layout/generic/ColumnUtils.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 /* A namespace class for static muti-column utilities. */
   8
   9 #include "mozilla/ColumnUtils.h"
  10
  11 #include <algorithm>
  12
  13 #include "nsContainerFrame.h"
  14 #include "nsLayoutUtils.h"
  15
  16 namespace mozilla {
  17
  18 /* static */
  19 nscoord ColumnUtils::GetColumnGap(const nsContainerFrame* aFrame,
  20                                   nscoord aPercentageBasis) {
  21   const auto& columnGap = aFrame->StylePosition()->mColumnGap;
  22   if (columnGap.IsNormal()) {
  23     return aFrame->StyleFont()->mFont.size.ToAppUnits();
  24   }
  25   return nsLayoutUtils::ResolveGapToLength(columnGap, aPercentageBasis);
  26 }
  27
  28 /* static */
  29 nscoord ColumnUtils::ClampUsedColumnWidth(const Length& aColumnWidth) {
  30   // Per spec, used values will be clamped to a minimum of 1px.
  31   return std::max(CSSPixel::ToAppUnits(1), aColumnWidth.ToAppUnits());
  32 }
  33
  34 /* static */
  35 nscoord ColumnUtils::IntrinsicISize(uint32_t aColCount, nscoord aColGap,
  36                                     nscoord aColISize) {
  37   MOZ_ASSERT(aColCount > 0, "Cannot compute with zero columns!");
  38
  39   // Column box's inline-size times number of columns (n), plus n-1 column gaps.
  40   nscoord iSize = aColISize * aColCount + aColGap * (aColCount - 1);
  41
  42   // The multiplication above can make 'iSize' negative (integer overflow),
  43   // so use std::max to protect against that.
  44   return std::max(iSize, aColISize);
  45 }
  46
  47 }  // namespace mozilla