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Position text relative to baseline #2109

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merged 2 commits into from
Jul 11, 2021
Merged

Position text relative to baseline #2109

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26ab018
Merge pull request #1 from niklasvh/master
Jan 11, 2020
6e2866e
fix: use baseline for text positioning
Jan 12, 2020
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36 changes: 26 additions & 10 deletions src/render/canvas/canvas-renderer.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -140,13 +140,13 @@ export class CanvasRenderer {
}
}

renderTextWithLetterSpacing(text: TextBounds, letterSpacing: number) {
renderTextWithLetterSpacing(text: TextBounds, letterSpacing: number, baseline: number) {
if (letterSpacing === 0) {
this.ctx.fillText(text.text, text.bounds.left, text.bounds.top + text.bounds.height);
this.ctx.fillText(text.text, text.bounds.left, text.bounds.top + baseline);
} else {
const letters = toCodePoints(text.text).map(i => fromCodePoint(i));
letters.reduce((left, letter) => {
this.ctx.fillText(letter, left, text.bounds.top + text.bounds.height);
this.ctx.fillText(letter, left, text.bounds.top + baseline);

return left + this.ctx.measureText(letter).width;
}, text.bounds.left);
Expand All @@ -173,10 +173,13 @@ export class CanvasRenderer {
const [font, fontFamily, fontSize] = this.createFontStyle(styles);

this.ctx.font = font;
this.ctx.textBaseline = 'alphabetic';

const {baseline, middle} = this.fontMetrics.getMetrics(fontFamily, fontSize);

text.textBounds.forEach(text => {
this.ctx.fillStyle = asString(styles.color);
this.renderTextWithLetterSpacing(text, styles.letterSpacing);
this.renderTextWithLetterSpacing(text, styles.letterSpacing, baseline);
const textShadows: TextShadow = styles.textShadow;

if (textShadows.length && text.text.trim().length) {
Expand Down Expand Up @@ -206,7 +209,6 @@ export class CanvasRenderer {
// Draws a line at the baseline of the font
// TODO As some browsers display the line as more than 1px if the font-size is big,
// need to take that into account both in position and size
const {baseline} = this.fontMetrics.getMetrics(fontFamily, fontSize);
this.ctx.fillRect(
text.bounds.left,
Math.round(text.bounds.top + baseline),
Expand All @@ -220,7 +222,6 @@ export class CanvasRenderer {
break;
case TEXT_DECORATION_LINE.LINE_THROUGH:
// TODO try and find exact position for line-through
const {middle} = this.fontMetrics.getMetrics(fontFamily, fontSize);
this.ctx.fillRect(
text.bounds.left,
Math.ceil(text.bounds.top + middle),
Expand Down Expand Up @@ -363,7 +364,10 @@ export class CanvasRenderer {
}

if (isTextInputElement(container) && container.value.length) {
[this.ctx.font] = this.createFontStyle(styles);
const [fontFamily, fontSize] = this.createFontStyle(styles);
const {baseline} = this.fontMetrics.getMetrics(fontFamily, fontSize);

this.ctx.font = fontFamily;
this.ctx.fillStyle = asString(styles.color);

this.ctx.textBaseline = 'middle';
Expand Down Expand Up @@ -393,7 +397,11 @@ export class CanvasRenderer {
]);

this.ctx.clip();
this.renderTextWithLetterSpacing(new TextBounds(container.value, textBounds), styles.letterSpacing);
this.renderTextWithLetterSpacing(
new TextBounds(container.value, textBounds),
styles.letterSpacing,
baseline
);
this.ctx.restore();
this.ctx.textBaseline = 'bottom';
this.ctx.textAlign = 'left';
Expand All @@ -413,7 +421,9 @@ export class CanvasRenderer {
}
}
} else if (paint.listValue && container.styles.listStyleType !== LIST_STYLE_TYPE.NONE) {
[this.ctx.font] = this.createFontStyle(styles);
const [fontFamily, fontSize] = this.createFontStyle(styles);

this.ctx.font = fontFamily;
this.ctx.fillStyle = asString(styles.color);

this.ctx.textBaseline = 'middle';
Expand All @@ -425,7 +435,13 @@ export class CanvasRenderer {
computeLineHeight(styles.lineHeight, styles.fontSize.number) / 2 + 1
);

this.renderTextWithLetterSpacing(new TextBounds(paint.listValue, bounds), styles.letterSpacing);
const {baseline} = this.fontMetrics.getMetrics(fontFamily, fontSize);

this.renderTextWithLetterSpacing(
new TextBounds(paint.listValue, bounds),
styles.letterSpacing,
baseline
);
this.ctx.textBaseline = 'bottom';
this.ctx.textAlign = 'left';
}
Expand Down