auto width

web/index.html

@@ -31,9 +31,13 @@
     <label for="canvas-width">Width</label>
     <input type="number" min="0" id="canvas-width" value="300">
     <select id="canvas-width-unit">
-        <option value="px" selected>px</option>
+        <option value="px">px</option>
         <option value="mm">mm</option>
+        <option value="auto" selected="selected">Auto</option>
     </select>
+    <span id="autoHelp">
+        Note: only left aligned elements are taking into account for determining the width.
+    </span>
 </p>
 <div id='tape'>
     <canvas id="preview" height="32" width="300"></canvas>

web/label.js

@@ -10,6 +10,7 @@ const addImageButton = document.getElementById('add-image');
 const printButton = document.getElementById('print');
 const widthInput = document.getElementById('canvas-width');
 const widthUnit = document.getElementById('canvas-width-unit');
+const autoHelp = document.getElementById('autoHelp');
 
 let tapeWidthMM = 0;
 let defaultFontSize = 24;
@@ -215,23 +216,29 @@ const getElements = () => {
     let rows = elementsTableBody.getElementsByTagName('tr');
     let elements = [];
     for (let row of rows) {
+        let size = parseInt(row.querySelector('.size input').value, 10);
+        let x =  parseInt(row.querySelector('.pos_x').value, 10);
+        let y = parseInt(row.querySelector('.pos_y').value, 10);
+        let base = row.querySelector('.pos_base').value;
         if (row.dataset.type === 'text') {
+            let text = row.querySelector('.text input').value;
             elements.push({
                 type: 'text',
-                text: row.querySelector('.text input').value,
-                size: parseInt(row.querySelector('.size input').value, 10),
-                x: parseInt(row.querySelector('.pos_x').value, 10),
-                y: parseInt(row.querySelector('.pos_y').value, 10),
-                base: row.querySelector('.pos_base').value,
+                text, size, x, y, base,
+                width: (renderCtx) => {
+                    renderCtx.font = `${size}px serif`;
+                    let textSize = renderCtx.measureText(text);
+                    return textSize.width;
+                }
             });
         } else if (row.dataset.type === 'image') {
+            let image = row.getElementsByTagName('img')[0];
+            let ratio = image.naturalWidth /  image.naturalHeight;
+            let width = size * ratio;
             elements.push({
                 type: 'image',
-                image: row.getElementsByTagName('img')[0],
-                size: parseInt(row.querySelector('.size input').value, 10),
-                x: parseInt(row.querySelector('.pos_x').value, 10),
-                y: parseInt(row.querySelector('.pos_y').value, 10),
-                base: row.querySelector('.pos_base').value,
+                image, size, x, y, base,
+                width: (_renderCtx) => width,
             });
         }
     }
@@ -240,6 +247,15 @@ const getElements = () => {
 
 const render = () => {
     let elements = getElements();
+    if (widthUnit.value === "auto") {
+        let autoWidth = 20;
+        for (let element of elements) {
+            if (element.base === 'left') {
+                autoWidth = Math.max(autoWidth, element.x + element.width(renderCtx));
+            }
+        }
+        preview.width = autoWidth;
+    }
     let width = preview.width;
     let height = preview.height;
     renderCtx.filter = '';
@@ -248,19 +264,18 @@ const render = () => {
 
     renderCtx.fillStyle = textColor;
     for (let element of elements) {
+        let width = element.width(renderCtx);
         if (element.type === 'text') {
             renderCtx.filter = '';
             renderCtx.font = `${element.size}px serif`;
             let textSize = renderCtx.measureText(element.text);
             let textHeight = textSize.fontBoundingBoxAscent - textSize.emHeightDescent;
-            renderCtx.fillText(element.text, calcX(element.base, element.x, textSize.width), element.y + textHeight);
+            renderCtx.fillText(element.text, calcX(element.base, element.x, width), element.y + textHeight);
         } else if (element.type === 'image' && element.image.naturalWidth > 0) {
             renderCtx.filter = 'grayscale() saturate(0%) brightness(70%) contrast(1000%)';
             if (textColor === 'white') {
                 renderCtx.filter = renderCtx.filter + ' invert()';
             }
-            let ratio = element.image.naturalWidth /  element.image.naturalHeight;
-            let width = element.size * ratio;
             renderCtx.drawImage(element.image, calcX(element.base, element.x, width), element.y, width, element.size);
         }
     }
@@ -268,7 +283,6 @@ const render = () => {
 
 const calcX = (base, x, width) => {
     let imageWidth = preview.width;
-    console.log(base, x, width, imageWidth);
     switch (base) {
         case 'left':
             return x;
@@ -313,10 +327,21 @@ widthUnit.addEventListener('change', () => {
     const pxPerMM = preview.height / tapeWidthMM;
     if (widthUnit.value === "mm") {
         widthInput.value = (preview.width / pxPerMM).toFixed(0);
-    } else {
+        widthInput.disabled = null;
+        widthInput.hidden = false;
+        autoHelp.classList.remove('show');
+    } else if (widthUnit.value === "px") {
         widthInput.value = preview.width;
+        widthInput.hidden = false;
+        widthInput.disabled = null;
+        autoHelp.classList.remove('show');
+    } else {
+        widthInput.disabled = "disabled";
+        widthInput.hidden = true;
+        autoHelp.classList.add('show');
     }
 });
+widthUnit.dispatchEvent(new Event('change'));
 
 const apiRoot = "";
 

web/style.css

@@ -86,4 +86,11 @@ input {
     display: inline-block;
     width: auto;
     background: var(--margin-color);
+}
+
+#autoHelp {
+    display: none;
+    &.show {
+        display: inline;
+    }
 }