From 80c4c3604c5c9fd0156e72bcc543267fc99c3170 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alexander=20Neuh=C3=A4user?= <alexander.neuhaeuser@tuta.io>
Date: Sat, 26 Jul 2025 17:17:05 +0200
Subject: [PATCH] Support lines in all directions and add squares

---
 README.md          |  3 ++-
 src/framebuffer.rs | 67 ++++++++++++++++++++++++++++++++++++++++++++--
 src/main.rs        | 18 ++++---------
 3 files changed, 72 insertions(+), 16 deletions(-)

diff --git a/README.md b/README.md
index 372bebc..325091c 100644
--- a/README.md
+++ b/README.md
@@ -10,6 +10,7 @@ NovaOS is a expository project where I build a kernel from scratch for a Raspber
 - UART ✓
 - GPIOs ✓
 - GPIO Interrupts ✓
-- Frame Buffer
+- Communicate with peripherals via mailboxes ✓
+- Frame Buffer ✓
 - MMU
 - Basic Terminal over UART
diff --git a/src/framebuffer.rs b/src/framebuffer.rs
index aa80896..939e3cf 100644
--- a/src/framebuffer.rs
+++ b/src/framebuffer.rs
@@ -103,7 +103,9 @@ impl FrameBuffer {
         }
     }
 
-    /*Bresenham's line algorithm */
+    /*Bresenham's line algorithm
+    TODO: check if its possible to optimize y1==y2 case
+    */
     pub fn draw_line(&self, x1: u32, y1: u32, x2: u32, y2: u32) {
         if x1 == x2 {
             for y in y1..=y2 {
@@ -111,6 +113,44 @@ impl FrameBuffer {
             }
             return;
         }
+
+        if (y2 as i32 - y1 as i32).abs() < (x2 as i32 - x1 as i32).abs() {
+            if x1 > x2 {
+                self.plot_line_low(x2, y2, x1, y1);
+            } else {
+                self.plot_line_low(x1, y1, x2, y2);
+            }
+        } else {
+            if y1 > y2 {
+                self.plot_line_high(x2, y2, x1, y1);
+            } else {
+                self.plot_line_high(x1, y1, x2, y2);
+            }
+        }
+    }
+
+    pub fn draw_square(&self, x1: u32, y1: u32, x2: u32, y2: u32) {
+        self.draw_line(x1, y1, x2, y1);
+        self.draw_line(x1, y2, x2, y2);
+        self.draw_line(x1, y1, x1, y2);
+        self.draw_line(x2, y1, x2, y2);
+    }
+
+    pub fn draw_square_fill(&self, x1: u32, y1: u32, x2: u32, y2: u32) {
+        let mut y_start = y1;
+        let mut y_end = y2;
+
+        if y2 < y1 {
+            y_start = y2;
+            y_end = y1;
+        }
+
+        for y in y_start..=y_end {
+            self.draw_line(x1, y, x2, y);
+        }
+    }
+
+    fn plot_line_low(&self, x1: u32, y1: u32, x2: u32, y2: u32) {
         let dx = x2 as i32 - x1 as i32;
         let mut dy = y2 as i32 - y1 as i32;
         let mut yi = 1;
@@ -126,13 +166,36 @@ impl FrameBuffer {
         for x in x1..=x2 {
             self.draw_pixel(x, y as u32);
             if d > 0 {
-                y = y + yi;
+                y += yi;
                 d += 2 * (dy - dx);
             } else {
                 d += 2 * dy;
             }
         }
     }
+    fn plot_line_high(&self, x1: u32, y1: u32, x2: u32, y2: u32) {
+        let mut dx = x2 as i32 - x1 as i32;
+        let dy = y2 as i32 - y1 as i32;
+        let mut xi: i32 = 1;
+
+        let mut d = 2 * dy - dx;
+        let mut x = x1 as i32;
+
+        if dx < 0 {
+            xi = -1;
+            dx = -dx;
+        }
+
+        for y in y1..=y2 {
+            self.draw_pixel(x as u32, y);
+            if d > 0 {
+                x += xi;
+                d += 2 * (dx - dy);
+            } else {
+                d += 2 * dx;
+            }
+        }
+    }
 }
 
 pub fn print_display_resolution() {
diff --git a/src/main.rs b/src/main.rs
index c072687..591688f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -98,19 +98,11 @@ pub extern "C" fn kernel_main() -> ! {
     print_display_resolution();
 
     fb.draw_line(10, 10, 1000, 10);
-    fb.draw_line(10, 10, 1000, 200);
-    fb.draw_line(10, 10, 1000, 300);
-    fb.draw_line(10, 10, 1000, 400);
-    fb.draw_line(10, 10, 1000, 500);
-    fb.draw_line(10, 10, 1000, 600);
-    fb.draw_line(10, 10, 1000, 700);
-    fb.draw_line(10, 10, 1000, 800);
-    fb.draw_line(10, 10, 1000, 900);
-    fb.draw_line(10, 10, 1000, 1000);
-    fb.draw_line(10, 10, 100, 1000);
-
-    fb.draw_line(1800, 10, 1000, 900);
-    fb.draw_line(1800, 500, 1000, 100);
+    fb.draw_line(1000, 20, 10, 20);
+    fb.draw_square(500, 500, 600, 700);
+    fb.draw_square_fill(800, 800, 900, 900);
+    fb.draw_square_fill(1000, 800, 1200, 700);
+    fb.draw_square_fill(900, 100, 800, 150);
 
     loop {
         let temp = read_soc_temp();