Make Label::GetHeightForWidth(0) take GetMaxLines() height.

Effectively, this says that zero-width labels are "as tall as possible",
not "always one line high".

Bug: none
Change-Id: If09da545ffd2dc0d92f5ffdc574fcc63f34f6144
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2420128
Auto-Submit: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Dana Fried <dfried@chromium.org>
Commit-Queue: Dana Fried <dfried@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809098}

ui/views/controls/label.cc

@@ -541,8 +541,10 @@ int Label::GetHeightForWidth(int w) const {
   w -= GetInsets().width();
   int height = 0;
   int base_line_height = GetLineHeight();
-  if (!GetMultiLine() || GetText().empty() || w <= 0) {
+  if (!GetMultiLine() || GetText().empty() || w < 0) {
     height = base_line_height;
+  } else if (w == 0) {
+    height = std::max(GetMaxLines(), 1) * base_line_height;
   } else {
     // SetDisplayRect() has a side effect for later calls of GetStringSize().
     // Be careful to invoke |full_text_->SetDisplayRect(gfx::Rect())| to

ui/views/controls/label_unittest.cc

@@ -488,6 +488,45 @@ TEST_F(LabelTest, MultilinePreferredSizeTest) {
   EXPECT_LT(multi_line_size.height(), new_size.height());
 }
 
+TEST_F(LabelTest, SingleLineGetHeightForWidth) {
+  // Even an empty label should take one line worth of height.
+  const int line_height = label()->GetLineHeight();
+  EXPECT_EQ(line_height, label()->GetHeightForWidth(100));
+
+  // Given any amount of width, the label should take one line.
+  label()->SetText(ASCIIToUTF16("This is an example."));
+  const int width = label()->GetPreferredSize().width();
+  EXPECT_EQ(line_height, label()->GetHeightForWidth(width));
+  EXPECT_EQ(line_height, label()->GetHeightForWidth(width * 2));
+  EXPECT_EQ(line_height, label()->GetHeightForWidth(width / 2));
+  EXPECT_EQ(line_height, label()->GetHeightForWidth(0));
+}
+
+TEST_F(LabelTest, MultiLineGetHeightForWidth) {
+  // Even an empty label should take one line worth of height.
+  label()->SetMultiLine(true);
+  const int line_height = label()->GetLineHeight();
+  EXPECT_EQ(line_height, label()->GetHeightForWidth(100));
+
+  // Given its preferred width or more, the label should take one line.
+  label()->SetText(ASCIIToUTF16("This is an example."));
+  const int width = label()->GetPreferredSize().width();
+  EXPECT_EQ(line_height, label()->GetHeightForWidth(width));
+  EXPECT_EQ(line_height, label()->GetHeightForWidth(width * 2));
+
+  // Given too little width, the required number of lines should increase.
+  // Linebreaking will affect this, so sanity-checks are sufficient.
+  const int height_for_half_width = label()->GetHeightForWidth(width / 2);
+  EXPECT_GT(height_for_half_width, line_height);
+  EXPECT_GT(label()->GetHeightForWidth(width / 4), height_for_half_width);
+
+  // Given zero width, the label should take GetMaxLines(); if this is not set,
+  // default to one.
+  EXPECT_EQ(line_height, label()->GetHeightForWidth(0));
+  label()->SetMaxLines(10);
+  EXPECT_EQ(line_height * 10, label()->GetHeightForWidth(0));
+}
+
 TEST_F(LabelTest, TooltipProperty) {
   label()->SetText(ASCIIToUTF16("My cool string."));