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Better smoothing of resolution and center constraints

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Previously the formula for the resolution constraint allowed going way past
the minimum zoom.
Also adjusted the center constraint to avoid a zigzag effect when going out
of resolution bounds.
This commit is contained in:
Olivier Guyot
2019-02-25 23:12:39 +01:00
parent f67baa0dc0
commit 447266cbe8
2 changed files with 24 additions and 9 deletions
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22
src/ol/centerconstraint.js
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@@ -29,12 +29,22 @@ export function createExtent(extent, onlyCenter, smooth) {
if (center) { if (center) {
const viewWidth = onlyCenter ? 0 : size[0] * resolution; const viewWidth = onlyCenter ? 0 : size[0] * resolution;
const viewHeight = onlyCenter ? 0 : size[1] * resolution; const viewHeight = onlyCenter ? 0 : size[1] * resolution;
const minX = extent[0] + viewWidth / 2; let minX = extent[0] + viewWidth / 2;
const maxX = extent[2] - viewWidth / 2; let maxX = extent[2] - viewWidth / 2;
const minY = extent[1] + viewHeight / 2; let minY = extent[1] + viewHeight / 2;
const maxY = extent[3] - viewHeight / 2; let maxY = extent[3] - viewHeight / 2;
let x = minX > maxX ? (maxX + minX) / 2 : clamp(center[0], minX, maxX);
let y = minY > maxY ? (maxY + minY) / 2 : clamp(center[1], minY, maxY); // note: when zooming out of bounds, min and max values for x and y may
// end up inverted (min > max); this has to be accounted for
if (minX > maxX) {
minX = maxX = (maxX + minX) / 2;
}
if (minY > maxY) {
minY = maxY = (maxY + minY) / 2;
}
let x = clamp(center[0], minX, maxX);
let y = clamp(center[1], minY, maxY);
const ratio = 30 * resolution; const ratio = 30 * resolution;
// during an interaction, allow some overscroll // during an interaction, allow some overscroll

11
src/ol/resolutionconstraint.js
View File

@@ -27,6 +27,10 @@ function getViewportClampedResolution(resolution, maxExtent, viewportSize) {
/** /**
* Returns a modified resolution to be between maxResolution and minResolution while * Returns a modified resolution to be between maxResolution and minResolution while
* still allowing the value to be slightly out of bounds. * still allowing the value to be slightly out of bounds.
* Note: the computation is based on the logarithm function (ln):
* - at 1, ln(x) is 0
* - above 1, ln(x) keeps increasing but at a much slower pace than x
* The final result is clamped to prevent getting too far away from bounds.
* @param {number} resolution Resolution. * @param {number} resolution Resolution.
* @param {number} maxResolution Max resolution. * @param {number} maxResolution Max resolution.
* @param {number} minResolution Min resolution. * @param {number} minResolution Min resolution.
@@ -34,13 +38,14 @@ function getViewportClampedResolution(resolution, maxExtent, viewportSize) {
*/ */
function getSmoothClampedResolution(resolution, maxResolution, minResolution) { function getSmoothClampedResolution(resolution, maxResolution, minResolution) {
let result = Math.min(resolution, maxResolution); let result = Math.min(resolution, maxResolution);
const ratio = 50;
result *= Math.log(Math.max(1, resolution / maxResolution)) * 0.1 + 1; result *= Math.log(1 + ratio * Math.max(0, resolution / maxResolution - 1)) / ratio + 1;
if (minResolution) { if (minResolution) {
result = Math.max(result, minResolution); result = Math.max(result, minResolution);
result /= Math.log(Math.max(1, minResolution / resolution)) * 0.1 + 1; result /= Math.log(1 + ratio * Math.max(0, minResolution / resolution - 1)) / ratio + 1;
} }
return result; return clamp(result, minResolution / 2, maxResolution * 2);
} }
/** /**