feat(image-zoom): enhance zoom functionality with loading states and improved interactions

- Updated CSS to include loading indicators and refined transition effects for zoomed images.
- Enhanced JavaScript to manage image loading states, ensuring a smoother user experience during zoom interactions.
- Improved gesture handling for touch devices, including better management of pinch and drag events.

assets/css/components/image-zoom.css

@@ -9,10 +9,13 @@
   opacity: 0;
   transition: opacity 260ms cubic-bezier(0.2, 0, 0, 1);
   cursor: zoom-out;
-  overscroll-behavior: auto;
-  touch-action: auto;
+  overscroll-behavior: contain;
+  touch-action: none;
   backdrop-filter: blur(var(--hextra-image-zoom-blur, 4px));
   -webkit-backdrop-filter: blur(var(--hextra-image-zoom-blur, 4px));
+  /* Prevent iOS bounce */
+  position: fixed;
+  overflow: hidden;
 }
 
 .hextra-zoom-image-overlay.show {
@@ -25,22 +28,37 @@
 }
 
 .hextra-zoom-image {
-  max-width: min(95vw, 1200px);
-  max-height: 95vh;
   border-radius: 8px;
-  box-shadow: 0 8px 40px rgba(0, 0, 0, 0.35);
+  box-shadow: 0 18px 80px rgba(0, 0, 0, 0.5);
+  image-rendering: -webkit-optimize-contrast;
+  image-rendering: high-quality;
   will-change: transform;
-  transform: scale(0.98);
+  /* Prevent image selection on mobile */
+  user-select: none;
+  -webkit-user-select: none;
+  -webkit-touch-callout: none;
+  /* Hardware acceleration */
+  transform: translateZ(0);
+  -webkit-transform: translateZ(0);
 }
 
 .hextra-zoom-image-overlay.show .hextra-zoom-image {
-  transform: scale(1);
-  transition: transform 320ms cubic-bezier(0.2, 0.8, 0.2, 1);
+  transition:
+    transform 320ms cubic-bezier(0.2, 0.8, 0.2, 1),
+    left 320ms cubic-bezier(0.2, 0.8, 0.2, 1),
+    top 320ms cubic-bezier(0.2, 0.8, 0.2, 1);
 }
 
 .hextra-zoom-image-overlay.closing .hextra-zoom-image {
-  transform: scale(0.98);
-  transition: transform 340ms cubic-bezier(0.3, 0, 0.2, 1);
+  transition:
+    transform 340ms cubic-bezier(0.3, 0, 0.2, 1),
+    left 340ms cubic-bezier(0.3, 0, 0.2, 1),
+    top 340ms cubic-bezier(0.3, 0, 0.2, 1);
+}
+
+/* Disable transitions during interaction */
+.hextra-zoom-image-overlay.interacting .hextra-zoom-image {
+  transition: none !important;
 }
 
 @media (prefers-reduced-motion: reduce) {
@@ -50,7 +68,16 @@
   }
 }
 
-/* Show magnifier cursor over zoomable images in content */
 .content img:not([data-no-zoom]) {
   cursor: zoom-in;
 }
+
+/* Loading indicator */
+.hextra-zoom-image.loading {
+  opacity: 0;
+}
+
+.hextra-zoom-image.loaded {
+  opacity: 1;
+  transition: opacity 200ms ease-in-out;
+}

assets/js/image-zoom.js

@@ -1,123 +1,403 @@
-/*!
- * Hextra Image Zoom
- * - Zooms images inside `.content` into a dark, blurred overlay.
- * - Dismiss: overlay click, Esc, wheel/scroll (non-ctrl).
- * - Pinch/trackpad pinch (wheel+ctrl) will NOT dismiss.
- * - Opt out per image via `data-no-zoom`.
- * - Customize via CSS vars: --hextra-image-zoom-backdrop, --hextra-image-zoom-blur.
- */
-
 (function () {
   'use strict';
 
-  function createOverlay(src, alt) {
+  function createOverlayFromTarget(targetImg) {
+    const src = targetImg.currentSrc || targetImg.src;
+    const alt = targetImg.alt || "";
+    if (!src) return;
+
+    const rect = targetImg.getBoundingClientRect();
+
     const overlay = document.createElement("div");
     overlay.className = "hextra-zoom-image-overlay";
     overlay.setAttribute("role", "dialog");
     overlay.setAttribute("aria-modal", "true");
+    overlay.setAttribute("aria-label", alt || "Zoomed image");
 
     const img = document.createElement("img");
-    img.className = "hextra-zoom-image";
+    img.className = "hextra-zoom-image loading";
     img.src = src;
     if (alt) img.alt = alt;
 
+    // Center-origin positioning for cleaner transforms
+    const startCX = rect.left + rect.width / 2;
+    const startCY = rect.top + rect.height / 2;
+    img.style.position = "fixed";
+    img.style.left = startCX + "px";
+    img.style.top = startCY + "px";
+    img.style.width = rect.width + "px";
+    img.style.height = rect.height + "px";
+    img.style.transformOrigin = "center center";
+    img.style.transform = "translate3d(-50%, -50%, 0) scale(1)";
+
     overlay.appendChild(img);
 
-    // Track pinch gesture
-    let pinching = false;
-    let pinchTimer = 0;
-    const activeTouchPointers = new Set();
-    function pinchingStart() {
-      pinching = true;
-      if (pinchTimer) clearTimeout(pinchTimer);
+    // Image loaded handler
+    img.addEventListener('load', function () {
+      img.classList.remove('loading');
+      img.classList.add('loaded');
+    });
+
+    // Gesture state management
+    let isPinching = false;
+    let isDragging = false;
+    let isInteracting = false;
+    let pinchEndTimer = null;
+
+    const pointers = new Map(); // pointerId -> {x, y, startX, startY}
+    let gestureState = {
+      scale: 1,
+      panX: 0,
+      panY: 0,
+      lastScale: 1,
+      lastPanX: 0,
+      lastPanY: 0,
+      initialDistance: 0,
+      midpointX: 0,
+      midpointY: 0
+    };
+
+    // Utility functions
+    function getDistance(p1, p2) {
+      const dx = p2.x - p1.x;
+      const dy = p2.y - p1.y;
+      return Math.sqrt(dx * dx + dy * dy);
     }
-    function pinchingEndSoon() {
-      if (pinchTimer) clearTimeout(pinchTimer);
-      pinchTimer = setTimeout(() => (pinching = false), 350);
+
+    function getMidpoint(p1, p2) {
+      return {
+        x: (p1.x + p2.x) / 2,
+        y: (p1.y + p2.y) / 2
+      };
     }
-    function onPointerDown(e) {
-      if (e.pointerType === 'touch') {
-        activeTouchPointers.add(e.pointerId);
-        if (activeTouchPointers.size > 1) pinchingStart();
-      }
-    }
-    function onPointerUp(e) {
-      if (e.pointerType === 'touch') {
-        activeTouchPointers.delete(e.pointerId);
-        if (activeTouchPointers.size < 2) pinchingEndSoon();
+
+    function setInteracting(value) {
+      isInteracting = value;
+      if (value) {
+        overlay.classList.add('interacting');
+      } else {
+        overlay.classList.remove('interacting');
       }
     }
 
+    // Pointer event handlers
+    function onPointerDown(e) {
+      e.preventDefault();
+
+      pointers.set(e.pointerId, {
+        x: e.clientX,
+        y: e.clientY,
+        startX: e.clientX,
+        startY: e.clientY
+      });
+
+      if (pointers.size === 1) {
+        // Single touch - start drag
+        isDragging = true;
+        setInteracting(true);
+        gestureState.lastPanX = gestureState.panX;
+        gestureState.lastPanY = gestureState.panY;
+      } else if (pointers.size === 2) {
+        // Two touches - start pinch
+        isDragging = false;
+        isPinching = true;
+        setInteracting(true);
+
+        const pts = Array.from(pointers.values());
+        gestureState.initialDistance = getDistance(pts[0], pts[1]);
+        gestureState.lastScale = gestureState.scale;
+
+        const midpoint = getMidpoint(pts[0], pts[1]);
+        gestureState.midpointX = midpoint.x;
+        gestureState.midpointY = midpoint.y;
+
+        if (pinchEndTimer) {
+          clearTimeout(pinchEndTimer);
+          pinchEndTimer = null;
+        }
+      }
+    }
+
+    function onPointerMove(e) {
+      if (!pointers.has(e.pointerId)) return;
+
+      e.preventDefault();
+
+      const pointer = pointers.get(e.pointerId);
+      pointer.x = e.clientX;
+      pointer.y = e.clientY;
+
+      if (isPinching && pointers.size === 2) {
+        // Handle pinch zoom
+        const pts = Array.from(pointers.values());
+        const currentDistance = getDistance(pts[0], pts[1]);
+        const scaleDelta = currentDistance / gestureState.initialDistance;
+
+        // Calculate new scale with limits - minimum is 1 (original zoom level)
+        const newScale = Math.max(1, Math.min(5, gestureState.lastScale * scaleDelta));
+
+        // Only update pan if scale is actually changing
+        // This prevents drift when pinching at minimum scale
+        if (Math.abs(newScale - gestureState.scale) > 0.001) {
+          gestureState.scale = newScale;
+
+          // Calculate pan based on pinch center movement
+          const currentMidpoint = getMidpoint(pts[0], pts[1]);
+          const panDeltaX = currentMidpoint.x - gestureState.midpointX;
+          const panDeltaY = currentMidpoint.y - gestureState.midpointY;
+
+          gestureState.panX = gestureState.lastPanX + panDeltaX;
+          gestureState.panY = gestureState.lastPanY + panDeltaY;
+        }
+
+        applyTransform();
+      } else if (isDragging && pointers.size === 1) {
+        // Handle drag/pan
+        const deltaX = pointer.x - pointer.startX;
+        const deltaY = pointer.y - pointer.startY;
+
+        gestureState.panX = gestureState.lastPanX + deltaX;
+        gestureState.panY = gestureState.lastPanY + deltaY;
+
+        applyTransform();
+      }
+    }
+
+    function onPointerUp(e) {
+      pointers.delete(e.pointerId);
+
+      if (pointers.size === 0) {
+        // All pointers released
+        isDragging = false;
+        setInteracting(false);
+
+        // Check if it was a tap (no significant movement)
+        const pointer = e;
+        const moveThreshold = 10;
+        const timeSinceDown = e.timeStamp;
+
+        // If minimal movement and not pinching, treat as tap to close
+        if (!isPinching && Math.abs(pointer.clientX - e.clientX) < moveThreshold &&
+          Math.abs(pointer.clientY - e.clientY) < moveThreshold) {
+          // Click on image or overlay should close
+          close();
+        }
+
+        if (isPinching) {
+          pinchEndTimer = setTimeout(() => {
+            isPinching = false;
+          }, 300);
+        }
+      } else if (pointers.size === 1) {
+        // Going from pinch to single touch
+        isPinching = false;
+        isDragging = true;
+        const remaining = Array.from(pointers.values())[0];
+        gestureState.lastPanX = gestureState.panX;
+        gestureState.lastPanY = gestureState.panY;
+        remaining.startX = remaining.x;
+        remaining.startY = remaining.y;
+      }
+    }
+
+    function onPointerCancel(e) {
+      onPointerUp(e);
+    }
+
+    // Mouse wheel zoom and scroll handling
+    function onWheel(e) {
+      e.preventDefault();
+
+      // If it's a regular scroll (not pinch), dismiss the overlay
+      if (!e.ctrlKey && !e.metaKey) {
+        // Regular scroll - dismiss overlay gracefully
+        close();
+        return;
+      }
+
+      // Handle trackpad pinch (ctrl+wheel or cmd+wheel on Mac)
+      const delta = e.deltaY;
+      const scaleFactor = 0.01;
+      const zoomSpeed = Math.exp(-delta * scaleFactor);
+
+      // Minimum scale is 1 (original zoom level), don't allow zooming out smaller
+      gestureState.scale = Math.max(1, Math.min(5, gestureState.scale * zoomSpeed));
+
+      // Zoom towards mouse position
+      const rect = img.getBoundingClientRect();
+      const centerX = rect.left + rect.width / 2;
+      const centerY = rect.top + rect.height / 2;
+      const offsetX = e.clientX - centerX;
+      const offsetY = e.clientY - centerY;
+
+      // Adjust pan to zoom towards cursor
+      const scaleDiff = gestureState.scale - (gestureState.scale / zoomSpeed);
+      gestureState.panX -= offsetX * scaleDiff * 0.1;
+      gestureState.panY -= offsetY * scaleDiff * 0.1;
+
+      setInteracting(true);
+      applyTransform();
+      setTimeout(() => setInteracting(false), 150);
+    }
+
+    // Keyboard navigation
+    function onKeyDown(e) {
+      if (e.key === "Escape") {
+        close();
+      } else if (e.key === "+" || e.key === "=") {
+        gestureState.scale = Math.min(5, gestureState.scale * 1.2);
+        applyTransform();
+      } else if (e.key === "-") {
+        gestureState.scale = Math.max(1, gestureState.scale / 1.2);
+        applyTransform();
+      } else if (e.key === "0") {
+        gestureState.scale = 1;
+        gestureState.panX = 0;
+        gestureState.panY = 0;
+        applyTransform();
+      }
+    }
+
+    // Apply transforms
+    let final = computeFinal();
+    let baseScale = final.scale;
+
+    function computeFinal() {
+      const vv = window.visualViewport;
+      const vw = vv ? vv.width : window.innerWidth;
+      const vh = vv ? vv.height : window.innerHeight;
+      const vx = vv ? vv.offsetLeft : 0;
+      const vy = vv ? vv.offsetTop : 0;
+
+      const margin = 20;
+      const maxW = Math.min(vw - margin * 2, 1200);
+      const maxH = vh - margin * 2;
+
+      const scale = Math.min(maxW / rect.width, maxH / rect.height, 2);
+      const centerX = vx + vw / 2;
+      const centerY = vy + vh / 2;
+
+      return { cx: centerX, cy: centerY, scale };
+    }
+
+    function applyTransform() {
+      img.style.left = final.cx + "px";
+      img.style.top = final.cy + "px";
+      const totalScale = baseScale * gestureState.scale;
+      const transform = `translate3d(-50%, -50%, 0) translate3d(${gestureState.panX}px, ${gestureState.panY}px, 0) scale(${totalScale})`;
+      img.style.transform = transform;
+    }
+
+    // Close function
     function close(immediate = false) {
-      // trigger dedicated closing transitions for smoother zoom-out
       overlay.classList.add("closing");
-      window.removeEventListener("keydown", onKeyDown, true);
-      window.removeEventListener("scroll", onScroll, true);
-      overlay.removeEventListener("wheel", onWheel);
-      overlay.removeEventListener("pointerdown", onPointerDown);
-      overlay.removeEventListener("pointerup", onPointerUp);
-      overlay.removeEventListener("pointercancel", onPointerUp);
-      activeTouchPointers.clear();
-      if (pinchTimer) clearTimeout(pinchTimer);
+
+      // Animate back to original position
+      img.style.left = startCX + "px";
+      img.style.top = startCY + "px";
+      img.style.transform = `translate3d(-50%, -50%, 0) scale(1)`;
+
+      // Cleanup event listeners
+      cleanup();
 
       if (immediate) {
         overlay.remove();
         return;
       }
-      overlay.addEventListener("transitionend", () => overlay.remove(), { once: true });
+
+      // Remove after animation
+      const done = () => overlay.remove();
+      overlay.addEventListener("transitionend", done, { once: true });
+      img.addEventListener("transitionend", done, { once: true });
+
+      // Fallback removal
+      setTimeout(() => {
+        if (overlay.parentNode) {
+          overlay.remove();
+        }
+      }, 400);
     }
 
-    function onKeyDown(e) {
-      if (e.key === "Escape") close();
+    function cleanup() {
+      window.removeEventListener("keydown", onKeyDown, true);
+      overlay.removeEventListener("wheel", onWheel);
+      overlay.removeEventListener("pointermove", onPointerMove);
+      overlay.removeEventListener("pointerdown", onPointerDown);
+      overlay.removeEventListener("pointerup", onPointerUp);
+      overlay.removeEventListener("pointercancel", onPointerCancel);
+      window.removeEventListener("resize", onResize);
+      if (window.visualViewport) {
+        window.visualViewport.removeEventListener("resize", onResize);
+        window.visualViewport.removeEventListener("scroll", onResize);
+      }
+      if (pinchEndTimer) {
+        clearTimeout(pinchEndTimer);
+      }
     }
 
-    overlay.addEventListener("click", () => close(false), { once: true });
-    window.addEventListener("keydown", onKeyDown, true);
-
-    function onWheel(e) {
-      // Ignore trackpad pinch (wheel + ctrlKey) and active pinch
-      if ((e && e.ctrlKey) || pinching) return;
-      close(true);
-    }
-    function onScroll() {
-      if (pinching) return;
-      close(true);
+    // Handle viewport changes
+    function onResize() {
+      final = computeFinal();
+      baseScale = final.scale;
+      applyTransform();
     }
 
-    overlay.addEventListener("wheel", onWheel, { passive: true });
-    // Standard W3C pointer events for multi-touch pinch detection
+    // Prevent click propagation on image
+    img.addEventListener("click", function (e) {
+      e.stopPropagation();
+    });
+
+    // Setup event listeners
+    overlay.addEventListener("wheel", onWheel, { passive: false });
+    overlay.addEventListener("pointermove", onPointerMove);
     overlay.addEventListener("pointerdown", onPointerDown);
     overlay.addEventListener("pointerup", onPointerUp);
-    overlay.addEventListener("pointercancel", onPointerUp);
-    window.addEventListener("scroll", onScroll, true);
+    overlay.addEventListener("pointercancel", onPointerCancel);
+    window.addEventListener("keydown", onKeyDown, true);
+    window.addEventListener("resize", onResize, { passive: true });
 
+    if (window.visualViewport) {
+      window.visualViewport.addEventListener("resize", onResize, { passive: true });
+      window.visualViewport.addEventListener("scroll", onResize, { passive: true });
+    }
+
+    // Click outside to close (on overlay background)
+    overlay.addEventListener("click", function (e) {
+      if (e.target === overlay) {
+        close();
+      }
+    });
+
+    // Add to DOM
     document.body.appendChild(overlay);
 
-    // trigger fade-in
-    requestAnimationFrame(() => overlay.classList.add("show"));
+    // Trigger opening animation
+    requestAnimationFrame(() => {
+      overlay.classList.add("show");
+      applyTransform();
+    });
   }
 
-  // Initialize after DOM is parsed; defer script ensures this usually fires immediately
-  document.addEventListener('DOMContentLoaded', function () {
+  // Initialize after DOM ready
+  function init() {
     const container = document.querySelector(".content");
     if (!container) return;
 
-    container.addEventListener(
-      "click",
-      function (e) {
-        const target = e.target;
-        if (!(target instanceof HTMLImageElement)) return;
-        if (target.dataset.noZoom === "" || target.dataset.noZoom === "true") return;
+    container.addEventListener("click", function (e) {
+      const target = e.target;
+      if (!(target instanceof HTMLImageElement)) return;
+      if (target.dataset.noZoom === "" || target.dataset.noZoom === "true") return;
 
-        // avoid following parent links when zooming
-        e.preventDefault();
-        e.stopPropagation();
+      e.preventDefault();
+      e.stopPropagation();
 
-        const src = target.currentSrc || target.src;
-        if (!src) return;
-        createOverlay(src, target.alt || "");
-      },
-      true
-    );
-  }, { once: true });
+      createOverlayFromTarget(target);
+    }, true);
+  }
+
+  if (document.readyState === 'loading') {
+    document.addEventListener('DOMContentLoaded', init, { once: true });
+  } else {
+    init();
+  }
 })();