working on a hover state for the headers

frontend/app/block/block.less

@@ -10,6 +10,7 @@
     height: 100%;
     overflow: hidden;
     min-height: 0;
+    position: relative;
 
     .block-content {
         display: flex;
@@ -19,6 +20,23 @@
         min-height: 0;
         padding: 5px;
     }
+
+    .block-header-animation-wrap {
+        max-height: 0;
+        transition:
+            max-height 0.3s ease-out,
+            opacity 0.3s ease-out;
+        overflow: hidden;
+        position: absolute;
+        top: 0;
+        width: 100%;
+        height: 30px;
+        z-index: var(--zindex-header-hover);
+
+        &.is-showing {
+            max-height: 30px;
+        }
+    }
 }
 
 .block-header {
@@ -34,6 +52,11 @@
     -webkit-user-select: none;
     cursor: default;
 
+    .block-header-icon {
+        font-size: 20px;
+        padding: 0 5px;
+    }
+
     .block-header-text {
         padding: 0 5px;
         flex-grow: 1;

frontend/app/block/block.tsx

@@ -8,10 +8,14 @@ import { TerminalView } from "@/app/view/term";
 import { ErrorBoundary } from "@/element/errorboundary";
 import { CenteredDiv } from "@/element/quickelems";
 import * as WOS from "@/store/wos";
+import clsx from "clsx";
 import * as React from "react";
 
 import "./block.less";
 
+const HoverPixels = 15;
+const HoverTimeoutMs = 100;
+
 interface BlockProps {
     blockId: string;
     onClose?: () => void;
@@ -34,8 +38,45 @@ const BlockHeader = ({ blockId, onClose }: BlockProps) => {
     );
 };
 
+const hoverStateOff = "off";
+const hoverStatePending = "pending";
+const hoverStateOn = "on";
+
 const Block = ({ blockId, onClose }: BlockProps) => {
     const blockRef = React.useRef<HTMLDivElement>(null);
+    const hoverState = React.useRef(hoverStateOff);
+    const [showHeader, setShowHeader] = React.useState(false);
+
+    React.useEffect(() => {
+        const block = blockRef.current;
+        let hoverTimeout: NodeJS.Timeout = null;
+        const handleMouseMove = (event) => {
+            const rect = block.getBoundingClientRect();
+            if (event.clientY - rect.top <= HoverPixels) {
+                if (hoverState.current == hoverStateOff) {
+                    hoverTimeout = setTimeout(() => {
+                        if (hoverState.current == hoverStatePending) {
+                            hoverState.current = hoverStateOn;
+                            setShowHeader(true);
+                        }
+                    }, HoverTimeoutMs);
+                    hoverState.current = hoverStatePending;
+                }
+            } else {
+                if (hoverTimeout) {
+                    if (hoverState.current == hoverStatePending) {
+                        hoverState.current = hoverStateOff;
+                    }
+                    clearTimeout(hoverTimeout);
+                    hoverTimeout = null;
+                }
+            }
+        };
+        block.addEventListener("mousemove", handleMouseMove);
+        return () => {
+            block.removeEventListener("mousemove", handleMouseMove);
+        };
+    });
 
     let blockElem: JSX.Element = null;
     const [blockData, blockDataLoading] = WOS.useWaveObjectValue<Block>(WOS.makeORef("block", blockId));
@@ -52,8 +93,23 @@ const Block = ({ blockId, onClose }: BlockProps) => {
         blockElem = <CodeEdit text={null} filename={null} />;
     }
     return (
-        <div className="block" ref={blockRef}>
+        <div
-            <BlockHeader blockId={blockId} onClose={onClose} />
+            className="block"
+            ref={blockRef}
+            onMouseLeave={() => {
+                setShowHeader(false);
+                hoverState.current = hoverStateOff;
+            }}
+        >
+            <div
+                className={clsx("block-header-animation-wrap", showHeader ? "is-showing" : null)}
+                onMouseLeave={() => {
+                    setShowHeader(false);
+                    hoverState.current = hoverStateOff;
+                }}
+            >
+                <BlockHeader blockId={blockId} onClose={onClose} />
+            </div>
             <div key="content" className="block-content">
                 <ErrorBoundary>
                     <React.Suspense fallback={<CenteredDiv>Loading...</CenteredDiv>}>{blockElem}</React.Suspense>

frontend/app/theme.less

@@ -22,4 +22,7 @@
     --scrollbar-background-color: var(--main-bg-color);
     --scrollbar-thumb-color: rgba(255, 255, 255, 0.3);
     --scrollbar-thumb-hover-color: rgba(255, 255, 255, 0.5);
+
+    /* z-index values */
+    --zindex-header-hover: 100;
 }