Reserve 1 DIP for the caret in Textfield default/min width calculations.

This matches what the underlying RenderText already does.  It probably
doesn't matter much, since the width itself is "average character
width * n", which isn't going to result in a reliable pixel-precise
value, but it does mean that, on Windows, sizing a Textfield to n
characters (which are in theory based on the width of 'x'), then typing
n 'x's, no longer results in the Textfield scrolling slightly.

Bug: none
Change-Id: Idea1473438037836f8a50e260c5b2ac261830a84
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2421028
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Auto-Submit: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Peter Boström <pbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809942}

ui/views/controls/textfield/textfield.cc

@@ -709,8 +709,7 @@ int Textfield::GetBaseline() const {
 gfx::Size Textfield::CalculatePreferredSize() const {
   DCHECK_GE(default_width_in_chars_, minimum_width_in_chars_);
   return gfx::Size(
-      GetFontList().GetExpectedTextWidth(default_width_in_chars_) +
-          GetInsets().width(),
+      CharsToDips(default_width_in_chars_),
       LayoutProvider::GetControlHeightForFont(style::CONTEXT_TEXTFIELD,
                                               GetTextStyle(), GetFontList()));
 }
@@ -719,9 +718,7 @@ gfx::Size Textfield::GetMinimumSize() const {
   DCHECK_LE(minimum_width_in_chars_, default_width_in_chars_);
   gfx::Size minimum_size = View::GetMinimumSize();
   if (minimum_width_in_chars_ >= 0)
-    minimum_size.set_width(
-        GetFontList().GetExpectedTextWidth(minimum_width_in_chars_) +
-        GetInsets().width());
+    minimum_size.set_width(CharsToDips(minimum_width_in_chars_));
   return minimum_size;
 }
 
@@ -2506,6 +2503,16 @@ bool Textfield::ShouldShowCursor() const {
          !drop_cursor_visible_ && GetRenderText()->cursor_enabled();
 }
 
+int Textfield::CharsToDips(int width_in_chars) const {
+  // Use a subset of the conditions in ShouldShowCursor() that are unlikely to
+  // change dynamically.  Dynamic changes can result in glitchy-looking visual
+  // effects like find boxes on different tabs being 1 DIP different width.
+  const int cursor_width =
+      (!GetReadOnly() && GetRenderText()->cursor_enabled()) ? 1 : 0;
+  return GetFontList().GetExpectedTextWidth(default_width_in_chars_) +
+         cursor_width + GetInsets().width();
+}
+
 bool Textfield::ShouldBlinkCursor() const {
   return ShouldShowCursor() && !Textfield::GetCaretBlinkInterval().is_zero();
 }

ui/views/controls/textfield/textfield.h

@@ -571,6 +571,10 @@ class VIEWS_EXPORT Textfield : public View,
   // placed at the point new text will be inserted).
   bool ShouldShowCursor() const;
 
+  // Converts a textfield width in "average characters" to the required number
+  // of DIPs, accounting for insets and cursor.
+  int CharsToDips(int width_in_chars) const;
+
   // Returns true if an insertion cursor should be visible and blinking.
   bool ShouldBlinkCursor() const;