Apply gradient effect to forgetting curve (#3604)

* Add gradient color for forgetting curve

* Add desiredRetention prop for CardInfo

* update CONTRIBUTORS

* Formatting

* Tweak range of gradient

* Tweak: salmon -> tomato

* Get desired retention of the card from backend

* Add a reference line for desired retention

* Fix: Corrected the steel blue's height & Hide desired retention line when yMin is higher than desiredRetentionY

* Add y axis title

* Show desired retention in the tooltip

* I18n: improve translation and vertical text display

* Revert rotatation&writing-mode of vertical title

* Tweak font-size of y axis title

* Fix: delete old desired retention line when changing duration

* Update ftl/core/card-stats.ftl

---------

Co-authored-by: Damien Elmes <dae@users.noreply.github.com>

CONTRIBUTORS

@@ -197,6 +197,7 @@ twwn <github.com/twwn>
 Cy Pokhrel <cy@cy7.sh>
 Park Hyunwoo <phu54321@naver.com>
 Tomas Fabrizio Orsi <torsi@fi.uba.ar>
+Dongjin Ouyang <1113117424@qq.com>
 Sawan Sunar <sawansunar24072002@gmail.com>
 hideo aoyama <https://github.com/boukendesho>
 Ross Brown <rbrownwsws@googlemail.com>

ftl/core/card-stats.ftl

@@ -35,6 +35,8 @@ card-stats-fsrs-forgetting-curve-first-week = First Week
 card-stats-fsrs-forgetting-curve-first-month = First Month
 card-stats-fsrs-forgetting-curve-first-year = First Year
 card-stats-fsrs-forgetting-curve-all-time = All Time
+card-stats-fsrs-forgetting-curve-probability-of-recalling = Probability of Recall
+card-stats-fsrs-forgetting-curve-desired-retention = Desired Retention
 
 ## Window Titles
 

proto/anki/stats.proto

@@ -64,6 +64,7 @@ message CardStatsResponse {
   string custom_data = 20;
   string preset = 21;
   optional string original_deck = 22;
+  optional float desired_retention = 23;
 }
 
 message GraphsRequest {

rslib/src/stats/card.rs

@@ -80,6 +80,7 @@ impl Collection {
             } else {
                 None
             },
+            desired_retention: card.desired_retention,
         })
     }
 

ts/routes/card-info/CardInfo.svelte

@@ -16,6 +16,7 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
     export let stats: CardStatsResponse | null = null;
     export let showRevlog: boolean = true;
     export let fsrsEnabled: boolean = stats?.memoryState != null;
+    export let desiredRetention: number = stats?.desiredRetention ?? 0.9;
 </script>
 
 <Container breakpoint="md" --gutter-inline="1rem" --gutter-block="0.5rem">
@@ -31,7 +32,7 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
         {/if}
         {#if fsrsEnabled}
             <Row>
-                <ForgettingCurve revlog={stats.revlog} />
+                <ForgettingCurve revlog={stats.revlog} {desiredRetention} />
             </Row>
         {/if}
     {:else}

ts/routes/card-info/ForgettingCurve.svelte

@@ -20,6 +20,7 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
     import HoverColumns from "../graphs/HoverColumns.svelte";
 
     export let revlog: RevlogEntry[];
+    export let desiredRetention: number;
     let svg = null as HTMLElement | SVGElement | null;
     const bounds = defaultGraphBounds();
     const title = tr.cardStatsFsrsForgettingCurveTitle();
@@ -35,7 +36,13 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
     }
     const timeRange = writable(defaultTimeRange);
 
-    $: renderForgettingCurve(filteredRevlog, $timeRange, svg as SVGElement, bounds);
+    $: renderForgettingCurve(
+        filteredRevlog,
+        $timeRange,
+        svg as SVGElement,
+        bounds,
+        desiredRetention,
+    );
 </script>
 
 <div class="forgetting-curve">

ts/routes/card-info/forgetting-curve.ts

@@ -161,6 +161,7 @@ export function renderForgettingCurve(
     timeRange: TimeRange,
     svgElem: SVGElement,
     bounds: GraphBounds,
+    desiredRetention: number,
 ) {
     const svg = select(svgElem);
     const trans = svg.transition().duration(600) as any;
@@ -204,18 +205,63 @@ export function renderForgettingCurve(
         .call((selection) => selection.transition(trans).call(axisLeft(y).tickSizeOuter(0)))
         .attr("direction", "ltr");
 
+    svg.select(".y-ticks .y-axis-title").remove();
+    svg.select(".y-ticks")
+        .append("text")
+        .attr("class", "y-axis-title")
+        .attr("transform", "rotate(-90)")
+        .attr("y", 0 - bounds.marginLeft)
+        .attr("x", 0 - (bounds.height / 2))
+        .attr("font-size", "1rem")
+        .attr("dy", "1.1em")
+        .attr("fill", "currentColor")
+        .style("text-anchor", "middle")
+        .text(`${tr.cardStatsFsrsForgettingCurveProbabilityOfRecalling()}(%)`);
+
     const lineGenerator = line<DataPoint>()
         .x((d) => x(d.date))
         .y((d) => y(d.retrievability));
 
+    // gradient color
+    const desiredRetentionY = desiredRetention * 100;
+    svg.append("linearGradient")
+        .attr("id", "line-gradient")
+        .attr("gradientUnits", "userSpaceOnUse")
+        .attr("x1", 0)
+        .attr("y1", y(0))
+        .attr("x2", 0)
+        .attr("y2", y(100))
+        .selectAll("stop")
+        .data([
+            { offset: "0%", color: "tomato" },
+            { offset: `${desiredRetentionY}%`, color: "steelblue" },
+            { offset: "100%", color: "green" },
+        ])
+        .enter().append("stop")
+        .attr("offset", d => d.offset)
+        .attr("stop-color", d => d.color);
+
     svg.append("path")
         .datum(data)
         .attr("class", "forgetting-curve-line")
         .attr("fill", "none")
-        .attr("stroke", "steelblue")
+        .attr("stroke", "url(#line-gradient)")
         .attr("stroke-width", 1.5)
         .attr("d", lineGenerator);
 
+    svg.select(".desired-retention-line").remove();
+    if (desiredRetentionY > yMin) {
+        svg.append("line")
+            .attr("class", "desired-retention-line")
+            .attr("x1", bounds.marginLeft)
+            .attr("x2", bounds.width - bounds.marginRight)
+            .attr("y1", y(desiredRetentionY))
+            .attr("y2", y(desiredRetentionY))
+            .attr("stroke", "steelblue")
+            .attr("stroke-dasharray", "4 4")
+            .attr("stroke-width", 1.2);
+    }
+
     const focusLine = svg.append("line")
         .attr("class", "focus-line")
         .attr("y1", bounds.marginTop)
@@ -248,11 +294,18 @@ export function renderForgettingCurve(
         .attr("fill", "transparent")
         .on("mousemove", (event: MouseEvent, d: DataPoint) => {
             const [x1, y1] = pointer(event, document.body);
+            const [_, y2] = pointer(event, svg.node());
+
+            const lineY = y(desiredRetentionY);
             focusLine.attr("x1", x(d.date) - 1).attr("x2", x(d.date) + 1).style(
                 "opacity",
                 1,
             );
-            showTooltip(tooltipText(d), x1, y1);
+            let text = tooltipText(d);
+            if (y2 >= lineY - 10 && y2 <= lineY + 10) {
+                text += `<br>${tr.cardStatsFsrsForgettingCurveDesiredRetention()}: ${desiredRetention.toFixed(2)}`;
+            }
+            showTooltip(text, x1, y1);
         })
         .on("mouseout", () => {
             focusLine.style("opacity", 0);