Add implementation of CanvasSkia based on RenderText.

ui/gfx/canvas_skia_skia.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/canvas_skia.h"
+
+#include "base/i18n/rtl.h"
+#include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/base/text/text_elider.h"
+#include "ui/gfx/font.h"
+#include "ui/gfx/font_list.h"
+#include "ui/gfx/rect.h"
+#include "ui/gfx/render_text.h"
+#include "ui/gfx/skia_util.h"
+
+namespace {
+
+// Based on |flags| and |text| content, returns whether text should be
+// rendered right-to-left.
+bool IsTextRTL(int flags, const string16& text) {
+  if (flags & gfx::Canvas::FORCE_RTL_DIRECTIONALITY)
+    return true;
+  if (flags & gfx::Canvas::FORCE_LTR_DIRECTIONALITY)
+    return false;
+  return base::i18n::IsRTL() && base::i18n::StringContainsStrongRTLChars(text);
+}
+
+// Checks each pixel immediately adjacent to the given pixel in the bitmap. If
+// any of them are not the halo color, returns true. This defines the halo of
+// pixels that will appear around the text. Note that we have to check each
+// pixel against both the halo color and transparent since |DrawStringWithHalo|
+// will modify the bitmap as it goes, and cleared pixels shouldn't count as
+// changed.
+bool PixelShouldGetHalo(const SkBitmap& bitmap,
+                        int x, int y,
+                        SkColor halo_color) {
+  if (x > 0 &&
+      *bitmap.getAddr32(x - 1, y) != halo_color &&
+      *bitmap.getAddr32(x - 1, y) != 0)
+    return true;  // Touched pixel to the left.
+  if (x < bitmap.width() - 1 &&
+      *bitmap.getAddr32(x + 1, y) != halo_color &&
+      *bitmap.getAddr32(x + 1, y) != 0)
+    return true;  // Touched pixel to the right.
+  if (y > 0 &&
+      *bitmap.getAddr32(x, y - 1) != halo_color &&
+      *bitmap.getAddr32(x, y - 1) != 0)
+    return true;  // Touched pixel above.
+  if (y < bitmap.height() - 1 &&
+      *bitmap.getAddr32(x, y + 1) != halo_color &&
+      *bitmap.getAddr32(x, y + 1) != 0)
+    return true;  // Touched pixel below.
+  return false;
+}
+
+// Apply vertical alignment per |flags|. Returns y-coordinate delta.
+int VAlignText(const gfx::Font& font,
+               int line_count,
+               int flags,
+               int available_height) {
+  const int text_size = font.GetFontSize();
+  int offset;
+  if (flags & gfx::Canvas::TEXT_VALIGN_TOP) {
+    offset = text_size;

[sky, 2012/01/23 23:01:17]

nit: I would be tempted to return here and in the other cases.

[Alexei Svitkine (slow), 2012/01/24 16:22:24]

Done.

+  } else if (flags & gfx::Canvas::TEXT_VALIGN_BOTTOM) {
+    offset = available_height + text_size - font.GetHeight() - 1;

[sky, 2012/01/23 23:01:17]

Why the -1 here and +1 @ 71?

[Alexei Svitkine (slow), 2012/01/24 16:22:24]

These values were picked empirically by observing the differences between the
existing Windows implementation and this code.

The middle alignment case is particularly strange below. It needs the + 1 added
to the value before dividing by two, to get the same rounding behaviour as the
canvas_skia_win.cc code, but then ends up subtracting 2.

[sky, 2012/01/24 17:05:28]

Please add a comment to this effect then.

+    if (line_count > 1)
+      offset -= (line_count * text_size);
+  } else {
+    int half_height = available_height + text_size + 1;
+    if (line_count > 1)
+      half_height -= (line_count * text_size);
+    offset = half_height/2 - 2;

[sky, 2012/01/23 23:01:17]

nit: 'half_height/2' -> 'half_height / 2'

[Alexei Svitkine (slow), 2012/01/24 16:22:24]

Done. I've also changed the variable name to better represent what it is (the
|half_height| name was from a version of this code that did the division by 2
earlier).

+  }
+  return offset;
+}
+
+// Updates |render_text| from the specified parameters.
+void UpdateRenderText(gfx::RenderText* render_text,
+                      const gfx::Rect& rect,
+                      const string16& text,
+                      const gfx::Font& font,
+                      int flags,
+                      SkColor color) {
+  int accelerated_char_pos = -1;
+  int accelerated_char_span = 0;
+  string16 transformed_text = text;
+
+  // Strip accelerator character prefixes.
+  if (flags & (gfx::Canvas::SHOW_PREFIX | gfx::Canvas::HIDE_PREFIX)) {
+    transformed_text = gfx::RemoveAcceleratorChar(text,
+                                                  '&',
+                                                  &accelerated_char_pos,
+                                                  &accelerated_char_span);
+  }
+
+  render_text->SetFontList(gfx::FontList(font));
+  render_text->SetText(transformed_text);
+  render_text->SetCursorEnabled(false);
+
+  gfx::Rect display_rect = rect;
+  display_rect.Offset(0, -font.GetFontSize());
+  display_rect.set_height(font.GetHeight());
+  render_text->SetDisplayRect(display_rect);
+
+  if (flags & gfx::Canvas::TEXT_ALIGN_RIGHT)
+    render_text->SetHorizontalAlignment(gfx::ALIGN_RIGHT);
+  else if (flags & gfx::Canvas::TEXT_ALIGN_CENTER)
+    render_text->SetHorizontalAlignment(gfx::ALIGN_CENTER);
+  else
+    render_text->SetHorizontalAlignment(gfx::ALIGN_LEFT);
+
+  gfx::StyleRange style;
+  style.foreground = color;
+  style.font_style = font.GetStyle();
+  if (font.GetStyle() & gfx::Font::UNDERLINED)
+    style.underline = true;
+  render_text->set_default_style(style);
+  render_text->ApplyDefaultStyle();
+
+  // Underline the accelerator char, if present.
+  if ((flags & gfx::Canvas::SHOW_PREFIX) && accelerated_char_pos != -1 &&
+      !style.underline) {
+    gfx::StyleRange underline_style = style;
+    int accelerated_char_end = accelerated_char_pos + accelerated_char_span;
+    underline_style.range.set_start(accelerated_char_pos);
+    underline_style.range.set_end(accelerated_char_end);
+    underline_style.underline = true;
+    render_text->ApplyStyleRange(underline_style);
+  }
+}
+
+}  // anonymous namespace
+
+namespace gfx {
+
+// static
+void CanvasSkia::SizeStringInt(const string16& text,
+                               const gfx::Font& font,
+                               int* width, int* height,
+                               int flags) {
+  DCHECK_GE(*width, 0);
+  DCHECK_GE(*height, 0);
+
+  if ((flags & MULTI_LINE) && *width != 0) {
+    ui::WordWrapBehavior wrap_behavior = ui::TRUNCATE_LONG_WORDS;
+    if (flags & CHARACTER_BREAK)
+      wrap_behavior = ui::WRAP_LONG_WORDS;
+    else if (!(flags & NO_ELLIPSIS))
+      wrap_behavior = ui::ELIDE_LONG_WORDS;
+
+    gfx::Rect rect(*width, INT_MAX);
+    std::vector<string16> strings;
+    ui::ElideRectangleText(text, font, rect.width(), rect.height(),
+                           wrap_behavior, &strings);
+    scoped_ptr<RenderText> render_text(RenderText::CreateRenderText());
+    UpdateRenderText(render_text.get(), rect, string16(), font, flags, 0);
+
+    int h = 0;
+    int w = 0;
+    for (size_t i = 0; i < strings.size(); ++i) {
+      if (flags & (SHOW_PREFIX | HIDE_PREFIX))
+        strings[i] = gfx::RemoveAcceleratorChar(strings[i], '&', NULL, NULL);
+      render_text->SetText(strings[i]);
+      w = std::max(w, render_text->GetStringWidth());
+      h += font.GetHeight();
+    }
+    *width = w;
+    *height = h;
+  } else {
+    // If the string is too long, the call by |RenderTextWin| to |ScriptShape()|
+    // will inexplicably fail with result E_INVALIDARG. Guard against this.
+    const size_t kMaxRenderTextLength = 5000;
+    if (text.length() >= kMaxRenderTextLength) {
+      *width = text.length() * font.GetAverageCharacterWidth();
+    } else {
+      scoped_ptr<RenderText> render_text(RenderText::CreateRenderText());
+      gfx::Rect rect(*width, *height);
+      UpdateRenderText(render_text.get(), rect, text, font, flags, 0);
+      *width = render_text->GetStringWidth();
+    }
+    *height = font.GetHeight();
+  }
+}
+
+void CanvasSkia::DrawStringInt(const string16& text,
+                               const gfx::Font& font,
+                               const SkColor& color,
+                               int x, int y, int w, int h,
+                               int flags) {
+  if (!IntersectsClipRectInt(x, y, w, h))
+    return;
+
+  // TODO(asvitkine): On Windows, MULTI_LINE implies top alignment.
+  //                  http://crbug.com/107357
+  if (flags & gfx::Canvas::MULTI_LINE) {
+    flags &= ~(gfx::Canvas::TEXT_VALIGN_MIDDLE |
+               gfx::Canvas::TEXT_VALIGN_BOTTOM);
+    flags |= gfx::Canvas::TEXT_VALIGN_TOP;
+  }
+
+  gfx::Rect rect(x, y, w, h);
+  canvas_->save(SkCanvas::kClip_SaveFlag);
+  ClipRect(rect);
+
+  string16 adjusted_text = text;
+  if (IsTextRTL(flags, text))
+    base::i18n::AdjustStringForLocaleDirection(&adjusted_text);
+
+  scoped_ptr<RenderText> render_text(RenderText::CreateRenderText());
+
+  if (flags & MULTI_LINE) {
+    ui::WordWrapBehavior wrap_behavior = ui::IGNORE_LONG_WORDS;
+    if (flags & CHARACTER_BREAK)
+      wrap_behavior = ui::WRAP_LONG_WORDS;
+    else if (!(flags & NO_ELLIPSIS))
+      wrap_behavior = ui::ELIDE_LONG_WORDS;
+
+    std::vector<string16> strings;
+    ui::ElideRectangleText(adjusted_text, font, w, h, wrap_behavior,
+                           &strings);
+
+    rect.Offset(0, VAlignText(font, strings.size(), flags, h));
+    for (size_t i = 0; i < strings.size(); i++) {
+      UpdateRenderText(render_text.get(), rect, strings[i], font, flags, color);
+      render_text->Draw(this);
+      rect.Offset(0, font.GetHeight());
+    }
+  } else {
+    if (!(flags & NO_ELLIPSIS))
+      adjusted_text = ui::ElideText(adjusted_text, font, w, ui::ELIDE_AT_END);
+
+    rect.Offset(0, VAlignText(font, 1, flags, h));
+    UpdateRenderText(render_text.get(), rect, adjusted_text, font, flags,
+                     color);
+    render_text->Draw(this);
+  }
+
+  canvas_->restore();
+}
+
+void CanvasSkia::DrawStringWithHalo(const string16& text,
+                                    const gfx::Font& font,
+                                    const SkColor& text_color,
+                                    const SkColor& halo_color_in,
+                                    int x, int y, int w, int h,
+                                    int flags) {
+  // Some callers will have semitransparent halo colors, which we don't handle
+  // (since the resulting image can have 1-bit transparency only).
+  SkColor halo_color = halo_color_in | 0xFF000000;
+
+  // Create a temporary buffer filled with the halo color. It must leave room
+  // for the 1-pixel border around the text.
+  gfx::Size size(w + 2, h + 2);
+  CanvasSkia text_canvas(size, true);
+  SkPaint bkgnd_paint;
+  bkgnd_paint.setColor(halo_color);
+  text_canvas.DrawRect(gfx::Rect(size), bkgnd_paint);
+
+  // Draw the text into the temporary buffer. This will have correct
+  // ClearType since the background color is the same as the halo color.
+  text_canvas.DrawStringInt(text, font, text_color, 1, 1, w, h, flags);
+
+  uint32_t halo_premul = SkPreMultiplyColor(halo_color);
+  SkBitmap& text_bitmap = const_cast<SkBitmap&>(
+      skia::GetTopDevice(*text_canvas.sk_canvas())->accessBitmap(true));
+
+  for (int cur_y = 0; cur_y < h + 2; cur_y++) {
+    uint32_t* text_row = text_bitmap.getAddr32(0, cur_y);
+    for (int cur_x = 0; cur_x < w + 2; cur_x++) {
+      if (text_row[cur_x] == halo_premul) {
+        // This pixel was not touched by the text routines. See if it borders
+        // a touched pixel in any of the 4 directions (not diagonally).
+        if (!PixelShouldGetHalo(text_bitmap, cur_x, cur_y, halo_premul))
+          text_row[cur_x] = 0;  // Make transparent.
+      } else {
+        text_row[cur_x] |= 0xff << SK_A32_SHIFT;  // Make opaque.
+      }
+    }
+  }
+
+  // Draw the halo bitmap with blur.
+  DrawBitmapInt(text_bitmap, x - 1, y - 1);
+}
+
+void CanvasSkia::DrawFadeTruncatingString(
+      const string16& text,
+      CanvasSkia::TruncateFadeMode truncate_mode,
+      size_t desired_characters_to_truncate_from_head,
+      const gfx::Font& font,
+      const SkColor& color,
+      const gfx::Rect& display_rect) {
+  int flags = NO_ELLIPSIS;
+
+  // If the whole string fits in the destination then just draw it directly.
+  if (font.GetStringWidth(text) <= display_rect.width()) {
+    DrawStringInt(text, font, color, display_rect.x(), display_rect.y(),
+                  display_rect.width(), display_rect.height(), flags);
+    return;
+  }
+
+  scoped_ptr<RenderText> render_text(RenderText::CreateRenderText());
+  string16 clipped_text = text;
+  const bool is_rtl = IsTextRTL(flags, text);
+  if (is_rtl)
+    base::i18n::AdjustStringForLocaleDirection(&clipped_text);
+
+  switch (truncate_mode) {
+    case TruncateFadeTail:
+      render_text->set_fade_tail(true);
+      if (is_rtl)
+        flags |= gfx::Canvas::TEXT_ALIGN_RIGHT;
+      break;
+    case TruncateFadeHead:
+      render_text->set_fade_head(true);
+      if (!is_rtl)
+        flags |= gfx::Canvas::TEXT_ALIGN_RIGHT;
+      break;
+    case TruncateFadeHeadAndTail:
+      DCHECK_GT(desired_characters_to_truncate_from_head, 0u);
+      // Due to the fade effect the first character is hard to see.
+      // We want to make sure that the first character starting at
+      // |desired_characters_to_truncate_from_head| is readable so we reduce
+      // the offset by a little bit.
+      desired_characters_to_truncate_from_head =
+          std::max<int>(0, desired_characters_to_truncate_from_head - 2);
+
+      if (desired_characters_to_truncate_from_head) {
+        // Make sure to clip the text at a UTF16 boundary.
+        U16_SET_CP_LIMIT(text.data(), 0,
+                         desired_characters_to_truncate_from_head,
+                         text.length());
+        clipped_text = text.substr(desired_characters_to_truncate_from_head);
+      }
+
+      render_text->set_fade_tail(true);
+      render_text->set_fade_head(true);
+      break;
+  }
+
+  gfx::Rect text_rect = display_rect;
+  text_rect.Offset(0, VAlignText(font, 1, flags, display_rect.height()));
+  UpdateRenderText(render_text.get(), text_rect, clipped_text, font, flags,
+                   color);
+
+  canvas_->save(SkCanvas::kClip_SaveFlag);
+  ClipRect(display_rect);
+  render_text->Draw(this);
+  canvas_->restore();
+}
+
+}  // namespace gfx