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 <head>
  <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
  <meta content="width=device-width, initial-scale=1, shrink-to-fit=no" name="viewport">
  <title>P1225R0: Feedback on 2D Graphics</title>
<style data-fill-with="stylesheet">/******************************************************************************
 *                   Style sheet for the W3C specifications                   *
 *
 * Special classes handled by this style sheet include:
 *
 * Indices
 *   - .toc for the Table of Contents (<ol class="toc">)
 *     + <span class="secno"> for the section numbers
 *   - #toc for the Table of Contents (<nav id="toc">)
 *   - ul.index for Indices (<a href="#ref">term</a><span>, in §N.M</span>)
 *   - table.index for Index Tables (e.g. for properties or elements)
 *
 * Structural Markup
 *   - table.data for general data tables
 *     -> use 'scope' attribute, <colgroup>, <thead>, and <tbody> for best results !
 *     -> use <table class='complex data'> for extra-complex tables
 *     -> use <td class='long'> for paragraph-length cell content
 *     -> use <td class='pre'> when manual line breaks/indentation would help readability
 *   - dl.switch for switch statements
 *   - ol.algorithm for algorithms (helps to visualize nesting)
 *   - .figure and .caption (HTML4) and figure and figcaption (HTML5)
 *     -> .sidefigure for right-floated figures
 *   - ins/del
 *
 * Code
 *   - pre and code
 *
 * Special Sections
 *   - .note       for informative notes             (div, p, span, aside, details)
 *   - .example    for informative examples          (div, p, pre, span)
 *   - .issue      for issues                        (div, p, span)
 *   - .assertion  for assertions                    (div, p, span)
 *   - .advisement for loud normative statements     (div, p, strong)
 *   - .annoying-warning for spec obsoletion notices (div, aside, details)
 *
 * Definition Boxes
 *   - pre.def   for WebIDL definitions
 *   - table.def for tables that define other entities (e.g. CSS properties)
 *   - dl.def    for definition lists that define other entitles (e.g. HTML elements)
 *
 * Numbering
 *   - .secno for section numbers in .toc and headings (<span class='secno'>3.2</span>)
 *   - .marker for source-inserted example/figure/issue numbers (<span class='marker'>Issue 4</span>)
 *   - ::before styled for CSS-generated issue/example/figure numbers:
 *     -> Documents wishing to use this only need to add
 *        figcaption::before,
 *        .caption::before { content: "Figure "  counter(figure) " ";  }
 *        .example::before { content: "Example " counter(example) " "; }
 *        .issue::before   { content: "Issue "   counter(issue) " ";   }
 *
 * Header Stuff (ignore, just don't conflict with these classes)
 *   - .head for the header
 *   - .copyright for the copyright
 *
 * Miscellaneous
 *   - .overlarge for things that should be as wide as possible, even if
 *     that overflows the body text area. This can be used on an item or
 *     on its container, depending on the effect desired.
 *     Note that this styling basically doesn't help at all when printing,
 *     since A4 paper isn't much wider than the max-width here.
 *     It's better to design things to fit into a narrower measure if possible.
 *   - js-added ToC jump links (see fixup.js)
 *
 ******************************************************************************/

/******************************************************************************/
/*                                   Body                                     */
/******************************************************************************/

	body {
		counter-reset: example figure issue;

		/* Layout */
		max-width: 50em;               /* limit line length to 50em for readability   */
		margin: 0 auto;                /* center text within page                     */
		padding: 1.6em 1.5em 2em 50px; /* assume 16px font size for downlevel clients */
		padding: 1.6em 1.5em 2em calc(26px + 1.5em); /* leave space for status flag     */

		/* Typography */
		line-height: 1.5;
		font-family: sans-serif;
		widows: 2;
		orphans: 2;
		word-wrap: break-word;
		overflow-wrap: break-word;
		hyphens: auto;

		/* Colors */
		color: black;
		background: white top left fixed no-repeat;
		background-size: 25px auto;
	}


/******************************************************************************/
/*                         Front Matter & Navigation                          */
/******************************************************************************/

/** Header ********************************************************************/

	div.head { margin-bottom: 1em }
	div.head hr { border-style: solid; }

	div.head h1 {
		font-weight: bold;
		margin: 0 0 .1em;
		font-size: 220%;
	}

	div.head h2 { margin-bottom: 1.5em;}

/** W3C Logo ******************************************************************/

	.head .logo {
		float: right;
		margin: 0.4rem 0 0.2rem .4rem;
	}

	.head img[src*="logos/W3C"] {
		display: block;
		border: solid #1a5e9a;
		border-width: .65rem .7rem .6rem;
		border-radius: .4rem;
		background: #1a5e9a;
		color: white;
		font-weight: bold;
	}

	.head a:hover > img[src*="logos/W3C"],
	.head a:focus > img[src*="logos/W3C"] {
		opacity: .8;
	}

	.head a:active > img[src*="logos/W3C"] {
		background: #c00;
		border-color: #c00;
	}

	/* see also additional rules in Link Styling section */

/** Copyright *****************************************************************/

	p.copyright,
	p.copyright small { font-size: small }

/** Back to Top / ToC Toggle **************************************************/

	@media print {
		#toc-nav {
			display: none;
		}
	}
	@media not print {
		#toc-nav {
			position: fixed;
			z-index: 2;
			bottom: 0; left: 0;
			margin: 0;
			min-width: 1.33em;
			border-top-right-radius: 2rem;
			box-shadow: 0 0 2px;
			font-size: 1.5em;
			color: black;
		}
		#toc-nav > a {
			display: block;
			white-space: nowrap;

			height: 1.33em;
			padding: .1em 0.3em;
			margin: 0;

			background: white;
			box-shadow: 0 0 2px;
			border: none;
			border-top-right-radius: 1.33em;
			background: white;
		}
		#toc-nav > #toc-jump {
			padding-bottom: 2em;
			margin-bottom: -1.9em;
		}

		#toc-nav > a:hover,
		#toc-nav > a:focus {
			background: #f8f8f8;
		}
		#toc-nav > a:not(:hover):not(:focus) {
			color: #707070;
		}

		/* statusbar gets in the way on keyboard focus; remove once browsers fix */
		#toc-nav > a[href="#toc"]:not(:hover):focus:last-child {
			padding-bottom: 1.5rem;
		}

		#toc-nav:not(:hover) > a:not(:focus) > span + span {
			/* Ideally this uses :focus-within on #toc-nav */
			display: none;
		}
		#toc-nav > a > span + span {
			padding-right: 0.2em;
		}

		#toc-toggle-inline {
			vertical-align: 0.05em;
			font-size: 80%;
			color: gray;
			color: hsla(203,20%,40%,.7);
			border-style: none;
			background: transparent;
			position: relative;
		}
		#toc-toggle-inline:hover:not(:active),
		#toc-toggle-inline:focus:not(:active) {
			text-shadow: 1px 1px silver;
			top: -1px;
			left: -1px;
		}

		#toc-nav :active {
			color: #C00;
		}
	}

/** ToC Sidebar ***************************************************************/

	/* Floating sidebar */
	@media screen {
		body.toc-sidebar #toc {
			position: fixed;
			top: 0; bottom: 0;
			left: 0;
			width: 23.5em;
			max-width: 80%;
			max-width: calc(100% - 2em - 26px);
			overflow: auto;
			padding: 0 1em;
			padding-left: 42px;
			padding-left: calc(1em + 26px);
			background: inherit;
			background-color: #f7f8f9;
			z-index: 1;
			box-shadow: -.1em 0 .25em rgba(0,0,0,.1) inset;
		}
		body.toc-sidebar #toc h2 {
			margin-top: .8rem;
			font-variant: small-caps;
			font-variant: all-small-caps;
			text-transform: lowercase;
			font-weight: bold;
			color: gray;
			color: hsla(203,20%,40%,.7);
		}
		body.toc-sidebar #toc-jump:not(:focus) {
			width: 0;
			height: 0;
			padding: 0;
			position: absolute;
			overflow: hidden;
		}
	}
	/* Hide main scroller when only the ToC is visible anyway */
	@media screen and (max-width: 28em) {
		body.toc-sidebar {
			overflow: hidden;
		}
	}

	/* Sidebar with its own space */
	@media screen and (min-width: 78em) {
		body:not(.toc-inline) #toc {
			position: fixed;
			top: 0; bottom: 0;
			left: 0;
			width: 23.5em;
			overflow: auto;
			padding: 0 1em;
			padding-left: 42px;
			padding-left: calc(1em + 26px);
			background: inherit;
			background-color: #f7f8f9;
			z-index: 1;
			box-shadow: -.1em 0 .25em rgba(0,0,0,.1) inset;
		}
		body:not(.toc-inline) #toc h2 {
			margin-top: .8rem;
			font-variant: small-caps;
			font-variant: all-small-caps;
			text-transform: lowercase;
			font-weight: bold;
			color: gray;
			color: hsla(203,20%,40%,.7);
		}

		body:not(.toc-inline) {
			padding-left: 29em;
		}
		/* See also Overflow section at the bottom */

		body:not(.toc-inline) #toc-jump:not(:focus) {
			width: 0;
			height: 0;
			padding: 0;
			position: absolute;
			overflow: hidden;
		}
	}
	@media screen and (min-width: 90em) {
		body:not(.toc-inline) {
			margin: 0 4em;
		}
	}

/******************************************************************************/
/*                                Sectioning                                  */
/******************************************************************************/

/** Headings ******************************************************************/

	h1, h2, h3, h4, h5, h6, dt {
		page-break-after: avoid;
		page-break-inside: avoid;
		font: 100% sans-serif;   /* Reset all font styling to clear out UA styles */
		font-family: inherit;    /* Inherit the font family. */
		line-height: 1.2;        /* Keep wrapped headings compact */
		hyphens: manual;         /* Hyphenated headings look weird */
	}

	h2, h3, h4, h5, h6 {
		margin-top: 3rem;
	}

	h1, h2, h3 {
		color: #005A9C;
		background: transparent;
	}

	h1 { font-size: 170%; }
	h2 { font-size: 140%; }
	h3 { font-size: 120%; }
	h4 { font-weight: bold; }
	h5 { font-style: italic; }
	h6 { font-variant: small-caps; }
	dt { font-weight: bold; }

/** Subheadings ***************************************************************/

	h1 + h2,
	#subtitle {
		/* #subtitle is a subtitle in an H2 under the H1 */
		margin-top: 0;
	}
	h2 + h3,
	h3 + h4,
	h4 + h5,
	h5 + h6 {
		margin-top: 1.2em; /* = 1 x line-height */
	}

/** Section divider ***********************************************************/

	:not(.head) > hr {
		font-size: 1.5em;
		text-align: center;
		margin: 1em auto;
		height: auto;
		border: transparent solid 0;
		background: transparent;
	}
	:not(.head) > hr::before {
		content: "\2727\2003\2003\2727\2003\2003\2727";
	}

/******************************************************************************/
/*                            Paragraphs and Lists                            */
/******************************************************************************/

	p {
		margin: 1em 0;
	}

	dd > p:first-child,
	li > p:first-child {
		margin-top: 0;
	}

	ul, ol {
		margin-left: 0;
		padding-left: 2em;
	}

	li {
		margin: 0.25em 0 0.5em;
		padding: 0;
	}

	dl dd {
		margin: 0 0 .5em 2em;
	}

	.head dd + dd { /* compact for header */
		margin-top: -.5em;
	}

	/* Style for algorithms */
	ol.algorithm ol:not(.algorithm),
	.algorithm > ol ol:not(.algorithm) {
	 border-left: 0.5em solid #DEF;
	}

	/* Put nice boxes around each algorithm. */
	[data-algorithm]:not(.heading) {
	  padding: .5em;
	  border: thin solid #ddd; border-radius: .5em;
	  margin: .5em calc(-0.5em - 1px);
	}
	[data-algorithm]:not(.heading) > :first-child {
	  margin-top: 0;
	}
	[data-algorithm]:not(.heading) > :last-child {
	  margin-bottom: 0;
	}

	/* Style for switch/case <dl>s */
	dl.switch > dd > ol.only,
	dl.switch > dd > .only > ol {
	 margin-left: 0;
	}
	dl.switch > dd > ol.algorithm,
	dl.switch > dd > .algorithm > ol {
	 margin-left: -2em;
	}
	dl.switch {
	 padding-left: 2em;
	}
	dl.switch > dt {
	 text-indent: -1.5em;
	 margin-top: 1em;
	}
	dl.switch > dt + dt {
	 margin-top: 0;
	}
	dl.switch > dt::before {
	 content: '\21AA';
	 padding: 0 0.5em 0 0;
	 display: inline-block;
	 width: 1em;
	 text-align: right;
	 line-height: 0.5em;
	}

/** Terminology Markup ********************************************************/


/******************************************************************************/
/*                                 Inline Markup                              */
/******************************************************************************/

/** Terminology Markup ********************************************************/
	dfn   { /* Defining instance */
		font-weight: bolder;
	}
	a > i { /* Instance of term */
		font-style: normal;
	}
	dt dfn code, code.idl {
		font-size: medium;
	}
	dfn var {
		font-style: normal;
	}

/** Change Marking ************************************************************/

	del { color: red;  text-decoration: line-through; }
	ins { color: #080; text-decoration: underline;    }

/** Miscellaneous improvements to inline formatting ***************************/

	sup {
		vertical-align: super;
		font-size: 80%
	}

/******************************************************************************/
/*                                    Code                                    */
/******************************************************************************/

/** General monospace/pre rules ***********************************************/

	pre, code, samp {
		font-family: Menlo, Consolas, "DejaVu Sans Mono", Monaco, monospace;
		font-size: .9em;
		page-break-inside: avoid;
		hyphens: none;
		text-transform: none;
	}
	pre code,
	code code {
		font-size: 100%;
	}

	pre {
		margin-top: 1em;
		margin-bottom: 1em;
		overflow: auto;
	}

/** Inline Code fragments *****************************************************/

  /* Do something nice. */

/******************************************************************************/
/*                                    Links                                   */
/******************************************************************************/

/** General Hyperlinks ********************************************************/

	/* We hyperlink a lot, so make it less intrusive */
	a[href] {
		color: #034575;
		text-decoration: none;
		border-bottom: 1px solid #707070;
		/* Need a bit of extending for it to look okay */
		padding: 0 1px 0;
		margin: 0 -1px 0;
	}
	a:visited {
		border-bottom-color: #BBB;
	}

	/* Use distinguishing colors when user is interacting with the link */
	a[href]:focus,
	a[href]:hover {
		background: #f8f8f8;
		background: rgba(75%, 75%, 75%, .25);
		border-bottom-width: 3px;
		margin-bottom: -2px;
	}
	a[href]:active {
		color: #C00;
		border-color: #C00;
	}

	/* Backout above styling for W3C logo */
	.head .logo,
	.head .logo a {
		border: none;
		text-decoration: none;
		background: transparent;
	}

/******************************************************************************/
/*                                    Images                                  */
/******************************************************************************/

	img {
		border-style: none;
	}

	/* For autogen numbers, add
	   .caption::before, figcaption::before { content: "Figure " counter(figure) ". "; }
	*/

	figure, .figure, .sidefigure {
		page-break-inside: avoid;
		text-align: center;
		margin: 2.5em 0;
	}
	.figure img,    .sidefigure img,    figure img,
	.figure object, .sidefigure object, figure object {
		max-width: 100%;
		margin: auto;
	}
	.figure pre, .sidefigure pre, figure pre {
		text-align: left;
		display: table;
		margin: 1em auto;
	}
	.figure table, figure table {
		margin: auto;
	}
	@media screen and (min-width: 20em) {
		.sidefigure {
			float: right;
			width: 50%;
			margin: 0 0 0.5em 0.5em
		}
	}
	.caption, figcaption, caption {
		font-style: italic;
		font-size: 90%;
	}
	.caption::before, figcaption::before, figcaption > .marker {
		font-weight: bold;
	}
	.caption, figcaption {
		counter-increment: figure;
	}

	/* DL list is indented 2em, but figure inside it is not */
	dd > .figure, dd > figure { margin-left: -2em }

/******************************************************************************/
/*                             Colored Boxes                                  */
/******************************************************************************/

	.issue, .note, .example, .assertion, .advisement, blockquote {
		padding: .5em;
		border: .5em;
		border-left-style: solid;
		page-break-inside: avoid;
	}
	span.issue, span.note {
		padding: .1em .5em .15em;
		border-right-style: solid;
	}

	.issue,
	.note,
	.example,
	.advisement,
	.assertion,
	blockquote {
		margin: 1em auto;
	}
	.note  > p:first-child,
	.issue > p:first-child,
	blockquote > :first-child {
		margin-top: 0;
	}
	blockquote > :last-child {
		margin-bottom: 0;
	}

/** Blockquotes ***************************************************************/

	blockquote {
		border-color: silver;
	}

/** Open issue ****************************************************************/

	.issue {
		border-color: #E05252;
		background: #FBE9E9;
		counter-increment: issue;
		overflow: auto;
	}
	.issue::before, .issue > .marker {
		text-transform: uppercase;
		color: #AE1E1E;
		padding-right: 1em;
		text-transform: uppercase;
	}
	/* Add .issue::before { content: "Issue " counter(issue) " "; } for autogen numbers,
	   or use class="marker" to mark up the issue number in source. */

/** Example *******************************************************************/

	.example {
		border-color: #E0CB52;
		background: #FCFAEE;
		counter-increment: example;
		overflow: auto;
		clear: both;
	}
	.example::before, .example > .marker {
		text-transform: uppercase;
		color: #827017;
		min-width: 7.5em;
		display: block;
	}
	/* Add .example::before { content: "Example " counter(example) " "; } for autogen numbers,
	   or use class="marker" to mark up the example number in source. */

/** Non-normative Note ********************************************************/

	.note {
		border-color: #52E052;
		background: #E9FBE9;
		overflow: auto;
	}

	.note::before, .note > .marker,
	details.note > summary::before,
	details.note > summary > .marker {
		text-transform: uppercase;
		display: block;
		color: hsl(120, 70%, 30%);
	}
	/* Add .note::before { content: "Note"; } for autogen label,
	   or use class="marker" to mark up the label in source. */

	details.note > summary {
		display: block;
		color: hsl(120, 70%, 30%);
	}
	details.note[open] > summary {
		border-bottom: 1px silver solid;
	}

/** Assertion Box *************************************************************/
	/*  for assertions in algorithms */

	.assertion {
		border-color: #AAA;
		background: #EEE;
	}

/** Advisement Box ************************************************************/
	/*  for attention-grabbing normative statements */

	.advisement {
		border-color: orange;
		border-style: none solid;
		background: #FFEECC;
	}
	strong.advisement {
		display: block;
		text-align: center;
	}
	.advisement > .marker {
		color: #B35F00;
	}

/** Spec Obsoletion Notice ****************************************************/
	/* obnoxious obsoletion notice for older/abandoned specs. */

	details {
		display: block;
	}
	summary {
		font-weight: bolder;
	}

	.annoying-warning:not(details),
	details.annoying-warning:not([open]) > summary,
	details.annoying-warning[open] {
		background: #fdd;
		color: red;
		font-weight: bold;
		padding: .75em 1em;
		border: thick red;
		border-style: solid;
		border-radius: 1em;
	}
	.annoying-warning :last-child {
		margin-bottom: 0;
	}

@media not print {
	details.annoying-warning[open] {
		position: fixed;
		left: 1em;
		right: 1em;
		bottom: 1em;
		z-index: 1000;
	}
}

	details.annoying-warning:not([open]) > summary {
		text-align: center;
	}

/** Entity Definition Boxes ***************************************************/

	.def {
		padding: .5em 1em;
		background: #DEF;
		margin: 1.2em 0;
		border-left: 0.5em solid #8CCBF2;
	}

/******************************************************************************/
/*                                    Tables                                  */
/******************************************************************************/

	th, td {
		text-align: left;
		text-align: start;
	}

/** Property/Descriptor Definition Tables *************************************/

	table.def {
		/* inherits .def box styling, see above */
		width: 100%;
		border-spacing: 0;
	}

	table.def td,
	table.def th {
		padding: 0.5em;
		vertical-align: baseline;
		border-bottom: 1px solid #bbd7e9;
	}

	table.def > tbody > tr:last-child th,
	table.def > tbody > tr:last-child td {
		border-bottom: 0;
	}

	table.def th {
		font-style: italic;
		font-weight: normal;
		padding-left: 1em;
		width: 3em;
	}

	/* For when values are extra-complex and need formatting for readability */
	table td.pre {
		white-space: pre-wrap;
	}

	/* A footnote at the bottom of a def table */
	table.def           td.footnote {
		padding-top: 0.6em;
	}
	table.def           td.footnote::before {
		content: " ";
		display: block;
		height: 0.6em;
		width: 4em;
		border-top: thin solid;
	}

/** Data tables (and properly marked-up index tables) *************************/
	/*
		 <table class="data"> highlights structural relationships in a table
		 when correct markup is used (e.g. thead/tbody, th vs. td, scope attribute)

		 Use class="complex data" for particularly complicated tables --
		 (This will draw more lines: busier, but clearer.)

		 Use class="long" on table cells with paragraph-like contents
		 (This will adjust text alignment accordingly.)
		 Alternately use class="longlastcol" on tables, to have the last column assume "long".
	*/

	table {
		word-wrap: normal;
		overflow-wrap: normal;
		hyphens: manual;
	}

	table.data,
	table.index {
		margin: 1em auto;
		border-collapse: collapse;
		border: hidden;
		width: 100%;
	}
	table.data caption,
	table.index caption {
		max-width: 50em;
		margin: 0 auto 1em;
	}

	table.data td,  table.data th,
	table.index td, table.index th {
		padding: 0.5em 1em;
		border-width: 1px;
		border-color: silver;
		border-top-style: solid;
	}

	table.data thead td:empty {
		padding: 0;
		border: 0;
	}

	table.data  thead,
	table.index thead,
	table.data  tbody,
	table.index tbody {
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 <body class="h-entry">
  <div class="head">
   <p data-fill-with="logo"></p>
   <h1 class="p-name no-ref" id="title">P1225R0<br>Feedback on 2D Graphics</h1>
   <h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="content">Published Proposal, <time class="dt-updated" datetime="2018-10-02">2018-10-02</time></span></h2>
   <div data-fill-with="spec-metadata">
    <dl>
     <dt>This version:
     <dd><a class="u-url" href="http://wg21.link/P1225R0">http://wg21.link/P1225R0</a>
     <dt>Author:
     <dd>
      <dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:jfbastien@apple.com">JF Bastien</a> (<span class="p-org org">Apple</span>)
     <dt>Audience:
     <dd>LEWG
     <dt>Project:
     <dd>ISO/IEC JTC1/SC22/WG21 14882: Programming Language — C++
     <dt>Source:
     <dd><a href="https://github.com/jfbastien/papers/blob/master/source/P1225R0.bs">github.com/jfbastien/papers/blob/master/source/P1225R0.bs</a>
    </dl>
   </div>
   <div data-fill-with="warning"></div>
   <hr title="Separator for header">
  </div>
  <nav data-fill-with="table-of-contents" id="toc">
   <h2 class="no-num no-toc no-ref" id="contents">Table of Contents</h2>
   <ol class="toc" role="directory">
    <li><a href="#abs"><span class="secno">1</span> <span class="content">Abstract</span></a>
    <li><a href="#design"><span class="secno">2</span> <span class="content">Design</span></a>
    <li><a href="#st"><span class="secno">3</span> <span class="content">Science and teaching</span></a>
    <li><a href="#level"><span class="secno">4</span> <span class="content">Abstraction Level</span></a>
    <li><a href="#missing"><span class="secno">5</span> <span class="content">Missing Details</span></a>
    <li><a href="#cpp"><span class="secno">6</span> <span class="content">C++ Aesthetics</span></a>
    <li><a href="#conc"><span class="secno">7</span> <span class="content">Conclusion</span></a>
    <li>
     <a href="#references"><span class="secno"></span> <span class="content">References</span></a>
     <ol class="toc">
      <li><a href="#informative"><span class="secno"></span> <span class="content">Informative References</span></a>
     </ol>
   </ol>
  </nav>
  <main>
   <h2 class="heading settled" data-level="1" id="abs"><span class="secno">1. </span><span class="content">Abstract</span><a class="self-link" href="#abs"></a></h2>
   <p>I’ve gathered input from a variety of folks involved in graphics at Apple, and here is our joint, considered, position regarding the 2D Graphics proposal.</p>
   <p>We’re worried that the 2D Graphics proposal in <a data-link-type="biblio" href="#biblio-p0267r8">[P0267R8]</a> might be detrimental to developers, students, and users of devices which contain C++ code. Graphics are important to the Apple ecosystem, and we can see them as an important part of C++. However, we don’t think P0267R8 meets the quality bar for acceptance into C++. We want to see the reference implementation prove orthogonality, extensibility, and performance across a handful of platforms.</p>
   <h2 class="heading settled" data-level="2" id="design"><span class="secno">2. </span><span class="content">Design</span><a class="self-link" href="#design"></a></h2>
   <p>Were we to design a 2D Graphics API, we’d do the following:</p>
   <ol>
    <li data-md>
     <p>Multiple output devices: Memory buffer, Window, SVG, PDF, etc.</p>
     <ol>
      <li data-md>
       <p>Memory buffer must be directly usable by graphics API</p>
      <li data-md>
       <p>Support types such as <code class="highlight"><c- n>fp16</c-></code> <a data-link-type="biblio" href="#biblio-p0303r0">[P0303R0]</a></p>
      <li data-md>
       <p>Alpha channel support</p>
     </ol>
    <li data-md>
     <p>Anti-aliasing should come for free where supported</p>
    <li data-md>
     <p>Text</p>
    <li data-md>
     <p>Consistent, DPI-independent, output</p>
    <li data-md>
     <p>Hardware support where available</p>
    <li data-md>
     <p>Reasonable performance</p>
    <li data-md>
     <p>Reasonable power consumption</p>
    <li data-md>
     <p>Color spaces and gamma support</p>
    <li data-md>
     <p>Possibility to build an interactive model with animation on top of the API</p>
   </ol>
   <p>From the current proposal we like:</p>
   <ol>
    <li data-md>
     <p>2D Matrix is 3×3, so homogeneous, presented as 2×3 in the API</p>
    <li data-md>
     <p>Decouples display points from actual points</p>
    <li data-md>
     <p>Vector graphics</p>
    <li data-md>
     <p>Compositing properly handled</p>
   </ol>
   <h2 class="heading settled" data-level="3" id="st"><span class="secno">3. </span><span class="content">Science and teaching</span><a class="self-link" href="#st"></a></h2>
   <p>We’ve heard the following reasons for including 2D Graphics in C++:</p>
   <ol>
    <li data-md>
     <p>Teaching</p>
    <li data-md>
     <p>Scientific plot generation</p>
   </ol>
   <p>We think putting pixels on the screen is great, but we want to do so responsibly.</p>
   <p>Both for science and teaching, we appreciate what’s available through solutions such as <a href="https://www.mathworks.com/help/matlab/ref/plot.html">Matlab</a> / <a href="https://matplotlib.org/users/pyplot_tutorial.html">matplotlib</a> / <a href="https://www.statmethods.net/graphs/line.html">R</a> / <a href="https://d3js.org/">D3.js</a>. These solutions are powerful and match the performance of the language they complement. For C++ we’d expect a solution which is able to deliver performance which at least approaches that of modern graphics frameworks, and surpassing those of Matlab / Python / R / JavaScript.</p>
   <p>As a teaching tool, the current proposal teaches fairly low-level capabilities (i.e. complex things are hard to create) and is missing critical functionality. We fear it will hinder students by teaching them to start everything from scratch, and by not teaching them a few key details.</p>
   <p>As a plotting tool it’s clearly falling short because it can’t label any axis (c.f. <a href="https://www.edwardtufte.com/tufte/books_vdqi">Tufte</a>). Even if text were supported, the sample libraries for Matlab, Python, R, and JavaScript are much easier to draw plots with. The 2D Graphics proposal is neither capable nor convenient in that regard.</p>
   <p>As a broad generalization, students currently learn data visualization (beyond what Excel + CSV files can do) in Matlab or Python if they do science, in R if they do math, and in JavaScript if they do anything else. We urge the Committee members at least try some of these, for example <a href="https://beta.observablehq.com/@mbostock/d3-scatterplot-matrix">scatterplot</a>, <a href="https://beta.observablehq.com/@mbostock/d3-histogram">histogram</a>, <a href="https://www.jasondavies.com/wordtree/">wordtree</a>. These aren’t teaching toys and are used, for example, by the <a href="https://archive.nytimes.com/www.nytimes.com/interactive/2012/10/15/us/politics/swing-history.html">New York Times</a>. There’s value in teaching students to pull themselves up from the language’s bootstraps, we therefore think the type of API in the current 2D Graphics library is useful. However, we want to know—i.e. we want to see it prototyped—that higher-level capabilities are also something that can be implemented. We think higher-level capabilities are more useful for teaching, yet we understand that C++ might want to offer lower-level primitives first.</p>
   <h2 class="heading settled" data-level="4" id="level"><span class="secno">4. </span><span class="content">Abstraction Level</span><a class="self-link" href="#level"></a></h2>
   <p>When we say the current proposal is too low-level, here are things we’d like to see at least prototyped to know that the proposal can grow into a powerful high-level library:</p>
   <ul>
    <li data-md>
     <p>Obtain a window object</p>
    <li data-md>
     <p>Load / transform / draw asset files</p>
    <li data-md>
     <p>Complex raster image support (including swizzled surfaces, compression, 2D form clipping, used as texture fill)</p>
    <li data-md>
     <p>New user-implemented rasterization primitives (such as ellipses or NURBS curve)</p>
    <li data-md>
     <p>Stacking geometric transforms before drawing (can this be done already?)</p>
    <li data-md>
     <p>Scissoring / clipping</p>
    <li data-md>
     <p>Handle user input</p>
    <li data-md>
     <p>Text support (glyph rasterization (e.g. FreeType), text Shaping (e.g. HarfBuzz), string Rendering (e.g. Pango)), or something platform specific (e.g. CoreText on Apple Platforms)</p>
    <li data-md>
     <p>Complex line drawing (e.g. dashed lines, along a path)</p>
    <li data-md>
     <p>Can all of the offered primitives be implemented directly on hardware using shaders?</p>
   </ul>
   <p>In other words, we understand that a proposal might want to start small and grow more features over time. We want to know that this growth is possible, and that features can be composed into higher-level primitives.</p>
   <h2 class="heading settled" data-level="5" id="missing"><span class="secno">5. </span><span class="content">Missing Details</span><a class="self-link" href="#missing"></a></h2>
   <p>When we say the current proposal has key details we find missing, here are what we want to see in an initial version:</p>
   <ul>
    <li data-md>
     <p>It’s unclear that buffering is implementable, and that’s critical to a high-performance implementation. We’d like to see it implemented. We want to see a deferred mode implementation, not just immediate mode.</p>
    <li data-md>
     <p>Support modern color spaces and gamma.</p>
    <li data-md>
     <p>DPI independence is needed.</p>
    <li data-md>
     <p>Display points seem to address individual pixels in the image. We’d like to be able to address at finer granularity (MSAA samples, typographer points, pica).</p>
    <li data-md>
     <p>We’re not convinced that animation can be supported efficiently (i.e. update a single matrix in the stack of transforms).</p>
    <li data-md>
     <p>The current proposal doesn’t specify which image format can be loaded, yet the reference implementation has PNG, JPEG, TIFF. This lack of specification makes portability difficult.</p>
    <li data-md>
     <p>We want to see an implementation generate PDF, SVG, raster output, as well as output in an OS window. This should be doable portably with zero code change.</p>
   </ul>
   <h2 class="heading settled" data-level="6" id="cpp"><span class="secno">6. </span><span class="content">C++ Aesthetics</span><a class="self-link" href="#cpp"></a></h2>
   <p>Aesthetically, this lacks the feel of a C++ standard library. In particular:</p>
   <ul>
    <li data-md>
     <p>The dual error handling mechanism, while reminiscent of filesystem, is quaint in the STL.</p>
    <li data-md>
     <p>Most APIs seem to be function-oriented and have a C API feel to them.</p>
    <li data-md>
     <p>We’re surprised that we don’t have iterators / ranges for e.g. a path. We’d expect STL algorithms to work on such primitives.</p>
    <li data-md>
     <p>We’d like to see linear algebra, trigonometry, and matrix math standardized separately.</p>
   </ul>
   <h2 class="heading settled" data-level="7" id="conc"><span class="secno">7. </span><span class="content">Conclusion</span><a class="self-link" href="#conc"></a></h2>
   <p>We want to offer developers a graphics solution which allows usage of the full capabilities of the hardware we ship, without wasting battery life. Were we to ship the 2D Graphics proposal, we’d be putting our and C++’s good name on an API. We want to be sure it doesn’t provides a disservice to developers and users.</p>
   <p>We’re surprised and worried that the reference implementation on Mac requires X11 and MacPorts. We want to see an implementation that re-uses platform primitives on more than Linux. What was the experience with <a href="https://github.com/mikekazakov/P0267_cg">CoreGraphics</a>?</p>
   <p>The windows + SVG proposal in <a data-link-type="biblio" href="#biblio-p1062r0">[P1062R0]</a> isn’t terrible. Obtaining a window seems like a simple step forward. SVG has some upsides and a few downsides, but overall we’re positive on them. We like that the proposal leans on existing standards.</p>
   <p>Web view from <a data-link-type="biblio" href="#biblio-p1108r0">[P1108R0]</a> is trivial to support if specified well, but we don’t think it does what graphics enthusiasts want to do. It might be an interesting proposal, but we think it stands separately from 2D Graphics.</p>
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  <h2 class="no-num no-ref heading settled" id="references"><span class="content">References</span><a class="self-link" href="#references"></a></h2>
  <h3 class="no-num no-ref heading settled" id="informative"><span class="content">Informative References</span><a class="self-link" href="#informative"></a></h3>
  <dl>
   <dt id="biblio-p0267r8">[P0267R8]
   <dd>Michael B. McLaughlin, Herb Sutter, Jason Zink, Guy Davidson, Michael Kazakov. <a href="https://wg21.link/p0267r8">A Proposal to Add 2D Graphics Rendering and Display to C++</a>. 26 June 2018. URL: <a href="https://wg21.link/p0267r8">https://wg21.link/p0267r8</a>
   <dt id="biblio-p0303r0">[P0303R0]
   <dd>Boris Fomitchev, Sergei Nikolaev, Olivier Giroux, Lawrence Crowl. <a href="https://wg21.link/p0303r0">Extensions to C++ for Short Float Type</a>. 15 October 2017. URL: <a href="https://wg21.link/p0303r0">https://wg21.link/p0303r0</a>
   <dt id="biblio-p1062r0">[P1062R0]
   <dd>Bryce Adelstein Lelbach, Olivier Giroux, Zach Laine, Corentin Jabot, Vittorio Romeo. <a href="https://wg21.link/p1062r0">Diet Graphics</a>. 7 May 2018. URL: <a href="https://wg21.link/p1062r0">https://wg21.link/p1062r0</a>
   <dt id="biblio-p1108r0">[P1108R0]
   <dd>Hal Finkel. <a href="https://wg21.link/p1108r0">web_view</a>. 22 June 2018. URL: <a href="https://wg21.link/p1108r0">https://wg21.link/p1108r0</a>
  </dl>