Bug 1224669 - Clamp width to be non-negative during intrinsic width calculation. r=dholbert

layout/generic/nsTextFrame.cpp

@@ -7872,7 +7872,9 @@ nsTextFrame::AddInlineMinISizeForFlow(nsRenderingContext *aRenderingContext,
 
     if (i > wordStart) {
       nscoord width =
-        NSToCoordCeilClamped(textRun->GetAdvanceWidth(wordStart, i - wordStart, &provider));
+        NSToCoordCeilClamped(textRun->GetAdvanceWidth(wordStart, i - wordStart,
+                                                      &provider));
+      width = std::max(0, width);
       aData->currentLine = NSCoordSaturatingAdd(aData->currentLine, width);
       aData->atStartOfLine = false;
 
@@ -7884,8 +7886,11 @@ nsTextFrame::AddInlineMinISizeForFlow(nsRenderingContext *aRenderingContext,
           aData->trailingWhitespace += width;
         } else {
           // Some non-whitespace so the old trailingWhitespace is no longer trailing
-          aData->trailingWhitespace =
-            NSToCoordCeilClamped(textRun->GetAdvanceWidth(trimStart, i - trimStart, &provider));
+          nscoord wsWidth =
+            NSToCoordCeilClamped(textRun->GetAdvanceWidth(trimStart,
+                                                          i - trimStart,
+                                                          &provider));
+          aData->trailingWhitespace = std::max(0, wsWidth);
         }
       } else {
         aData->trailingWhitespace = 0;
@@ -8024,7 +8029,9 @@ nsTextFrame::AddInlinePrefISizeForFlow(nsRenderingContext *aRenderingContext,
 
     if (i > lineStart) {
       nscoord width =
-        NSToCoordCeilClamped(textRun->GetAdvanceWidth(lineStart, i - lineStart, &provider));
+        NSToCoordCeilClamped(textRun->GetAdvanceWidth(lineStart, i - lineStart,
+                                                      &provider));
+      width = std::max(0, width);
       aData->currentLine = NSCoordSaturatingAdd(aData->currentLine, width);
 
       if (collapseWhitespace) {
@@ -8035,8 +8042,11 @@ nsTextFrame::AddInlinePrefISizeForFlow(nsRenderingContext *aRenderingContext,
           aData->trailingWhitespace += width;
         } else {
           // Some non-whitespace so the old trailingWhitespace is no longer trailing
-          aData->trailingWhitespace =
-            NSToCoordCeilClamped(textRun->GetAdvanceWidth(trimStart, i - trimStart, &provider));
+          nscoord wsWidth =
+            NSToCoordCeilClamped(textRun->GetAdvanceWidth(trimStart,
+                                                          i - trimStart,
+                                                          &provider));
+          aData->trailingWhitespace = std::max(0, wsWidth);
         }
       } else {
         aData->trailingWhitespace = 0;

layout/reftests/text/reftest.list

@@ -326,4 +326,4 @@ pref(layout.css.control-characters.visible,true) != control-chars-04d.html contr
 HTTP(..) == space-font-1.html space-font-1-ref.html
 
 # handling of highly negative letter-spacing and intrinsic width
-fails == negative-letter-spacing-1.html negative-letter-spacing-1-ref.html
+== negative-letter-spacing-1.html negative-letter-spacing-1-ref.html