canvas_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.h"

#include "base/i18n/rtl.h"
#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
#include "base/numerics/safe_conversions.h"
#include "third_party/skia/include/core/SkBitmap.h"
#include "third_party/skia/include/core/SkPixmap.h"
#include "ui/gfx/font_list.h"
#include "ui/gfx/geometry/insets.h"
#include "ui/gfx/geometry/rect.h"
#include "ui/gfx/range/range.h"
#include "ui/gfx/render_text.h"
#include "ui/gfx/shadow_value.h"
#include "ui/gfx/text_elider.h"
#include "ui/gfx/text_utils.h"

namespace gfx {

namespace {

// 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
// |DrawStringRectWithHalo| will modify the bitmap as it goes, and cleared
// pixels shouldn't count as changed.
bool PixelShouldGetHalo(const SkPixmap& pixmap,
                        int x, int y,
                        SkColor halo_color) {
  if (x > 0 &&
      *pixmap.addr32(x - 1, y) != halo_color &&
      *pixmap.addr32(x - 1, y) != 0)
    return true;  // Touched pixel to the left.
  if (x < pixmap.width() - 1 &&
      *pixmap.addr32(x + 1, y) != halo_color &&
      *pixmap.addr32(x + 1, y) != 0)
    return true;  // Touched pixel to the right.
  if (y > 0 &&
      *pixmap.addr32(x, y - 1) != halo_color &&
      *pixmap.addr32(x, y - 1) != 0)
    return true;  // Touched pixel above.
  if (y < pixmap.height() - 1 &&
      *pixmap.addr32(x, y + 1) != halo_color &&
      *pixmap.addr32(x, y + 1) != 0)
    return true;  // Touched pixel below.
  return false;
}

// Strips accelerator character prefixes in |text| if needed, based on |flags|.
// Returns a range in |text| to underline or Range::InvalidRange() if
// underlining is not needed.
Range StripAcceleratorChars(int flags, base::string16* text) {
  if (flags & (Canvas::SHOW_PREFIX | Canvas::HIDE_PREFIX)) {
    int char_pos = -1;
    int char_span = 0;
    *text = RemoveAcceleratorChar(*text, '&', &char_pos, &char_span);
    if ((flags & Canvas::SHOW_PREFIX) && char_pos != -1)
      return Range(char_pos, char_pos + char_span);
  }
  return Range::InvalidRange();
}

// Elides |text| and adjusts |range| appropriately. If eliding causes |range|
// to no longer point to the same character in |text|, |range| is made invalid.
void ElideTextAndAdjustRange(const FontList& font_list,
                             float width,
                             base::string16* text,
                             Range* range) {
  const base::char16 start_char =
      (range->IsValid() ? text->at(range->start()) : 0);
  *text = ElideText(*text, font_list, width, ELIDE_TAIL);
  if (!range->IsValid())
    return;
  if (range->start() >= text->length() ||
      text->at(range->start()) != start_char) {
    *range = Range::InvalidRange();
  }
}

// Updates |render_text| from the specified parameters.
void UpdateRenderText(const Rect& rect,
                      const base::string16& text,
                      const FontList& font_list,
                      int flags,
                      SkColor color,
                      RenderText* render_text) {
  render_text->SetFontList(font_list);
  render_text->SetText(text);
  render_text->SetCursorEnabled(false);
  render_text->SetDisplayRect(rect);

  // Set the text alignment explicitly based on the directionality of the UI,
  // if not specified.
  if (!(flags & (Canvas::TEXT_ALIGN_CENTER |
                 Canvas::TEXT_ALIGN_RIGHT |
                 Canvas::TEXT_ALIGN_LEFT |
                 Canvas::TEXT_ALIGN_TO_HEAD))) {
    flags |= Canvas::DefaultCanvasTextAlignment();
  }

  if (flags & Canvas::TEXT_ALIGN_TO_HEAD)
    render_text->SetHorizontalAlignment(ALIGN_TO_HEAD);
  else if (flags & Canvas::TEXT_ALIGN_RIGHT)
    render_text->SetHorizontalAlignment(ALIGN_RIGHT);
  else if (flags & Canvas::TEXT_ALIGN_CENTER)
    render_text->SetHorizontalAlignment(ALIGN_CENTER);
  else
    render_text->SetHorizontalAlignment(ALIGN_LEFT);

  render_text->set_subpixel_rendering_suppressed(
      (flags & Canvas::NO_SUBPIXEL_RENDERING) != 0);

  render_text->SetColor(color);
  const int font_style = font_list.GetFontStyle();
  render_text->SetStyle(BOLD, (font_style & Font::BOLD) != 0);
  render_text->SetStyle(ITALIC, (font_style & Font::ITALIC) != 0);
  render_text->SetStyle(UNDERLINE, (font_style & Font::UNDERLINE) != 0);
}

}  // namespace

// static
void Canvas::SizeStringFloat(const base::string16& text,
                             const FontList& font_list,
                             float* width, float* height,
                             int line_height,
                             int flags) {
  DCHECK_GE(*width, 0);
  DCHECK_GE(*height, 0);

  if ((flags & MULTI_LINE) && *width != 0) {
    WordWrapBehavior wrap_behavior = TRUNCATE_LONG_WORDS;
    if (flags & CHARACTER_BREAK)
      wrap_behavior = WRAP_LONG_WORDS;
    else if (!(flags & NO_ELLIPSIS))
      wrap_behavior = ELIDE_LONG_WORDS;

    std::vector<base::string16> strings;
    ElideRectangleText(text, font_list, *width, INT_MAX, wrap_behavior,
                       &strings);
    Rect rect(base::saturated_cast<int>(*width), INT_MAX);
    scoped_ptr<RenderText> render_text(RenderText::CreateInstance());
    UpdateRenderText(rect, base::string16(), font_list, flags, 0,
                     render_text.get());

    float h = 0;
    float w = 0;
    for (size_t i = 0; i < strings.size(); ++i) {
      StripAcceleratorChars(flags, &strings[i]);
      render_text->SetText(strings[i]);
      const SizeF& string_size = render_text->GetStringSizeF();
      w = std::max(w, string_size.width());
      h += (i > 0 && line_height > 0) ?
               std::max(static_cast<float>(line_height), string_size.height())
                   : string_size.height();
    }
    *width = w;
    *height = h;
  } else {
    scoped_ptr<RenderText> render_text(RenderText::CreateInstance());
    Rect rect(base::saturated_cast<int>(*width),
              base::saturated_cast<int>(*height));
    base::string16 adjusted_text = text;
    StripAcceleratorChars(flags, &adjusted_text);
    UpdateRenderText(rect, adjusted_text, font_list, flags, 0,
                     render_text.get());
    const SizeF& string_size = render_text->GetStringSizeF();
    *width = string_size.width();
    *height = string_size.height();
  }
}

void Canvas::DrawStringRectWithShadows(const base::string16& text,
                                       const FontList& font_list,
                                       SkColor color,
                                       const Rect& text_bounds,
                                       int line_height,
                                       int flags,
                                       const ShadowValues& shadows) {
  if (!IntersectsClipRect(text_bounds))
    return;

  Rect clip_rect(text_bounds);
  clip_rect.Inset(ShadowValue::GetMargin(shadows));

  canvas_->save();
  ClipRect(clip_rect);

  Rect rect(text_bounds);

  scoped_ptr<RenderText> render_text(RenderText::CreateInstance());
  render_text->set_shadows(shadows);

  if (flags & MULTI_LINE) {
    WordWrapBehavior wrap_behavior = IGNORE_LONG_WORDS;
    if (flags & CHARACTER_BREAK)
      wrap_behavior = WRAP_LONG_WORDS;
    else if (!(flags & NO_ELLIPSIS))
      wrap_behavior = ELIDE_LONG_WORDS;

    std::vector<base::string16> strings;
    ElideRectangleText(text, font_list,
                       static_cast<float>(text_bounds.width()),
                       text_bounds.height(), wrap_behavior, &strings);

    for (size_t i = 0; i < strings.size(); i++) {
      Range range = StripAcceleratorChars(flags, &strings[i]);
      UpdateRenderText(rect, strings[i], font_list, flags, color,
                       render_text.get());
      int line_padding = 0;
      if (line_height > 0)
        line_padding = line_height - render_text->GetStringSize().height();
      else
        line_height = render_text->GetStringSize().height();

      // TODO(msw|asvitkine): Center Windows multi-line text: crbug.com/107357
#if !defined(OS_WIN)
      if (i == 0) {
        // TODO(msw|asvitkine): Support multi-line text with varied heights.
        const int text_height = strings.size() * line_height - line_padding;
        rect += Vector2d(0, (text_bounds.height() - text_height) / 2);
      }
#endif

      rect.set_height(line_height - line_padding);

      if (range.IsValid())
        render_text->ApplyStyle(UNDERLINE, true, range);
      render_text->SetDisplayRect(rect);
      render_text->Draw(this);
      rect += Vector2d(0, line_height);
    }
  } else {
    base::string16 adjusted_text = text;
    Range range = StripAcceleratorChars(flags, &adjusted_text);
    bool elide_text = ((flags & NO_ELLIPSIS) == 0);

#if defined(OS_LINUX)
    // On Linux, eliding really means fading the end of the string. But only
    // for LTR text. RTL text is still elided (on the left) with "...".
    if (elide_text) {
      render_text->SetText(adjusted_text);
      if (render_text->GetDisplayTextDirection() == base::i18n::LEFT_TO_RIGHT) {
        render_text->SetElideBehavior(FADE_TAIL);
        elide_text = false;
      }
    }
#endif

    if (elide_text) {
      ElideTextAndAdjustRange(font_list,
                              static_cast<float>(text_bounds.width()),
                              &adjusted_text, &range);
    }

    UpdateRenderText(rect, adjusted_text, font_list, flags, color,
                     render_text.get());
    if (range.IsValid())
      render_text->ApplyStyle(UNDERLINE, true, range);
    render_text->Draw(this);
  }

  canvas_->restore();
}

void Canvas::DrawStringRectWithHalo(const base::string16& text,
                                    const FontList& font_list,
                                    SkColor text_color,
                                    SkColor halo_color_in,
                                    const Rect& display_rect,
                                    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 = SkColorSetA(halo_color_in, 0xFF);

  // Create a temporary buffer filled with the halo color. It must leave room
  // for the 1-pixel border around the text.
  Size size(display_rect.width() + 2, display_rect.height() + 2);
  Canvas text_canvas(size, image_scale(), false);
  SkPaint bkgnd_paint;
  bkgnd_paint.setColor(halo_color);
  text_canvas.DrawRect(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.DrawStringRectWithFlags(
      text, font_list, text_color,
      Rect(1, 1, display_rect.width(), display_rect.height()), flags);

  uint32_t halo_premul = SkPreMultiplyColor(halo_color);
  SkPixmap pixmap;
  skia::GetWritablePixels(text_canvas.sk_canvas(), &pixmap);

  for (int cur_y = 0; cur_y < pixmap.height(); cur_y++) {
    uint32_t* text_row = pixmap.writable_addr32(0, cur_y);
    for (int cur_x = 0; cur_x < pixmap.width(); 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(pixmap, 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.
  SkBitmap bitmap;
  bitmap.installPixels(pixmap.info(), pixmap.writable_addr(),
                       pixmap.rowBytes());
  ImageSkia text_image = ImageSkia(ImageSkiaRep(bitmap,
      text_canvas.image_scale()));
  DrawImageInt(text_image, display_rect.x() - 1, display_rect.y() - 1);
}

void Canvas::DrawFadedString(const base::string16& text,
                             const FontList& font_list,
                             SkColor color,
                             const Rect& display_rect,
                             int flags) {
  // If the whole string fits in the destination then just draw it directly.
  if (GetStringWidth(text, font_list) <= display_rect.width()) {
    DrawStringRectWithFlags(text, font_list, color, display_rect, flags);
    return;
  }
  // Align with content directionality instead of fading both ends.
  flags &= ~TEXT_ALIGN_CENTER;
  if (!(flags & (TEXT_ALIGN_LEFT | TEXT_ALIGN_RIGHT)))
    flags |= TEXT_ALIGN_TO_HEAD;
  flags |= NO_ELLIPSIS;

  scoped_ptr<RenderText> render_text(RenderText::CreateInstance());
  Rect rect = display_rect;
  UpdateRenderText(rect, text, font_list, flags, color, render_text.get());
  render_text->SetElideBehavior(FADE_TAIL);

  canvas_->save();
  ClipRect(display_rect);
  render_text->Draw(this);
  canvas_->restore();
}

}  // namespace gfx