feat(tab): add H/P text labels to hammer-on and pull-off arcs

In the Tab renderer, the arc connecting hammer-on and pull-off notes
is now annotated with an "H" (ascending fret = hammer-on) or "P"
(descending fret = pull-off) label above the arc midpoint.

The label is drawn via an overridden paint() in TabSlurGlyph, reusing
the same canvas.fillText path already used for whammy/bend slurText.
TieGlyph's coordinate fields (_startX/Y, _endX/Y, _tieHeight,
_shouldPaint) are widened from private to protected to allow the
subclass to read them during paint.

Fixes #2608

Author: rafaelsales

packages/alphatab/src/rendering/glyphs/TabBeatContainerGlyph.ts

@@ -66,12 +66,17 @@ export class TabBeatContainerGlyph extends BeatContainerGlyph {
                 }
             }
             if (!expanded) {
+                let slurText: string | undefined = undefined;
+                if (n.isHammerPullOrigin && n.hammerPullDestination) {
+                    slurText = n.hammerPullDestination.fret >= n.fret ? 'H' : 'P';
+                }
                 const effectSlur: TabSlurGlyph = new TabSlurGlyph(
                     `tab.slur.effect.${n.id}`,
                     n,
                     n.effectSlurDestination,
                     false,
-                    false
+                    false,
+                    slurText
                 );
                 this._effectSlurs.push(effectSlur);
                 this.addTie(effectSlur);

packages/alphatab/src/rendering/glyphs/TabSlurGlyph.ts

@@ -7,16 +7,22 @@ import { BeamDirection } from '@coderline/alphatab/rendering/utils/BeamDirection
  */
 export class TabSlurGlyph extends TabTieGlyph {
     private _forSlide: boolean;
+    private readonly _slurText?: string;
 
-    public constructor(slurEffectId: string, startNote: Note, endNote: Note, forSlide: boolean, forEnd:boolean) {
+    public constructor(slurEffectId: string, startNote: Note, endNote: Note, forSlide: boolean, forEnd:boolean, slurText?: string) {
         super(slurEffectId, startNote, endNote, forEnd);
         this._forSlide = forSlide;
+        this._slurText = slurText;
     }
 
     public override getTieHeight(startX: number, _startY: number, endX: number, _endY: number): number {
         return (Math.log(endX - startX + 1) * this.renderer.settings.notation.slurHeight) / 2;
     }
 
+    protected override getSlurText(): string | undefined {
+        return this._slurText;
+    }
+
     public tryExpand(startNote: Note, endNote: Note, forSlide: boolean, forEnd: boolean): boolean {
         // same type required
         if (this._forSlide !== forSlide) {

packages/alphatab/src/rendering/glyphs/TieGlyph.ts

@@ -165,14 +165,16 @@ export abstract class TieGlyph extends Glyph implements ITieGlyph {
             return;
         }
 
+        const isDown = this.tieDirection === BeamDirection.Down;
+
         if (this.shouldDrawBendSlur()) {
             TieGlyph.drawBendSlur(
                 canvas,
                 cx + this._startX,
                 cy + this._startY,
                 cx + this._endX,
                 cy + this._endY,
-                this.tieDirection === BeamDirection.Down,
+                isDown,
                 this.renderer.smuflMetrics.tieHeight
             );
         } else {
@@ -183,11 +185,27 @@ export abstract class TieGlyph extends Glyph implements ITieGlyph {
                 cy + this._startY,
                 cx + this._endX,
                 cy + this._endY,
-                this.tieDirection === BeamDirection.Down,
+                isDown,
                 this._tieHeight,
                 this.renderer.smuflMetrics.tieMidpointThickness
             );
         }
+
+        const slurText = this.getSlurText();
+        if (slurText) {
+            const midX = cx + (this._startX + this._endX) / 2;
+            const midY = cy + (this._startY + this._endY) / 2;
+            const apexOffset = this._tieHeight * 0.75;
+            const apexY = midY + (isDown ? apexOffset : -apexOffset);
+            const w = canvas.measureText(slurText).width;
+            const padding = canvas.font.size * 0.35;
+            const textY = isDown ? apexY + padding : apexY - canvas.font.size - padding;
+            canvas.fillText(slurText, midX - w / 2, textY);
+        }
+    }
+
+    protected getSlurText(): string | undefined {
+        return undefined;
     }
 
     protected abstract shouldDrawBendSlur(): boolean;