calculatePanelSizes method

void calculatePanelSizes(BoxConstraints constraints, double dividerWidth)

Calculates the sizes of the child panel when they change, or when the parent viewport dimensions change

Implementation

void calculatePanelSizes(BoxConstraints constraints, double dividerWidth) {
  if (panels.isEmpty) return;

  final axisSize =
      axis == Axis.horizontal ? constraints.maxWidth : constraints.maxHeight;

  // Calculate panel sizes, if we have to
  // Calculate new sizes if:
  //  1. it's the first layout or
  //  2. the number of panels changed

  if (panelSizes == null ||
      panelSizes!.isEmpty ||
      panelSizes!.length != panels.length) {
    panelSizes = _computeInitialSizes(axisSize, dividerWidth);
  }
  // Otherwise, resize the panels keeping their aspect ratios
  else {
    var newPanelSize = (axis == Axis.horizontal
        ? constraints.maxWidth
        : constraints.maxHeight);

    final panelSize = (axis == Axis.horizontal
            ? this.constraints?.maxWidth
            : this.constraints?.maxHeight) ??
        newPanelSize;
    if (newPanelSize != panelSize) {
      // To account for rounding errors, the last panel should take up
      // the remaining available space, this accumulates the amount of space used up
      var usedSize = 0.0;
      for (var i = 0; i < panelSizes!.length; i++) {
        if (i != panelSizes!.length - 1) {
          panelSizes![i] = panelSizes![i] * newPanelSize / panelSize;
          usedSize += panelSizes![i];
        } else {
          panelSizes![i] =
              newPanelSize - dividerWidth * (panels.length - 1) - usedSize;
        }
      }
    }
  }
}