Map API functions such as easeTo and flyTo now support padding: PaddingOptions which lets developers shift the center of perspective for a map when building floating sidebars.

Asymmetric viewport (mapbox#8638)


Co-authored-by: Vladimir Agafonkin <agafonkin@gmail.com>

Author: 2 people

src/geo/edge_insets.js

@@ -0,0 +1,102 @@
+// @flow
+import {number} from "../style-spec/util/interpolate";
+import Point  from "@mapbox/point-geometry";
+import {clamp} from "../util/util";
+
+/**
+ * An `EdgeInset` object represents screen space padding applied to the edges of the viewport.
+ * This shifts the apprent center or the vanishing point of the map. This is useful for adding floating UI elements
+ * on top of the map and having the vanishing point shift as UI elements resize.
+ *
+ * @param {number} [top=0]
+ * @param {number} [bottom=0]
+ * @param {number} [left=0]
+ * @param {number} [right=0]
+ */
+class EdgeInsets {
+    top: number;
+    bottom: number;
+    left: number;
+    right: number;
+
+    constructor(top: number = 0, bottom: number = 0, left: number = 0, right: number = 0) {
+        if (isNaN(top) || top < 0 ||
+            isNaN(bottom) || bottom < 0 ||
+            isNaN(left) || left < 0 ||
+            isNaN(right) || right < 0
+        ) {
+            throw new Error('Invalid value for edge-insets, top, bottom, left and right must all be numbers');
+        }
+
+        this.top = top;
+        this.bottom = bottom;
+        this.left = left;
+        this.right = right;
+    }
+
+    /**
+     * Interpolates the inset in-place.
+     * This maintains the current inset value for any inset not present in `target`.
+     *
+     * @param {PaddingOptions} target
+     * @param {number} t
+     * @returns {EdgeInsets}
+     * @memberof EdgeInsets
+     */
+    interpolate(start: PaddingOptions | EdgeInsets, target: PaddingOptions, t: number): EdgeInsets {
+        if (target.top != null && start.top != null) this.top = number(start.top, target.top, t);
+        if (target.bottom != null && start.bottom != null) this.bottom = number(start.bottom, target.bottom, t);
+        if (target.left != null && start.left != null) this.left = number(start.left, target.left, t);
+        if (target.right != null && start.right != null) this.right = number(start.right, target.right, t);
+
+        return this;
+    }
+
+    /**
+     * Utility method that computes the new apprent center or vanishing point after applying insets.
+     * This is in pixels and with the top left being (0.0) and +y being downwards.
+     *
+     * @param {number} width
+     * @param {number} height
+     * @returns {Point}
+     * @memberof EdgeInsets
+     */
+    getCenter(width: number, height: number): Point {
+        // Clamp insets so they never overflow width/height and always calculate a valid center
+        const x = clamp((this.left + width - this.right) / 2, 0, width);
+        const y = clamp((this.top + height - this.bottom) / 2, 0, height);
+
+        return new Point(x, y);
+    }
+
+    equals(other: PaddingOptions): boolean {
+        return this.top === other.top &&
+            this.bottom === other.bottom &&
+            this.left === other.left &&
+            this.right === other.right;
+    }
+
+    clone(): EdgeInsets {
+        return new EdgeInsets(this.top, this.bottom, this.left, this.right);
+    }
+
+    /**
+     * Returns the current sdtate as json, useful when you want to have a
+     * read-only representation of the inset.
+     *
+     * @returns {PaddingOptions}
+     * @memberof EdgeInsets
+     */
+    toJSON(): PaddingOptions {
+        return {
+            top: this.top,
+            bottom: this.bottom,
+            left: this.left,
+            right: this.right
+        };
+    }
+}
+
+export type PaddingOptions = {top: ?number, bottom: ?number, right: ?number, left: ?number};
+
+export default EdgeInsets;

src/geo/transform.js

@@ -9,8 +9,10 @@ import {number as interpolate} from '../style-spec/util/interpolate';
 import EXTENT from '../data/extent';
 import {vec4, mat4, mat2, vec2} from 'gl-matrix';
 import {Aabb, Frustum} from '../util/primitives.js';
+import EdgeInsets from './edge_insets';
 
 import {UnwrappedTileID, OverscaledTileID, CanonicalTileID} from '../source/tile_id';
+import type {PaddingOptions} from './edge_insets';
 
 /**
  * A single transform, generally used for a single tile to be
@@ -49,6 +51,7 @@ class Transform {
     _minPitch: number;
     _maxPitch: number;
     _center: LngLat;
+    _edgeInsets: EdgeInsets;
     _constraining: boolean;
     _posMatrixCache: {[string]: Float32Array};
     _alignedPosMatrixCache: {[string]: Float32Array};
@@ -74,6 +77,7 @@ class Transform {
         this._fov = 0.6435011087932844;
         this._pitch = 0;
         this._unmodified = true;
+        this._edgeInsets = new EdgeInsets();
         this._posMatrixCache = {};
         this._alignedPosMatrixCache = {};
     }
@@ -90,6 +94,7 @@ class Transform {
         clone._fov = this._fov;
         clone._pitch = this._pitch;
         clone._unmodified = this._unmodified;
+        clone._edgeInsets = this._edgeInsets.clone();
         clone._calcMatrices();
         return clone;
     }
@@ -137,8 +142,8 @@ class Transform {
         return this.tileSize * this.scale;
     }
 
-    get centerPoint(): Point {
-        return this.size._div(2);
+    get centerOffset(): Point {
+        return this.centerPoint._sub(this.size._div(2));
     }
 
     get size(): Point {
@@ -204,6 +209,52 @@ class Transform {
         this._calcMatrices();
     }
 
+    get padding(): PaddingOptions { return this._edgeInsets.toJSON(); }
+    set padding(padding: PaddingOptions) {
+        if (this._edgeInsets.equals(padding)) return;
+        this._unmodified = false;
+        //Update edge-insets inplace
+        this._edgeInsets.interpolate(this._edgeInsets, padding, 1);
+        this._calcMatrices();
+    }
+
+    /**
+     * The center of the screen in pixels with the top-left corner being (0,0)
+     * and +y axis pointing downwards. This accounts for padding.
+     *
+     * @readonly
+     * @type {Point}
+     * @memberof Transform
+     */
+    get centerPoint(): Point {
+        return this._edgeInsets.getCenter(this.width, this.height);
+    }
+
+    /**
+     * Returns if the padding params match
+     *
+     * @param {PaddingOptions} padding
+     * @returns {boolean}
+     * @memberof Transform
+     */
+    isPaddingEqual(padding: PaddingOptions): boolean {
+        return this._edgeInsets.equals(padding);
+    }
+
+    /**
+     * Helper method to upadte edge-insets inplace
+     *
+     * @param {PaddingOptions} target
+     * @param {number} t
+     * @memberof Transform
+     */
+    interpolatePadding(start: PaddingOptions, target: PaddingOptions, t: number) {
+        this._unmodified = false;
+        this._edgeInsets.interpolate(start, target, t);
+        this._constrain();
+        this._calcMatrices();
+    }
+
     /**
      * Return a zoom level that will cover all tiles the transform
      * @param {Object} options
@@ -281,9 +332,10 @@ class Transform {
         const centerPoint = [numTiles * centerCoord.x, numTiles * centerCoord.y, 0];
         const cameraFrustum = Frustum.fromInvProjectionMatrix(this.invProjMatrix, this.worldSize, z);
 
-        // No change of LOD behavior for pitch lower than 60: return only tile ids from the requested zoom level
+        // No change of LOD behavior for pitch lower than 60 and when there is no top padding: return only tile ids from the requested zoom level
         let minZoom = options.minzoom || 0;
-        if (this.pitch <= 60.0)
+        // Use 0.1 as an epsilon to avoid for explicit == 0.0 floating point checks
+        if (this.pitch <= 60.0 && this._edgeInsets.top < 0.1)
             minZoom = z;
 
         // There should always be a certain number of maximum zoom level tiles surrounding the center location
@@ -616,15 +668,17 @@ class Transform {
     _calcMatrices() {
         if (!this.height) return;
 
-        this.cameraToCenterDistance = 0.5 / Math.tan(this._fov / 2) * this.height;
+        const halfFov = this._fov / 2;
+        const offset = this.centerOffset;
+        this.cameraToCenterDistance = 0.5 / Math.tan(halfFov) * this.height;
 
-        // Find the distance from the center point [width/2, height/2] to the
-        // center top point [width/2, 0] in Z units, using the law of sines.
+        // Find the distance from the center point [width/2 + offset.x, height/2 + offset.y] to the
+        // center top point [width/2 + offset.x, 0] in Z units, using the law of sines.
         // 1 Z unit is equivalent to 1 horizontal px at the center of the map
         // (the distance between[width/2, height/2] and [width/2 + 1, height/2])
-        const halfFov = this._fov / 2;
         const groundAngle = Math.PI / 2 + this._pitch;
-        const topHalfSurfaceDistance = Math.sin(halfFov) * this.cameraToCenterDistance / Math.sin(clamp(Math.PI - groundAngle - halfFov, 0.01, Math.PI - 0.01));
+        const fovAboveCenter = this._fov * (0.5 + offset.y / this.height);
+        const topHalfSurfaceDistance = Math.sin(fovAboveCenter) * this.cameraToCenterDistance / Math.sin(clamp(Math.PI - groundAngle - fovAboveCenter, 0.01, Math.PI - 0.01));
         const point = this.point;
         const x = point.x, y = point.y;
 
@@ -646,6 +700,10 @@ class Transform {
         let m = new Float64Array(16);
         mat4.perspective(m, this._fov, this.width / this.height, nearZ, farZ);
 
+        //Apply center of perspective offset
+        m[8] = -offset.x * 2 / this.width;
+        m[9] = offset.y * 2 / this.height;
+
         mat4.scale(m, m, [1, -1, 1]);
         mat4.translate(m, m, [0, 0, -this.cameraToCenterDistance]);
         mat4.rotateX(m, m, this._pitch);

src/render/draw_debug.js

@@ -11,13 +11,63 @@ import StencilMode from '../gl/stencil_mode';
 import CullFaceMode from '../gl/cull_face_mode';
 import {debugUniformValues} from './program/debug_program';
 import Color from '../style-spec/util/color';
+import browser from '../util/browser';
 
 import type Painter from './painter';
 import type SourceCache from '../source/source_cache';
 import type {OverscaledTileID} from '../source/tile_id';
 
 export default drawDebug;
 
+const topColor = new Color(1, 0, 0, 1);
+const btmColor = new Color(0, 1, 0, 1);
+const leftColor = new Color(0, 0, 1, 1);
+const rightColor = new Color(1, 0, 1, 1);
+const centerColor = new Color(0, 1, 1, 1);
+
+export function drawDebugPadding(painter: Painter) {
+    const padding = painter.transform.padding;
+    const lineWidth = 3;
+    // Top
+    drawHorizontalLine(painter, painter.transform.height - (padding.top || 0), lineWidth, topColor);
+    // Bottom
+    drawHorizontalLine(painter, padding.bottom || 0, lineWidth, btmColor);
+    // Left
+    drawVerticalLine(painter, padding.left || 0, lineWidth, leftColor);
+    // Right
+    drawVerticalLine(painter, painter.transform.width - (padding.right || 0), lineWidth, rightColor);
+    // Center
+    const center = painter.transform.centerPoint;
+    drawCrosshair(painter, center.x, painter.transform.height - center.y, centerColor);
+}
+
+function drawCrosshair(painter: Painter, x: number, y: number, color: Color) {
+    const size = 20;
+    const lineWidth = 2;
+    //Vertical line
+    drawDebugSSRect(painter, x - lineWidth / 2, y - size / 2, lineWidth, size, color);
+    //Horizontal line
+    drawDebugSSRect(painter, x - size / 2, y - lineWidth / 2, size, lineWidth, color);
+}
+
+function drawHorizontalLine(painter: Painter, y: number, lineWidth: number, color: Color) {
+    drawDebugSSRect(painter, 0, y  + lineWidth / 2, painter.transform.width,  lineWidth, color);
+}
+
+function drawVerticalLine(painter: Painter, x: number, lineWidth: number, color: Color) {
+    drawDebugSSRect(painter, x - lineWidth / 2, 0, lineWidth,  painter.transform.height, color);
+}
+
+function drawDebugSSRect(painter: Painter, x: number, y: number, width: number, height: number, color: Color) {
+    const context = painter.context;
+    const gl = context.gl;
+
+    gl.enable(gl.SCISSOR_TEST);
+    gl.scissor(x * browser.devicePixelRatio, y * browser.devicePixelRatio, width * browser.devicePixelRatio, height * browser.devicePixelRatio);
+    context.clear({color});
+    gl.disable(gl.SCISSOR_TEST);
+}
+
 function drawDebug(painter: Painter, sourceCache: SourceCache, coords: Array<OverscaledTileID>) {
     for (let i = 0; i < coords.length; i++) {
         drawDebugTile(painter, sourceCache, coords[i]);

src/render/painter.js

@@ -33,7 +33,7 @@ import fillExtrusion from './draw_fill_extrusion';
 import hillshade from './draw_hillshade';
 import raster from './draw_raster';
 import background from './draw_background';
-import debug from './draw_debug';
+import debug, {drawDebugPadding} from './draw_debug';
 import custom from './draw_custom';
 
 const draw = {
@@ -69,6 +69,7 @@ export type RenderPass = 'offscreen' | 'opaque' | 'translucent';
 type PainterOptions = {
     showOverdrawInspector: boolean,
     showTileBoundaries: boolean,
+    showPadding: boolean,
     rotating: boolean,
     zooming: boolean,
     moving: boolean,
@@ -473,6 +474,10 @@ class Painter {
             }
         }
 
+        if (this.options.showPadding) {
+            drawDebugPadding(this);
+        }
+
         // Set defaults for most GL values so that anyone using the state after the render
         // encounters more expected values.
         this.context.setDefault();