From 2c507b6ecb5aed884afb21e79f13ecb16e6adff4 Mon Sep 17 00:00:00 2001
From: xenia <xenia.agda@gmail.com>
Date: Wed, 7 Feb 2024 22:52:21 +0100
Subject: [PATCH] Implement text rendering

---
 gen/fontgen.py  |  82 ++++++++++++--------
 xenrom/main.asm |  60 ++++++++++++--
 xenrom/text.asm | 202 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 306 insertions(+), 38 deletions(-)

diff --git a/gen/fontgen.py b/gen/fontgen.py
index 237c74d..846f58d 100644
--- a/gen/fontgen.py
+++ b/gen/fontgen.py
@@ -2,22 +2,23 @@ import json
 import struct
 
 # generates:
-#   font_data.dat (binary file, expected to load at location 0xf000_0100)
-#   font_data.inc (fox32 assembly)
-# font_data.inc defines constants
-#   N_CHARS: number of defined characters (u32)
-#   CHAR_TABLE: pointer to main char table (&Char)
-#   UNKNOWN_CHAR: pointer to unknown character (&Char)
+#   font_data.bin
+#   font_table.bin
+#   font_data.inc
 #
 # struct Char {
 #   width: u8, height: u8, baseline: u8,
-#   data_ptr: &[u8],
+#   data_offset: offset into font_data
 # } (7 bytes)
 
-DATA_FILE_ORIGIN = 0xf000_0100
+CODEPAGE = {
+    0: None,
+    128: 'Ξ',
+}
+for x in range(32, 127):
+    CODEPAGE[x] = chr(x)
 
 BASELINE = 7
-N_CHARS = 127
 
 codepoints = json.load(open("ultlf/codepoints.json"))
 font_data = json.load(open("ultlf/data.json"))
@@ -33,34 +34,51 @@ UNKNOWN = [
     "#   #   #",
 ]
 
-with open("xenrom/data/font_data.inc", "w") as inc, open("xenrom/data/font_data.dat", "wb") as dat:
-    table = b''
-    char_data = b''
+SPACE = ["   "]
 
-    for ch in [None] + list(range(N_CHARS)):
-        if ch in codepoints:
-            i = codepoints.index(ch)
-            glyph = font_data[i]
-            baseline = baselines[i]
-            if '?' in "".join(glyph):
-                print(f"Font doesn't have char {ch}")
-                glyph = UNKNOWN
-                baseline = 6
-        else:
+SCALE = 2
+def scale(glyph):
+    out = []
+    for line in glyph:
+        line_scaled = ""
+        for ch in line:
+            line_scaled += ch * SCALE
+        out.extend([line_scaled] * SCALE)
+    return out
+
+with open("xenrom/data/font_table.dat", "wb") as table_file, open("xenrom/data/font_data.dat", "wb") as data_file, open("xenrom/data/font_data.inc", "w") as inc_file:
+    table = b''
+    data = b''
+
+    for i in range(256):
+        ch = CODEPAGE.get(i, None)
+        unicode_codepoint = ord(ch) if ch is not None else None
+        if unicode_codepoint is None:
             glyph = UNKNOWN
             baseline = 6
-            print(f"Couldn't find char {ch}")
+        elif unicode_codepoint == 32:
+            glyph = SPACE
+            baseline = 1
+        else:
+            ultlf_idx = codepoints.index(unicode_codepoint)
+            glyph = font_data[ultlf_idx]
+            baseline = baselines[ultlf_idx]
 
-        table += struct.pack("BBBI", len(glyph[0]), len(glyph), baseline, DATA_FILE_ORIGIN + len(char_data))
+        if "X" in "".join(glyph):
+            glyph = UNKNOWN
+            baseline = 6
+
+        glyph = scale(glyph)
+        baseline *= SCALE
+
+        table += struct.pack("<BBBI", len(glyph[0]), len(glyph), baseline, len(data))
 
         for line in glyph:
-            for ch in glyph:
-                char_data += b'\x00' if ch == ' ' else b'\x01'
+            for ch in line:
+                data += b'\x00' if ch == ' ' else b'\x01'
 
-    dat.write(char_data + table)
+    table_file.write(table)
+    data_file.write(data)
 
-    inc.write(f'''
-const N_CHARS: {N_CHARS}
-const CHAR_TABLE: {hex(DATA_FILE_ORIGIN + len(char_data))}
-const UNKNOWN_CHAR: {hex(DATA_FILE_ORIGIN)}
-    ''')
+    inc_file.write(f"const FONT_SIZE: {SCALE}\n")
+    inc_file.write(f"const FONT_LINE_HEIGHT: {8 * SCALE}\n")
diff --git a/xenrom/main.asm b/xenrom/main.asm
index bb77664..18b8eb1 100644
--- a/xenrom/main.asm
+++ b/xenrom/main.asm
@@ -6,6 +6,9 @@ const BG_FRAMEBUFFER: 0x2000000
 const SCREEN_WIDTH: 640
 const SCREEN_HEIGHT: 480
 
+const COLOR_WHITE: 0xffffffc0
+const COLOR_BLUE: 0xffffff40
+const COLOR_ORANGE: 0xff4080ff
 
 ; Globals
 const FRAMENR: 0x00000000
@@ -17,8 +20,6 @@ entry:
     mcl ; disable MMU
     mov rsp, SYS_STACK_START ; set stack pointer
 
-    mov r0, entry_str
-    call serial_print
     mov r0, version_str_1
     call serial_print
     mov r0, version_str
@@ -32,18 +33,64 @@ entry:
 
     call show_logo
 
+    mov r0, BG_FRAMEBUFFER
+    mov r1, 640 ; width
+    mov r2, entry_str
+    mov r3, 20 ; x
+    mov r4, 20 ; y
+    mov r5, 20 ; l
+    mov r6, 620 ; r
+    mov r7, 100000 ; bot
+    mov r30, 2
+    mov r31, COLOR_WHITE
+
+    call draw_str_at
+    mov r2, version_str_1
+    call draw_str_at
+    mov r2, version_str
+    mov r31, COLOR_BLUE
+    call draw_str_at
+    mov r2, version_str_2
+    mov r31, COLOR_WHITE
+    call draw_str_at
+    mov r2, sha_str
+    mov r31, COLOR_ORANGE
+    call draw_str_at
+    mov r31, COLOR_WHITE
+    mov r2, version_str_3
+    call draw_str_at
+
+    mov r31, COLOR_WHITE
+    mov r2, credit_str_1
+    call draw_str_at
+    mov r31, COLOR_BLUE
+    mov r2, credit_str_2
+    call draw_str_at
+    mov r31, COLOR_WHITE
+    mov r2, credit_str_3
+    call draw_str_at
+    mov r31, COLOR_ORANGE
+    mov r2, credit_str_4
+    call draw_str_at
+
+
     mov r0, booting_str
     call serial_print
 
     halt
 
-entry_str: data.str "== Welcome to Xen32OS" data.8 0
+entry_str: data.str "= " data.8 128 data.str "EN32OS =" data.8 10 data.8 0
 ; defines version_str, sha_str
 #include "data/version.inc"
 
-version_str_1: data.str " - version " data.8 0
-version_str_2: data.str " (" data.8 0
-version_str_3: data.str ") ==" data.8 10 data.8 0
+version_str_1: data.str "version " data.8 0
+version_str_2: data.str " (commit " data.8 0
+version_str_3: data.str ")" data.8 10 data.8 0
+
+credit_str_1: data.str "font by " data.8 0
+credit_str_2: data.str "ultlang" data.8 0
+credit_str_3: data.str ", os by " data.8 0
+credit_str_4: data.str "xenia" data.8 0
 
 booting_str: data.str "booting..." data.8 10 data.8 0
 
@@ -96,4 +143,5 @@ serial_print_nl:
     ret
 
 #include "logo.asm"
+#include "text.asm"
 
diff --git a/xenrom/text.asm b/xenrom/text.asm
index 8b13789..f3080a0 100644
--- a/xenrom/text.asm
+++ b/xenrom/text.asm
@@ -1 +1,203 @@
+font_table: #include_bin "data/font_table.dat"
+font_data: #include_bin "data/font_data.dat"
+; defines FONT_SIZE and FONT_LINE_HEIGHT
+#include "data/font_data.inc"
 
+
+; input:
+;   r0: pointer to frame buffer
+;   r1: frame buffer width
+;   r2: pointer to string to draw
+;   r3: x coordinate to draw at
+;   r4: y coordinate to draw at
+;   r5: text box left
+;   r6: text box right
+;   r7: text box bottom
+;   r30: text delay (ms, blocking)
+;   r31: text color
+; returns:
+;   r0, r1, r5, r6, r7, r30, r31 kept
+;   r2: pointer to last char drawn
+;   r3: x coordinate to next char to draw
+;   r4: y coordinate to next char to draw
+
+draw_str_at:
+    ; store char pointer in r8
+    mov r8, r2
+
+  draw_str_at_loop:
+    cmp r30, 0
+    ifnz call font_sleep
+
+    ; r2: current char
+    movz.8 r2, [r8]
+    cmp r2, 0 ; check for null terminator
+    ifz jmp draw_str_at_loop_end
+
+    ; check for newline
+    cmp r2, 10
+    ifz jmp draw_str_at_newline
+
+    ; r9: char entry
+    mov r9, r2
+    mul r9, 7
+    add r9, font_table
+    ; r10: width, r11: end x
+    movz.8 r10, [r9]
+    mov r11, r3
+    add r11, r10
+
+    ; are we after the edge?
+    cmp r11, r6
+    iflt jmp draw_str_at_loop_draw
+    ; if we have a space, don't reset
+    cmp r2, 32
+    ifz jmp draw_str_at_loop_draw
+
+  draw_str_at_linebreak:
+
+    mov r3, r5 ; reset x
+    ; update end x
+    mov r11, r5
+    add r11, r10
+    ; step to next line, check if we've overrun the box
+    add r4, FONT_LINE_HEIGHT
+    cmp r4, r7
+    ifgteq jmp draw_str_at_loop_end
+
+  draw_str_at_loop_draw:
+    push r0
+    push r1
+    push r2
+    push r3
+    push r4
+    call draw_char_at
+    pop r4
+    pop r3
+    pop r2
+    pop r1
+    pop r0
+
+  draw_str_at_spaceskip:
+    inc r8 ; update string index
+    mov r3, r11 ; update x coordinate
+    add r3, FONT_SIZE ; padding
+    jmp draw_str_at_loop
+
+  draw_str_at_newline:
+    inc r8 ; update string index
+    mov r3, r5 ; reset x
+    ; step to next line, check if we've overrur the box
+    add r4, FONT_LINE_HEIGHT
+    cmp r4, r7
+    ifgteq jmp draw_str_at_loop_end
+    jmp draw_str_at_loop
+
+  draw_str_at_loop_end:
+
+    ; restore char pointer into r2
+    mov r2, r8
+
+    ret
+
+
+; input:
+;   r0: pointer to frame buffer
+;   r1: frame buffer width
+;   r2: char to draw
+;   r3: x coordinate to draw at
+;   r4: y coordinate to draw at
+;   r31: color
+; returns:
+;   nothing
+
+draw_char_at:
+    push r5
+    push r6
+    push r7
+    push r8
+    push r9
+    ; r5: width
+    ; r7: baseline
+    ; r8: char data pointer
+    ; r9: number of pixels to draw
+
+    mul r2, 7 ; size of char
+    add r2, font_table
+
+    movz.8 r5, [r2]
+    inc r2
+    movz.8 r9, [r2]
+    mul r9, r5
+
+    inc r2
+    movz.8 r7, [r2]
+    inc r2
+    mov r8, [r2]
+    add r8, font_data
+
+    ; adjust y for baseline
+    sub r4, r7
+
+    ; calculate init framebuffer address into r4
+    mul r4, r1
+    add r4, r3
+    mul r4, 4
+    add r4, r0
+
+    ; r6: x counter in glyph
+    ; r9: countdown
+    mov r6, 0
+  draw_char_at_loop:
+    cmp r9, 0 ; zero terminator
+    ifz jmp draw_char_at_loop_done
+
+    cmp.8 [r8], 0
+    ifnz mov [r4], r31
+
+    inc r8 ; advance glyph data pointer
+    dec r9 ; lower count
+    add r4, 4 ; advance screen pointer
+    inc r6 ; advance x counter
+    cmp r6, r5 ; are we at the end of the glyph line?
+    ifnz jmp draw_char_at_loop
+    ; move screen pointer down one (x4 for 4 bytes per pixel)
+    add r4, r1
+    add r4, r1
+    add r4, r1
+    add r4, r1
+    sub r4, r5
+    sub r4, r5
+    sub r4, r5
+    sub r4, r5
+    mov r6, 0
+
+    jmp draw_char_at_loop
+
+  draw_char_at_loop_done:
+
+    pop r9
+    pop r8
+    pop r7
+    pop r6
+    pop r5
+
+    ret
+
+; input
+;   r30: time to sleep (ms)
+font_sleep:
+    push r0
+    push r1
+    ; r0: end time
+    ; r1: current time
+    in r0, 0x8000_0706 ; RTC uptime (ms)
+    add r0, 30
+  font_sleep_busyloop:
+    in r1, 0x8000_0706
+    cmp r1, r0
+    iflt jmp font_sleep_busyloop
+
+    pop r1
+    pop r0
+    ret