gecko-dev/layout/generic/nsTextPaintStyle.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsTextPaintStyle.h"

#include "nsCSSColorUtils.h"
#include "nsCSSRendering.h"
#include "nsFrameSelection.h"
#include "nsLayoutUtils.h"
#include "nsTextFrame.h"
#include "nsStyleConsts.h"

#include "mozilla/LookAndFeel.h"

using namespace mozilla;
using namespace mozilla::dom;

static nscolor EnsureDifferentColors(nscolor colorA, nscolor colorB) {
  if (colorA == colorB) {
    nscolor res;
    res = NS_RGB(NS_GET_R(colorA) ^ 0xff, NS_GET_G(colorA) ^ 0xff,
                 NS_GET_B(colorA) ^ 0xff);
    return res;
  }
  return colorA;
}

nsTextPaintStyle::nsTextPaintStyle(nsTextFrame* aFrame)
    : mFrame(aFrame),
      mPresContext(aFrame->PresContext()),
      mInitCommonColors(false),
      mInitSelectionColorsAndShadow(false),
      mResolveColors(true),
      mSelectionTextColor(NS_RGBA(0, 0, 0, 0)),
      mSelectionBGColor(NS_RGBA(0, 0, 0, 0)),
      mSufficientContrast(0),
      mFrameBackgroundColor(NS_RGBA(0, 0, 0, 0)),
      mSystemFieldForegroundColor(NS_RGBA(0, 0, 0, 0)),
      mSystemFieldBackgroundColor(NS_RGBA(0, 0, 0, 0)) {
  for (uint32_t i = 0; i < ArrayLength(mSelectionStyle); i++)
    mSelectionStyle[i].mInit = false;
}

bool nsTextPaintStyle::EnsureSufficientContrast(nscolor* aForeColor,
                                                nscolor* aBackColor) {
  InitCommonColors();

  const bool sameAsForeground = *aForeColor == NS_SAME_AS_FOREGROUND_COLOR;
  if (sameAsForeground) {
    *aForeColor = GetTextColor();
  }

  // If the combination of selection background color and frame background color
  // has sufficient contrast, don't exchange the selection colors.
  //
  // Note we use a different threshold here: mSufficientContrast is for contrast
  // between text and background colors, but since we're diffing two
  // backgrounds, we don't need that much contrast.  We match the heuristic from
  // NS_SUFFICIENT_LUMINOSITY_DIFFERENCE_BG and use 20% of mSufficientContrast.
  const int32_t minLuminosityDifferenceForBackground = mSufficientContrast / 5;
  const int32_t backLuminosityDifference =
      NS_LUMINOSITY_DIFFERENCE(*aBackColor, mFrameBackgroundColor);
  if (backLuminosityDifference >= minLuminosityDifferenceForBackground) {
    return false;
  }

  // Otherwise, we should use the higher-contrast color for the selection
  // background color.
  //
  // For NS_SAME_AS_FOREGROUND_COLOR we only do this if the background is
  // totally indistinguishable, that is, if the luminosity difference is 0.
  if (sameAsForeground && backLuminosityDifference) {
    return false;
  }

  int32_t foreLuminosityDifference =
      NS_LUMINOSITY_DIFFERENCE(*aForeColor, mFrameBackgroundColor);
  if (backLuminosityDifference < foreLuminosityDifference) {
    std::swap(*aForeColor, *aBackColor);
    // Ensure foreground color is opaque to guarantee contrast.
    *aForeColor = NS_RGB(NS_GET_R(*aForeColor), NS_GET_G(*aForeColor),
                         NS_GET_B(*aForeColor));
    return true;
  }
  return false;
}

nscolor nsTextPaintStyle::GetTextColor() {
  if (mFrame->IsInSVGTextSubtree()) {
    if (!mResolveColors) {
      return NS_SAME_AS_FOREGROUND_COLOR;
    }

    const nsStyleSVG* style = mFrame->StyleSVG();
    switch (style->mFill.kind.tag) {
      case StyleSVGPaintKind::Tag::None:
        return NS_RGBA(0, 0, 0, 0);
      case StyleSVGPaintKind::Tag::Color:
        return nsLayoutUtils::GetColor(mFrame, &nsStyleSVG::mFill);
      default:
        NS_ERROR("cannot resolve SVG paint to nscolor");
        return NS_RGBA(0, 0, 0, 255);
    }
  }

  return nsLayoutUtils::GetColor(mFrame, &nsStyleText::mWebkitTextFillColor);
}

bool nsTextPaintStyle::GetSelectionColors(nscolor* aForeColor,
                                          nscolor* aBackColor) {
  NS_ASSERTION(aForeColor, "aForeColor is null");
  NS_ASSERTION(aBackColor, "aBackColor is null");

  if (!InitSelectionColorsAndShadow()) {
    return false;
  }

  *aForeColor = mSelectionTextColor;
  *aBackColor = mSelectionBGColor;
  return true;
}

void nsTextPaintStyle::GetHighlightColors(nscolor* aForeColor,
                                          nscolor* aBackColor) {
  NS_ASSERTION(aForeColor, "aForeColor is null");
  NS_ASSERTION(aBackColor, "aBackColor is null");

  const nsFrameSelection* frameSelection = mFrame->GetConstFrameSelection();
  const Selection* selection =
      frameSelection->GetSelection(SelectionType::eFind);
  const SelectionCustomColors* customColors = nullptr;
  if (selection) {
    customColors = selection->GetCustomColors();
  }

  if (!customColors) {
    nscolor backColor = LookAndFeel::Color(
        LookAndFeel::ColorID::TextHighlightBackground, mFrame);
    nscolor foreColor = LookAndFeel::Color(
        LookAndFeel::ColorID::TextHighlightForeground, mFrame);
    EnsureSufficientContrast(&foreColor, &backColor);
    *aForeColor = foreColor;
    *aBackColor = backColor;
    return;
  }

  if (customColors->mForegroundColor && customColors->mBackgroundColor) {
    nscolor foreColor = *customColors->mForegroundColor;
    nscolor backColor = *customColors->mBackgroundColor;

    if (EnsureSufficientContrast(&foreColor, &backColor) &&
        customColors->mAltForegroundColor &&
        customColors->mAltBackgroundColor) {
      foreColor = *customColors->mAltForegroundColor;
      backColor = *customColors->mAltBackgroundColor;
    }

    *aForeColor = foreColor;
    *aBackColor = backColor;
    return;
  }

  InitCommonColors();

  if (customColors->mBackgroundColor) {
    // !mForegroundColor means "currentColor"; the current color of the text.
    nscolor foreColor = GetTextColor();
    nscolor backColor = *customColors->mBackgroundColor;

    int32_t luminosityDifference =
        NS_LUMINOSITY_DIFFERENCE(foreColor, backColor);

    if (mSufficientContrast > luminosityDifference &&
        customColors->mAltBackgroundColor) {
      int32_t altLuminosityDifference = NS_LUMINOSITY_DIFFERENCE(
          foreColor, *customColors->mAltBackgroundColor);

      if (luminosityDifference < altLuminosityDifference) {
        backColor = *customColors->mAltBackgroundColor;
      }
    }

    *aForeColor = foreColor;
    *aBackColor = backColor;
    return;
  }

  if (customColors->mForegroundColor) {
    nscolor foreColor = *customColors->mForegroundColor;
    // !mBackgroundColor means "transparent"; the current color of the
    // background.

    int32_t luminosityDifference =
        NS_LUMINOSITY_DIFFERENCE(foreColor, mFrameBackgroundColor);

    if (mSufficientContrast > luminosityDifference &&
        customColors->mAltForegroundColor) {
      int32_t altLuminosityDifference = NS_LUMINOSITY_DIFFERENCE(
          *customColors->mForegroundColor, mFrameBackgroundColor);

      if (luminosityDifference < altLuminosityDifference) {
        foreColor = *customColors->mAltForegroundColor;
      }
    }

    *aForeColor = foreColor;
    *aBackColor = NS_TRANSPARENT;
    return;
  }

  // There are neither mForegroundColor nor mBackgroundColor.
  *aForeColor = GetTextColor();
  *aBackColor = NS_TRANSPARENT;
}

bool nsTextPaintStyle::GetCustomHighlightTextColor(nsAtom* aHighlightName,
                                                   nscolor* aForeColor) {
  NS_ASSERTION(aForeColor, "aForeColor is null");

  // non-existing highlights will be stored as `aHighlightName->nullptr`,
  // so subsequent calls only need a hashtable lookup and don't have
  // to enter the style engine.
  RefPtr<ComputedStyle> highlightStyle =
      mCustomHighlightPseudoStyles.LookupOrInsertWith(
          aHighlightName, [this, &aHighlightName] {
            return mFrame->ComputeHighlightSelectionStyle(aHighlightName);
          });
  if (!highlightStyle) {
    // highlight `aHighlightName` doesn't exist or has no style rules.
    return false;
  }

  *aForeColor = highlightStyle->GetVisitedDependentColor(
      &nsStyleText::mWebkitTextFillColor);

  return highlightStyle->HasAuthorSpecifiedTextColor();
}

bool nsTextPaintStyle::GetCustomHighlightBackgroundColor(nsAtom* aHighlightName,
                                                         nscolor* aBackColor) {
  NS_ASSERTION(aBackColor, "aBackColor is null");
  // non-existing highlights will be stored as `aHighlightName->nullptr`,
  // so subsequent calls only need a hashtable lookup and don't have
  // to enter the style engine.
  RefPtr<ComputedStyle> highlightStyle =
      mCustomHighlightPseudoStyles.LookupOrInsertWith(
          aHighlightName, [this, &aHighlightName] {
            return mFrame->ComputeHighlightSelectionStyle(aHighlightName);
          });
  if (!highlightStyle) {
    // highlight `aHighlightName` doesn't exist or has no style rules.
    return false;
  }

  *aBackColor = highlightStyle->GetVisitedDependentColor(
      &nsStyleBackground::mBackgroundColor);
  return NS_GET_A(*aBackColor) != 0;
}

void nsTextPaintStyle::GetURLSecondaryColor(nscolor* aForeColor) {
  NS_ASSERTION(aForeColor, "aForeColor is null");

  const nscolor textColor = GetTextColor();
  *aForeColor = NS_RGBA(NS_GET_R(textColor), NS_GET_G(textColor),
                        NS_GET_B(textColor), 127);
}

void nsTextPaintStyle::GetIMESelectionColors(int32_t aIndex,
                                             nscolor* aForeColor,
                                             nscolor* aBackColor) {
  NS_ASSERTION(aForeColor, "aForeColor is null");
  NS_ASSERTION(aBackColor, "aBackColor is null");
  NS_ASSERTION(aIndex >= 0 && aIndex < 5, "Index out of range");

  nsSelectionStyle* selectionStyle = GetSelectionStyle(aIndex);
  *aForeColor = selectionStyle->mTextColor;
  *aBackColor = selectionStyle->mBGColor;
}

bool nsTextPaintStyle::GetSelectionUnderlineForPaint(
    int32_t aIndex, nscolor* aLineColor, float* aRelativeSize,
    StyleTextDecorationStyle* aStyle) {
  NS_ASSERTION(aLineColor, "aLineColor is null");
  NS_ASSERTION(aRelativeSize, "aRelativeSize is null");
  NS_ASSERTION(aIndex >= 0 && aIndex < 5, "Index out of range");

  nsSelectionStyle* selectionStyle = GetSelectionStyle(aIndex);
  if (selectionStyle->mUnderlineStyle == StyleTextDecorationStyle::None ||
      selectionStyle->mUnderlineColor == NS_TRANSPARENT ||
      selectionStyle->mUnderlineRelativeSize <= 0.0f)
    return false;

  *aLineColor = selectionStyle->mUnderlineColor;
  *aRelativeSize = selectionStyle->mUnderlineRelativeSize;
  *aStyle = selectionStyle->mUnderlineStyle;
  return true;
}

void nsTextPaintStyle::InitCommonColors() {
  if (mInitCommonColors) {
    return;
  }

  auto bgColor = nsCSSRendering::FindEffectiveBackgroundColor(mFrame);
  mFrameBackgroundColor = bgColor.mColor;

  mSystemFieldForegroundColor =
      LookAndFeel::Color(LookAndFeel::ColorID::Fieldtext, mFrame);
  mSystemFieldBackgroundColor =
      LookAndFeel::Color(LookAndFeel::ColorID::Field, mFrame);

  if (bgColor.mIsThemed) {
    // Assume a native widget has sufficient contrast always
    mSufficientContrast = 0;
    mInitCommonColors = true;
    return;
  }

  nscolor defaultWindowBackgroundColor =
      LookAndFeel::Color(LookAndFeel::ColorID::Window, mFrame);
  nscolor selectionTextColor =
      LookAndFeel::Color(LookAndFeel::ColorID::Highlighttext, mFrame);
  nscolor selectionBGColor =
      LookAndFeel::Color(LookAndFeel::ColorID::Highlight, mFrame);

  mSufficientContrast = std::min(
      std::min(NS_SUFFICIENT_LUMINOSITY_DIFFERENCE,
               NS_LUMINOSITY_DIFFERENCE(selectionTextColor, selectionBGColor)),
      NS_LUMINOSITY_DIFFERENCE(defaultWindowBackgroundColor, selectionBGColor));

  mInitCommonColors = true;
}

nscolor nsTextPaintStyle::GetSystemFieldForegroundColor() {
  InitCommonColors();
  return mSystemFieldForegroundColor;
}

nscolor nsTextPaintStyle::GetSystemFieldBackgroundColor() {
  InitCommonColors();
  return mSystemFieldBackgroundColor;
}

bool nsTextPaintStyle::InitSelectionColorsAndShadow() {
  if (mInitSelectionColorsAndShadow) {
    return true;
  }

  int16_t selectionFlags;
  const int16_t selectionStatus = mFrame->GetSelectionStatus(&selectionFlags);
  if (!(selectionFlags & nsISelectionDisplay::DISPLAY_TEXT) ||
      selectionStatus < nsISelectionController::SELECTION_ON) {
    // Not displaying the normal selection.
    // We're not caching this fact, so every call to GetSelectionColors
    // will come through here. We could avoid this, but it's not really worth
    // it.
    return false;
  }

  mInitSelectionColorsAndShadow = true;

  // Use ::selection pseudo class if applicable.
  if (RefPtr<ComputedStyle> style =
          mFrame->ComputeSelectionStyle(selectionStatus)) {
    mSelectionBGColor =
        style->GetVisitedDependentColor(&nsStyleBackground::mBackgroundColor);
    mSelectionTextColor =
        style->GetVisitedDependentColor(&nsStyleText::mWebkitTextFillColor);
    mSelectionPseudoStyle = std::move(style);
    return true;
  }

  mSelectionTextColor =
      LookAndFeel::Color(LookAndFeel::ColorID::Highlighttext, mFrame);

  nscolor selectionBGColor =
      LookAndFeel::Color(LookAndFeel::ColorID::Highlight, mFrame);

  switch (selectionStatus) {
    case nsISelectionController::SELECTION_ATTENTION: {
      mSelectionTextColor = LookAndFeel::Color(
          LookAndFeel::ColorID::TextSelectAttentionForeground, mFrame);
      mSelectionBGColor = LookAndFeel::Color(
          LookAndFeel::ColorID::TextSelectAttentionBackground, mFrame);
      mSelectionBGColor =
          EnsureDifferentColors(mSelectionBGColor, selectionBGColor);
      break;
    }
    case nsISelectionController::SELECTION_ON: {
      mSelectionBGColor = selectionBGColor;
      break;
    }
    default: {
      mSelectionBGColor = LookAndFeel::Color(
          LookAndFeel::ColorID::TextSelectDisabledBackground, mFrame);
      mSelectionBGColor =
          EnsureDifferentColors(mSelectionBGColor, selectionBGColor);
      break;
    }
  }

  if (mResolveColors) {
    EnsureSufficientContrast(&mSelectionTextColor, &mSelectionBGColor);
  }
  return true;
}

nsTextPaintStyle::nsSelectionStyle* nsTextPaintStyle::GetSelectionStyle(
    int32_t aIndex) {
  InitSelectionStyle(aIndex);
  return &mSelectionStyle[aIndex];
}

struct StyleIDs {
  LookAndFeel::ColorID mForeground, mBackground, mLine;
  LookAndFeel::IntID mLineStyle;
  LookAndFeel::FloatID mLineRelativeSize;
};
static StyleIDs SelectionStyleIDs[] = {
    {LookAndFeel::ColorID::IMERawInputForeground,
     LookAndFeel::ColorID::IMERawInputBackground,
     LookAndFeel::ColorID::IMERawInputUnderline,
     LookAndFeel::IntID::IMERawInputUnderlineStyle,
     LookAndFeel::FloatID::IMEUnderlineRelativeSize},
    {LookAndFeel::ColorID::IMESelectedRawTextForeground,
     LookAndFeel::ColorID::IMESelectedRawTextBackground,
     LookAndFeel::ColorID::IMESelectedRawTextUnderline,
     LookAndFeel::IntID::IMESelectedRawTextUnderlineStyle,
     LookAndFeel::FloatID::IMEUnderlineRelativeSize},
    {LookAndFeel::ColorID::IMEConvertedTextForeground,
     LookAndFeel::ColorID::IMEConvertedTextBackground,
     LookAndFeel::ColorID::IMEConvertedTextUnderline,
     LookAndFeel::IntID::IMEConvertedTextUnderlineStyle,
     LookAndFeel::FloatID::IMEUnderlineRelativeSize},
    {LookAndFeel::ColorID::IMESelectedConvertedTextForeground,
     LookAndFeel::ColorID::IMESelectedConvertedTextBackground,
     LookAndFeel::ColorID::IMESelectedConvertedTextUnderline,
     LookAndFeel::IntID::IMESelectedConvertedTextUnderline,
     LookAndFeel::FloatID::IMEUnderlineRelativeSize},
    {LookAndFeel::ColorID::End, LookAndFeel::ColorID::End,
     LookAndFeel::ColorID::SpellCheckerUnderline,
     LookAndFeel::IntID::SpellCheckerUnderlineStyle,
     LookAndFeel::FloatID::SpellCheckerUnderlineRelativeSize}};

void nsTextPaintStyle::InitSelectionStyle(int32_t aIndex) {
  NS_ASSERTION(aIndex >= 0 && aIndex < 5, "aIndex is invalid");
  nsSelectionStyle* selectionStyle = &mSelectionStyle[aIndex];
  if (selectionStyle->mInit) {
    return;
  }

  StyleIDs* styleIDs = &SelectionStyleIDs[aIndex];

  nscolor foreColor, backColor;
  if (styleIDs->mForeground == LookAndFeel::ColorID::End) {
    foreColor = NS_SAME_AS_FOREGROUND_COLOR;
  } else {
    foreColor = LookAndFeel::Color(styleIDs->mForeground, mFrame);
  }
  if (styleIDs->mBackground == LookAndFeel::ColorID::End) {
    backColor = NS_TRANSPARENT;
  } else {
    backColor = LookAndFeel::Color(styleIDs->mBackground, mFrame);
  }

  // Convert special color to actual color
  NS_ASSERTION(foreColor != NS_TRANSPARENT,
               "foreColor cannot be NS_TRANSPARENT");
  NS_ASSERTION(backColor != NS_SAME_AS_FOREGROUND_COLOR,
               "backColor cannot be NS_SAME_AS_FOREGROUND_COLOR");
  NS_ASSERTION(backColor != NS_40PERCENT_FOREGROUND_COLOR,
               "backColor cannot be NS_40PERCENT_FOREGROUND_COLOR");

  if (mResolveColors) {
    foreColor = GetResolvedForeColor(foreColor, GetTextColor(), backColor);

    if (NS_GET_A(backColor) > 0) {
      EnsureSufficientContrast(&foreColor, &backColor);
    }
  }

  nscolor lineColor;
  float relativeSize;
  StyleTextDecorationStyle lineStyle;
  GetSelectionUnderline(mFrame, aIndex, &lineColor, &relativeSize, &lineStyle);

  if (mResolveColors) {
    lineColor = GetResolvedForeColor(lineColor, foreColor, backColor);
  }

  selectionStyle->mTextColor = foreColor;
  selectionStyle->mBGColor = backColor;
  selectionStyle->mUnderlineColor = lineColor;
  selectionStyle->mUnderlineStyle = lineStyle;
  selectionStyle->mUnderlineRelativeSize = relativeSize;
  selectionStyle->mInit = true;
}

/* static */
bool nsTextPaintStyle::GetSelectionUnderline(nsIFrame* aFrame, int32_t aIndex,
                                             nscolor* aLineColor,
                                             float* aRelativeSize,
                                             StyleTextDecorationStyle* aStyle) {
  NS_ASSERTION(aFrame, "aFrame is null");
  NS_ASSERTION(aRelativeSize, "aRelativeSize is null");
  NS_ASSERTION(aStyle, "aStyle is null");
  NS_ASSERTION(aIndex >= 0 && aIndex < 5, "Index out of range");

  StyleIDs& styleID = SelectionStyleIDs[aIndex];

  nscolor color = LookAndFeel::Color(styleID.mLine, aFrame);
  const int32_t lineStyle = LookAndFeel::GetInt(styleID.mLineStyle);
  auto style = static_cast<StyleTextDecorationStyle>(lineStyle);
  if (lineStyle > static_cast<int32_t>(StyleTextDecorationStyle::Sentinel)) {
    NS_ERROR("Invalid underline style value is specified");
    style = StyleTextDecorationStyle::Solid;
  }
  float size = LookAndFeel::GetFloat(styleID.mLineRelativeSize);

  NS_ASSERTION(size, "selection underline relative size must be larger than 0");

  if (aLineColor) {
    *aLineColor = color;
  }
  *aRelativeSize = size;
  *aStyle = style;

  return style != StyleTextDecorationStyle::None && color != NS_TRANSPARENT &&
         size > 0.0f;
}

bool nsTextPaintStyle::GetSelectionShadow(
    Span<const StyleSimpleShadow>* aShadows) {
  if (!InitSelectionColorsAndShadow()) {
    return false;
  }

  if (mSelectionPseudoStyle) {
    *aShadows = mSelectionPseudoStyle->StyleText()->mTextShadow.AsSpan();
    return true;
  }

  return false;
}

inline nscolor Get40PercentColor(nscolor aForeColor, nscolor aBackColor) {
  nscolor foreColor = NS_RGBA(NS_GET_R(aForeColor), NS_GET_G(aForeColor),
                              NS_GET_B(aForeColor), (uint8_t)(255 * 0.4f));
  // Don't use true alpha color for readability.
  return NS_ComposeColors(aBackColor, foreColor);
}

nscolor nsTextPaintStyle::GetResolvedForeColor(nscolor aColor,
                                               nscolor aDefaultForeColor,
                                               nscolor aBackColor) {
  if (aColor == NS_SAME_AS_FOREGROUND_COLOR) {
    return aDefaultForeColor;
  }

  if (aColor != NS_40PERCENT_FOREGROUND_COLOR) {
    return aColor;
  }

  // Get actual background color
  nscolor actualBGColor = aBackColor;
  if (actualBGColor == NS_TRANSPARENT) {
    InitCommonColors();
    actualBGColor = mFrameBackgroundColor;
  }
  return Get40PercentColor(aDefaultForeColor, actualBGColor);
}

nscolor nsTextPaintStyle::GetWebkitTextStrokeColor() {
  if (mFrame->IsInSVGTextSubtree()) {
    return 0;
  }
  return mFrame->StyleText()->mWebkitTextStrokeColor.CalcColor(mFrame);
}

float nsTextPaintStyle::GetWebkitTextStrokeWidth() {
  if (mFrame->IsInSVGTextSubtree()) {
    return 0.0f;
  }
  nscoord coord = mFrame->StyleText()->mWebkitTextStrokeWidth;
  return mFrame->PresContext()->AppUnitsToFloatDevPixels(coord);
}