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Make zoom speed independent of event granularity

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Before, touchpads would give "smoother" scrolling by delivering lots of
mousewheel events with small distance changes. Because the code only
looked at the sign of deltaY, ten 5px scrolls would zoom 10x more than
one 50px scroll.

This change makes zooming with a touchpad more like zooming with a
mousewheel. On my laptop, a full-scale zoom (fully out to fully in) was
about a 5mm finger movement before, and is now about 3cm.

Fixes #758.
This commit is contained in:
Rodrigo Queiro
2016-12-09 10:55:44 +01:00
parent 30a4a1930f
commit 8384f8fe05
1 changed files with 7 additions and 4 deletions
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11
core/workspace_svg.js
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@@ -882,7 +882,9 @@ Blockly.WorkspaceSvg.prototype.isDragging = function() {
Blockly.WorkspaceSvg.prototype.onMouseWheel_ = function(e) {
// TODO: Remove terminateDrag and compensate for coordinate skew during zoom.
Blockly.terminateDrag_();
var delta = e.deltaY > 0 ? -1 : 1;
// The vertical scroll distance that corresponds to a click of a zoom button.
const PIXELS_PER_ZOOM_STEP = 50;
var delta = -e.deltaY / PIXELS_PER_ZOOM_STEP;
var position = Blockly.utils.mouseToSvg(e, this.getParentSvg(),
this.getInverseScreenCTM());
this.zoom(position.x, position.y, delta);
@@ -1219,9 +1221,10 @@ Blockly.WorkspaceSvg.prototype.markFocused = function() {
* Zooming the blocks centered in (x, y) coordinate with zooming in or out.
* @param {number} x X coordinate of center.
* @param {number} y Y coordinate of center.
* @param {number} type Type of zooming (-1 zooming out and 1 zooming in).
* @param {number} amount Amount of zooming
* (negative zooms out and positive zooms in).
*/
Blockly.WorkspaceSvg.prototype.zoom = function(x, y, type) {
Blockly.WorkspaceSvg.prototype.zoom = function(x, y, amount) {
var speed = this.options.zoomOptions.scaleSpeed;
var metrics = this.getMetrics();
var center = this.getParentSvg().createSVGPoint();
@@ -1232,7 +1235,7 @@ Blockly.WorkspaceSvg.prototype.zoom = function(x, y, type) {
y = center.y;
var canvas = this.getCanvas();
// Scale factor.
var scaleChange = (type == 1) ? speed : 1 / speed;
var scaleChange = Math.pow(speed, amount);
// Clamp scale within valid range.
var newScale = this.scale * scaleChange;
if (newScale > this.options.zoomOptions.maxScale) {