Disable buttons when zooming is not possible

frontend/src/App.tsx

@@ -16,7 +16,12 @@ import { SeekBar } from './SeekBar';
 import { firstValueFrom, from, Observable } from 'rxjs';
 import { first, map } from 'rxjs/operators';
 import millisFromDuration from './helpers/millisFromDuration';
-import { zoomViewportIn, zoomViewportOut } from './helpers/zoom';
+import {
+  canZoomViewportIn,
+  canZoomViewportOut,
+  zoomViewportIn,
+  zoomViewportOut,
+} from './helpers/zoom';
 import toHHMMSS from './helpers/toHHMMSS';
 import framesToDuration from './helpers/framesToDuration';
 import { ClockIcon, ExternalLinkIcon } from '@heroicons/react/solid';
@@ -448,6 +453,8 @@ function App(): JSX.Element {
             </div>
             <ControlBar
               playState={playState}
+              zoomInEnabled={canZoomViewportIn(viewport, selection, zoomFactor)}
+              zoomOutEnabled={canZoomViewportOut(viewport, mediaSet.audioFrames)}
               onTogglePlay={togglePlay}
               onClip={handleClip}
               onZoomIn={handleZoomIn}

frontend/src/ControlBar.tsx

@@ -12,6 +12,8 @@ import {
 
 interface Props {
   playState: PlayState;
+  zoomInEnabled: boolean;
+  zoomOutEnabled: boolean;
   onTogglePlay: () => void;
   onClip: () => void;
   onZoomIn: () => void;
@@ -21,11 +23,14 @@ interface Props {
 
 const ControlBar: React.FC<Props> = React.memo((props: Props) => {
   const buttonStyle =
-    'bg-gray-700 hover:bg-gray-600 text-white font-bold py-2 px-4 rounded';
+    'bg-gray-600 hover:bg-gray-500 text-white font-bold py-2 px-4 rounded';
+
+  const disabledButtonStyle =
+    'bg-gray-700 text-white font-bold py-2 px-4 rounded cursor-auto';
 
   const downloadButtonStyle = props.downloadClipEnabled
-    ? 'bg-green-700 hover:bg-green-600 text-white font-bold py-2 px-4 rounded absolute right-0'
+    ? 'bg-green-600 hover:bg-green-600 text-white font-bold py-2 px-4 rounded absolute right-0'
-    : 'bg-gray-700 hover:cursor-not-allowed text-gray-500 font-bold py-2 px-4 rounded absolute right-0';
+    : 'bg-gray-600 hover:cursor-not-allowed text-gray-500 font-bold py-2 px-4 rounded absolute right-0';
 
   const iconStyle = 'inline h-7 w-7 text-white-500';
 
@@ -67,13 +72,13 @@ const ControlBar: React.FC<Props> = React.memo((props: Props) => {
           <FastForwardIcon className={iconStyle} />
         </button>
         <button
-          className={buttonStyle}
+          className={props.zoomInEnabled ? buttonStyle : disabledButtonStyle}
           onClick={(evt) => filterMouseEvent(evt, props.onZoomIn)}
         >
           <ZoomInIcon className={iconStyle} />
         </button>
         <button
-          className={buttonStyle}
+          className={props.zoomOutEnabled ? buttonStyle : disabledButtonStyle}
           onClick={(evt) => filterMouseEvent(evt, props.onZoomOut)}
         >
           <ZoomOutIcon className={iconStyle} />

frontend/src/helpers/zoom.test.ts

@@ -1,4 +1,9 @@
-import { zoomViewportIn, zoomViewportOut } from './zoom';
+import {
+  zoomViewportIn,
+  zoomViewportOut,
+  canZoomViewportIn,
+  canZoomViewportOut,
+} from './zoom';
 
 // zf is the zoom factor.
 const zf = 2;
@@ -220,3 +225,49 @@ describe('zoomViewportOut', () => {
     });
   });
 });
+
+describe('canZoomViewportIn', () => {
+  it('does now allow zooming when the viewport is inactive', () => {
+    const result = canZoomViewportIn(
+      { start: 0, end: 0 },
+      { start: 0, end: 0 },
+      zf
+    );
+    expect(result).toBeFalsy();
+  });
+
+  it('does not allow zooming past the selection', () => {
+    const result = canZoomViewportIn(
+      { start: 1000, end: 2000 },
+      { start: 1100, end: 1900 },
+      zf
+    );
+    expect(result).toBeFalsy();
+  });
+
+  it('allows zooming', () => {
+    const result = canZoomViewportIn(
+      { start: 1000, end: 2000 },
+      { start: 0, end: 100 },
+      zf
+    );
+    expect(result).toBeTruthy();
+  });
+});
+
+describe('canZoomViewportOut', () => {
+  it('does now allow zooming when the viewport is inactive', () => {
+    const result = canZoomViewportOut({ start: 0, end: 0 }, 1000);
+    expect(result).toBeFalsy();
+  });
+
+  it('does now allow zooming when already at maximum zoom', () => {
+    const result = canZoomViewportOut({ start: 0, end: 1000 }, 1000);
+    expect(result).toBeFalsy();
+  });
+
+  it('allows zooming', () => {
+    const result = canZoomViewportOut({ start: 1000, end: 2000 }, 5000);
+    expect(result).toBeTruthy();
+  });
+});

frontend/src/helpers/zoom.ts

@@ -7,7 +7,7 @@ export function zoomViewportIn(
   position: number,
   factor: number
 ): Frames {
-  if (viewport.start == viewport.end) {
+  if (!canZoomViewportIn(viewport, selection, factor)) {
     return viewport;
   }
 
@@ -27,7 +27,7 @@ export function zoomViewportOut(
   position: number,
   factor: number
 ): Frames {
-  if (viewport.start == viewport.end) {
+  if (!canZoomViewportOut(viewport, numFrames)) {
     return viewport;
   }
 
@@ -74,3 +74,31 @@ function zoom(
 
   return { start: newStart, end: newEnd };
 }
+
+export function canZoomViewportIn(
+  viewport: Frames,
+  selection: Frames,
+  factor: number
+): boolean {
+  if (viewport.start == viewport.end) {
+    return false;
+  }
+
+  if (selection.start != selection.end) {
+    const newWidth = Math.round((viewport.end - viewport.start) / factor);
+    return newWidth > selection.end - selection.start;
+  }
+
+  return true;
+}
+
+export function canZoomViewportOut(
+  viewport: Frames,
+  numFrames: number
+): boolean {
+  if (viewport.start == viewport.end) {
+    return false;
+  }
+
+  return viewport.start > 0 || viewport.end < numFrames;
+}