Add option to trigger "selection changed" callback in realtime

frontend/src/App.tsx

@@ -214,10 +214,18 @@ function App(): JSX.Element {
   };
 
   // handler called when the selection in the main waveform view is changed.
-  const handleWaveformSelectionChange = (newSelection: Frames) => {
+  const handleWaveformSelectionChange = (
+    newSelection: Frames,
+    final: boolean
+  ) => {
+    if (mediaSet == null) {
+      return;
+    }
+
     setSelection(newSelection);
 
-    if (mediaSet == null) {
+    // only update playback position when the selection is final.
+    if (!final) {
       return;
     }
 

frontend/src/HudCanvas.tsx

@@ -14,7 +14,7 @@ interface Props {
   styles: Styles;
   position: number | null;
   selection: Selection;
-  onSelectionChange: (selection: Selection) => void;
+  onSelectionChange: (selection: Selection, final: boolean) => void;
 }
 
 enum Mode {
@@ -79,6 +79,10 @@ export const HudCanvas: React.FC<Props> = ({
     };
   }, [mode, newSelection]);
 
+  useEffect(() => {
+    onSelectionChange({ ...newSelection }, mode == Mode.Normal);
+  }, [mode, newSelection]);
+
   // draw the overview HUD
   useEffect(() => {
     requestAnimationFrame(() => {
@@ -279,8 +283,6 @@ export const HudCanvas: React.FC<Props> = ({
       handleEmptySelectionAction();
       return;
     }
-
-    onSelectionChange({ ...newSelection });
   };
 
   const handleEmptySelectionAction = () => {
@@ -289,7 +291,8 @@ export const HudCanvas: React.FC<Props> = ({
         setNewSelection({ ...selection });
         break;
       case EmptySelectionAction.SelectNothing:
-        onSelectionChange({ start: 0, end: 0 });
+        setMode(Mode.Normal);
+        setNewSelection({ start: 0, end: 0 });
         break;
     }
   };

frontend/src/Overview.tsx

@@ -56,7 +56,10 @@ export const Overview: React.FC<Props> = ({
   // handlers
 
   // convert selection change from canvas pixels to frames, and trigger callback.
-  const handleSelectionChange = ({ start, end }: Selection) => {
+  const handleSelectionChange = ({ start, end }: Selection, final: boolean) => {
+    if (!final) {
+      return;
+    }
     onSelectionChange({
       start: Math.round((start / CanvasLogicalWidth) * mediaSet.audioFrames),
       end: Math.round((end / CanvasLogicalWidth) * mediaSet.audioFrames),

frontend/src/Waveform.tsx

@@ -10,7 +10,7 @@ interface Props {
   mediaSet: MediaSet;
   position: VideoPosition;
   viewport: Frames;
-  onSelectionChange: (selection: Selection) => void;
+  onSelectionChange: (selection: Selection, final: boolean) => void;
 }
 
 export const CanvasLogicalWidth = 2000;
@@ -91,17 +91,19 @@ export const Waveform: React.FC<Props> = ({
 
   // handlers
 
-  const handleSelectionChange = (selection: Selection) => {
+  const handleSelectionChange = (selection: Selection, final: boolean) => {
-    setSelectedPixels(selection);
-
     const framesPerPixel = (viewport.end - viewport.start) / CanvasLogicalWidth;
     const selectedFrames = {
       start: Math.round(viewport.start + selection.start * framesPerPixel),
       end: Math.round(viewport.start + selection.end * framesPerPixel),
     };
 
+    if (final) {
+      setSelectedPixels(selection);
       setSelectedFrames(selectedFrames);
-    onSelectionChange(selectedFrames);
+    }
+
+    onSelectionChange(selectedFrames, final);
   };
 
   // helpers