4 files changed, 53 insertions, 1 deletions
diff --git a/layout/forms/nsComboboxControlFrame.cpp b/layout/forms/nsComboboxControlFrame.cpp
index 459c6f7ecc..2d0395d7a1 100644
--- a/layout/forms/nsComboboxControlFrame.cpp
+++ b/layout/forms/nsComboboxControlFrame.cpp
@@ -1322,7 +1322,8 @@ nsComboboxDisplayFrame::Reflow(nsPresContext*           aPresContext,
     // Note that the only way we can have a computed block size here is
     // if the combobox had a specified block size.  If it didn't, size
     // based on what our rows look like, for lack of anything better.
-    state.SetComputedBSize(mComboBox->mListControlFrame->GetBSizeOfARow());
+    //state.SetComputedBSize(mComboBox->mListControlFrame->GetBSizeOfARow());
+    state.SetLineHeight(state.mParentReflowInput->GetLineHeight());
   }
   WritingMode wm = aReflowInput.GetWritingMode();
   nscoord computedISize = mComboBox->mDisplayISize -
diff --git a/layout/forms/test/test_issue1970_manual.html b/layout/forms/test/test_issue1970_manual.html
new file mode 100644
index 0000000000..223c6e845d
--- /dev/null
+++ b/layout/forms/test/test_issue1970_manual.html
@@ -0,0 +1,35 @@
+<!doctype html>
+<html>
+<head>
+<meta charset="utf-8">
+<style>
+.fontA {
+    font-family: "Noto Sans";
+}
+.fontB {
+    font-family: "Noto Sans CJK TC";
+}
+.fontC {
+    font-family: "WenQuanYi Zen Hei";
+}
+</style>
+</head>
+<body>
+<p>No clipping of the font glyphs should occur.</p>
+<select>
+    <option>Latin Text jpg</option>
+</select>
+<select>
+    <option>漢字 jpg</option>
+</select>
+<select class="fontA">
+    <option>漢字 jpg</option>
+</select>
+<select class="fontB">
+    <option>漢字 jpg</option>
+</select>
+<select class="fontC">
+    <option>漢字 jpg</option>
+</select>
+</body>
+</html>
+\ No newline at end of file
diff --git a/layout/generic/ReflowInput.cpp b/layout/generic/ReflowInput.cpp
index f308ebcdf5..01f36cc9db 100644
--- a/layout/generic/ReflowInput.cpp
+++ b/layout/generic/ReflowInput.cpp
@@ -2813,6 +2813,17 @@ nscoord ReflowInput::GetLineHeight() const {
                                nsLayoutUtils::FontSizeInflationFor(mFrame));
 }
 
+void ReflowInput::SetLineHeight(nscoord aLineHeight) {
+  MOZ_ASSERT(aLineHeight >= 0, "aLineHeight must be >= 0!");
+
+  if (mLineHeight != aLineHeight) {
+    mLineHeight = aLineHeight;
+    // Setting used line height can change a frame's block-size if mFrame's
+    // block-size behaves as auto.
+    InitResizeFlags(mFrame->PresContext(), mFrame->GetType());
+  }
+}
+
 /* static */ nscoord
 ReflowInput::CalcLineHeight(nsIContent* aContent,
                                   nsStyleContext* aStyleContext,
diff --git a/layout/generic/ReflowInput.h b/layout/generic/ReflowInput.h
index d8e0518399..a70549d8eb 100644
--- a/layout/generic/ReflowInput.h
+++ b/layout/generic/ReflowInput.h
@@ -747,6 +747,11 @@ public:
    * Get the used line-height property. The return value will be >= 0.
    */
   nscoord GetLineHeight() const;
+  
+  /**
+   * Set the used line-height. aLineHeight must be >= 0.
+   */
+  void SetLineHeight(nscoord aLineHeight);
 
   /**
    * Calculate the used line-height property without a reflow input instance.