The Tor Browser: editor/libeditor/html/nsHTMLAbsPosition.cpp@b8a032363ba2 (annotated)

editor/libeditor/html/nsHTMLAbsPosition.cpp@b8a032363ba2 (annotated)

editor/libeditor/html/nsHTMLAbsPosition.cpp

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* 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 <math.h>
 #include "mozilla/Preferences.h"
 #include "mozilla/dom/Selection.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/mozalloc.h"
 #include "nsAString.h"
 #include "nsAlgorithm.h"
 #include "nsAutoPtr.h"
 #include "nsCOMPtr.h"
 #include "nsComputedDOMStyle.h"
 #include "nsDebug.h"
 #include "nsEditProperty.h"
 #include "nsEditRules.h"
 #include "nsEditor.h"
 #include "nsEditorUtils.h"
 #include "nsError.h"
 #include "nsGkAtoms.h"
 #include "nsHTMLCSSUtils.h"
 #include "nsHTMLEditRules.h"
 #include "nsHTMLEditUtils.h"
 #include "nsHTMLEditor.h"
 #include "nsHTMLObjectResizer.h"
 #include "nsIContent.h"
 #include "nsROCSSPrimitiveValue.h"
 #include "nsIDOMCSSStyleDeclaration.h"
 #include "nsIDOMElement.h"
 #include "nsIDOMEventListener.h"
 #include "nsIDOMEventTarget.h"
 #include "nsIDOMNode.h"
 #include "nsDOMCSSRGBColor.h"
 #include "nsIDOMWindow.h"
 #include "nsIEditor.h"
 #include "nsIHTMLEditor.h"
 #include "nsIHTMLObjectResizer.h"
 #include "nsINode.h"
 #include "nsIPresShell.h"
 #include "nsISelection.h"
 #include "nsISupportsImpl.h"
 #include "nsISupportsUtils.h"
 #include "nsLiteralString.h"
 #include "nsReadableUtils.h"
 #include "nsString.h"
 #include "nsStringFwd.h"
 #include "nsTextEditRules.h"
 #include "nsTextEditUtils.h"
 #include "nscore.h"
 #include <algorithm>
 using namespace mozilla;
 using namespace mozilla::dom;
 #define  BLACK_BG_RGB_TRIGGER 0xd0
 NS_IMETHODIMP
 nsHTMLEditor::AbsolutePositionSelection(bool aEnabled)
 {
   nsAutoEditBatch beginBatching(this);
   nsAutoRules beginRulesSniffing(this,
                                  aEnabled ? EditAction::setAbsolutePosition :
                                             EditAction::removeAbsolutePosition,
                                  nsIEditor::eNext);
   // the line below does not match the code; should it be removed?
   // Find out if the selection is collapsed:
   nsRefPtr<Selection> selection = GetSelection();
   NS_ENSURE_TRUE(selection, NS_ERROR_NULL_POINTER);
   nsTextRulesInfo ruleInfo(aEnabled ? EditAction::setAbsolutePosition :
                                       EditAction::removeAbsolutePosition);
   bool cancel, handled;
   // Protect the edit rules object from dying
   nsCOMPtr<nsIEditRules> kungFuDeathGrip(mRules);
   nsresult res = mRules->WillDoAction(selection, &ruleInfo, &cancel, &handled);
   if (NS_FAILED(res) || cancel)
     return res;
   return mRules->DidDoAction(selection, &ruleInfo, res);
 }
 NS_IMETHODIMP
 nsHTMLEditor::GetAbsolutelyPositionedSelectionContainer(nsIDOMElement **_retval)
 {
   nsCOMPtr<nsIDOMElement> element;
   nsresult res = GetSelectionContainer(getter_AddRefs(element));
   NS_ENSURE_SUCCESS(res, res);
   nsAutoString positionStr;
   nsCOMPtr<nsIDOMNode> node = do_QueryInterface(element);
   nsCOMPtr<nsIDOMNode> resultNode;
   while (!resultNode && node && !nsEditor::NodeIsType(node, nsEditProperty::html)) {
     res = mHTMLCSSUtils->GetComputedProperty(node, nsEditProperty::cssPosition,
                                              positionStr);
     NS_ENSURE_SUCCESS(res, res);
     if (positionStr.EqualsLiteral("absolute"))
       resultNode = node;
     else {
       nsCOMPtr<nsIDOMNode> parentNode;
       res = node->GetParentNode(getter_AddRefs(parentNode));
       NS_ENSURE_SUCCESS(res, res);
       node.swap(parentNode);
     }
   }
   element = do_QueryInterface(resultNode );
   *_retval = element;
   NS_IF_ADDREF(*_retval);
   return NS_OK;
 }
 NS_IMETHODIMP
 nsHTMLEditor::GetSelectionContainerAbsolutelyPositioned(bool *aIsSelectionContainerAbsolutelyPositioned)
 {
   *aIsSelectionContainerAbsolutelyPositioned = (mAbsolutelyPositionedObject != nullptr);
   return NS_OK;
 }
 NS_IMETHODIMP
 nsHTMLEditor::GetAbsolutePositioningEnabled(bool * aIsEnabled)
 {
   *aIsEnabled = mIsAbsolutelyPositioningEnabled;
   return NS_OK;
 }
 NS_IMETHODIMP
 nsHTMLEditor::SetAbsolutePositioningEnabled(bool aIsEnabled)
 {
   mIsAbsolutelyPositioningEnabled = aIsEnabled;
   return NS_OK;
 }
 NS_IMETHODIMP
 nsHTMLEditor::RelativeChangeElementZIndex(nsIDOMElement * aElement,
                                           int32_t aChange,
                                           int32_t * aReturn)
 {
   NS_ENSURE_ARG_POINTER(aElement);
   NS_ENSURE_ARG_POINTER(aReturn);
   if (!aChange) // early way out, no change
     return NS_OK;
   int32_t zIndex;
   nsresult res = GetElementZIndex(aElement, &zIndex);
   NS_ENSURE_SUCCESS(res, res);
   zIndex = std::max(zIndex + aChange, 0);
   SetElementZIndex(aElement, zIndex);
   *aReturn = zIndex;
   return NS_OK;
 }
 NS_IMETHODIMP
 nsHTMLEditor::SetElementZIndex(nsIDOMElement * aElement,
                                int32_t aZindex)
 {
   NS_ENSURE_ARG_POINTER(aElement);
   nsAutoString zIndexStr;
   zIndexStr.AppendInt(aZindex);
   mHTMLCSSUtils->SetCSSProperty(aElement,
                                 nsEditProperty::cssZIndex,
                                 zIndexStr,
                                 false);
   return NS_OK;
 }
 NS_IMETHODIMP
 nsHTMLEditor::RelativeChangeZIndex(int32_t aChange)
 {
   nsAutoEditBatch beginBatching(this);
   nsAutoRules beginRulesSniffing(this,
                                  (aChange < 0) ? EditAction::decreaseZIndex :
                                                  EditAction::increaseZIndex,
                                  nsIEditor::eNext);
   // brade: can we get rid of this comment?
   // Find out if the selection is collapsed:
   nsRefPtr<Selection> selection = GetSelection();
   NS_ENSURE_TRUE(selection, NS_ERROR_NULL_POINTER);
   nsTextRulesInfo ruleInfo(aChange < 0 ? EditAction::decreaseZIndex :
                                          EditAction::increaseZIndex);
   bool cancel, handled;
   // Protect the edit rules object from dying
   nsCOMPtr<nsIEditRules> kungFuDeathGrip(mRules);
   nsresult res = mRules->WillDoAction(selection, &ruleInfo, &cancel, &handled);
   if (cancel || NS_FAILED(res))
     return res;
   return mRules->DidDoAction(selection, &ruleInfo, res);
 }
 NS_IMETHODIMP
 nsHTMLEditor::GetElementZIndex(nsIDOMElement * aElement,
                                int32_t * aZindex)
 {
   nsAutoString zIndexStr;
   *aZindex = 0;
   nsresult res = mHTMLCSSUtils->GetSpecifiedProperty(aElement,
                                                      nsEditProperty::cssZIndex,
                                                      zIndexStr);
   NS_ENSURE_SUCCESS(res, res);
   if (zIndexStr.EqualsLiteral("auto")) {
     // we have to look at the positioned ancestors
     // cf. CSS 2 spec section 9.9.1
     nsCOMPtr<nsIDOMNode> parentNode;
     res = aElement->GetParentNode(getter_AddRefs(parentNode));
     NS_ENSURE_SUCCESS(res, res);
     nsCOMPtr<nsIDOMNode> node = parentNode;
     nsAutoString positionStr;
     while (node &&
            zIndexStr.EqualsLiteral("auto") &&
            !nsTextEditUtils::IsBody(node)) {
       res = mHTMLCSSUtils->GetComputedProperty(node,
                                                nsEditProperty::cssPosition,
                                                positionStr);
       NS_ENSURE_SUCCESS(res, res);
       if (positionStr.EqualsLiteral("absolute")) {
         // ah, we found one, what's its z-index ? If its z-index is auto,
         // we have to continue climbing the document's tree
         res = mHTMLCSSUtils->GetComputedProperty(node,
                                                  nsEditProperty::cssZIndex,
                                                  zIndexStr);
         NS_ENSURE_SUCCESS(res, res);
       }
       res = node->GetParentNode(getter_AddRefs(parentNode));
       NS_ENSURE_SUCCESS(res, res);
       node = parentNode;
     }
   }
   if (!zIndexStr.EqualsLiteral("auto")) {
     nsresult errorCode;
     *aZindex = zIndexStr.ToInteger(&errorCode);
   }
   return NS_OK;
 }
 nsresult
 nsHTMLEditor::CreateGrabber(nsIDOMNode * aParentNode, nsIDOMElement ** aReturn)
 {
   // let's create a grabber through the element factory
   nsresult res = CreateAnonymousElement(NS_LITERAL_STRING("span"),
                                         aParentNode,
                                         NS_LITERAL_STRING("mozGrabber"),
                                         false,
                                         aReturn);
   NS_ENSURE_TRUE(*aReturn, NS_ERROR_FAILURE);
   // add the mouse listener so we can detect a click on a resizer
   nsCOMPtr<nsIDOMEventTarget> evtTarget(do_QueryInterface(*aReturn));
   evtTarget->AddEventListener(NS_LITERAL_STRING("mousedown"),
                               mEventListener, false);
   return res;
 }
 NS_IMETHODIMP
 nsHTMLEditor::RefreshGrabber()
 {
   NS_ENSURE_TRUE(mAbsolutelyPositionedObject, NS_ERROR_NULL_POINTER);
   nsresult res = GetPositionAndDimensions(mAbsolutelyPositionedObject,
                                          mPositionedObjectX,
                                          mPositionedObjectY,
                                          mPositionedObjectWidth,
                                          mPositionedObjectHeight,
                                          mPositionedObjectBorderLeft,
                                          mPositionedObjectBorderTop,
                                          mPositionedObjectMarginLeft,
                                          mPositionedObjectMarginTop);
   NS_ENSURE_SUCCESS(res, res);
   SetAnonymousElementPosition(mPositionedObjectX+12,
                               mPositionedObjectY-14,
                               mGrabber);
   return NS_OK;
 }
 NS_IMETHODIMP
 nsHTMLEditor::HideGrabber()
 {
   nsresult res =
     mAbsolutelyPositionedObject->RemoveAttribute(NS_LITERAL_STRING("_moz_abspos"));
   NS_ENSURE_SUCCESS(res, res);
   mAbsolutelyPositionedObject = nullptr;
   NS_ENSURE_TRUE(mGrabber, NS_ERROR_NULL_POINTER);
   // get the presshell's document observer interface.
   nsCOMPtr<nsIPresShell> ps = GetPresShell();
   // We allow the pres shell to be null; when it is, we presume there
   // are no document observers to notify, but we still want to
   // UnbindFromTree.
   nsCOMPtr<nsIDOMNode> parentNode;
   res = mGrabber->GetParentNode(getter_AddRefs(parentNode));
   NS_ENSURE_SUCCESS(res, res);
   nsCOMPtr<nsIContent> parentContent = do_QueryInterface(parentNode);
   NS_ENSURE_TRUE(parentContent, NS_ERROR_NULL_POINTER);
   DeleteRefToAnonymousNode(mGrabber, parentContent, ps);
   mGrabber = nullptr;
   DeleteRefToAnonymousNode(mPositioningShadow, parentContent, ps);
   mPositioningShadow = nullptr;
   return NS_OK;
 }
 NS_IMETHODIMP
 nsHTMLEditor::ShowGrabberOnElement(nsIDOMElement * aElement)
 {
   NS_ENSURE_ARG_POINTER(aElement);
   if (mGrabber) {
     NS_ERROR("call HideGrabber first");
     return NS_ERROR_UNEXPECTED;
   }
   nsAutoString classValue;
   nsresult res = CheckPositionedElementBGandFG(aElement, classValue);
   NS_ENSURE_SUCCESS(res, res);
   res = aElement->SetAttribute(NS_LITERAL_STRING("_moz_abspos"),
                                classValue);
   NS_ENSURE_SUCCESS(res, res);
   // first, let's keep track of that element...
   mAbsolutelyPositionedObject = aElement;
   nsCOMPtr<nsIDOMNode> parentNode;
   res = aElement->GetParentNode(getter_AddRefs(parentNode));
   NS_ENSURE_SUCCESS(res, res);
   res = CreateGrabber(parentNode, getter_AddRefs(mGrabber));
   NS_ENSURE_SUCCESS(res, res);
   // and set its position
   return RefreshGrabber();
 }
 nsresult
 nsHTMLEditor::StartMoving(nsIDOMElement *aHandle)
 {
   nsCOMPtr<nsIDOMNode> parentNode;
   nsresult res = mGrabber->GetParentNode(getter_AddRefs(parentNode));
   NS_ENSURE_SUCCESS(res, res);
   // now, let's create the resizing shadow
   res = CreateShadow(getter_AddRefs(mPositioningShadow),
                                  parentNode, mAbsolutelyPositionedObject);
   NS_ENSURE_SUCCESS(res,res);
   res = SetShadowPosition(mPositioningShadow, mAbsolutelyPositionedObject,
                              mPositionedObjectX, mPositionedObjectY);
   NS_ENSURE_SUCCESS(res,res);
   // make the shadow appear
   mPositioningShadow->RemoveAttribute(NS_LITERAL_STRING("class"));
   // position it
   mHTMLCSSUtils->SetCSSPropertyPixels(mPositioningShadow,
                                       NS_LITERAL_STRING("width"),
                                       mPositionedObjectWidth);
   mHTMLCSSUtils->SetCSSPropertyPixels(mPositioningShadow,
                                       NS_LITERAL_STRING("height"),
                                       mPositionedObjectHeight);
   mIsMoving = true;
   return res;
 }
 void
 nsHTMLEditor::SnapToGrid(int32_t & newX, int32_t & newY)
 {
   if (mSnapToGridEnabled && mGridSize) {
     newX = (int32_t) floor( ((float)newX / (float)mGridSize) + 0.5f ) * mGridSize;
     newY = (int32_t) floor( ((float)newY / (float)mGridSize) + 0.5f ) * mGridSize;
   }
 }
 nsresult
 nsHTMLEditor::GrabberClicked()
 {
   // add a mouse move listener to the editor
   nsresult res = NS_OK;
   if (!mMouseMotionListenerP) {
     mMouseMotionListenerP = new ResizerMouseMotionListener(this);
     if (!mMouseMotionListenerP) {return NS_ERROR_NULL_POINTER;}
     nsCOMPtr<nsIDOMEventTarget> piTarget = GetDOMEventTarget();
     NS_ENSURE_TRUE(piTarget, NS_ERROR_FAILURE);
     res = piTarget->AddEventListener(NS_LITERAL_STRING("mousemove"),
                                      mMouseMotionListenerP,
                                      false, false);
     NS_ASSERTION(NS_SUCCEEDED(res),
                  "failed to register mouse motion listener");
   }
   mGrabberClicked = true;
   return res;
 }
 nsresult
 nsHTMLEditor::EndMoving()
 {
   if (mPositioningShadow) {
     nsCOMPtr<nsIPresShell> ps = GetPresShell();
     NS_ENSURE_TRUE(ps, NS_ERROR_NOT_INITIALIZED);
     nsCOMPtr<nsIDOMNode> parentNode;
     nsresult res = mGrabber->GetParentNode(getter_AddRefs(parentNode));
     NS_ENSURE_SUCCESS(res, res);
     nsCOMPtr<nsIContent> parentContent( do_QueryInterface(parentNode) );
     NS_ENSURE_TRUE(parentContent, NS_ERROR_FAILURE);
     DeleteRefToAnonymousNode(mPositioningShadow, parentContent, ps);
     mPositioningShadow = nullptr;
   }
   nsCOMPtr<nsIDOMEventTarget> piTarget = GetDOMEventTarget();
   if (piTarget && mMouseMotionListenerP) {
 #ifdef DEBUG
     nsresult res =
 #endif
     piTarget->RemoveEventListener(NS_LITERAL_STRING("mousemove"),
                                   mMouseMotionListenerP,
                                   false);
     NS_ASSERTION(NS_SUCCEEDED(res), "failed to remove mouse motion listener");
   }
   mMouseMotionListenerP = nullptr;
   mGrabberClicked = false;
   mIsMoving = false;
   nsCOMPtr<nsISelection> selection;
   GetSelection(getter_AddRefs(selection));
   if (!selection) {
     return NS_ERROR_NOT_INITIALIZED;
   }
   return CheckSelectionStateForAnonymousButtons(selection);
 }
 nsresult
 nsHTMLEditor::SetFinalPosition(int32_t aX, int32_t aY)
 {
   nsresult res = EndMoving();
   NS_ENSURE_SUCCESS(res, res);
   // we have now to set the new width and height of the resized object
   // we don't set the x and y position because we don't control that in
   // a normal HTML layout
   int32_t newX = mPositionedObjectX + aX - mOriginalX - (mPositionedObjectBorderLeft+mPositionedObjectMarginLeft);
   int32_t newY = mPositionedObjectY + aY - mOriginalY - (mPositionedObjectBorderTop+mPositionedObjectMarginTop);
   SnapToGrid(newX, newY);
   nsAutoString x, y;
   x.AppendInt(newX);
   y.AppendInt(newY);
   // we want one transaction only from a user's point of view
   nsAutoEditBatch batchIt(this);
   mHTMLCSSUtils->SetCSSPropertyPixels(mAbsolutelyPositionedObject,
                                       nsEditProperty::cssTop,
                                       newY,
                                       false);
   mHTMLCSSUtils->SetCSSPropertyPixels(mAbsolutelyPositionedObject,
                                       nsEditProperty::cssLeft,
                                       newX,
                                       false);
   // keep track of that size
   mPositionedObjectX  = newX;
   mPositionedObjectY  = newY;
   return RefreshResizers();
 }
 void
 nsHTMLEditor::AddPositioningOffset(int32_t & aX, int32_t & aY)
 {
   // Get the positioning offset
   int32_t positioningOffset =
     Preferences::GetInt("editor.positioning.offset", 0);
   aX += positioningOffset;
   aY += positioningOffset;
 }
 NS_IMETHODIMP
 nsHTMLEditor::AbsolutelyPositionElement(nsIDOMElement * aElement,
                                         bool aEnabled)
 {
   NS_ENSURE_ARG_POINTER(aElement);
   nsAutoString positionStr;
   mHTMLCSSUtils->GetComputedProperty(aElement, nsEditProperty::cssPosition,
                                      positionStr);
   bool isPositioned = (positionStr.EqualsLiteral("absolute"));
   // nothing to do if the element is already in the state we want
   if (isPositioned == aEnabled)
     return NS_OK;
   nsAutoEditBatch batchIt(this);
   if (aEnabled) {
     int32_t x, y;
     GetElementOrigin(aElement, x, y);
     mHTMLCSSUtils->SetCSSProperty(aElement,
                                   nsEditProperty::cssPosition,
                                   NS_LITERAL_STRING("absolute"),
                                   false);
     AddPositioningOffset(x, y);
     SnapToGrid(x, y);
     SetElementPosition(aElement, x, y);
     // we may need to create a br if the positioned element is alone in its
     // container
     nsCOMPtr<nsINode> element = do_QueryInterface(aElement);
     NS_ENSURE_STATE(element);
     nsINode* parentNode = element->GetParentNode();
     if (parentNode->GetChildCount() == 1) {
       nsCOMPtr<nsIDOMNode> brNode;
       nsresult res = CreateBR(parentNode->AsDOMNode(), 0, address_of(brNode));
       NS_ENSURE_SUCCESS(res, res);
     }
   }
   else {
     mHTMLCSSUtils->RemoveCSSProperty(aElement,
                                      nsEditProperty::cssPosition,
                                      EmptyString(), false);
     mHTMLCSSUtils->RemoveCSSProperty(aElement,
                                      nsEditProperty::cssTop,
                                      EmptyString(), false);
     mHTMLCSSUtils->RemoveCSSProperty(aElement,
                                      nsEditProperty::cssLeft,
                                      EmptyString(), false);
     mHTMLCSSUtils->RemoveCSSProperty(aElement,
                                      nsEditProperty::cssZIndex,
                                      EmptyString(), false);
     if (!nsHTMLEditUtils::IsImage(aElement)) {
       mHTMLCSSUtils->RemoveCSSProperty(aElement,
                                        nsEditProperty::cssWidth,
                                        EmptyString(), false);
       mHTMLCSSUtils->RemoveCSSProperty(aElement,
                                        nsEditProperty::cssHeight,
                                        EmptyString(), false);
     }
     nsCOMPtr<dom::Element> element = do_QueryInterface(aElement);
     if (element && element->IsHTML(nsGkAtoms::div) && !HasStyleOrIdOrClass(element)) {
       nsRefPtr<nsHTMLEditRules> htmlRules = static_cast<nsHTMLEditRules*>(mRules.get());
       NS_ENSURE_TRUE(htmlRules, NS_ERROR_FAILURE);
       nsresult res = htmlRules->MakeSureElemStartsOrEndsOnCR(aElement);
       NS_ENSURE_SUCCESS(res, res);
       res = RemoveContainer(aElement);
       NS_ENSURE_SUCCESS(res, res);
     }
   }
   return NS_OK;
 }
 NS_IMETHODIMP
 nsHTMLEditor::SetSnapToGridEnabled(bool aEnabled)
 {
   mSnapToGridEnabled = aEnabled;
   return NS_OK;
 }
 NS_IMETHODIMP
 nsHTMLEditor::GetSnapToGridEnabled(bool * aIsEnabled)
 {
   *aIsEnabled = mSnapToGridEnabled;
   return NS_OK;
 }
 NS_IMETHODIMP
 nsHTMLEditor::SetGridSize(uint32_t aSize)
 {
   mGridSize = aSize;
   return NS_OK;
 }
 NS_IMETHODIMP
 nsHTMLEditor::GetGridSize(uint32_t * aSize)
 {
   *aSize = mGridSize;
   return NS_OK;
 }
 // self-explanatory
 NS_IMETHODIMP
 nsHTMLEditor::SetElementPosition(nsIDOMElement *aElement, int32_t aX, int32_t aY)
 {
   nsAutoEditBatch batchIt(this);
   mHTMLCSSUtils->SetCSSPropertyPixels(aElement,
                                       nsEditProperty::cssLeft,
                                       aX,
                                       false);
   mHTMLCSSUtils->SetCSSPropertyPixels(aElement,
                                       nsEditProperty::cssTop,
                                       aY,
                                       false);
   return NS_OK;
 }
 // self-explanatory
 NS_IMETHODIMP
 nsHTMLEditor::GetPositionedElement(nsIDOMElement ** aReturn)
 {
   *aReturn = mAbsolutelyPositionedObject;
   NS_IF_ADDREF(*aReturn);
   return NS_OK;
 }
 nsresult
 nsHTMLEditor::CheckPositionedElementBGandFG(nsIDOMElement * aElement,
                                             nsAString & aReturn)
 {
   // we are going to outline the positioned element and bring it to the
   // front to overlap any other element intersecting with it. But
   // first, let's see what's the background and foreground colors of the
   // positioned element.
   // if background-image computed value is 'none,
   //   If the background color is 'auto' and R G B values of the foreground are
   //       each above #d0, use a black background
   //   If the background color is 'auto' and at least one of R G B values of
   //       the foreground is below #d0, use a white background
   // Otherwise don't change background/foreground
   aReturn.Truncate();
   nsAutoString bgImageStr;
   nsresult res =
     mHTMLCSSUtils->GetComputedProperty(aElement,
                                        nsEditProperty::cssBackgroundImage,
                                        bgImageStr);
   NS_ENSURE_SUCCESS(res, res);
   if (bgImageStr.EqualsLiteral("none")) {
     nsAutoString bgColorStr;
     res =
       mHTMLCSSUtils->GetComputedProperty(aElement,
                                          nsEditProperty::cssBackgroundColor,
                                          bgColorStr);
     NS_ENSURE_SUCCESS(res, res);
     if (bgColorStr.EqualsLiteral("transparent")) {
       nsRefPtr<nsComputedDOMStyle> cssDecl =
         mHTMLCSSUtils->GetComputedStyle(aElement);
       NS_ENSURE_STATE(cssDecl);
       // from these declarations, get the one we want and that one only
       ErrorResult error;
       nsRefPtr<dom::CSSValue> cssVal = cssDecl->GetPropertyCSSValue(NS_LITERAL_STRING("color"), error);
       NS_ENSURE_SUCCESS(error.ErrorCode(), error.ErrorCode());
       nsROCSSPrimitiveValue* val = cssVal->AsPrimitiveValue();
       NS_ENSURE_TRUE(val, NS_ERROR_FAILURE);
       if (nsIDOMCSSPrimitiveValue::CSS_RGBCOLOR == val->PrimitiveType()) {
         nsDOMCSSRGBColor* rgbVal = val->GetRGBColorValue(error);
         NS_ENSURE_SUCCESS(error.ErrorCode(), error.ErrorCode());
         float r = rgbVal->Red()->
           GetFloatValue(nsIDOMCSSPrimitiveValue::CSS_NUMBER, error);
         NS_ENSURE_SUCCESS(error.ErrorCode(), error.ErrorCode());
         float g = rgbVal->Green()->
           GetFloatValue(nsIDOMCSSPrimitiveValue::CSS_NUMBER, error);
         NS_ENSURE_SUCCESS(error.ErrorCode(), error.ErrorCode());
         float b = rgbVal->Blue()->
           GetFloatValue(nsIDOMCSSPrimitiveValue::CSS_NUMBER, error);
         NS_ENSURE_SUCCESS(error.ErrorCode(), error.ErrorCode());
         if (r >= BLACK_BG_RGB_TRIGGER &&
             g >= BLACK_BG_RGB_TRIGGER &&
             b >= BLACK_BG_RGB_TRIGGER)
           aReturn.AssignLiteral("black");
         else
           aReturn.AssignLiteral("white");
         return NS_OK;
       }
     }
   }
   return NS_OK;
 }

The Tor Browser / annotate

editor/libeditor/html/nsHTMLAbsPosition.cpp@b8a032363ba2 (annotated)

editor/libeditor/html/nsHTMLAbsPosition.cpp