parallax/jsPDF

context2d initial property values are not applied

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#3319 opened on Nov 16, 2021

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Bugdifficulty:mediumhelp wanted

Description

Example borrowed from #2701:

var doc = new jsPDF()
var ctx = doc.context2d
ctx.strokeText(`font: ${ctx.font}, line: ${ctx.lineWidth}`, 10, 10)
ctx.font = ctx.font // font size is changed(16px → 10px)
ctx.strokeText(`font: ${ctx.font}, line: ${ctx.lineWidth}`, 10, 20)
ctx.lineWidth = ctx.lineWidth // line width is changed(0.2px → 1px)
ctx.strokeText(`font: ${ctx.font}, line: ${ctx.lineWidth}`, 10, 30)

The same thing happens after manually switching or creating pages with addPage or setPage.

A correct solution would probably check if the current document state is the same as the context2d state and if not would apply the properties that are different before executing a command like fill, fillText, stroke, etc.

Contributor guide

Tech stack
javascript
Domain
frontend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
JavaScriptjsPDF basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
Investigate the context2d implementation in jsPDF, specifically the initialization of properties like font and lineWidth. The issue highlights that setting a property to its current value changes the value, indicating a state mismatch. Look at the context2d plugin code, likely in files like `src/plugins/context2d.js`, to understand how state is managed. The suggested solution is to compare the current document state with the context2d state before executing drawing commands. Examine methods like `fill`, `stroke`, `fillText`, and `strokeText` to see where to apply this check.