From c46bc484c57b47514b1442504cdb7fe4dff01601 Mon Sep 17 00:00:00 2001
From: Daniel Friesel <derf@finalrewind.org>
Date: Tue, 31 May 2022 21:56:47 +0200
Subject: add framebuffer

---
 framebuffer.lua | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 framebuffer.lua

diff --git a/framebuffer.lua b/framebuffer.lua
new file mode 100644
index 0000000..6b588b2
--- /dev/null
+++ b/framebuffer.lua
@@ -0,0 +1,55 @@
+local fb = {}
+
+fb.w = 0
+fb.h = 0
+fb.x = 0
+fb.y = 0
+fb.buf = nil
+
+function fb.init(w, h)
+	fb.w = w
+	fb.h = h
+	fb.x = 0
+	fb.y = 0
+	fb.buf = {}
+end
+
+function fb.scroll()
+	for x = 0, fb.w-1 do
+		for y = 1, fb.h/8-1 do
+			fb.buf[x*(fb.h/8) + y-1 + 1] = fb.buf[x*(fb.h/8) + y + 1] or nil
+		end
+		fb.buf[x*(fb.h/8) + fb.h/8] = nil
+	end
+	fb.y = fb.y - 8
+end
+
+function fb.put(font, c)
+	if c == 10 then
+		fb.x = 0
+		fb.y = fb.y + font.height
+		return
+	end
+	if c < 32 or c > 126 then
+		c = 0x3f
+	end
+	if fb.y >= fb.h then
+		fb.scroll()
+	end
+	local glyph = font.glyphs[c - 31]
+	for i = 1, table.getn(glyph) do
+		fb.buf[fb.y/8 + (fb.x + i-1) * (fb.h/8) + 1] = glyph[i]
+	end
+	fb.x = fb.x + table.getn(glyph) + 2
+	if fb.x > fb.w then
+		fb.put(font, 10)
+	end
+end
+
+function fb.print(font, str)
+	for i = 1, string.len(str) do
+		fb.put(font, string.byte(str, i))
+	end
+end
+
+return fb
-- 
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