Bug 423385 - "floating parent does not size correctly with floating child using negative margin" [p=roc@ocallahan.org (Robert O'Callahan [roc]) r+sr=dbaron a1.9b5=beltzner]

layout/generic/nsFrame.cpp

@@ -2871,11 +2871,14 @@ nsIFrame::InlinePrefWidthData::ForceBreak(nsIRenderingContext *aRenderingContext
 
       nscoord &floats_cur = floatDisp->mFloats == NS_STYLE_FLOAT_LEFT
                               ? floats_cur_left : floats_cur_right;
-      floats_cur =
-        NSCoordSaturatingAdd(floats_cur,
+      nscoord floatWidth =
           nsLayoutUtils::IntrinsicForContainer(aRenderingContext,
                                                floatFrame,
-                                               nsLayoutUtils::PREF_WIDTH));
+                                               nsLayoutUtils::PREF_WIDTH);
+      // Negative-width floats don't change the available space so they
+      // shouldn't change our intrinsic line width either.
+      floats_cur =
+        NSCoordSaturatingAdd(floats_cur, PR_MAX(0, floatWidth));
     }
 
     nscoord floats_cur =

layout/reftests/bugs/reftest.list

@@ -773,5 +773,6 @@ fails == 413027-3.html 413027-3-ref.html
 == 421419-1.html 421419-1-ref.html
 == 422394-1.html 422394-1-ref.html
 == 423130-1.html 423130-1-ref.html
+== 423385-1.html 423385-1-ref.html
 == 423599-1.html 423599-1-ref.html
 == 423676-1.html 423676-1-ref.html