Switch FramebuferWriter to using a grid of character cells to represent the screen

src/main.rs

@@ -22,10 +22,9 @@
 use core::str;
 use std::{
     borrow::Cow,
-    collections::HashMap,
+    collections::{HashMap, VecDeque},
     fmt::{self, Write},
     os::mikros::{address_space::ACTIVE_SPACE, ipc, syscalls},
-    usize,
 };
 
 use fontdue::{
@@ -95,14 +94,14 @@ impl Bga {
         }
         self.draw_buffer
             .resize(xres as usize * yres as usize * 4 * 2, 0);
-        self.draw_buffer.fill(0);
+        self.draw_buffer.fill(32);
         self.scroll_offset = 0;
         self.xres = xres as usize;
         self.yres = yres as usize;
     }
 
     pub fn clear(&mut self) {
-        self.draw_buffer.fill(0);
+        self.draw_buffer.fill(32);
         self.scroll_offset = 0;
     }
 
@@ -120,7 +119,7 @@ impl Bga {
         let visible_buf = &self.draw_buffer[scroll_top_byte_offset..scroll_bot_byte_offset];
         unsafe {
             self.framebuffer_base
-                .copy_from_nonoverlapping(&visible_buf[0], visible_buf.len())
+                .copy_from_nonoverlapping(&visible_buf[0], visible_buf.len());
         };
     }
 
@@ -139,7 +138,7 @@ impl Bga {
             return;
         }
         let offset = self.row_byte_offset(row);
-        self.draw_buffer[offset..][..(self.xres * 4)].fill(0);
+        self.draw_buffer[offset..][..(self.xres * 4)].fill(32);
     }
 
     pub fn clear_row(&mut self, row: usize) {
@@ -176,13 +175,17 @@ impl Bga {
 }
 
 pub struct FramebufferWriter {
-    out_string: String,
     font: Font,
     layout: Layout,
-    next_line_y: usize,
     glyph_cache: HashMap<GlyphRasterConfig, Vec<u8>>,
-    cursor_top: usize,
+    line_height: usize,
-    cursor_bot: usize,
+    render_buf: VecDeque<Vec<char>>,
+    dirty_lines: Vec<usize>,
+    write_cursor: (usize, usize),
+    waiting_scroll_offset: usize,
+    buf_height: usize,
+    buf_width: usize,
+    prev_line_hard_end: bool,
 }
 
 impl FramebufferWriter {
@@ -194,42 +197,54 @@ impl FramebufferWriter {
             wrap_style: WrapStyle::Letter,
             ..Default::default()
         });
+        let line_height = font
+            .horizontal_line_metrics(12.0)
+            .unwrap()
+            .new_line_size
+            .ceil() as usize;
+        let char_width = font.metrics('a', 12.0).advance_width.ceil() as usize;
+        println!(
+            "Buffer is {}x{} px, ({} chars x {} lines)",
+            fbuf.xres,
+            fbuf.yres,
+            fbuf.xres / char_width,
+            fbuf.yres / line_height
+        );
         Self {
-            out_string: String::new(),
             font,
             layout,
-            next_line_y: 0,
             glyph_cache: HashMap::new(),
-            cursor_top: 0,
+            line_height,
-            cursor_bot: 0,
+            render_buf: vec![vec![' '; fbuf.xres / char_width]; fbuf.yres / line_height].into(),
+            dirty_lines: vec![],
+            write_cursor: (0, 0),
+            waiting_scroll_offset: 0,
+            buf_height: fbuf.yres / line_height,
+            buf_width: fbuf.xres / char_width,
+            prev_line_hard_end: false,
         }
     }
 
     fn update_screen(&mut self, fbuf: &mut Bga) {
-        self.layout.clear();
+        if self.waiting_scroll_offset > 0 {
-        self.layout
+            fbuf.scroll_by(self.line_height * self.waiting_scroll_offset);
-            .append(&[&self.font], &TextStyle::new(&self.out_string, 12.0, 0));
+            self.waiting_scroll_offset = 0;
-        let text_height = self.layout.height();
-        self.layout
-            .append(&[&self.font], &TextStyle::new("\u{2588}", 12.0, 0));
-
-        for row in self.cursor_top..self.cursor_bot {
-            fbuf.clear_row(row);
         }
+        for line_no in self.dirty_lines.drain(..) {
+            for row in (line_no * self.line_height)..(line_no * self.line_height + self.line_height)
+            {
+                fbuf.clear_row(row);
+            }
+            let line_str = self.render_buf[line_no].iter().collect::<String>();
+            self.layout.clear();
+            self.layout
+                .append(&[&self.font], &TextStyle::new(&line_str, 12.0, 0));
+            let glyphs = self.layout.glyphs();
+            let lines = self.layout.lines().unwrap();
 
-        if (self.next_line_y + self.layout.height() as usize) > fbuf.yres {
+            let line = lines[0];
-            let excess_y = self.layout.height() as usize - (fbuf.yres - self.next_line_y);
+            let top_offset = (line.baseline_y - line.max_ascent).floor() as usize;
-            fbuf.scroll_by(excess_y);
-            self.next_line_y -= excess_y;
-        }
 
-        let glyphs = self.layout.glyphs();
-        let lines = self.layout.lines().unwrap();
-
-        let first_line = lines[0];
-        let first_line_top_offset = (first_line.baseline_y - first_line.max_ascent) as usize;
-
-        for line in self.layout.lines().unwrap() {
             for glyph_pos in &glyphs[line.glyph_start..=line.glyph_end] {
                 if glyph_pos.width == 0 || glyph_pos.height == 0 {
                     continue;
@@ -245,57 +260,76 @@ impl FramebufferWriter {
                     let row = i / glyph_pos.width;
                     let col = i % glyph_pos.width;
                     fbuf.set_pixel(
-                        row + glyph_pos.y as usize - first_line_top_offset + self.next_line_y,
+                        row + glyph_pos.y as usize - top_offset + (line_no * self.line_height),
                         col + glyph_pos.x as usize,
                         pixel,
                     );
                 }
             }
         }
-
         fbuf.update_screen();
+    }
 
-        let cursor_glyph = glyphs.last().unwrap();
+    fn set_char(&mut self, x: usize, y: usize, c: char) {
-
+        self.render_buf[y][x] = c;
-        self.cursor_top = cursor_glyph.y as usize - first_line_top_offset + self.next_line_y;
+        if !self.dirty_lines.contains(&y) {
-        self.cursor_bot = cursor_glyph.y as usize - first_line_top_offset
+            self.dirty_lines.push(y);
-            + self.next_line_y
-            + cursor_glyph.height;
-
-        let last_line = self.layout.lines().unwrap().last().unwrap();
-        let log_line_slice = if last_line.glyph_start == last_line.glyph_end {
-            ""
-        } else {
-            let first_char_offset = glyphs[last_line.glyph_start].byte_offset;
-            let last_char_offset = glyphs[last_line.glyph_end - 1].byte_offset;
-            let mut last_char_end = last_char_offset + 1;
-            while last_char_end < self.out_string.len()
-                && !self.out_string.is_char_boundary(last_char_end)
-            {
-                last_char_end += 1;
-            }
-            &self.out_string[first_char_offset..last_char_end]
-        };
-
-        let before_last_height = (last_line.baseline_y - last_line.max_ascent) as usize;
-
-        if self.out_string.ends_with('\n') {
-            self.out_string.clear();
-            self.next_line_y += text_height as usize;
-        } else {
-            self.out_string = log_line_slice.to_string();
-            self.next_line_y += before_last_height;
         }
     }
 }
 
 impl fmt::Write for FramebufferWriter {
     fn write_char(&mut self, c: char) -> fmt::Result {
+        self.set_char(self.write_cursor.0, self.write_cursor.1, ' '); // Clear old cursor
         if c == '\u{8}' {
-            self.out_string.pop();
+            if self.write_cursor.0 == 0 {
-        } else {
+                if self.write_cursor.1 != 0 && !self.prev_line_hard_end {
-            self.out_string.push(c);
+                    self.write_cursor.1 -= 1;
+                    self.write_cursor.0 = self.buf_width - 1;
+                }
+            } else {
+                self.write_cursor.0 -= 1;
+            }
+        } else if c == '\n' {
+            self.prev_line_hard_end = true;
+            self.write_cursor.0 = 0;
+            self.write_cursor.1 += 1;
+            if self.write_cursor.1 == self.buf_height {
+                // Fixup dirty_lines
+                self.dirty_lines = self
+                    .dirty_lines
+                    .iter()
+                    .filter(|&&line| line != 0)
+                    .map(|&line| line - 1)
+                    .collect();
+                self.write_cursor.1 -= 1;
+                self.render_buf.pop_front();
+                self.render_buf.push_back(vec![' '; self.buf_width]);
+                self.waiting_scroll_offset += 1;
+            }
+        } else if !c.is_control() {
+            self.set_char(self.write_cursor.0, self.write_cursor.1, c);
+            self.write_cursor.0 += 1;
+            if self.write_cursor.0 == self.buf_width {
+                self.prev_line_hard_end = false;
+                self.write_cursor.0 = 0;
+                self.write_cursor.1 += 1;
+                if self.write_cursor.1 == self.buf_height {
+                    // Fixup dirty_lines
+                    self.dirty_lines = self
+                        .dirty_lines
+                        .iter()
+                        .filter(|&&line| line != 0)
+                        .map(|&line| line - 1)
+                        .collect();
+                    self.write_cursor.1 -= 1;
+                    self.render_buf.pop_front();
+                    self.render_buf.push_back(vec![' '; self.buf_width]);
+                    self.waiting_scroll_offset += 1;
+                }
+            }
         }
+        self.set_char(self.write_cursor.0, self.write_cursor.1, '\u{2588}');
         Ok(())
     }
     fn write_str(&mut self, s: &str) -> core::fmt::Result {
@@ -434,7 +468,11 @@ fn main() {
         FontSettings::default(),
     )
     .unwrap();
-    let writer = FramebufferWriter::new(font, &bga);
+
+    let mut writer = FramebufferWriter::new(font, &bga);
+    writer.render_buf[0][0] = '\u{2588}';
+    writer.dirty_lines.push(0);
+    writer.update_screen(&mut bga);
 
     dev_driver_rpc::register_server(Box::new(DevServ));
     file_rpc::register_server(Box::new(FileServ {