waveterm/src/textmeasure.ts

import {boundInt} from "./util";

const MinTermCols = 10;
const MaxTermCols = 1024;

let MonoFontSizes : {height : number, width : number}[] = [];

// MonoFontSizes[8] = {height: 11, width: 4.797};
// MonoFontSizes[9] = {height: 12, width: 5.398};
// MonoFontSizes[10] = {height: 13, width: 6};
// MonoFontSizes[11] = {height: 15, width: 6.602};
// MonoFontSizes[12] = {height: 16, width: 7.203};
// MonoFontSizes[13] = {height: 18, width: 7.797};
// MonoFontSizes[14] = {height: 19, width: 8.398};
// MonoFontSizes[15] = {height: 20, width: 9};
// MonoFontSizes[16] = {height: 22, width: 9.594};

function getMonoFontSize(fontSize : number) : {height : number, width : number} {
    if (MonoFontSizes[fontSize] != null) {
        return MonoFontSizes[fontSize];
    }
    let size = measureText("W", {pre: true, mono: true, fontSize: fontSize});
    if (size.height != 0 && size.width != 0) {
        MonoFontSizes[fontSize] = size;
    }
    return size;
}

function measureText(text : string, textOpts? : {pre? : boolean, mono? : boolean, fontSize? : number|string}) : {height : number, width : number} {
    if (textOpts == null) {
        textOpts = {};
    }
    let textElem = document.createElement("span");
    if (textOpts.pre) {
        textElem.classList.add("pre");
    }
    if (textOpts.mono) {
        textElem.classList.add("mono");
    }
    if (textOpts.fontSize != null) {
        if (typeof(textOpts.fontSize) == "number") {
            textElem.style.fontSize = textOpts.fontSize + "px";
        }
        else {
            textElem.style.fontSize = textOpts.fontSize;
        }
    }
    textElem.innerText = text;
    let measureDiv = document.getElementById("measure");
    if (measureDiv == null) {
        throw new Error("cannot measure text, no #measure div");
    }
    measureDiv.replaceChildren(textElem);
    let rect = textElem.getBoundingClientRect()
    return {width: rect.width, height: Math.ceil(rect.height)};
}

function windowWidthToCols(width : number, fontSize : number) : number {
    let dr = getMonoFontSize(fontSize);
    let cols = Math.trunc((width - 50) / dr.width) - 1;
    cols = boundInt(cols, MinTermCols, MaxTermCols);
    return cols;
}

function windowHeightToRows(height : number, fontSize : number) : number {
    let dr = getMonoFontSize(fontSize);
    let rows = Math.floor((height - 80) / dr.height) - 1;
    if (rows <= 0) {
        rows = 1;
    }
    return rows;
}

function termWidthFromCols(cols : number, fontSize : number) : number {
    let dr = getMonoFontSize(fontSize);
    return Math.ceil(dr.width*cols) + 15;
}

function termHeightFromRows(rows : number, fontSize : number) : number {
    let dr = getMonoFontSize(fontSize);
    return Math.ceil(dr.height*rows);
}

export {measureText, getMonoFontSize, windowWidthToCols, windowHeightToRows, termWidthFromCols, termHeightFromRows};