client: WikiRect utilities + math

1 files changed, 401 insertions, 38 deletions

diff --git a/src/static/client3.js b/src/static/client3.js
index 48a69bac..37bcee57 100644
--- a/src/static/client3.js
+++ b/src/static/client3.js
@@ -177,6 +177,394 @@ function dispatchInternalEvent(event, eventName, ...args) {
   return results;
 }
 
+// Rectangle math -----------------------------------------
+
+class WikiRect extends DOMRect {
+  // Useful constructors
+
+  static fromWindow() {
+    const {clientWidth: width, clientHeight: height} =
+      document.documentElement;
+
+    return Reflect.construct(this, [0, 0, width, height]);
+  }
+
+  static fromElement(element) {
+    return this.fromRect(element.getBoundingClientRect());
+  }
+
+  static leftOf(origin, offset = 0) {
+    // Returns a rectangle representing everywhere to the left of the provided
+    // point or rectangle (with no top or bottom bounds), towards negative x.
+    // If an offset is provided, this is added onto the origin.
+
+    return this.#past(origin, offset, {
+      origin: 'x',
+      extent: 'width',
+      edge: 'left',
+      direction: -Infinity,
+      construct: from =>
+        [from, -Infinity, -Infinity, Infinity],
+    });
+  }
+
+  static rightOf(origin, offset = 0) {
+    // Returns a rectangle representing everywhere to the right of the
+    // provided point or rectangle (with no top or bottom bounds), towards
+    // positive x. If an offset is provided, this is added onto the origin.
+
+    return this.#past(origin, offset, {
+      origin: 'x',
+      extent: 'width',
+      edge: 'right',
+      direction: Infinity,
+      construct: from =>
+        [from, -Infinity, Infinity, Infinity],
+    });
+  }
+
+  static above(origin, offset = 0) {
+    // Returns a rectangle representing everywhere above the provided point
+    // or rectangle (with no left or right bounds), towards negative y.
+    // If an offset is provided, this is added onto the origin.
+
+    return this.#past(origin, offset, {
+      origin: 'y',
+      extent: 'height',
+      edge: 'top',
+      direction: -Infinity,
+      construct: from =>
+        [-Infinity, from, Infinity, -Infinity],
+    });
+  }
+
+  static beneath(origin, offset = 0) {
+    // Returns a rectangle representing everywhere beneath the provided point
+    // or rectangle (with no left or right bounds), towards positive y.
+    // If an offset is provided, this is added onto the origin.
+
+    return this.#past(origin, offset, {
+      origin: 'y',
+      extent: 'height',
+      edge: 'bottom',
+      direction: Infinity,
+      construct: from =>
+        [-Infinity, from, Infinity, Infinity],
+    });
+  }
+
+  // Constructor helpers
+
+  static #past(origin, offset, opts) {
+    if (!isFinite(offset)) {
+      throw new TypeError(`Didn't expect infinite offset`);
+    }
+
+    const {direction, edge} = opts;
+
+    if (typeof origin === 'object') {
+      const {origin: originProperty, extent: extentProperty} = opts;
+
+      const normalized =
+        WikiRect.fromRect(origin).toNormalized();
+
+      if (normalized[extentProperty] === direction) {
+        throw new TypeError(`Provided rectangle already extends to ${edge} edge`);
+      }
+
+      if (normalized[extentProperty] === -direction) {
+        return this.#past(normalized[originProperty], offset, opts);
+      }
+
+      if (normalized.y === direction) {
+        throw new TypeError(`Provided rectangle already starts at ${edge} edge`);
+      }
+
+      return this.#past(normalized[edge], offset, opts);
+    }
+
+    const {construct} = opts;
+
+    if (origin === direction) {
+      throw new TypeError(`Provided point is already at ${edge} edge`);
+    }
+
+    return Reflect.construct(this, construct(origin + offset)).toNormalized();
+  }
+
+  // Predicates
+
+  static rejectInfiniteOriginNonZeroFiniteExtent({origin, extent}) {
+    // Indicate that, in this context, it's meaningless to provide
+    // a finite extent starting at an infinite origin and going towards
+    // or away from zero (i.e. a rectangle along a cardinal edge).
+
+    if (!isFinite(origin) && isFinite(extent) && extent !== 0) {
+      throw new TypeError(`Didn't expect infinite origin paired with finite extent`);
+    }
+  }
+
+  static rejectInfiniteOriginZeroExtent({origin, extent}) {
+    // Indicate that, in this context, it's meaningless to provide
+    // a zero extent at an infinite origin (i.e. a cardinal edge).
+
+    if (!isFinite(origin) && extent === 0) {
+      throw new TypeError(`Didn't expect infinite origin paired with zero extent`);
+    }
+  }
+
+  static rejectNonOpposingInfiniteOriginInfiniteExtent({origin, extent}) {
+    // Indicate that, in this context, it's meaningless to provide
+    // an infinite extent going in the same direction as its infinite
+    // origin (an area "infinitely past" a cardinal edge).
+
+    if (!isFinite(origin) && origin === extent) {
+      throw new TypeError(`Didn't expect non-opposing infinite origin and extent`);
+    }
+  }
+
+  // Transformations
+
+  static normalizeOriginExtent({origin, extent}) {
+    // Varying behavior based on inputs:
+    //
+    //  - For finite origin and finite extent, flip the orientation
+    //    (if necessary) so that extent is positive.
+    //  - For finite origin and infinite extent (i.e. an origin up to
+    //    a cardinal edge), leave as-is.
+    //  - For infinite origin and infinite extent, flip the orientation
+    //    (if necessary) so origin is negative and extent is positive.
+    //  - For infinite origin and zero extent (i.e. a cardinal edge),
+    //    leave as-is.
+    //  - For all other cases, error.
+    //
+
+    this.rejectInfiniteOriginNonZeroFiniteExtent({origin, extent});
+    this.rejectNonOpposingInfiniteOriginInfiniteExtent({origin, extent});
+
+    if (isFinite(origin) && isFinite(extent) && extent < 0) {
+      return {origin: origin + extent, extent: -extent};
+    }
+
+    if (!isFinite(origin) && !isFinite(extent)) {
+      return {origin: -Infinity, extent: Infinity};
+    }
+
+    return {origin, extent};
+  }
+
+  toNormalized() {
+    const {origin: newX, extent: newWidth} =
+      WikiRect.normalizeOriginExtent({
+        origin: this.x,
+        extent: this.width,
+      });
+
+    const {origin: newY, extent: newHeight} =
+      WikiRect.normalizeOriginExtent({
+        origin: this.y,
+        extent: this.height,
+      });
+
+    return Reflect.construct(this.constructor, [newX, newY, newWidth, newHeight]);
+  }
+
+  static intersectionFromOriginsExtents(...entries) {
+    // An intersection is the common subsection across two or more regions.
+
+    const [first, second, ...rest] = entries;
+
+    if (entries.length >= 3) {
+      return this.intersection(first, this.intersection(second, ...rest));
+    }
+
+    if (entries.length === 2) {
+      if (first === null || second === null) {
+        return null;
+      }
+
+      this.rejectInfiniteOriginZeroExtent(first);
+      this.rejectInfiniteOriginZeroExtent(second);
+
+      const {origin: origin1, extent: extent1} = this.normalizeOriginExtent(first);
+      const {origin: origin2, extent: extent2} = this.normalizeOriginExtent(second);
+
+      // After normalizing, *each* region will be one of these:
+      //
+      //  - Finite origin, finite extent
+      //    (a standard region, bounded on both sides)
+      //  - Finite origin, infinite extent
+      //    (everything to one direction of a given origin)
+      //  - Infinite origin, infinite extent
+      //    (everything everywhere)
+      //
+      // So we need to handle any *combination* of these kinds of regions.
+
+      // If either origin is infinite, that region represents everywhere,
+      // so it'll never limit the region of the other.
+
+      if (!isFinite(origin1)) {
+        return {origin: origin2, extent: extent2};
+      }
+
+      if (!isFinite(origin2)) {
+        return {origin: origin1, extent: extent1};
+      }
+
+      // If neither origin is infinite, both regions are bounded on at least
+      // one side, and may limit the other accordingly. Find the minimum and
+      // maximum points in each region, letting Infinity propagate through,
+      // which represents no boundary in that direction.
+
+      const minimum1 = Math.min(origin1, origin1 + extent1);
+      const minimum2 = Math.min(origin2, origin2 + extent2);
+      const maximum1 = Math.max(origin1, origin1 + extent1);
+      const maximum2 = Math.max(origin2, origin2 + extent2);
+
+      // Now get the maximum of the regions' minimums, and the minimum of the
+      // regions' maximums. These are the limits of the new region; computing
+      // with minimums and maximums in this way "polarizes" the limits, so we
+      // can perform specific polarized math in the following steps.
+      //
+      // Infinity will also propagate here, but with some important
+      // restricitons: only maxOfMinimums can be positive Infinity, and only
+      // minOfMaximums can be negative Infinity; and if either is Infinity,
+      // the other is not, since otherwise we'd be working with two everywhere
+      // regions, and would've just returned an everywhere region above.
+
+      const maxOfMinimums = Math.max(minimum1, minimum2);
+      const minOfMaximums = Math.min(maximum1, maximum2);
+
+      // Now check if the maximum of minimums is greater than the minimum of
+      // maximums. If so, the regions don't have any overlap - one region
+      // limits the overlap to end before the other region starts. This works
+      // because we've polarized the limits above!
+
+      if (maxOfMinimums > minOfMaximums) {
+        return null;
+      }
+
+      // Otherwise there's at least some overlap, even if it's just one point
+      // (i.e. one ends exactly where the other begins). We have to take care
+      // of infinities in particular, now. As mentioned above, only one of the
+      // points will be infinity (at most). So the origin is the non-infinite
+      // point, and the extent is in the direction of the infinite point.
+
+      if (minOfMaximums === -Infinity) {
+        return {origin: maxOfMinimums, extent: -Infinity};
+      }
+
+      if (maxOfMinimums === Infinity) {
+        return {origin: minOfMaximums, extent: Infinity};
+      }
+
+      // If neither point is infinity, we're working with two regions that are
+      // both bounded on both sides, so the overlapping region is just the
+      // region constrained by the limits above. Since these are polarized,
+      // start from maxOfMinimums and extend to minOfMaximums, resulting in
+      // a standard, already-normalized region.
+
+      return {
+        origin: maxOfMinimums,
+        extent: minOfMaximums - maxOfMinimums,
+      };
+    }
+
+    if (entries.length === 1) {
+      return first;
+    }
+
+    throw new TypeError(`Expected at least one {origin, extent} entry`);
+  }
+
+  intersectionWith(rect) {
+    const {origin: x, extent: width} =
+      WikiRect.intersectionFromOriginsExtents(
+        {origin: this.x, extent: this.width},
+        {origin: rect.x, extent: rect.width});
+
+    const {origin: y, extent: height} =
+      WikiRect.intersectionFromOriginsExtents(
+        {origin: this.y, extent: this.height},
+        {origin: rect.y, extent: rect.height});
+
+    return Reflect.construct(this.constructor, [x, y, width, height]);
+  }
+
+  chopExtendingOutside(rect) {
+    this.intersectionWith(rect).writeOnto(this);
+  }
+
+  static insetOriginExtent({origin, extent, start = 0, end = 0}) {
+    const normalized =
+      this.normalizeOriginExtent({origin, extent});
+
+    // If this would crush the bounds past each other, just return
+    // the halfway point.
+    if (extent < start + end) {
+      return {origin: origin + (start + end) / 2, extent: 0};
+    }
+
+    return {
+      origin: origin + start,
+      extent: extent - start - end,
+    };
+  }
+
+  toInset(arg1, arg2) {
+    if (typeof arg1 === 'number' && typeof arg2 === 'number') {
+      return this.toInset({
+        left: arg1,
+        right: arg1,
+        top: arg1,
+        bottom: arg1,
+      });
+    } else if (typeof arg1 === 'number') {
+      return this.toInset({
+        left: arg2,
+        right: arg2,
+        top: arg1,
+        bottom: arg1,
+      });
+    }
+
+    const {top, left, bottom, right} = arg1;
+
+    const {origin: x, extent: width} =
+      WikiRect.insetOriginExtent({
+        origin: this.x,
+        extent: this.width,
+        start: left,
+        end: right,
+      });
+
+    const {origin: y, extent: height} =
+      WikiRect.insetOriginExtent({
+        origin: this.y,
+        extent: this.height,
+        start: top,
+        end: bottom,
+      });
+
+    return Reflect.construct(this.constructor, [x, y, width, height]);
+  }
+
+  // Interfacing utilities
+
+  static fromRect(rect) {
+    return Reflect.construct(this, [rect.x, rect.y, rect.width, rect.height]);
+  }
+
+  writeOnto(destination) {
+    Object.assign(destination, {
+      x: this.x,
+      y: this.y,
+      width: this.width,
+      height: this.height,
+    });
+  }
+}
+
 // CSS compatibility-assistant ----------------------------
 
 const cssCompatibilityAssistantInfo = clientInfo.cssCompatibilityAssistantInfo = {
@@ -1108,23 +1496,19 @@ function getTooltipFromHoverablePlacementOpportunityAreas(hoverable) {
 
 function getTooltipBaselineOpportunityArea(tooltip) {
   const {stickyContainers} = stickyHeadingInfo;
-  const {documentElement} = document;
 
   const windowRect =
-    new DOMRect(
-      0, 0,
-      documentElement.clientWidth,
-      documentElement.clientHeight);
+    WikiRect.fromWindow();
 
   const baselineRect =
-    DOMRect.fromRect(windowRect);
+    WikiRect.fromRect(windowRect);
 
   const containingParent =
     getVisuallyContainingElement(tooltip);
 
   if (containingParent) {
     const containingRect =
-      containingParent.getBoundingClientRect();
+      WikiRect.fromElement(containingParent);
 
     // Only respect a portion of the container's padding, giving
     // the tooltip the impression of a "raised" element.
@@ -1133,31 +1517,14 @@ function getTooltipBaselineOpportunityArea(tooltip) {
       parseFloat(cssProp(containingParent, 'padding-' + side));
 
     const insetContainingRect =
-      new DOMRect(
-        containingRect.x + padding('left'),
-        containingRect.y + padding('top'),
-        containingRect.width - padding('left') - padding('right'),
-        containingRect.height - padding('top') - padding('bottom'));
-
-    const subtractFromTop =
-      Math.max(0, insetContainingRect.top);
-
-    const subtractFromBottom =
-      Math.max(0, windowRect.height - insetContainingRect.bottom);
-
-    const subtractFromLeft =
-      Math.max(0, insetContainingRect.left);
-
-    const subtractFromRight =
-      Math.max(0, windowRect.width - insetContainingRect.right);
-
-    baselineRect.y += subtractFromTop;
-    baselineRect.height -= subtractFromTop;
-    baselineRect.height -= subtractFromBottom;
+      containingRect.toInset({
+        left: padding('left'),
+        right: padding('right'),
+        top: padding('top'),
+        bottom: padding('bottom'),
+      });
 
-    baselineRect.x += subtractFromLeft;
-    baselineRect.width -= subtractFromLeft;
-    baselineRect.width -= subtractFromRight;
+    baselineRect.chopExtendingOutside(insetContainingRect);
   }
 
   // This currently assumes a maximum of one sticky container
@@ -1173,14 +1540,10 @@ function getTooltipBaselineOpportunityArea(tooltip) {
 
     // Add some padding so the tooltip doesn't line up exactly
     // with the edge of the sticky container.
-    const stickyBottom =
-      stickyRect.bottom + 10;
-
-    const overlap =
-      Math.max(0, stickyBottom - baselineRect.top);
+    const beneathStickyContainer =
+      WikiRect.beneath(stickyRect, 10);
 
-    baselineRect.y += overlap;
-    baselineRect.height -= overlap;
+    baselineRect.chopExtendingOutside(beneathStickyContainer);
   }
 
   return baselineRect;