Initial bg/fg renderer decoration proof of concept

Part of #3770

src/common/services/DecorationService.ts

@@ -6,6 +6,7 @@
 import { EventEmitter } from 'common/EventEmitter';
 import { Disposable } from 'common/Lifecycle';
 import { IDecorationService, IInternalDecoration } from 'common/services/Services';
+import { IColorRGB } from 'common/Types';
 import { IDecorationOptions, IDecoration, IMarker, IEvent } from 'xterm';
 
 export class DecorationService extends Disposable implements IDecorationService {
@@ -45,6 +46,15 @@ export class DecorationService extends Disposable implements IDecorationService
     return decoration;
   }
 
+  public *getDecorationsOnLine(line: number): IterableIterator<IInternalDecoration> {
+    // TODO: This could be made much faster if _decorations was sorted by line (and col?)
+    for (const d of this.decorations) {
+      if (d.marker.line === line) {
+        yield d;
+      }
+    }
+  }
+
   public dispose(): void {
     for (const decoration of this._decorations) {
       this._onDecorationRemoved.fire(decoration);
@@ -64,6 +74,32 @@ class Decoration extends Disposable implements IInternalDecoration {
   private _onDispose = this.register(new EventEmitter<void>());
   public readonly onDispose = this._onDispose.event;
 
+  // TODO: React to changes on options
+  private _cachedBg: IColorRGB | undefined | null = null;
+  public get backgroundColorRGB(): IColorRGB | undefined {
+    if (this._cachedBg === null) {
+      if (this.options.backgroundColor) {
+        this._cachedBg = toColorRGB(this.options.backgroundColor);
+      } else {
+        this._cachedBg = undefined;
+      }
+    }
+    return this._cachedBg;
+  }
+
+  // TODO: React to changes on options
+  private _cachedFg: IColorRGB | undefined | null = null;
+  public get foregroundColorRGB(): IColorRGB | undefined {
+    if (this._cachedFg === null) {
+      if (this.options.foregroundColor) {
+        this._cachedFg = toColorRGB(this.options.foregroundColor);
+      } else {
+        this._cachedFg = undefined;
+      }
+    }
+    return this._cachedFg;
+  }
+
   constructor(
     public readonly options: IDecorationOptions
   ) {
@@ -73,6 +109,7 @@ class Decoration extends Disposable implements IInternalDecoration {
       this.options.overviewRulerOptions.position = 'full';
     }
   }
+
   public override dispose(): void {
     if (this._isDisposed) {
       return;
@@ -82,3 +119,11 @@ class Decoration extends Disposable implements IInternalDecoration {
     super.dispose();
   }
 }
+
+function toColorRGB(css: string): IColorRGB {
+  // #rrggbb
+  if (css.length === 7) {
+    return [parseInt(css.slice(1, 3), 16), parseInt(css.slice(3, 5), 16), parseInt(css.slice(5, 7), 16)];
+  }
+  throw new Error('css.toColor: Unsupported css format');
+}