ui/src/frontend/notes_panel.ts - third_party/perfetto - Git at Google

 // Copyright (C) 2019 The Android Open Source Project
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use size file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //      http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.

 import m from 'mithril';
 import {currentTargetOffset} from '../base/dom_utils';
 import {Icons} from '../base/semantic_icons';
 import {randomColor} from '../public/lib/colorizer';
 import {SpanNote, Note} from '../public/note';
 import {raf} from '../core/raf_scheduler';
 import {Button, ButtonBar} from '../widgets/button';
 import {TRACK_SHELL_WIDTH} from './css_constants';
 import {getMaxMajorTicks, generateTicks, TickType} from './gridline_helper';
 import {Size2D} from '../base/geom';
 import {Panel} from './panel_container';
 import {Timestamp} from './widgets/timestamp';
 import {assertUnreachable} from '../base/logging';
 import {DetailsPanel} from '../public/details_panel';
 import {TimeScale} from '../base/time_scale';
 import {canvasClip} from '../base/canvas_utils';
 import {Selection} from '../public/selection';
 import {TraceImpl} from '../core/trace_impl';

 const FLAG_WIDTH = 16;
 const AREA_TRIANGLE_WIDTH = 10;
 const FLAG = `\uE153`;

 function toSummary(s: string) {
   const newlineIndex = s.indexOf('\n') > 0 ? s.indexOf('\n') : s.length;
   return s.slice(0, Math.min(newlineIndex, s.length, 16));
 }

 function getStartTimestamp(note: Note | SpanNote) {
   const noteType = note.noteType;
   switch (noteType) {
     case 'SPAN':
       return note.start;
     case 'DEFAULT':
       return note.timestamp;
     default:
       assertUnreachable(noteType);
   }
 }

 export class NotesPanel implements Panel {
   readonly kind = 'panel';
   readonly selectable = false;
   private readonly trace: TraceImpl;
   private timescale?: TimeScale; // The timescale from the last render()
   private hoveredX: null | number = null;
   private mouseDragging = false;

   constructor(trace: TraceImpl) {
     this.trace = trace;
   }

   render(): m.Children {
     const allCollapsed = this.trace.workspace.flatTracks.every(
       (n) => n.collapsed,
     );

     return m(
       '.notes-panel',
       {
         onmousedown: () => {
           // If the user clicks & drags, very likely they just want to measure
           // the time horizontally, not set a flag. This debouncing is done to
           // avoid setting accidental flags like measuring the time on the brush
           // timeline.
           this.mouseDragging = false;
         },
         onclick: (e: MouseEvent) => {
           if (!this.mouseDragging) {
             const x = currentTargetOffset(e).x - TRACK_SHELL_WIDTH;
             this.onClick(x);
             e.stopPropagation();
           }
         },
         onmousemove: (e: MouseEvent) => {
           this.mouseDragging = true;
           this.hoveredX = currentTargetOffset(e).x - TRACK_SHELL_WIDTH;
           raf.scheduleCanvasRedraw();
         },
         onmouseenter: (e: MouseEvent) => {
           this.hoveredX = currentTargetOffset(e).x - TRACK_SHELL_WIDTH;
           raf.scheduleCanvasRedraw();
         },
         onmouseout: () => {
           this.hoveredX = null;
           this.trace.timeline.hoveredNoteTimestamp = undefined;
         },
       },
       m(
         ButtonBar,
         {className: 'pf-toolbar'},
         m(Button, {
           onclick: (e: Event) => {
             e.preventDefault();
             if (allCollapsed) {
               this.trace.commands.runCommand(
                 'perfetto.CoreCommands#ExpandAllGroups',
               );
             } else {
               this.trace.commands.runCommand(
                 'perfetto.CoreCommands#CollapseAllGroups',
               );
             }
           },
           title: allCollapsed ? 'Expand all' : 'Collapse all',
           icon: allCollapsed ? 'unfold_more' : 'unfold_less',
           compact: true,
         }),
         m(Button, {
           onclick: (e: Event) => {
             e.preventDefault();
             this.trace.workspace.pinnedTracks.forEach((t) =>
               this.trace.workspace.unpinTrack(t),
             );
             raf.scheduleFullRedraw();
           },
           title: 'Clear all pinned tracks',
           icon: 'clear_all',
           compact: true,
         }),
         // TODO(stevegolton): Re-introduce this when we fix track filtering
         // m(TextInput, {
         //   placeholder: 'Filter tracks...',
         //   title:
         //     'Track filter - enter one or more comma-separated search terms',
         //   value: this.trace.state.trackFilterTerm,
         //   oninput: (e: Event) => {
         //     const filterTerm = (e.target as HTMLInputElement).value;
         //     this.trace.dispatch(Actions.setTrackFilterTerm({filterTerm}));
         //   },
         // }),
         // m(Button, {
         //   type: 'reset',
         //   icon: 'backspace',
         //   onclick: () => {
         //     this.trace.dispatch(
         //       Actions.setTrackFilterTerm({filterTerm: undefined}),
         //     );
         //   },
         //   title: 'Clear track filter',
         // }),
       ),
     );
   }

   renderCanvas(ctx: CanvasRenderingContext2D, size: Size2D) {
     ctx.fillStyle = '#999';
     ctx.fillRect(TRACK_SHELL_WIDTH - 2, 0, 2, size.height);

     const trackSize = {...size, width: size.width - TRACK_SHELL_WIDTH};

     ctx.save();
     ctx.translate(TRACK_SHELL_WIDTH, 0);
     canvasClip(ctx, 0, 0, trackSize.width, trackSize.height);
     this.renderPanel(ctx, trackSize);
     ctx.restore();
   }

   private renderPanel(ctx: CanvasRenderingContext2D, size: Size2D): void {
     let aNoteIsHovered = false;

     const visibleWindow = this.trace.timeline.visibleWindow;
     const timescale = new TimeScale(visibleWindow, {
       left: 0,
       right: size.width,
     });
     const timespan = visibleWindow.toTimeSpan();

     this.timescale = timescale;

     if (size.width > 0 && timespan.duration > 0n) {
       const maxMajorTicks = getMaxMajorTicks(size.width);
       const offset = this.trace.timeline.timestampOffset();
       const tickGen = generateTicks(timespan, maxMajorTicks, offset);
       for (const {type, time} of tickGen) {
         const px = Math.floor(timescale.timeToPx(time));
         if (type === TickType.MAJOR) {
           ctx.fillRect(px, 0, 1, size.height);
         }
       }
     }

     ctx.textBaseline = 'bottom';
     ctx.font = '10px Helvetica';

     for (const note of this.trace.notes.notes.values()) {
       const timestamp = getStartTimestamp(note);
       // TODO(hjd): We should still render area selection marks in viewport is
       // *within* the area (e.g. both lhs and rhs are out of bounds).
       if (
         (note.noteType === 'DEFAULT' &&
           !visibleWindow.contains(note.timestamp)) ||
         (note.noteType === 'SPAN' &&
           !visibleWindow.overlaps(note.start, note.end))
       ) {
         continue;
       }
       const currentIsHovered =
         this.hoveredX !== null && this.hitTestNote(this.hoveredX, note);
       if (currentIsHovered) aNoteIsHovered = true;

       const selection = this.trace.selection.selection;
       const isSelected = selection.kind === 'note' && selection.id === note.id;
       const x = timescale.timeToPx(timestamp);
       const left = Math.floor(x);

       // Draw flag or marker.
       if (note.noteType === 'SPAN') {
         this.drawAreaMarker(
           ctx,
           left,
           Math.floor(timescale.timeToPx(note.end)),
           note.color,
           isSelected,
         );
       } else {
         this.drawFlag(ctx, left, size.height, note.color, isSelected);
       }

       if (note.text) {
         const summary = toSummary(note.text);
         const measured = ctx.measureText(summary);
         // Add a white semi-transparent background for the text.
         ctx.fillStyle = 'rgba(255, 255, 255, 0.8)';
         ctx.fillRect(
           left + FLAG_WIDTH + 2,
           size.height + 2,
           measured.width + 2,
           -12,
         );
         ctx.fillStyle = '#3c4b5d';
         ctx.fillText(summary, left + FLAG_WIDTH + 3, size.height + 1);
       }
     }

     // A real note is hovered so we don't need to see the preview line.
     // TODO(hjd): Change cursor to pointer here.
     if (aNoteIsHovered) {
       this.trace.timeline.hoveredNoteTimestamp = undefined;
     }

     // View preview note flag when hovering on notes panel.
     if (!aNoteIsHovered && this.hoveredX !== null) {
       const timestamp = timescale.pxToHpTime(this.hoveredX).toTime();
       if (visibleWindow.contains(timestamp)) {
         this.trace.timeline.hoveredNoteTimestamp = timestamp;
         const x = timescale.timeToPx(timestamp);
         const left = Math.floor(x);
         this.drawFlag(ctx, left, size.height, '#aaa', /* fill */ true);
       }
     }

     ctx.restore();
   }

   private drawAreaMarker(
     ctx: CanvasRenderingContext2D,
     x: number,
     xEnd: number,
     color: string,
     fill: boolean,
   ) {
     ctx.fillStyle = color;
     ctx.strokeStyle = color;
     const topOffset = 10;
     // Don't draw in the track shell section.
     if (x >= 0) {
       // Draw left triangle.
       ctx.beginPath();
       ctx.moveTo(x, topOffset);
       ctx.lineTo(x, topOffset + AREA_TRIANGLE_WIDTH);
       ctx.lineTo(x + AREA_TRIANGLE_WIDTH, topOffset);
       ctx.lineTo(x, topOffset);
       if (fill) ctx.fill();
       ctx.stroke();
     }
     // Draw right triangle.
     ctx.beginPath();
     ctx.moveTo(xEnd, topOffset);
     ctx.lineTo(xEnd, topOffset + AREA_TRIANGLE_WIDTH);
     ctx.lineTo(xEnd - AREA_TRIANGLE_WIDTH, topOffset);
     ctx.lineTo(xEnd, topOffset);
     if (fill) ctx.fill();
     ctx.stroke();

     // Start line after track shell section, join triangles.
     const startDraw = Math.max(x, 0);
     ctx.beginPath();
     ctx.moveTo(startDraw, topOffset);
     ctx.lineTo(xEnd, topOffset);
     ctx.stroke();
   }

   private drawFlag(
     ctx: CanvasRenderingContext2D,
     x: number,
     height: number,
     color: string,
     fill?: boolean,
   ) {
     const prevFont = ctx.font;
     const prevBaseline = ctx.textBaseline;
     ctx.textBaseline = 'alphabetic';
     // Adjust height for icon font.
     ctx.font = '24px Material Symbols Sharp';
     ctx.fillStyle = color;
     ctx.strokeStyle = color;
     // The ligatures have padding included that means the icon is not drawn
     // exactly at the x value. This adjusts for that.
     const iconPadding = 6;
     if (fill) {
       ctx.fillText(FLAG, x - iconPadding, height + 2);
     } else {
       ctx.strokeText(FLAG, x - iconPadding, height + 2.5);
     }
     ctx.font = prevFont;
     ctx.textBaseline = prevBaseline;
   }

   private onClick(x: number) {
     if (!this.timescale) {
       return;
     }

     // Select the hovered note, or create a new single note & select it
     if (x < 0) return;
     for (const note of this.trace.notes.notes.values()) {
       if (this.hoveredX !== null && this.hitTestNote(this.hoveredX, note)) {
         this.trace.selection.selectNote({id: note.id});
         return;
       }
     }
     const timestamp = this.timescale.pxToHpTime(x).toTime();
     const color = randomColor();
     const noteId = this.trace.notes.addNote({timestamp, color});
     this.trace.selection.selectNote({id: noteId});
   }

   private hitTestNote(x: number, note: SpanNote | Note): boolean {
     if (!this.timescale) {
       return false;
     }

     const timescale = this.timescale;
     const noteX = timescale.timeToPx(getStartTimestamp(note));
     if (note.noteType === 'SPAN') {
       return (
         (noteX <= x && x < noteX + AREA_TRIANGLE_WIDTH) ||
         (timescale.timeToPx(note.end) > x &&
           x > timescale.timeToPx(note.end) - AREA_TRIANGLE_WIDTH)
       );
     } else {
       const width = FLAG_WIDTH;
       return noteX <= x && x < noteX + width;
     }
   }
 }

 export class NotesEditorTab implements DetailsPanel {
   constructor(private trace: TraceImpl) {}

   render(selection: Selection) {
     if (selection.kind !== 'note') {
       return undefined;
     }

     const id = selection.id;

     const note = this.trace.notes.getNote(id);
     if (note === undefined) {
       return m('.', `No Note with id ${id}`);
     }
     const startTime = getStartTimestamp(note);
     return m(
       '.notes-editor-panel',
       {
         key: id, // Every note shoul get its own brand new DOM.
       },
       m(
         '.notes-editor-panel-heading-bar',
         m(
           '.notes-editor-panel-heading',
           `Annotation at `,
           m(Timestamp, {ts: startTime}),
         ),
         m('input[type=text]', {
           oncreate: (v: m.VnodeDOM) => {
             // NOTE: due to bad design decisions elsewhere this component is
             // rendered every time the mouse moves on the canvas. We cannot set
             // `value: note.text` as an input as that will clobber the input
             // value as we move the mouse.
             const inputElement = v.dom as HTMLInputElement;
             inputElement.value = note.text;
             inputElement.focus();
           },
           onchange: (e: InputEvent) => {
             const newText = (e.target as HTMLInputElement).value;
             this.trace.notes.changeNote(id, {text: newText});
           },
         }),
         m(
           'span.color-change',
           `Change color: `,
           m('input[type=color]', {
             value: note.color,
             onchange: (e: Event) => {
               const newColor = (e.target as HTMLInputElement).value;
               this.trace.notes.changeNote(id, {color: newColor});
             },
           }),
         ),
         m(Button, {
           label: 'Remove',
           icon: Icons.Delete,
           onclick: () => this.trace.notes.removeNote(id),
         }),
       ),
     );
   }
 }
	// Copyright (C) 2019 The Android Open Source Project
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use size file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.

	import m from 'mithril';
	import {currentTargetOffset} from '../base/dom_utils';
	import {Icons} from '../base/semantic_icons';
	import {randomColor} from '../public/lib/colorizer';
	import {SpanNote, Note} from '../public/note';
	import {raf} from '../core/raf_scheduler';
	import {Button, ButtonBar} from '../widgets/button';
	import {TRACK_SHELL_WIDTH} from './css_constants';
	import {getMaxMajorTicks, generateTicks, TickType} from './gridline_helper';
	import {Size2D} from '../base/geom';
	import {Panel} from './panel_container';
	import {Timestamp} from './widgets/timestamp';
	import {assertUnreachable} from '../base/logging';
	import {DetailsPanel} from '../public/details_panel';
	import {TimeScale} from '../base/time_scale';
	import {canvasClip} from '../base/canvas_utils';
	import {Selection} from '../public/selection';
	import {TraceImpl} from '../core/trace_impl';

	const FLAG_WIDTH = 16;
	const AREA_TRIANGLE_WIDTH = 10;
	const FLAG = `\uE153`;

	function toSummary(s: string) {
	const newlineIndex = s.indexOf('\n') > 0 ? s.indexOf('\n') : s.length;
	return s.slice(0, Math.min(newlineIndex, s.length, 16));
	}

	function getStartTimestamp(note: Note \| SpanNote) {
	const noteType = note.noteType;
	switch (noteType) {
	case 'SPAN':
	return note.start;
	case 'DEFAULT':
	return note.timestamp;
	default:
	assertUnreachable(noteType);
	}
	}

	export class NotesPanel implements Panel {
	readonly kind = 'panel';
	readonly selectable = false;
	private readonly trace: TraceImpl;
	private timescale?: TimeScale; // The timescale from the last render()
	private hoveredX: null \| number = null;
	private mouseDragging = false;

	constructor(trace: TraceImpl) {
	this.trace = trace;
	}

	render(): m.Children {
	const allCollapsed = this.trace.workspace.flatTracks.every(
	(n) => n.collapsed,
	);

	return m(
	'.notes-panel',
	{
	onmousedown: () => {
	// If the user clicks & drags, very likely they just want to measure
	// the time horizontally, not set a flag. This debouncing is done to
	// avoid setting accidental flags like measuring the time on the brush
	// timeline.
	this.mouseDragging = false;
	},
	onclick: (e: MouseEvent) => {
	if (!this.mouseDragging) {
	const x = currentTargetOffset(e).x - TRACK_SHELL_WIDTH;
	this.onClick(x);
	e.stopPropagation();
	}
	},
	onmousemove: (e: MouseEvent) => {
	this.mouseDragging = true;
	this.hoveredX = currentTargetOffset(e).x - TRACK_SHELL_WIDTH;
	raf.scheduleCanvasRedraw();
	},
	onmouseenter: (e: MouseEvent) => {
	this.hoveredX = currentTargetOffset(e).x - TRACK_SHELL_WIDTH;
	raf.scheduleCanvasRedraw();
	},
	onmouseout: () => {
	this.hoveredX = null;
	this.trace.timeline.hoveredNoteTimestamp = undefined;
	},
	},
	m(
	ButtonBar,
	{className: 'pf-toolbar'},
	m(Button, {
	onclick: (e: Event) => {
	e.preventDefault();
	if (allCollapsed) {
	this.trace.commands.runCommand(
	'perfetto.CoreCommands#ExpandAllGroups',
	);
	} else {
	this.trace.commands.runCommand(
	'perfetto.CoreCommands#CollapseAllGroups',
	);
	}
	},
	title: allCollapsed ? 'Expand all' : 'Collapse all',
	icon: allCollapsed ? 'unfold_more' : 'unfold_less',
	compact: true,
	}),
	m(Button, {
	onclick: (e: Event) => {
	e.preventDefault();
	this.trace.workspace.pinnedTracks.forEach((t) =>
	this.trace.workspace.unpinTrack(t),
	);
	raf.scheduleFullRedraw();
	},
	title: 'Clear all pinned tracks',
	icon: 'clear_all',
	compact: true,
	}),
	// TODO(stevegolton): Re-introduce this when we fix track filtering
	// m(TextInput, {
	// placeholder: 'Filter tracks...',
	// title:
	// 'Track filter - enter one or more comma-separated search terms',
	// value: this.trace.state.trackFilterTerm,
	// oninput: (e: Event) => {
	// const filterTerm = (e.target as HTMLInputElement).value;
	// this.trace.dispatch(Actions.setTrackFilterTerm({filterTerm}));
	// },
	// }),
	// m(Button, {
	// type: 'reset',
	// icon: 'backspace',
	// onclick: () => {
	// this.trace.dispatch(
	// Actions.setTrackFilterTerm({filterTerm: undefined}),
	// );
	// },
	// title: 'Clear track filter',
	// }),
	),
	);
	}

	renderCanvas(ctx: CanvasRenderingContext2D, size: Size2D) {
	ctx.fillStyle = '#999';
	ctx.fillRect(TRACK_SHELL_WIDTH - 2, 0, 2, size.height);

	const trackSize = {...size, width: size.width - TRACK_SHELL_WIDTH};

	ctx.save();
	ctx.translate(TRACK_SHELL_WIDTH, 0);
	canvasClip(ctx, 0, 0, trackSize.width, trackSize.height);
	this.renderPanel(ctx, trackSize);
	ctx.restore();
	}

	private renderPanel(ctx: CanvasRenderingContext2D, size: Size2D): void {
	let aNoteIsHovered = false;

	const visibleWindow = this.trace.timeline.visibleWindow;
	const timescale = new TimeScale(visibleWindow, {
	left: 0,
	right: size.width,
	});
	const timespan = visibleWindow.toTimeSpan();

	this.timescale = timescale;

	if (size.width > 0 && timespan.duration > 0n) {
	const maxMajorTicks = getMaxMajorTicks(size.width);
	const offset = this.trace.timeline.timestampOffset();
	const tickGen = generateTicks(timespan, maxMajorTicks, offset);
	for (const {type, time} of tickGen) {
	const px = Math.floor(timescale.timeToPx(time));
	if (type === TickType.MAJOR) {
	ctx.fillRect(px, 0, 1, size.height);
	}
	}
	}

	ctx.textBaseline = 'bottom';
	ctx.font = '10px Helvetica';

	for (const note of this.trace.notes.notes.values()) {
	const timestamp = getStartTimestamp(note);
	// TODO(hjd): We should still render area selection marks in viewport is
	// within the area (e.g. both lhs and rhs are out of bounds).
	if (
	(note.noteType === 'DEFAULT' &&
	!visibleWindow.contains(note.timestamp)) \|\|
	(note.noteType === 'SPAN' &&
	!visibleWindow.overlaps(note.start, note.end))
	) {
	continue;
	}
	const currentIsHovered =
	this.hoveredX !== null && this.hitTestNote(this.hoveredX, note);
	if (currentIsHovered) aNoteIsHovered = true;

	const selection = this.trace.selection.selection;
	const isSelected = selection.kind === 'note' && selection.id === note.id;
	const x = timescale.timeToPx(timestamp);
	const left = Math.floor(x);

	// Draw flag or marker.
	if (note.noteType === 'SPAN') {
	this.drawAreaMarker(
	ctx,
	left,
	Math.floor(timescale.timeToPx(note.end)),
	note.color,
	isSelected,
	);
	} else {
	this.drawFlag(ctx, left, size.height, note.color, isSelected);
	}

	if (note.text) {
	const summary = toSummary(note.text);
	const measured = ctx.measureText(summary);
	// Add a white semi-transparent background for the text.
	ctx.fillStyle = 'rgba(255, 255, 255, 0.8)';
	ctx.fillRect(
	left + FLAG_WIDTH + 2,
	size.height + 2,
	measured.width + 2,
	-12,
	);
	ctx.fillStyle = '#3c4b5d';
	ctx.fillText(summary, left + FLAG_WIDTH + 3, size.height + 1);
	}
	}

	// A real note is hovered so we don't need to see the preview line.
	// TODO(hjd): Change cursor to pointer here.
	if (aNoteIsHovered) {
	this.trace.timeline.hoveredNoteTimestamp = undefined;
	}

	// View preview note flag when hovering on notes panel.
	if (!aNoteIsHovered && this.hoveredX !== null) {
	const timestamp = timescale.pxToHpTime(this.hoveredX).toTime();
	if (visibleWindow.contains(timestamp)) {
	this.trace.timeline.hoveredNoteTimestamp = timestamp;
	const x = timescale.timeToPx(timestamp);
	const left = Math.floor(x);
	this.drawFlag(ctx, left, size.height, '#aaa', /* fill */ true);
	}
	}

	ctx.restore();
	}

	private drawAreaMarker(
	ctx: CanvasRenderingContext2D,
	x: number,
	xEnd: number,
	color: string,
	fill: boolean,
	) {
	ctx.fillStyle = color;
	ctx.strokeStyle = color;
	const topOffset = 10;
	// Don't draw in the track shell section.
	if (x >= 0) {
	// Draw left triangle.
	ctx.beginPath();
	ctx.moveTo(x, topOffset);
	ctx.lineTo(x, topOffset + AREA_TRIANGLE_WIDTH);
	ctx.lineTo(x + AREA_TRIANGLE_WIDTH, topOffset);
	ctx.lineTo(x, topOffset);
	if (fill) ctx.fill();
	ctx.stroke();
	}
	// Draw right triangle.
	ctx.beginPath();
	ctx.moveTo(xEnd, topOffset);
	ctx.lineTo(xEnd, topOffset + AREA_TRIANGLE_WIDTH);
	ctx.lineTo(xEnd - AREA_TRIANGLE_WIDTH, topOffset);
	ctx.lineTo(xEnd, topOffset);
	if (fill) ctx.fill();
	ctx.stroke();

	// Start line after track shell section, join triangles.
	const startDraw = Math.max(x, 0);
	ctx.beginPath();
	ctx.moveTo(startDraw, topOffset);
	ctx.lineTo(xEnd, topOffset);
	ctx.stroke();
	}

	private drawFlag(
	ctx: CanvasRenderingContext2D,
	x: number,
	height: number,
	color: string,
	fill?: boolean,
	) {
	const prevFont = ctx.font;
	const prevBaseline = ctx.textBaseline;
	ctx.textBaseline = 'alphabetic';
	// Adjust height for icon font.
	ctx.font = '24px Material Symbols Sharp';
	ctx.fillStyle = color;
	ctx.strokeStyle = color;
	// The ligatures have padding included that means the icon is not drawn
	// exactly at the x value. This adjusts for that.
	const iconPadding = 6;
	if (fill) {
	ctx.fillText(FLAG, x - iconPadding, height + 2);
	} else {
	ctx.strokeText(FLAG, x - iconPadding, height + 2.5);
	}
	ctx.font = prevFont;
	ctx.textBaseline = prevBaseline;
	}

	private onClick(x: number) {
	if (!this.timescale) {
	return;
	}

	// Select the hovered note, or create a new single note & select it
	if (x < 0) return;
	for (const note of this.trace.notes.notes.values()) {
	if (this.hoveredX !== null && this.hitTestNote(this.hoveredX, note)) {
	this.trace.selection.selectNote({id: note.id});
	return;
	}
	}
	const timestamp = this.timescale.pxToHpTime(x).toTime();
	const color = randomColor();
	const noteId = this.trace.notes.addNote({timestamp, color});
	this.trace.selection.selectNote({id: noteId});
	}

	private hitTestNote(x: number, note: SpanNote \| Note): boolean {
	if (!this.timescale) {
	return false;
	}

	const timescale = this.timescale;
	const noteX = timescale.timeToPx(getStartTimestamp(note));
	if (note.noteType === 'SPAN') {
	return (
	(noteX <= x && x < noteX + AREA_TRIANGLE_WIDTH) \|\|
	(timescale.timeToPx(note.end) > x &&
	x > timescale.timeToPx(note.end) - AREA_TRIANGLE_WIDTH)
	);
	} else {
	const width = FLAG_WIDTH;
	return noteX <= x && x < noteX + width;
	}
	}
	}

	export class NotesEditorTab implements DetailsPanel {
	constructor(private trace: TraceImpl) {}

	render(selection: Selection) {
	if (selection.kind !== 'note') {
	return undefined;
	}

	const id = selection.id;

	const note = this.trace.notes.getNote(id);
	if (note === undefined) {
	return m('.', `No Note with id ${id}`);
	}
	const startTime = getStartTimestamp(note);
	return m(
	'.notes-editor-panel',
	{
	key: id, // Every note shoul get its own brand new DOM.
	},
	m(
	'.notes-editor-panel-heading-bar',
	m(
	'.notes-editor-panel-heading',
	`Annotation at `,
	m(Timestamp, {ts: startTime}),
	),
	m('input[type=text]', {
	oncreate: (v: m.VnodeDOM) => {
	// NOTE: due to bad design decisions elsewhere this component is
	// rendered every time the mouse moves on the canvas. We cannot set
	// `value: note.text` as an input as that will clobber the input
	// value as we move the mouse.
	const inputElement = v.dom as HTMLInputElement;
	inputElement.value = note.text;
	inputElement.focus();
	},
	onchange: (e: InputEvent) => {
	const newText = (e.target as HTMLInputElement).value;
	this.trace.notes.changeNote(id, {text: newText});
	},
	}),
	m(
	'span.color-change',
	`Change color: `,
	m('input[type=color]', {
	value: note.color,
	onchange: (e: Event) => {
	const newColor = (e.target as HTMLInputElement).value;
	this.trace.notes.changeNote(id, {color: newColor});
	},
	}),
	),
	m(Button, {
	label: 'Remove',
	icon: Icons.Delete,
	onclick: () => this.trace.notes.removeNote(id),
	}),
	),
	);
	}
	}