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| -rw-r--r-- | ui/DisplayElement.js | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/ui/DisplayElement.js b/ui/DisplayElement.js index 1ba9852..66d29aa 100644 --- a/ui/DisplayElement.js +++ b/ui/DisplayElement.js @@ -132,6 +132,40 @@ module.exports = class DisplayElement extends EventEmitter { this.h = this.parent.contentH } + fitToParent() { + // Utility function to position this element so that it stays within its + // parent's bounds. Must be called only when it has a parent. + // + // This function is useful when (and only when) the right or bottom edge + // of this element may be past the right or bottom edge of its parent. + // In such a case, the element will first be moved left or up by the + // distance that its edge exceeds that of its parent, so that its edge is + // no longer past the parent's. Then, if the left or top edge of the + // element is less than zero, i.e. outside the parent, it is set to zero + // and the element's width or height is adjusted so that it does not go + // past the bounds of the parent. + + if (this.x + this.w > this.parent.right) { + const offendExtent = (this.x + this.w) - this.parent.contentW + this.x -= offendExtent + if (this.x < 0) { + const offstartExtent = 0 - this.x + this.w -= offstartExtent + this.x = 0 + } + } + + if (this.y + this.h > this.parent.bottom) { + const offendExtent = (this.y + this.h) - this.parent.contentH + this.y -= offendExtent + if (this.y < 0) { + const offstartExtent = 0 - this.y + this.h -= offstartExtent + this.y = 0 + } + } + } + get root() { let el = this while (el.parent) { |