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Support dynamically sized legend elements #9532

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Support dynamically sized legend elements #9532

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2 changes: 1 addition & 1 deletion src/helpers/helpers.canvas.js
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Original file line number Diff line number Diff line change
Expand Up @@ -135,7 +135,7 @@ export function drawPoint(ctx, options, x, y) {
ctx.save();
ctx.translate(x, y);
ctx.rotate(rad);
ctx.drawImage(style, -style.width / 2, -style.height / 2, style.width, style.height);
ctx.drawImage(style, 0, -style.height / 2, style.width, style.height);
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What's the reason for this change? When this function is normally called, x,y is the center of the point and thus the center of the image

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Centering the image looks to be done because there is an assumed (fixed) width where the image will exist.

With this approach, because the space for the legend image is identical to the size of the legend image itself, there's no need to center it.

Screenshot from 2021-08-11 13-39-22

That being said this was me hacking around and it resulted in no padding so centering might actually be a good idea if the "boxWidth" (legend icon width) is expected to include padding.

ctx.restore();
return;
}
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24 changes: 14 additions & 10 deletions src/plugins/plugin.legend.js
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Expand Up @@ -170,7 +170,9 @@ export class Legend extends Element {
let row = -1;
let top = -lineHeight;
me.legendItems.forEach((legendItem, i) => {
const itemWidth = boxWidth + (fontSize / 2) + ctx.measureText(legendItem.text).width;
const pointStyle = legendItem?.pointStyle;
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We are at es2018, so no optional chaining. Althought it looks like all the supported browsers already support optional chaining, we should wait for a major version before changing the env requirements.

const pointWidth = pointStyle?.offsetWidth || pointStyle?.width || boxWidth;
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Would make sense to render this to the DOM in a visibility: hidden element, get offsetWidth, then remove from dom

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I think we should avoid DOM manipulation.

const itemWidth = pointWidth + fontSize / 2 + ctx.measureText(legendItem.text).width;

if (i === 0 || lineWidths[lineWidths.length - 1] + itemWidth + 2 * padding > maxWidth) {
totalHeight += lineHeight;
Expand Down Expand Up @@ -202,7 +204,8 @@ export class Legend extends Element {
let col = 0;

me.legendItems.forEach((legendItem, i) => {
const itemWidth = boxWidth + (fontSize / 2) + ctx.measureText(legendItem.text).width;
const pointWidth = legendItem?.pointStyle?.offsetWidth || boxWidth;
const itemWidth = pointWidth + fontSize / 2 + ctx.measureText(legendItem.text).width;

// If too tall, go to new column
if (i > 0 && currentColHeight + itemHeight + 2 * padding > heightLimit) {
Expand Down Expand Up @@ -327,7 +330,7 @@ export class Legend extends Element {
// Recalculate x and y for drawPoint() because its expecting
// x and y to be center of figure (instead of top left)
const drawOptions = {
radius: boxWidth * Math.SQRT2 / 2,
radius: (legendItem.boxWidth) || boxWidth * Math.SQRT2 / 2,
pointStyle: legendItem.pointStyle,
rotation: legendItem.rotation,
borderWidth: lineWidth
Expand All @@ -340,8 +343,8 @@ export class Legend extends Element {
} else {
// Draw box as legend symbol
// Adjust position when boxHeight < fontSize (want it centered)
const yBoxTop = y + Math.max((fontSize - boxHeight) / 2, 0);
const xBoxLeft = rtlHelper.leftForLtr(x, boxWidth);
const yBoxTop = y + Math.max((fontSize - (legendItem.boxHeight || boxHeight)) / 2, 0);
const xBoxLeft = rtlHelper.leftForLtr(x, legendItem.boxWidth || boxWidth);
const borderRadius = toTRBLCorners(legendItem.borderRadius);

ctx.beginPath();
Expand All @@ -350,9 +353,9 @@ export class Legend extends Element {
addRoundedRectPath(ctx, {
x: xBoxLeft,
y: yBoxTop,
w: boxWidth,
h: boxHeight,
radius: borderRadius,
w: legendItem.boxWidth || boxWidth,
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What's the reason for this change?

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I found it unusual that boxWidth could be set for all legend items, but not an individual one.

Might just be me - can revert if needed 👍

h: legendItem.boxHeight || boxHeight,
radius: borderRadius
});
} else {
ctx.rect(xBoxLeft, yBoxTop, boxWidth, boxHeight);
Expand Down Expand Up @@ -401,7 +404,8 @@ export class Legend extends Element {

const textWidth = ctx.measureText(legendItem.text).width;
const textAlign = rtlHelper.textAlign(legendItem.textAlign || (legendItem.textAlign = labelOpts.textAlign));
const width = boxWidth + halfFontSize + textWidth;
const pointerWidth = legendItem.pointStyle?.offsetWidth || legendItem.pointStyle?.width || boxWidth;
const width = pointerWidth + halfFontSize + textWidth;
let x = cursor.x;
let y = cursor.y;

Expand All @@ -423,7 +427,7 @@ export class Legend extends Element {

drawLegendBox(realX, y, legendItem);

x = _textX(textAlign, x + boxWidth + halfFontSize, isHorizontal ? x + width : me.right, opts.rtl);
x = _textX(textAlign, x + pointerWidth + halfFontSize, isHorizontal ? x + width : me.right, opts.rtl);

// Fill the actual label
fillText(rtlHelper.x(x), y, legendItem);
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