Text Width / Height Measurement

About 2 min

Text Width / Height Measurement

Automatic drawing often needs the laid-out size of text before placing table rows, columns, or blocks. WebCAD provides local WASM measurement and server-side ODA measurement.

Online Examples

Example	Description	Link
Text size	`measureTextLocal` / `measureTexts` local vs server	Online Demo{target="_blank"}
Measure text (template)	Same batch measured locally and on the server	Online Demo{target="_blank"}

API Overview

API	Description
`measureTextLocal(item)`	Sync local measure of one item; returns `null` if WASM/fonts are not ready
`measureTextsLocal(items)`	Sync batch local measure
`measureTextsOnServer(mapid, version, items)`	Batch server measure against a template
`measureTexts(items, options?)`	Unified entry; default `mode: 'auto'` routes by source

const {
    measureTextLocal,
    measureTexts,
    measureTextsOnServer
} = vjcad;

Local Measurement

Does not add entities to the drawing or wait for a render frame:

const size = measureTextLocal({
    type: 'TEXT',
    text: 'WebCAD',
    height: 8,
    styleName: 'Standard'
});

if (!size) {
    // WASM not initialized, or no fonts loaded via MainView.fonts
    return;
}

console.log(size.width, size.height, size.bounds, size.isFallbackFont);

For MTEXT, pass column width width (same meaning as entity width):

const m = measureTextLocal({
    type: 'MTEXT',
    text: 'Multiline text wraps by column width',
    height: 3,
    width: 120
});

Lay out by measured widths

const tags = ['Layer', 'Linetype', 'Color'];
const sizes = await measureTexts(
    tags.map(text => ({ type: 'TEXT', text, height: 8 })),
    { mode: 'local' }
);

let x = 0;
tags.forEach((text, i) => {
    const w = sizes[i]?.width ?? 0;
    x += w + 4;
});

Unified Entry: measureTexts

const results = await measureTexts([
    // With clone source → server in auto mode (real template fonts)
    {
        text: 'Silty clay',
        height: 2.5,
        width: 30,
        cloneSource: 'clone_96BA_template_sect_v1'
    },
    // No clone source → local WASM
    { text: 'Plain text', height: 3, type: 'TEXT', styleName: 'Standard' }
], {
    mode: 'auto' // 'auto' | 'local' | 'server'
});

Options `ITextMeasureOptions`

Field	Description
`mode`	`'auto'` (default) / `'local'` / `'server'`
`mapid`	Default template map id when `mode: 'server'`
`version`	Default template version, `'v1'`

Result fields

Field	Description
`width` / `height`	Laid-out size; MTEXT `height` is logical height summed per line
`geomWidth` / `geomHeight`	Content bounding-box size (use to hug the glyphs)
`bounds`	`[minX, minY, maxX, maxY]` relative to insertion point
`source`	`'local'` or `'server'`
`isFallbackFont`	Local measure fell back to another font — treat as approximate

Failed items return null without aborting the batch.

Template DWG fonts (FangSong, SimSun, …) are usually not in MainView.fonts. Local resolveFontForName silently falls back; CJK widths may be close, but Latin/punctuation differences change wrapping and thus height. The server lays out with ODA on the real DWG (OdDbMText::actualWidth() / actualHeight()), matching exported DWG.

const server = await measureTextsOnServer('template_sect', 'v1', [
    { handle: '96BA', text: 'Silty clay', height: 2.5, width: 30 }
]);

Requires the backend measureText command. Server batches in measureTexts are grouped by template (few round-trips).

Notes

Local measure needs WASM initialized and at least one font from MainView.fonts
Do not use isFallbackFont === true results for precise published layouts
See Template Drawing for clone-based server measure