Resolve fonts using CSS Level 3 algorithm when using html() #3040

allansson · 2020-12-17T10:45:32Z

Issue

The context2d.font property uses a different algorithm from the browser when choosing a font. This causes jsPDF to choose a different font, meaning that the rendered PDF will not look the same as the rendered page. Additionally the current algorithm does not fully support all the possible values for font-weights, font-stretch and font-styles. This PR is related to #2920 and its PR #3036.

Feature

This PR adds an option to specify font-faces to the html() method, which will make the context2d.font use the same algorithm as the browser (with some limitations) when deciding which font to use.

The supported properties of the font style matching algorithm of the CSS Level 3 specification are:

font-family
font-stretch
font-style
font-weight

In order to use this feature, the user has to specify font-faces matching the ones in given by the user's CSS:

doc.html(el, {
    fontFaces: [{
        family: 'Roboto',
        weight: 700,
        style: italic,
        src: [{
            format: "truetype",
            url: "https://mysite.test/roboto.ttf"
        }]
    }]
})

The interface of each font-face object is modelled to, as close as possible, match the interface of the CSS Font Loading API specified in CSS Font Loading Module Level 3 in the hopes that, as browser support increases, users can use that API to get the available font-faces from the browser instead of defining them a second time. The one exception is the src-property, which is not included in the specification but is required in order to fetch the fonts.

All fonts configured will be automatically downloaded and added to the document.

The change should be backwards compatible since the algorithm only takes effect when the fontFaces option is set.

Limitations

While implementation of the font style matching algorithm takes the font-stretch into account, the context2d.font property currently does not support extracting font-stretch values from the given value. This is due to difficulties in modifying the regex used to parse the font value.
The font style matching algorithm rules out fonts that don't support a given unicode character. This has not been implemented.
The implementation does not take font-size into consideration when selecting a font. It will use matched fonts no matter the size.
It only supports TrueType fonts.

There are probably a lot more limitations, but I don't have the time figure them all out.

HackbrettXXX · 2020-12-18T15:03:43Z

Wow, thanks for this great PR! I will have a closer look at it as soon as I find the time ;)

allansson · 2020-12-28T08:56:27Z

There are four build errors (three in IE11 and 1 in Chrome).

* addImage: base64 validation in use with addImage-Call : 2 ok, 1 failed
* addImage: validateStringAsBase64 : 2 ok, 1 failed
* addImage: extractImageFromDataUrl : 2 ok, 1 failed
 ---
* renders font-faces : failed

I cannot figure out what's going wrong with the first three, since my changes haven't touched anything related to addImage.

The last one works on my computer. The only reason I can think of that would cause such a huge difference is that the fonts cannot be downloaded, making the algorithm choose the default fonts instead.

HackbrettXXX

The last one works on my computer. The only reason I can think of that would cause such a huge difference is that the fonts cannot be downloaded, making the algorithm choose the default fonts instead.

Yeah, that's odd. I get different results on my machine, as well. Seems like the fonts are correct, but the line height is computed differently. I assume html2canvas doesn't correctly pick up the fonts or the browser hasn't loaded the font yet when measuring the line height. I committed the file my PC creates, maybe that helps.

The errors in IE are probably due to non-es5 code in the src folder. Currently, we can't use es6, because the code is not transpiled. We should probably change this some time ;)

HackbrettXXX · 2021-01-12T15:16:18Z

src/libs/fontFace.js

@@ -0,0 +1,292 @@
+function toLookup(arr) {
+  return arr.reduce((lookup, name, index) => {


Can't use arrow functions. All code must be completely es5 compliant, since it is not transpiled (except for import/export statements).

HackbrettXXX · 2021-01-12T15:24:14Z

src/modules/context2d.js

+        if (this.fontFaces) {
+          var fontFaceMap = getFontFaceMap(this.pdf, this.fontFaces);
+
+          var rules = parts.map(ff => ({


no arrow functions ;)

Aarrgh... muscle memory you know. 😅

HackbrettXXX · 2021-01-12T15:28:12Z

src/modules/context2d.js

@@ -436,6 +525,23 @@ import { console } from "../libs/console.js";

        this.pdf.setFontSize(fontSize);

+        var parts = fontFamily.replace(/"|'/g, "").split(/\s*,\s*/);


I think this will fail if a font name contains a ",": e.g. `foo, "foo,bar", bar".

I have pushed a (mostly) proper parser for this, but I am a bit wary of it being too strict. 🤔

The string-split above matches the previous behaviour, so maybe it's best to keep that?

HackbrettXXX · 2021-01-12T15:35:56Z

src/modules/html.js

+        if (fontFaces) {
+          for (var i = 0; i < fontFaces.length; ++i) {
+            var font = fontFaces[i];
+            var src = font.src.find(src => src.format === "truetype");


arrow function ;)

HackbrettXXX · 2021-01-12T16:14:01Z

test/saucelabs/karma.conf.js

      {
        pattern: "test/**/*.+(svg|png|jpg|jpeg|ttf|txt)",
        included: false,
        served: true
      },
      {
-        pattern: "test/reference/**/*.pdf",
+        pattern: "test/reference/**/*.*",


don't think that's necessary. The *.ttf files should be served correctly by the previous rule.

This was more of a test to see if there was something weird going on with serving the fonts on saucelabs. I just copied the pattern from unit/karma.conf.js since it was working locally.

I'll revert it, but would you prefer that I do a git revert or git reset HEAD^ --hard?

Since it was just a test, I'll reset the commit. No point in having two unnecessary commits.

I'll squash the PR commits anyway when merging, so it won't make a difference in the end.

HackbrettXXX · 2021-01-12T16:20:47Z

test/specs/fontfaces.spec.mjs

+      it("should match exact weight when 500", () => {
+        const fontFaces = buildFontFaceMap([w300, w400, w500]);
+
+        const result = resolveFontFace(fontFaces, [w400]);


I think this should be w500, right?

Great catch!

HackbrettXXX · 2021-01-12T16:23:42Z

test/specs/fontfaces.spec.mjs

+        expect(result).toEqual(normalizeFontFace(w900));
+      });
+
+      it("should pick larger font-weight when no smaller is available", () => {


I think the description doesn't fit to the test case here.

Yeah, it should be the reverse: smaller font-weight when no larger is available. There's another test-case with the same name on line 227, and this is basically the inverse of that.

This reverts commit 8ff3cca.

HackbrettXXX

Thanks for implementing a better font family algorithm.

HackbrettXXX · 2021-01-14T10:29:00Z

src/libs/fontFace.js

+        return [input.substring(0, index), input.substring(index + 1)];
+
+      // Mismatching quote
+      case ",":


As far as I know "," is allowed within a font family name and not an error. At least the browser accepts it, e.g.

font-family: "comma,comma", sans-serif;

Fixed! Thanks for pointing out my brain fart!

HackbrettXXX · 2021-01-14T10:35:38Z

src/libs/fontFace.js

+  return result.map(function(f) {
+    return f.toLowerCase();
+  });


I think we should not call toLowerCase here, although technically this would be correct. The old font matching algorithm won't work anymore with lowercase font names, since jsPDF stores the fonts case sensitive. The test case Context2D: standard tests > context2d: custom fonts currently fails because of that. I think we should move the toLowerCase call to the context2d font property:

if (this.fontFaces) { parts = parts.map(function(f) { return f.toLowerCase(); } // ... }

Fixed this as well. Thanks for being so thorough!

HackbrettXXX · 2021-01-14T11:02:07Z

I found out what made the AMD test fail: due to the asynchronous loading of the html2canvas module with AMD require, the browser has time to load the fonts leading to different scroll heights of the div. In all the other tests, html2canvas is already loaded in a global variable, so the browser has no time to load the fonts.

I set the div to fixed dimensions as a workaround.

HackbrettXXX · 2021-01-14T15:14:12Z

Alright, I think it's fine now. I'll merge it as soon as CI is done. Thanks again for this awesome pull request!

allansson · 2021-01-14T16:48:21Z

Alright, I think it's fine now. I'll merge it as soon as CI is done. Thanks again for this awesome pull request!

And thank you for a great code review!

allansson added 5 commits January 8, 2021 10:25

add prettier config to ensure formatting in editors

e11d663

Fix missing parenthesis when invoking toLowerCase

329c82f

Add CSS font matching algorithm when rendering html

16f8b53

[fix] fix unused imports

c24053b

serve fonts when running tests in saucelabs

8ff3cca

allansson force-pushed the master branch from aa6e4d7 to 8ff3cca Compare January 8, 2021 09:25

update html-font-faces reference

0c7fafa

HackbrettXXX requested changes Jan 12, 2021

View reviewed changes

allansson added 4 commits January 13, 2021 16:08

Revert "serve fonts when running tests in saucelabs"

43ea15c

This reverts commit 8ff3cca.

remove arrow functions

64127ef

fix some copy paste errors in test cases for fontfaces

8204a5c

improve logic for parsing font family strings

5e5cf96

allansson force-pushed the master branch from 5e5cf96 to 8204a5c Compare January 13, 2021 16:38

HackbrettXXX requested changes Jan 14, 2021

View reviewed changes

make html font faces test-amd work

efa3331

allansson and others added 5 commits January 14, 2021 13:07

allow commas in font family names

075449c

don't lowercase font-family names

dbe57f2

change html-font-faces.pdf to make it easier to spot mismatches in fonts

28a28d0

update html-font-faces reference

f0fd7c6

Merge branch 'master' into master

5ad9914

HackbrettXXX approved these changes Jan 14, 2021

View reviewed changes

HackbrettXXX merged commit 6579099 into parallax:master Jan 14, 2021

This was referenced Mar 10, 2021

Bump jspdf from 1.5.3 to 2.3.1 in /frontend digital-bauhaus/Ferienpass#229

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Resolve fonts using CSS Level 3 algorithm when using html() #3040

Resolve fonts using CSS Level 3 algorithm when using html() #3040

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allansson commented Jan 14, 2021

		@@ -0,0 +1,292 @@
		function toLookup(arr) {
		return arr.reduce((lookup, name, index) => {

		@@ -436,6 +525,23 @@ import { console } from "../libs/console.js";

		this.pdf.setFontSize(fontSize);

		var parts = fontFamily.replace(/"\|'/g, "").split(/\s,\s/);

Resolve fonts using CSS Level 3 algorithm when using html() #3040

Resolve fonts using CSS Level 3 algorithm when using html() #3040

Conversation

allansson commented Dec 17, 2020

Issue

Feature

Limitations

HackbrettXXX commented Dec 18, 2020

allansson commented Dec 28, 2020 • edited Loading

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HackbrettXXX commented Jan 14, 2021

HackbrettXXX commented Jan 14, 2021

allansson commented Jan 14, 2021

allansson commented Dec 28, 2020 •

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