Initial RenderTextMac implementation using CoreText.

ui/gfx/render_text_mac.cc

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/gfx/render_text_mac.h"
+
+#include <ApplicationServices/ApplicationServices.h>
+
+#include <cmath>
+#include <utility>
+
+#include "base/mac/foundation_util.h"
+#include "base/mac/scoped_cftyperef.h"
+#include "base/sys_string_conversions.h"
+#include "skia/ext/skia_utils_mac.h"
+
+namespace {
+
+// Returns the pixel height of |ct_font|.
+CGFloat GetCTFontPixelSize(CTFontRef ct_font) {
+  return CTFontGetAscent(ct_font) + CTFontGetDescent(ct_font);

[Nico, 2012/06/22 18:04:10]

Have you checked that GetAscent() actually returns pixels and now view
coordinates?
https://developer.apple.com/library/mac/#documentation/Carbon/reference/CTFon...
doesn't say either way. (You can put your normal lion laptop into hidpi mode to
check)

[Alexei Svitkine (slow), 2012/06/22 19:35:29]

I'll have to check.

[Alexei Svitkine (slow), 2012/07/16 22:43:08]

I've verified that the metrics values returned are the same regardless of
whether the system is using a HiDPI resolution or not. (For the values returned
here and elsewhere in the file.)

+}
+
+// Creates a CTFont with the given font name and pixel size. Ownership is
+// transferred to the caller.
+CTFontRef CreateCTFontWithPixelSize(const std::string& font_name,
+                                    const int target_pixel_size) {
+  // Epsilon value used for comparing font sizes.
+  const CGFloat kEpsilon = 0.001;
+  // The observed pixel to points ratio for Lucida Grande on 10.6. Other fonts
+  // have other ratios and the documentation doesn't provide a guarantee that
+  // the relation is linear. So this ratio is used as a first try before
+  // falling back to the bisection method.
+  const CGFloat kPixelsToPointsRatio = 0.849088;
+
+  base::mac::ScopedCFTypeRef<CFStringRef> font_name_cf_string(
+      base::SysUTF8ToCFStringRef(font_name));
+
+  // First, try using |kPixelsToPointsRatio|.
+  CGFloat point_size = target_pixel_size * kPixelsToPointsRatio;
+  base::mac::ScopedCFTypeRef<CTFontRef> ct_font(
+      CTFontCreateWithName(font_name_cf_string, point_size, NULL));
+  CGFloat actual_pixel_size = GetCTFontPixelSize(ct_font);
+  if (std::fabs(actual_pixel_size - target_pixel_size) < kEpsilon)
+    return ct_font.release();
+
+  // |kPixelsToPointsRatio| wasn't correct. Use the bisection method to find the
+  // right size.
+
+  // First, find the initial bisection range, so that the point size that
+  // corresponds to |target_pixel_size| is between |lo| and |hi|.
+  CGFloat lo = 0;
+  CGFloat hi = point_size;
+  while (actual_pixel_size < target_pixel_size) {
+    lo = hi;
+    hi *= 2;
+    ct_font.reset(CTFontCreateWithName(font_name_cf_string, hi, NULL));
+    actual_pixel_size = GetCTFontPixelSize(ct_font);
+  }
+
+  // Now, bisect to find the right size.
+  while (lo < hi) {
+    point_size = (hi - lo) * 0.5 + lo;
+    ct_font.reset(CTFontCreateWithName(font_name_cf_string, point_size, NULL));
+    actual_pixel_size = GetCTFontPixelSize(ct_font);
+    if (std::fabs(actual_pixel_size - target_pixel_size) < kEpsilon)
+      break;
+    if (target_pixel_size > actual_pixel_size)
+      lo = point_size;
+    else
+      hi = point_size;
+  }
+
+  return ct_font.release();
+}
+
+}  // namespace
+
+namespace gfx {
+
+RenderTextMac::RenderTextMac() : common_baseline_(0), runs_valid_(false) {
+}
+
+RenderTextMac::~RenderTextMac() {
+}
+
+base::i18n::TextDirection RenderTextMac::GetTextDirection() {
+  return base::i18n::LEFT_TO_RIGHT;
+}
+
+Size RenderTextMac::GetStringSize() {
+  EnsureLayout();
+  return string_size_;
+}
+
+int RenderTextMac::GetBaseline() {
+  EnsureLayout();
+  return common_baseline_;
+}
+
+SelectionModel RenderTextMac::FindCursorPosition(const Point& point) {
+  // TODO(asvitkine): Implement this. http://crbug.com/131618
+  return SelectionModel();
+}
+
+std::vector<RenderText::FontSpan> RenderTextMac::GetFontSpansForTesting() {
+  EnsureLayout();
+  if (!runs_valid_)
+    ComputeRuns();
+
+  std::vector<RenderText::FontSpan> spans;
+  for (size_t i = 0; i < runs_.size(); ++i) {
+    gfx::Font font(runs_[i].font_name, runs_[i].text_size);
+    const CFRange cf_range = CTRunGetStringRange(runs_[i].ct_run);
+    const ui::Range range(cf_range.location,
+                          cf_range.location + cf_range.length);
+    spans.push_back(RenderText::FontSpan(font, range));
+  }
+
+  return spans;
+}
+
+SelectionModel RenderTextMac::AdjacentCharSelectionModel(
+    const SelectionModel& selection,
+    VisualCursorDirection direction) {
+  // TODO(asvitkine): Implement this. http://crbug.com/131618
+  return SelectionModel();
+}
+
+SelectionModel RenderTextMac::AdjacentWordSelectionModel(
+    const SelectionModel& selection,
+    VisualCursorDirection direction) {
+  // TODO(asvitkine): Implement this. http://crbug.com/131618
+  return SelectionModel();
+}
+
+void RenderTextMac::GetGlyphBounds(size_t index,
+                                   ui::Range* xspan,
+                                   int* height) {
+  // TODO(asvitkine): Implement this. http://crbug.com/131618
+}
+
+std::vector<Rect> RenderTextMac::GetSubstringBounds(ui::Range range) {
+  // TODO(asvitkine): Implement this. http://crbug.com/131618
+  return std::vector<Rect>();
+}
+
+bool RenderTextMac::IsCursorablePosition(size_t position) {
+  // TODO(asvitkine): Implement this. http://crbug.com/131618
+  return false;
+}
+
+void RenderTextMac::ResetLayout() {
+  line_.reset();
+  runs_.clear();
+  runs_valid_ = false;
+}
+
+void RenderTextMac::EnsureLayout() {
+  if (line_.get())
+    return;
+  runs_.clear();
+  runs_valid_ = false;
+
+  const Font& font = GetFont();
+  CTFontRef ct_font =
+      CreateCTFontWithPixelSize(font.GetFontName(), font.GetFontSize());
+
+  const void* keys[] = { kCTFontAttributeName };
+  const void* values[] = { ct_font };
+  base::mac::ScopedCFTypeRef<CFDictionaryRef> attributes(
+      CFDictionaryCreate(NULL, keys, values, arraysize(keys), NULL, NULL));
+
+  base::mac::ScopedCFTypeRef<CFStringRef> cf_text(
+      base::SysUTF16ToCFStringRef(text()));
+  base::mac::ScopedCFTypeRef<CFAttributedStringRef> attr_text(
+      CFAttributedStringCreate(NULL, cf_text, attributes));
+  base::mac::ScopedCFTypeRef<CFMutableAttributedStringRef> attr_text_mutable(
+      CFAttributedStringCreateMutableCopy(NULL, 0, attr_text));
+
+  ApplyStyles(attr_text_mutable, ct_font);
+  line_.reset(CTLineCreateWithAttributedString(attr_text_mutable));
+
+  CGFloat ascent = 0;
+  CGFloat descent = 0;
+  CGFloat leading = 0;
+  // TODO(asvitkine): Consider using CTLineGetBoundsWithOptions() on 10.8+.
+  double width = CTLineGetTypographicBounds(line_, &ascent, &descent, &leading);
+  string_size_ = Size(width, ascent + descent + leading);
+  common_baseline_ = ascent;
+}
+
+void RenderTextMac::DrawVisualText(Canvas* canvas) {
+  DCHECK(line_);
+  if (!runs_valid_)
+    ComputeRuns();
+
+  internal::SkiaTextRenderer renderer(canvas);
+  ApplyFadeEffects(&renderer);
+  ApplyTextShadows(&renderer);
+
+  for (size_t i = 0; i < runs_.size(); ++i) {
+    const TextRun& run = runs_[i];
+    renderer.SetForegroundColor(run.foreground);
+    renderer.SetTextSize(run.text_size);
+    renderer.SetFontFamilyWithStyle(run.font_name, run.font_style);
+    renderer.DrawPosText(&run.glyph_positions[0], &run.glyphs[0],
+                         run.glyphs.size());
+    renderer.DrawDecorations(run.origin.x(), run.origin.y(), run.width,
+                             run.style);
+  }
+}
+
+RenderTextMac::TextRun::TextRun()
+    : ct_run(NULL),
+      origin(SkPoint::Make(0, 0)),
+      width(0),
+      font_style(Font::NORMAL),
+      text_size(0),
+      foreground(SK_ColorBLACK) {
+}
+
+RenderTextMac::TextRun::~TextRun() {
+}
+
+void RenderTextMac::ApplyStyles(CFMutableAttributedStringRef attr_string,
+                                CTFontRef font) {
+  // https://developer.apple.com/library/mac/#documentation/Carbon/Reference/CoreText_StringAttributes_Ref/Reference/reference.html
+  for (size_t i = 0; i < style_ranges().size(); ++i) {
+    const StyleRange& style = style_ranges()[i];
+    const CFRange range = CFRangeMake(style.range.start(),
+                                      style.range.length());
+
+    CGColorRef foreground = gfx::SkColorToCGColorRef(style.foreground);

[Nico, 2012/06/22 18:04:10]

color space?

[Alexei Svitkine (slow), 2012/06/22 19:35:29]

Can you elaborate the concern? This code only sets the color so that it could
later retrieve it in |ComputeRuns()| - since CoreText isn't actually used to
draw the text.

So assuming that CoreText doesn't do any munging to the color and that 
gfx::CGColorRefToSkColor(gfx::SkColorToCGColorRef()) is an identity function,
this should be fine I think.

[Nico, 2012/06/22 19:38:05]

Ok.

+    CFAttributedStringSetAttribute(attr_string, range,
+                                   kCTForegroundColorAttributeName,
+                                   foreground);
+
+    if (style.font_style & Font::UNDERLINED) {
+      CTUnderlineStyle value = kCTUnderlineStyleSingle;
+      CFNumberRef underline = CFNumberCreate(NULL, kCFNumberSInt32Type, &value);

[Nico, 2012/06/22 18:04:10]

Leaks (?)

[Alexei Svitkine (slow), 2012/06/22 19:35:29]

Fixed.

Why is this case different than kCTForegroundColorAttributeName with a
CGColorRef? For that case, it seems the param doesn't get retained by the call,
whereas for these two, it does.

[Nico, 2012/06/22 19:38:05]

I didn't notice this for the color because SkCOlorToCGColorRef isn't called
CreateCGColorRefWithSkColor() (I think the latter would be a better name). Are
you sure the color isn't retained above? That'd be weird.

[Alexei Svitkine (slow), 2012/07/16 22:43:08]

It indeed seems to be the case. If I CFRelease() |foreground| in ApplyStyles(),
I later get the following error when I try to retrive it in ComputeRuns():

[90095:-1600719552:272684540156830:WARNING:foundation_util.h(322)] Expected
value for key CTForegroundColor to be CGColor but it was Not A Type instead

(i.e. probably that memory location is no longer a CGColor since it was
completely deallocated and possibly allocated for another object...)

[Alexei Svitkine (slow), 2012/07/21 14:10:58]

Thinking about this some more, this really sounds like a bug in CoreText.

I guess the right way to work-around this is to keep track of the CGColor
objects we create and manage their lifetimes so that their lifetimes are greater
than that of |line_|, assuming CoreText holds weak references to them. (If the
CoreText bug gets fixed, then this extra book-keeping will be harmless.)

Do you agree that that's the right solution here?

[Nico, 2012/07/21 16:17:23]

That sounds right to me. Bonus points for filing a rdar with apple.

[Alexei Svitkine (slow), 2012/07/23 14:33:35]

I did some more testing here and it appears it's actually consistent for all the
values that I'm setting via CFAttributedStringSetAttribute(). None of them get
retained (according to CFGetRetainCount()).

I also checked whether they end up getting released when the CoreText |line_|
gets released, and they don't. So they're proper weak refs and we'll have to
keep track of all of these ourselves and make sure to CFRelease() them when
necessary.

I've changed these back to not use ScopedCFTypeRef for now and added a big TODO
that I plan to address in a followup CL.

+      CFAttributedStringSetAttribute(attr_string, range,
+                                     kCTUnderlineStyleAttributeName,
+                                     underline);
+    }
+
+    if (style.font_style & (Font::BOLD | Font::ITALIC)) {
+      int traits = 0;
+      if (style.font_style & Font::BOLD)
+        traits |= kCTFontBoldTrait;
+      if (style.font_style & Font::ITALIC)
+        traits |= kCTFontItalicTrait;
+      CTFontRef styled_font =
+          CTFontCreateCopyWithSymbolicTraits(font, 0.0, NULL, traits, traits);

[Nico, 2012/06/22 18:04:10]

Leaks?

[Alexei Svitkine (slow), 2012/06/22 19:35:29]

Fixed.

+      CFAttributedStringSetAttribute(attr_string, range, kCTFontAttributeName,
+                                     styled_font);
+    }
+  }
+}
+
+void RenderTextMac::ComputeRuns() {
+  DCHECK(line_);
+
+  CFArrayRef ct_runs = CTLineGetGlyphRuns(line_);
+  const CFIndex ct_runs_count = CFArrayGetCount(ct_runs);
+
+  Point offset(GetTextOrigin());
+  // Skia will draw glyphs with respect to the baseline.
+  offset.Offset(0, common_baseline_);
+
+  const SkScalar x = SkIntToScalar(offset.x());
+  const SkScalar y = SkIntToScalar(offset.y());
+  SkPoint run_origin = SkPoint::Make(offset.x(), offset.y());
+
+  const CFRange empty_cf_range = CFRangeMake(0, 0);
+  for (CFIndex i = 0; i < ct_runs_count; ++i) {
+    CTRunRef ct_run =
+        base::mac::CFCast<CTRunRef>(CFArrayGetValueAtIndex(ct_runs, i));
+    const size_t glyph_count = CTRunGetGlyphCount(ct_run);
+    const double run_width =
+        CTRunGetTypographicBounds(ct_run, empty_cf_range, NULL, NULL, NULL);
+    if (glyph_count == 0) {
+      run_origin.offset(run_width, 0);
+      continue;
+    }
+
+    runs_.push_back(TextRun());
+    TextRun* run = &runs_.back();
+    run->ct_run = ct_run;
+    run->origin = run_origin;
+    run->width = run_width;
+    run->glyphs.resize(glyph_count);
+    CTRunGetGlyphs(ct_run, empty_cf_range, &run->glyphs[0]);
+
+    run->glyph_positions.resize(glyph_count);
+    const CGPoint* positions_ptr = CTRunGetPositionsPtr(ct_run);
+    std::vector<CGPoint> positions;
+    if (positions_ptr == NULL) {
+      positions.resize(glyph_count);
+      CTRunGetPositions(ct_run, empty_cf_range, &positions[0]);
+      positions_ptr = &positions[0];
+    }
+    for (size_t glyph = 0; glyph < glyph_count; glyph++) {
+      SkPoint* point = &run->glyph_positions[glyph];
+      point->set(x + SkDoubleToScalar(positions_ptr[glyph].x),
+                 y + SkDoubleToScalar(positions_ptr[glyph].y));
+    }
+
+    CFDictionaryRef attributes = CTRunGetAttributes(ct_run);
+    CTFontRef ct_font =
+        base::mac::GetValueFromDictionary<CTFontRef>(attributes,
+                                                     kCTFontAttributeName);
+    base::mac::ScopedCFTypeRef<CFStringRef> font_name_ref(
+        CTFontCopyFamilyName(ct_font));
+    run->font_name = base::SysCFStringRefToUTF8(font_name_ref);
+    run->text_size = GetCTFontPixelSize(ct_font);
+
+    CTFontSymbolicTraits traits = CTFontGetSymbolicTraits(ct_font);
+    if (traits & kCTFontBoldTrait)
+      run->font_style |= Font::BOLD;
+    if (traits & kCTFontItalicTrait)
+      run->font_style |= Font::ITALIC;
+
+    const CGColorRef foreground =
+        base::mac::GetValueFromDictionary<CGColorRef>(
+            attributes, kCTForegroundColorAttributeName);
+    run->foreground = gfx::CGColorRefToSkColor(foreground);
+
+    const CFNumberRef underline =
+        base::mac::GetValueFromDictionary<CFNumberRef>(
+            attributes, kCTUnderlineStyleAttributeName);
+    CTUnderlineStyle value = kCTUnderlineStyleNone;
+    if (underline && CFNumberGetValue(underline, kCFNumberSInt32Type, &value))
+      run->style.underline = (value == kCTUnderlineStyleSingle);
+
+    run_origin.offset(run_width, 0);
+  }
+  runs_valid_ = true;
+}
+
+RenderText* RenderText::CreateRenderText() {
+  return new RenderTextMac;
+}
+
+}  // namespace gfx