Display relative change

ftl/core/deck-config.ftl

@@ -470,12 +470,10 @@ deck-config-compute-optimal-retention-tooltip4 =
     willing to invest more study time to achieve it. Setting your desired retention lower than the minimum
     is not recommended, as it will lead to a higher workload, because of the high forgetting rate.
 deck-config-please-save-your-changes-first = Please save your changes first.
-deck-config-a-100-day-interval = 
-    { $days ->
-        [one] A 100 day interval will become { $days } day.
-       *[other] A 100 day interval will become { $days } days.
-    }
-deck-config-90-percent-desired-retention-warning = The higher this value, the more frequently cards will be shown to you.
+deck-config-intervals-percentage-increase = Your intervals will increase by { $percent }%.
+deck-config-intervals-percentage-decrease = Your intervals will decrease by { $percent }%.
+deck-config-intervals-percentage-unchanged = Your intervals will remain unchanged
+
 deck-config-percent-of-reviews =  
     { $reviews ->
         [one] { $pct }% of { $reviews } review
@@ -513,6 +511,12 @@ deck-config-fsrs-simulator-radio-memorized = Memorized
 
 ## NO NEED TO TRANSLATE. This text is no longer used by Anki, and will be removed in the future.
 
+deck-config-a-100-day-interval = 
+    { $days ->
+        [one] A 100 day interval will become { $days } day.
+       *[other] A 100 day interval will become { $days } days.
+    }
+
 deck-config-fsrs-simulator-y-axis-title-time = Review Time/Day
 deck-config-fsrs-simulator-y-axis-title-count = Review Count/Day
 deck-config-fsrs-simulator-y-axis-title-memorized = Memorized Total

ts/routes/deck-options/FsrsOptions.svelte

@@ -42,7 +42,10 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
         $daysSinceLastOptimization > 30 ? tr.deckConfigTimeToOptimize() : "";
     let desiredRetentionFocused = false;
     let desiredRetentionEverFocused = false;
-    $: if (desiredRetentionFocused) desiredRetentionEverFocused = true
+    const startingDesiredRetention = $config.desiredRetention.toFixed(2);
+    $: if (desiredRetentionFocused) {
+        desiredRetentionEverFocused = true;
+    }
     $: showDesiredRetentionTooltip = newlyEnabled || desiredRetentionEverFocused;
 
     let computeParamsProgress: ComputeParamsProgress | undefined;
@@ -55,7 +58,7 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
     $: desiredRetentionWarning = getRetentionWarning(
         roundedRetention,
         fsrsParams($config),
-        showDesiredRetentionTooltip
+        showDesiredRetentionTooltip,
     );
     $: retentionWarningClass = getRetentionWarningClass(roundedRetention);
 
@@ -73,20 +76,38 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
         reviewOrder: $config.reviewOrder,
     });
 
-    function getRetentionWarning(retention: number, params: number[], showDesiredRetentionTooltip: boolean): string {
-        if (!showDesiredRetentionTooltip && getRetentionWarningClass(retention) === "alert-info") {
-            return "";
-        }
+    function getInterval(retention: number, params: number[]) {
         const decay = params.length > 20 ? -params[20] : -0.5; // default decay for FSRS-4.5 and FSRS-5
         const factor = 0.9 ** (1 / decay) - 1;
         const stability = 100;
         const days = Math.round(
             (stability / factor) * (Math.pow(retention, 1 / decay) - 1),
         );
-        if (days === 100) {
-            return tr.deckConfig90PercentDesiredRetentionWarning();
+        return days;
+    }
+
+    function getRetentionWarning(
+        retention: number,
+        params: number[],
+        showDesiredRetentionTooltip: boolean,
+    ): string {
+        if (
+            !showDesiredRetentionTooltip &&
+            getRetentionWarningClass(retention) === "alert-info"
+        ) {
+            return "";
+        }
+        if (+startingDesiredRetention == roundedRetention) {
+            return tr.deckConfigIntervalsPercentageUnchanged();
+        }
+        const before = getInterval(+startingDesiredRetention, params);
+        const after = getInterval(retention, params);
+        const percent = 100 * (after / before) - 100;
+        if (percent > 0) {
+            return tr.deckConfigIntervalsPercentageIncrease({ percent });
+        } else {
+            return tr.deckConfigIntervalsPercentageDecrease({ percent: -percent });
         }
-        return tr.deckConfigA100DayInterval({ days });
     }
 
     function getRetentionWarningClass(retention: number): string {

ts/routes/deck-options/FsrsOptionsOuter.svelte

@@ -26,7 +26,9 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
 
     const fsrs = state.fsrs;
     let newlyEnabled = false;
-    $: if (!$fsrs) newlyEnabled = true
+    $: if (!$fsrs) {
+        newlyEnabled = true;
+    }
 
     const settings = {
         fsrs: {