From 8b977f9f9ebcb6df8237af64d8dd178e2415c955 Mon Sep 17 00:00:00 2001
From: Ry <ryanst755@gmail.com>
Date: Mon, 21 Nov 2022 21:43:58 -0800
Subject: [PATCH] terminal: Add various "control characters"

---
 terminal/stream.asm |  2 +-
 terminal/text.asm   | 61 ++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/terminal/stream.asm b/terminal/stream.asm
index 2c0bf2a..afcd796 100644
--- a/terminal/stream.asm
+++ b/terminal/stream.asm
@@ -4,7 +4,7 @@
 ; inputs:
 ; r0: pointer to ASCII character
 stream_write_to_terminal:
-    mov r0, [r0]
+    movz.8 r0, [r0]
     jmp print_character_to_terminal
 
 stream_get_input:
diff --git a/terminal/text.asm b/terminal/text.asm
index e5c930d..6da9208 100644
--- a/terminal/text.asm
+++ b/terminal/text.asm
@@ -8,10 +8,20 @@ const BACKGROUND_COLOR: 0xFF000000
 
 ; print a single character to the terminal
 ; inputs:
-; r0: ASCII character
+; r0: ASCII character or control character
 ; outputs:
 ; none
 print_character_to_terminal:
+    ; if we're in a control state, or the char has the highest bit set
+    ; then handle it as a control character
+    ; allow character 0x8A (the block cursor itself) to pass through
+    cmp.8 r0, 0x8A
+    ifz jmp print_character_to_terminal_allow
+    cmp.8 [terminal_state], 0
+    ifnz jmp handle_control_character
+    bts r0, 7
+    ifnz jmp handle_control_character
+print_character_to_terminal_allow:
     push r0
     push r1
     push r2
@@ -69,6 +79,51 @@ print_character_to_terminal_end:
     pop r0
     ret
 
+; control character state machine
+; inputs:
+; r0: control character or parameter
+; outputs:
+; none
+handle_control_character:
+    cmp.8 [terminal_state], 0 ; got control character
+    ifz mov.8 [terminal_control_char], r0
+    ifz mov.8 [terminal_state], 1
+    ifz ret
+    cmp.8 [terminal_state], 1 ; got first parameter
+    ifz mov.8 [terminal_control_parameter_1], r0
+    ifz mov.8 [terminal_state], 2
+    ifz ret
+    cmp.8 [terminal_state], 2 ; got second parameter, now execute
+    ifz mov.8 [terminal_control_parameter_2], r0
+    ifz mov.8 [terminal_state], 0
+
+    ; fill terminal
+    cmp.8 [terminal_control_char], 0xF0
+    ifz jmp handle_control_character_fill_term
+
+    ; set cursor position
+    cmp.8 [terminal_control_char], 0xF1
+    ifz jmp handle_control_character_set_cursor_pos
+
+    ret
+handle_control_character_fill_term:
+    push r0
+    push r31
+    mov r0, terminal_text_buf
+    mov r31, 1000
+handle_control_character_fill_term_loop:
+    mov.8 [r0], [terminal_control_parameter_1]
+    inc r0
+    loop handle_control_character_fill_term_loop
+    call redraw_terminal
+    pop r31
+    pop r0
+    ret
+handle_control_character_set_cursor_pos:
+    mov.8 [terminal_x], [terminal_control_parameter_1]
+    mov.8 [terminal_y], [terminal_control_parameter_2]
+    ret
+
 ; scroll the terminal
 ; inputs:
 ; none
@@ -225,3 +280,7 @@ redraw_terminal_line_loop_x:
 terminal_x: data.8 0
 terminal_y: data.8 0
 terminal_text_buf: data.fill 0, 1000 ; 40x25 = 1000 bytes
+terminal_state: data.8 0 ; 0: normal, 1: awaiting first control parameter, 2: awaiting second control parameter
+terminal_control_char: data.8 0
+terminal_control_parameter_1: data.8 0
+terminal_control_parameter_2: data.8 0