Automattic/node-canvas

fontBoundingBox is not implemented

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#1,940 opened on 2021年11月29日

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 (1 comment) (2 reactions) (0 assignees)JavaScript (9,524 stars) (1,140 forks)batch import
Help wantedText & Fonts

説明

Issue or Feature

Hi! I was expecting to use fontBoundingBox, but as it turns out there's a TODO in code left and it isn't done. I saw some PR's that said it couldn't be done. Could there be some kind of resolution or workaround to experience the same effect as fontBoundingBox?

In the visible image, I would like to get the blue part. (fontBoundingBox) image

Steps to Reproduce

import Canvas from 'canvas';

const canvas = Canvas.createCanvas(10, 10);

const ctx = canvas.getContext('2d')
const measure = ctx.measureText("woohoo!");

console.log(measure.fontBoundingBoxAscent) // undefined :(

Your Environment

  • Version of node-canvas (output of npm list canvas or yarn list canvas): canvas@2.8.0
  • Environment (e.g. node 4.2.0 on Mac OS X 10.8): v16.4.2 on Windows

コントリビューターガイド

技術スタック
javascript
領域
api
Issue 種別
feature
難度新しい貢献者にとっての実装難度です。1 は非常に小さな変更、5 は専門的な作業です。
4
推定時間経験ある貢献者が調査、実装、テスト、pull request 準備にかけるおおよその時間範囲です。
over 1 week
活動状況Issue が今どれだけ取り組みやすいかを示します。新しい、活発、古い、ブロック中、またはメンテナー入力待ちなどです。
stale
明確さ期待される変更、受け入れ条件、次の手順がどれだけ明確かを示します。
needs investigation
前提条件
Basic C++ knowledgeUnderstanding of Node.js native addonsFamiliarity with Cairo library
初心者向け度初回貢献者にどれだけ取り組みやすいかを 1-100 で推定したスコアです。
20
調査方針
The issue requests the implementation of fontBoundingBox property in the CanvasRenderingContext2D. The TODO is likely in the C++ binding code for the measureText function. Start by examining the current measureText implementation in src/Canvas.cc or similar. Previous PRs attempting this may have discussions about limitations. Investigate the Cairo API for font metrics and how to expose them. The maintainers have not responded, so consider asking for clarification on the desired behavior and any prior attempts.