Sakurai/pdf.js
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Don't scale single-char text divs.

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This change makes scrolling noticeably smoother on files with many
single-char text divs, such as the one in #1045. The trade-off is that
the visual appearance of text selection in such documents is slightly
worse, because more text divs overlap.

This change also uses `scaleX(N)` instead of `scale(N, 1)`. This might
be marginally more efficient in terms of JS string concatenation.
This commit is contained in:
Nicholas Nethercote 2014-08-20 19:08:15 -07:00
parent b4fb1e21e7
commit cd61aad24f
1 changed files with 20 additions and 8 deletions
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28
web/text_layer_builder.js
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@ -83,14 +83,21 @@ var TextLayerBuilder = (function TextLayerBuilderClosure() {
var width = ctx.measureText(textDiv.textContent).width;
if (width > 0) {
textLayerFrag.appendChild(textDiv);
// Dataset values come of type string.
var textScale = textDiv.dataset.canvasWidth / width;
var transform;
if (textDiv.dataset.canvasWidth !== undefined) {
// Dataset values come of type string.
var textScale = textDiv.dataset.canvasWidth / width;
transform = 'scaleX(' + textScale + ')';
} else {
transform = '';
}
var rotation = textDiv.dataset.angle;
var transform = 'scale(' + textScale + ', 1)';
if (rotation) {
transform = 'rotate(' + rotation + 'deg) ' + transform;
}
CustomStyle.setProp('transform' , textDiv, transform);
if (transform) {
CustomStyle.setProp('transform' , textDiv, transform);
}
}
}
@ -165,10 +172,15 @@ var TextLayerBuilder = (function TextLayerBuilderClosure() {
if (angle !== 0) {
textDiv.dataset.angle = angle * (180 / Math.PI);
}
if (style.vertical) {
textDiv.dataset.canvasWidth = geom.height * this.viewport.scale;
} else {
textDiv.dataset.canvasWidth = geom.width * this.viewport.scale;
// We don't bother scaling single-char text divs, because it has very
// little effect on text highlighting. This makes scrolling on docs with
// lots of such divs a lot faster.
if (textDiv.textContent.length > 1) {
if (style.vertical) {
textDiv.dataset.canvasWidth = geom.height * this.viewport.scale;
} else {
textDiv.dataset.canvasWidth = geom.width * this.viewport.scale;
}
}
},