feat(projects): add accessible draggable carousel scrollbar

src/components/ProjectsSection.tsx

@@ -6,6 +6,8 @@ import { projects } from '@/data/projects';
 import { ProjectThumbnail } from './ProjectThumbnail';
 import styles from './ProjectsSection.module.css';
 
+const MIN_SCROLLBAR_THUMB_PERCENT = 12.5;
+
 export const ProjectsSection: React.FC = () => {
   const viewportRef = useRef<HTMLDivElement>(null);
   const dragState = useRef({
@@ -20,8 +22,17 @@ export const ProjectsSection: React.FC = () => {
     pointerId: -1,
     directionLocked: null as 'horizontal' | 'vertical' | null,
   });
+  const scrollbarDragState = useRef({
+    active: false,
+    pointerId: -1,
+    grabOffset: 0,
+  });
   const [isDragging, setIsDragging] = useState(false);
+  const [isScrollbarDragging, setIsScrollbarDragging] = useState(false);
   const [scrollProgress, setScrollProgress] = useState(0);
+  const [scrollbarThumbPercent, setScrollbarThumbPercent] = useState(
+    MIN_SCROLLBAR_THUMB_PERCENT,
+  );
   const [canScrollPrev, setCanScrollPrev] = useState(false);
   const [canScrollNext, setCanScrollNext] = useState(true);
 
@@ -30,9 +41,16 @@ export const ProjectsSection: React.FC = () => {
     if (!viewport) return;
 
     const maxScroll = Math.max(0, viewport.scrollWidth - viewport.clientWidth);
-    const progress = maxScroll > 0 ? (viewport.scrollLeft / maxScroll) * 100 : 0;
 
-    setScrollProgress(progress);
+    setScrollProgress(
+      maxScroll > 0 ? Math.max(0, Math.min(viewport.scrollLeft / maxScroll, 1)) : 0,
+    );
+    setScrollbarThumbPercent(
+      Math.max(
+        MIN_SCROLLBAR_THUMB_PERCENT,
+        Math.min((viewport.clientWidth / viewport.scrollWidth) * 100, 100),
+      ),
+    );
     setCanScrollPrev(viewport.scrollLeft > 1);
     setCanScrollNext(viewport.scrollLeft < maxScroll - 1);
   };
@@ -196,6 +214,94 @@ export const ProjectsSection: React.FC = () => {
     }
   };
 
+  const scrollFromScrollbarPointer = (
+    track: HTMLDivElement,
+    clientX: number,
+    grabOffset: number,
+  ) => {
+    const viewport = viewportRef.current;
+    if (!viewport) return;
+
+    const trackRect = track.getBoundingClientRect();
+    const thumb = track.firstElementChild as HTMLElement | null;
+    const thumbWidth = thumb?.getBoundingClientRect().width ?? 0;
+    const availableTrack = trackRect.width - thumbWidth;
+    const maxScroll = Math.max(0, viewport.scrollWidth - viewport.clientWidth);
+    if (availableTrack <= 0 || maxScroll <= 0) return;
+
+    const thumbLeft = Math.max(
+      0,
+      Math.min(clientX - trackRect.left - grabOffset, availableTrack),
+    );
+    const nextProgress = thumbLeft / availableTrack;
+    setScrollProgress(nextProgress);
+    viewport.scrollLeft = nextProgress * maxScroll;
+  };
+
+  const handleScrollbarPointerDown = (event: React.PointerEvent<HTMLDivElement>) => {
+    if (event.button !== 0 && event.pointerType === 'mouse') return;
+
+    const track = event.currentTarget;
+    const thumb = track.firstElementChild as HTMLElement | null;
+    if (!thumb) return;
+
+    const thumbRect = thumb.getBoundingClientRect();
+    const clickedThumb = thumb.contains(event.target as Node);
+    const grabOffset = clickedThumb
+      ? event.clientX - thumbRect.left
+      : thumbRect.width / 2;
+
+    scrollbarDragState.current = {
+      active: true,
+      pointerId: event.pointerId,
+      grabOffset,
+    };
+    track.setPointerCapture(event.pointerId);
+    setIsScrollbarDragging(true);
+
+    if (!clickedThumb) {
+      scrollFromScrollbarPointer(track, event.clientX, grabOffset);
+    }
+    event.preventDefault();
+  };
+
+  const handleScrollbarPointerMove = (event: React.PointerEvent<HTMLDivElement>) => {
+    const drag = scrollbarDragState.current;
+    if (!drag.active || drag.pointerId !== event.pointerId) return;
+
+    scrollFromScrollbarPointer(event.currentTarget, event.clientX, drag.grabOffset);
+  };
+
+  const stopScrollbarDragging = (event: React.PointerEvent<HTMLDivElement>) => {
+    const drag = scrollbarDragState.current;
+    if (!drag.active || drag.pointerId !== event.pointerId) return;
+
+    drag.active = false;
+    if (event.currentTarget.hasPointerCapture(event.pointerId)) {
+      event.currentTarget.releasePointerCapture(event.pointerId);
+    }
+    setIsScrollbarDragging(false);
+  };
+
+  const handleScrollbarKeyDown = (event: React.KeyboardEvent<HTMLDivElement>) => {
+    const viewport = viewportRef.current;
+    if (!viewport) return;
+
+    if (event.key === 'ArrowLeft') {
+      event.preventDefault();
+      scrollByCard(-1);
+    } else if (event.key === 'ArrowRight') {
+      event.preventDefault();
+      scrollByCard(1);
+    } else if (event.key === 'Home' || event.key === 'End') {
+      event.preventDefault();
+      viewport.scrollTo({
+        left: event.key === 'Home' ? 0 : viewport.scrollWidth - viewport.clientWidth,
+        behavior: 'smooth',
+      });
+    }
+  };
+
   return (
     <section
       id="projects"
@@ -238,6 +344,7 @@ export const ProjectsSection: React.FC = () => {
         </div>
 
         <div
+          id="projects-carousel"
           ref={viewportRef}
           className={`${styles.carouselViewport} ${isDragging ? styles.dragging : ''}`}
           onScroll={syncScrollState}
@@ -301,16 +408,29 @@ export const ProjectsSection: React.FC = () => {
 
         <div className={styles.scrollbarWrapper} data-reveal="soft">
           <div
-            className={styles.progressTrack}
-            role="progressbar"
+            className={`${styles.scrollbarTrack} ${isScrollbarDragging ? styles.scrollbarDragging : ''}`}
+            role="scrollbar"
+            tabIndex={0}
             aria-label="Project carousel position"
+            aria-controls="projects-carousel"
+            aria-orientation="horizontal"
             aria-valuemin={0}
             aria-valuemax={100}
-            aria-valuenow={Math.round(scrollProgress)}
+            aria-valuenow={Math.round(scrollProgress * 100)}
+            onPointerDown={handleScrollbarPointerDown}
+            onPointerMove={handleScrollbarPointerMove}
+            onPointerUp={stopScrollbarDragging}
+            onPointerCancel={stopScrollbarDragging}
+            onKeyDown={handleScrollbarKeyDown}
           >
             <span
-              className={styles.progressValue}
-              style={{ width: `${12.5 + scrollProgress * 0.875}%` }}
+              className={styles.scrollbarThumb}
+              style={{
+                width: `${scrollbarThumbPercent}%`,
+                transform: `translate3d(${scrollbarThumbPercent < 100
+                  ? scrollProgress * ((100 - scrollbarThumbPercent) / scrollbarThumbPercent) * 100
+                  : 0}%, 0, 0)`,
+              }}
             />
           </div>
         </div>