Optimize ansi character writing

ansi.ts

@@ -7,6 +7,8 @@ import { Display } from "./display.ts";
 export class AnsiTerminalDisplay implements Display {
   private palette_bg: readonly Uint8Array[] = [];
   private palette_fg: readonly Uint8Array[] = [];
+  private width = 1;
+  private state = { x: -1, y: -1, f: -1, b: -1 }; // current location and color
 
   constructor(
     private writer: Deno.Writer = Deno.stdout,
@@ -16,6 +18,7 @@ export class AnsiTerminalDisplay implements Display {
 
   async getSize(): Promise<BufferSize> {
     const size = Deno.consoleSize(Deno.stdout.rid);
+    this.width = size.columns;
     return {
       w: size.columns,
       h: size.rows,
@@ -39,13 +42,32 @@ export class AnsiTerminalDisplay implements Display {
   }
 
   async setChar(at: BufferLocation, char: Char): Promise<void> {
-    // TODO do not move the cursor if already at good location
-    // TODO do not change the color if already good
-    const fg = this.palette_fg[char.fg];
-    const bg = this.palette_bg[char.bg];
-    await this.writer.write(fg);
-    await this.writer.write(bg);
-    await this.writer.write(escape(`[${at.y};${at.x}H${char.ch}`));
+    let { x, y, f, b } = this.state;
+
+    if (f != char.fg) {
+      f = char.fg;
+      await this.writer.write(this.palette_fg[f]);
+    }
+
+    if (b != char.bg) {
+      b = char.bg;
+      await this.writer.write(this.palette_bg[b]);
+    }
+
+    if (x != at.x || y != at.y) {
+      x = at.x;
+      y = at.y;
+      await this.writer.write(escape(`[${at.y};${at.x}H`));
+    }
+
+    await this.writer.write(new TextEncoder().encode(char.ch));
+
+    x += 1;
+    if (x > this.width) {
+      x = 0;
+      y += 1;
+    }
+    this.state = { x, y, f, b };
   }
 }
 

mod.ts

@@ -1,11 +1,15 @@
 import { AnsiTerminalDisplay } from "./ansi.ts";
-import { TextUI } from "./ui.ts";
+import { TextUI, UIPalette } from "./ui.ts";
 export { TextUI } from "./ui.ts";
 
-export async function createTextUI(): Promise<TextUI> {
+export type UIConfig = {
+  palette: UIPalette;
+};
+
+export async function createTextUI(config: UIConfig): Promise<TextUI> {
   // TODO detect platform
   var display = new AnsiTerminalDisplay();
   var ui = new TextUI(display);
-  await ui.init();
+  await ui.init(config.palette);
   return ui;
 }

ui.ts

@@ -44,8 +44,8 @@ export class TextUI {
   async flush(): Promise<void> {
     // TODO only dirty chars
     const { w, h } = this.screen.getSize();
-    for (let x = 0; x < w; x++) {
-      for (let y = 0; y < h; y++) {
+    for (let y = 0; y < h; y++) {
+      for (let x = 0; x < w; x++) {
         await this.display.setChar({ x, y }, this.screen.get({ x, y }));
       }
     }