0x0f
+	db 'E', TITLEBAR_ATTRIBUTE, 'r', TITLEBAR_ATTRIBUTE, 'r', TITLEBAR_ATTRIBUTE, 'o', TITLEBAR_ATTRIBUTE, 'r', TITLEBAR_ATTRIBUTE
-	times 13-5-1 db 0x00, 0x0f
+	times 13-5-1 db 0x00, TITLEBAR_ATTRIBUTE
-	db 'x', 0x0f
+	db 'x', TITLEBAR_ATTRIBUTE
-	db 'O', 0xf0, 'u', 0xf0, 't', 0xf0, ' ', 0xf0, 'o', 0xf0, 'f', 0xf0
+	db 'O', WINDOW_ATTRIBUTE, 'u', WINDOW_ATTRIBUTE, 't', WINDOW_ATTRIBUTE, ' ', WINDOW_ATTRIBUTE, 'o', WINDOW_ATTRIBUTE, 'f', WINDOW_ATTRIBUTE
-	db ' ', 0xf0, 'm', 0xf0, 'e', 0xf0, 'm', 0xf0, 'o', 0xf0, 'r', 0xf0
+	db ' ', WINDOW_ATTRIBUTE, 'm', WINDOW_ATTRIBUTE, 'e', WINDOW_ATTRIBUTE, 'm', WINDOW_ATTRIBUTE, 'o', WINDOW_ATTRIBUTE, 'r', WINDOW_ATTRIBUTE
-	db 'y', 0xf0
+	db 'y', WINDOW_ATTRIBUTE
 
 launch_error_dialog:
-	db 'E', 0x0f, 'r', 0x0f, 'r', 0x0f, 'o', 0x0f, 'r', 0x0f
+	db 'E', TITLEBAR_ATTRIBUTE, 'r', TITLEBAR_ATTRIBUTE, 'r', TITLEBAR_ATTRIBUTE, 'o', TITLEBAR_ATTRIBUTE, 'r', TITLEBAR_ATTRIBUTE
-	times FS_DIRENT_NAME_SIZE-1-5-1 db 0x00, 0x0f
+	times FS_DIRENT_NAME_SIZE-1-5-1 db 0x00, TITLEBAR_ATTRIBUTE
-	db 'x', 0x0f
+	db 'x', TITLEBAR_ATTRIBUTE
-	db 'C', 0xf0, 'a', 0xf0, 'n', 0xf0, 'n', 0xf0, 'o', 0xf0, 't', 0xf0
+	db 'C', WINDOW_ATTRIBUTE, 'a', WINDOW_ATTRIBUTE, 'n', WINDOW_ATTRIBUTE, 'n', WINDOW_ATTRIBUTE, 'o', WINDOW_ATTRIBUTE, 't', WINDOW_ATTRIBUTE
-	db ' ', 0xf0, 'l', 0xf0, 'a', 0xf0, 'u', 0xf0, 'n', 0xf0, 'c', 0xf0
+	db ' ', WINDOW_ATTRIBUTE, 'l', WINDOW_ATTRIBUTE, 'a', WINDOW_ATTRIBUTE, 'u', WINDOW_ATTRIBUTE, 'n', WINDOW_ATTRIBUTE, 'c', WINDOW_ATTRIBUTE
-	db 'h', 0xf0, ' ', 0xf0, 'f', 0xf0, 'i', 0xf0, 'l', 0xf0, 'e', 0xf0
+	db 'h', WINDOW_ATTRIBUTE, ' ', WINDOW_ATTRIBUTE, 'f', WINDOW_ATTRIBUTE, 'i', WINDOW_ATTRIBUTE, 'l', WINDOW_ATTRIBUTE, 'e', WINDOW_ATTRIBUTE
-	db ':', 0xf0
+	db ':', WINDOW_ATTRIBUTE
-	times FS_DIRENT_NAME_SIZE-1-19 db 0x00, 0xf0
+	times FS_DIRENT_NAME_SIZE-1-19 db 0x00, WINDOW_ATTRIBUTE
-	.filename times FS_DIRENT_NAME_SIZE-1 db 0x00, 0xf0
+	.filename times FS_DIRENT_NAME_SIZE-1 db 0x00, WINDOW_ATTRIBUTE
 
 windows:
 	times window.size db 0

viewer.asm

@@ -2,6 +2,19 @@
 cpu 8086
 bits 16
 
+%ifdef BLINKY
+TITLEBAR_ATTRIBUTE equ 0x07
+WINDOW_ATTRIBUTE equ 0x70
+CANCEL_ATTRIBUTE equ 0x07
+%else
+TITLEBAR_ATTRIBUTE equ 0x0f
+WINDOW_ATTRIBUTE equ 0xf0
+CANCEL_ATTRIBUTE equ 0x8f
+%endif
+OK_ATTRIBUTE equ 0x20
+OPEN_DIALOG_ATTRIBUTE equ 0x70
+FILENAME_ATTRIBUTE equ WINDOW_ATTRIBUTE
+
 WINDOW_STATUS_NORMAL equ 0
 WINDOW_STATUS_MOVE equ 1
 WINDOW_STATUS_RESIZE equ 2
@@ -591,14 +604,14 @@ event_click:
 		mov bx, ax
 		inc bx
 
-		cmp byte [bx], CANCEL_COLOR
+		cmp byte [bx], CANCEL_ATTRIBUTE
 		jne .not_cancel
 		.cancel:
 			call unhook_self_from_window_chain
 			mov byte [exiting], 1
 			jmp .end
 		.not_cancel:
-		cmp byte [bx], OK_COLOR
+		cmp byte [bx], OK_ATTRIBUTE
 		jne .not_ok
 		.ok:
 			call filename_ok
@@ -921,12 +934,12 @@ render_window:
 	mov cx, [window.height]
 	mul cx
 	mov cx, ax
-	mov ax, 0xf000 ; Attribute is in the high byte
+	mov ax, WINDOW_ATTRIBUTE<<8 ; Attribute is in the high byte
 	rep stosw
 
 	; Set title bar to be white-on-black
 	mov di, text_window_data
-	mov ax, 0x0f00
+	mov ax, TITLEBAR_ATTRIBUTE<<8
 	mov cx, [window.width]
 	rep stosw
 
@@ -1233,46 +1246,44 @@ cur_filename_address dw filename_window_data.filename
 file_opened db 0
 
 ; pre-built windows
-CANCEL_COLOR equ 0x8f
-OK_COLOR equ 0x20
 filename_window_data:
 	; header
-	db 'V', 0x0f, 'i', 0x0f, 'e', 0x0f, 'w', 0x0f, 'e', 0x0f, 'r', 0x0f
+	db 'V', TITLEBAR_ATTRIBUTE, 'i', TITLEBAR_ATTRIBUTE, 'e', TITLEBAR_ATTRIBUTE, 'w', TITLEBAR_ATTRIBUTE, 'e', TITLEBAR_ATTRIBUTE, 'r', TITLEBAR_ATTRIBUTE
-	times FS_DIRENT_NAME_SIZE + 2 - 7 db 0, 0x0f
+	times FS_DIRENT_NAME_SIZE + 2 - 7 db 0, TITLEBAR_ATTRIBUTE
-	db 'x', 0x0f
+	db 'x', TITLEBAR_ATTRIBUTE
 	; blank line
-	times FS_DIRENT_NAME_SIZE + 2 db 0, 0x70
+	times FS_DIRENT_NAME_SIZE + 2 db 0, OPEN_DIALOG_ATTRIBUTE
 	; filename
-	db 0, 0x70
+	db 0, OPEN_DIALOG_ATTRIBUTE
 	.filename:
-	times FS_DIRENT_NAME_SIZE db 0, 0xf0
+	times FS_DIRENT_NAME_SIZE db 0, FILENAME_ATTRIBUTE
-	db 0, 0x70
+	db 0, OPEN_DIALOG_ATTRIBUTE
 	; blank line
-	times FS_DIRENT_NAME_SIZE + 2 db 0, 0x70
+	times FS_DIRENT_NAME_SIZE + 2 db 0, OPEN_DIALOG_ATTRIBUTE
 	; buttons line
-	times 7 db 0, 0x70
+	times 7 db 0, OPEN_DIALOG_ATTRIBUTE
-	db 0, 0x8f, 'C', 0x8f, 'a', 0x8f, 'n', 0x8f, 'c', 0x8f, 'e', 0x8f, 'l', 0x8f, 0, 0x8f
+	db 0, CANCEL_ATTRIBUTE, 'C', CANCEL_ATTRIBUTE, 'a', CANCEL_ATTRIBUTE, 'n', CANCEL_ATTRIBUTE, 'c', CANCEL_ATTRIBUTE, 'e', CANCEL_ATTRIBUTE, 'l', CANCEL_ATTRIBUTE, 0, CANCEL_ATTRIBUTE
-	times 5 db 0, 0x70
+	times 5 db 0, OPEN_DIALOG_ATTRIBUTE
-	db 0, 0x20, 'O', 0x20, 'K', 0x20, 0x, 0x20
+	db 0, OK_ATTRIBUTE, 'O', OK_ATTRIBUTE, 'K', OK_ATTRIBUTE, 0x, OK_ATTRIBUTE
-	times 8 db 0, 0x70
+	times 8 db 0, OPEN_DIALOG_ATTRIBUTE
 	; blank line
-	times FS_DIRENT_NAME_SIZE + 2 db 0, 0x70
+	times FS_DIRENT_NAME_SIZE + 2 db 0, OPEN_DIALOG_ATTRIBUTE
 
 oom_window_data:
-	db 'E', 0x0f, 'r', 0x0f, 'r', 0x0f, 'o', 0x0f, 'r', 0x0f
+	db 'E', TITLEBAR_ATTRIBUTE, 'r', TITLEBAR_ATTRIBUTE, 'r', TITLEBAR_ATTRIBUTE, 'o', TITLEBAR_ATTRIBUTE, 'r', TITLEBAR_ATTRIBUTE
-	times 13-5-1 db 0x00, 0x0f
+	times 13-5-1 db 0x00, TITLEBAR_ATTRIBUTE
-	db 'x', 0x0f
+	db 'x', TITLEBAR_ATTRIBUTE
-	db 'O', 0xf0, 'u', 0xf0, 't', 0xf0, ' ', 0xf0, 'o', 0xf0, 'f', 0xf0
+	db 'O', WINDOW_ATTRIBUTE, 'u', WINDOW_ATTRIBUTE, 't', WINDOW_ATTRIBUTE, ' ', WINDOW_ATTRIBUTE, 'o', WINDOW_ATTRIBUTE, 'f', WINDOW_ATTRIBUTE
-	db ' ', 0xf0, 'm', 0xf0, 'e', 0xf0, 'm', 0xf0, 'o', 0xf0, 'r', 0xf0
+	db ' ', WINDOW_ATTRIBUTE, 'm', WINDOW_ATTRIBUTE, 'e', WINDOW_ATTRIBUTE, 'm', WINDOW_ATTRIBUTE, 'o', WINDOW_ATTRIBUTE, 'r', WINDOW_ATTRIBUTE
-	db 'y', 0xf0
+	db 'y', WINDOW_ATTRIBUTE
 
 ood_window_data:
-	db 'E', 0x0f, 'r', 0x0f, 'r', 0x0f, 'o', 0x0f, 'r', 0x0f
+	db 'E', TITLEBAR_ATTRIBUTE, 'r', TITLEBAR_ATTRIBUTE, 'r', TITLEBAR_ATTRIBUTE, 'o', TITLEBAR_ATTRIBUTE, 'r', TITLEBAR_ATTRIBUTE
-	times 17-5-1 db 0x00, 0x0f
+	times 17-5-1 db 0x00, TITLEBAR_ATTRIBUTE
-	db 'x', 0x0f
+	db 'x', TITLEBAR_ATTRIBUTE
-	db 'O', 0xf0, 'u', 0xf0, 't', 0xf0, ' ', 0xf0, 'o', 0xf0, 'f', 0xf0
+	db 'O', WINDOW_ATTRIBUTE, 'u', WINDOW_ATTRIBUTE, 't', WINDOW_ATTRIBUTE, ' ', WINDOW_ATTRIBUTE, 'o', WINDOW_ATTRIBUTE, 'f', WINDOW_ATTRIBUTE
-	db ' ', 0xf0, 'd', 0xf0, 'i', 0xf0, 's', 0xf0, 'k', 0xf0, ' ', 0xf0
+	db ' ', WINDOW_ATTRIBUTE, 'd', WINDOW_ATTRIBUTE, 'i', WINDOW_ATTRIBUTE, 's', WINDOW_ATTRIBUTE, 'k', WINDOW_ATTRIBUTE, ' ', WINDOW_ATTRIBUTE
-	db 's', 0xf0, 'p', 0xf0, 'a', 0xf0, 'c', 0xf0, 'e', 0xf0
+	db 's', WINDOW_ATTRIBUTE, 'p', WINDOW_ATTRIBUTE, 'a', WINDOW_ATTRIBUTE, 'c', WINDOW_ATTRIBUTE, 'e', WINDOW_ATTRIBUTE
 
 section .bss
 text_window_data resw ROWS*COLUMNS