path: root/ui/gfx/canvas_skia_linux.cc

// Copyright (c) 2011 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 <algorithm>

#include <cairo/cairo.h>
#include <gtk/gtk.h>
#include <pango/pango.h>
#include <pango/pangocairo.h>

#include "base/i18n/rtl.h"
#include "base/logging.h"
#include "base/utf_string_conversions.h"
#include "ui/gfx/font.h"
#include "ui/gfx/gtk_util.h"
#include "ui/gfx/platform_font_gtk.h"
#include "ui/gfx/rect.h"
#include "ui/gfx/skia_util.h"

using std::max;

namespace {

const gunichar kAcceleratorChar = '&';

// Multiply by the text height to determine how much text should be faded
// when elliding.
const double kFadeWidthFactor = 1.5;

// End state of the elliding fade.
const double kFadeFinalAlpha = 0.15;

// Width of the border drawn around haloed text.
const double kTextHaloWidth = 1.0;

// Font settings that we initialize once and then use when drawing text in
// DrawStringInt().
cairo_font_options_t* cairo_font_options = NULL;

// Update |cairo_font_options| based on GtkSettings, allocating it if needed.
void UpdateCairoFontOptions() {
  if (!cairo_font_options)
    cairo_font_options = cairo_font_options_create();

  gint antialias = 0;
  gint hinting = 0;
  gchar* hint_style = NULL;
  gchar* rgba_style = NULL;

#if !defined(USE_WAYLAND)
  GtkSettings* gtk_settings = gtk_settings_get_default();
  g_object_get(gtk_settings,
               "gtk-xft-antialias", &antialias,
               "gtk-xft-hinting", &hinting,
               "gtk-xft-hintstyle", &hint_style,
               "gtk-xft-rgba", &rgba_style,
               NULL);
#endif

  // g_object_get() doesn't tell us whether the properties were present or not,
  // but if they aren't (because gnome-settings-daemon isn't running), we'll get
  // NULL values for the strings.
  if (hint_style && rgba_style) {
    if (!antialias) {
      cairo_font_options_set_antialias(cairo_font_options,
                                       CAIRO_ANTIALIAS_NONE);
    } else if (strcmp(rgba_style, "none") == 0) {
      cairo_font_options_set_antialias(cairo_font_options,
                                       CAIRO_ANTIALIAS_GRAY);
    } else {
      cairo_font_options_set_antialias(cairo_font_options,
                                       CAIRO_ANTIALIAS_SUBPIXEL);
      cairo_subpixel_order_t cairo_subpixel_order =
          CAIRO_SUBPIXEL_ORDER_DEFAULT;
      if (strcmp(rgba_style, "rgb") == 0) {
        cairo_subpixel_order = CAIRO_SUBPIXEL_ORDER_RGB;
      } else if (strcmp(rgba_style, "bgr") == 0) {
        cairo_subpixel_order = CAIRO_SUBPIXEL_ORDER_BGR;
      } else if (strcmp(rgba_style, "vrgb") == 0) {
        cairo_subpixel_order = CAIRO_SUBPIXEL_ORDER_VRGB;
      } else if (strcmp(rgba_style, "vbgr") == 0) {
        cairo_subpixel_order = CAIRO_SUBPIXEL_ORDER_VBGR;
      }
      cairo_font_options_set_subpixel_order(cairo_font_options,
                                            cairo_subpixel_order);
    }

    cairo_hint_style_t cairo_hint_style = CAIRO_HINT_STYLE_DEFAULT;
    if (hinting == 0 || strcmp(hint_style, "hintnone") == 0) {
      cairo_hint_style = CAIRO_HINT_STYLE_NONE;
    } else if (strcmp(hint_style, "hintslight") == 0) {
      cairo_hint_style = CAIRO_HINT_STYLE_SLIGHT;
    } else if (strcmp(hint_style, "hintmedium") == 0) {
      cairo_hint_style = CAIRO_HINT_STYLE_MEDIUM;
    } else if (strcmp(hint_style, "hintfull") == 0) {
      cairo_hint_style = CAIRO_HINT_STYLE_FULL;
    }
    cairo_font_options_set_hint_style(cairo_font_options, cairo_hint_style);
  }

  if (hint_style)
    g_free(hint_style);
  if (rgba_style)
    g_free(rgba_style);
}

// Pass a width > 0 to force wrapping and elliding.
void SetupPangoLayout(PangoLayout* layout,
                      const string16& text,
                      const gfx::Font& font,
                      int width,
                      base::i18n::TextDirection text_direction,
                      int flags) {
  if (!cairo_font_options)
    UpdateCairoFontOptions();
  // This needs to be done early on; it has no effect when called just before
  // pango_cairo_show_layout().
  pango_cairo_context_set_font_options(
      pango_layout_get_context(layout), cairo_font_options);

  // Callers of DrawStringInt handle RTL layout themselves, so tell pango to not
  // scope out RTL characters.
  pango_layout_set_auto_dir(layout, FALSE);

  if (width > 0)
    pango_layout_set_width(layout, width * PANGO_SCALE);

  if (flags & gfx::Canvas::TEXT_ALIGN_CENTER) {
    // We don't support center aligned w/ eliding.
    DCHECK(gfx::Canvas::NO_ELLIPSIS);
    pango_layout_set_alignment(layout, PANGO_ALIGN_CENTER);
  } else if (flags & gfx::Canvas::TEXT_ALIGN_RIGHT) {
    pango_layout_set_alignment(layout, PANGO_ALIGN_RIGHT);
  }

  if (flags & gfx::Canvas::NO_ELLIPSIS) {
    pango_layout_set_ellipsize(layout, PANGO_ELLIPSIZE_NONE);
    if (flags & gfx::Canvas::MULTI_LINE) {
      pango_layout_set_wrap(layout,
          (flags & gfx::Canvas::CHARACTER_BREAK) ?
              PANGO_WRAP_WORD_CHAR : PANGO_WRAP_WORD);
    }
  } else if (text_direction == base::i18n::RIGHT_TO_LEFT){
    pango_layout_set_ellipsize(layout, PANGO_ELLIPSIZE_END);
  } else {
    // Fading the text will be handled in the draw operation.
    // that the text is only on one line.
    pango_layout_set_ellipsize(layout, PANGO_ELLIPSIZE_NONE);
    pango_layout_set_width(layout, -1);
  }

  // Set the resolution to match that used by Gtk. If we don't set the
  // resolution and the resolution differs from the default, Gtk and Chrome end
  // up drawing at different sizes.
  double resolution = gfx::GetPangoResolution();
  if (resolution > 0) {
    pango_cairo_context_set_resolution(pango_layout_get_context(layout),
                                       resolution);
  }

  PangoFontDescription* desc = font.GetNativeFont();
  pango_layout_set_font_description(layout, desc);
  pango_font_description_free(desc);

  // Set text and accelerator character if needed.
  std::string utf8 = UTF16ToUTF8(text);
  if (flags & gfx::Canvas::SHOW_PREFIX) {
    // Escape the text string to be used as markup.
    gchar* escaped_text = g_markup_escape_text(utf8.c_str(), utf8.size());
    pango_layout_set_markup_with_accel(layout,
                                       escaped_text,
                                       strlen(escaped_text),
                                       kAcceleratorChar, NULL);
    g_free(escaped_text);
  } else if (flags & gfx::Canvas::HIDE_PREFIX) {
    // Remove the ampersand character.  A double ampersand is output as
    // a single ampersand.
    DCHECK_EQ(1, g_unichar_to_utf8(kAcceleratorChar, NULL));
    const std::string accelerator_removed =
        gfx::RemoveAcceleratorChar(utf8, static_cast<char>(kAcceleratorChar));

    pango_layout_set_text(layout,
        accelerator_removed.data(), accelerator_removed.size());
  } else {
    pango_layout_set_text(layout, utf8.data(), utf8.size());
  }
}

// A class to encapsulate string drawing params and operations.
class DrawStringContext {
 public:
  DrawStringContext(gfx::CanvasSkia* canvas,
                    const string16& text,
                    const gfx::Font& font,
                    const gfx::Rect& bounds,
                    const gfx::Rect& clip,
                    int flags);
  ~DrawStringContext();

  void Draw(const SkColor& text_color);
  void DrawWithHalo(const SkColor& text_color, const SkColor& halo_color);

 private:
  // Draw an underline under the text using |cr|, which must already be
  // initialized with the correct source.  |extra_edge_width| is added to the
  // outer edge of the line.  Helper method for Draw() and DrawWithHalo().
  void DrawUnderline(cairo_t* cr, double extra_edge_width);

  const gfx::Rect& bounds_;
  int flags_;
  const gfx::Font& font_;

  gfx::CanvasSkia* canvas_;
  cairo_t* cr_;
  PangoLayout* layout_;

  int text_x_;
  int text_y_;
  int text_width_;
  int text_height_;

  base::i18n::TextDirection text_direction_;

  DISALLOW_COPY_AND_ASSIGN(DrawStringContext);
};

DrawStringContext::DrawStringContext(gfx::CanvasSkia* canvas,
                                     const string16& text,
                                     const gfx::Font& font,
                                     const gfx::Rect& bounds,
                                     const gfx::Rect& clip,
                                     int flags)
    : bounds_(bounds),
      flags_(flags),
      font_(font),
      canvas_(canvas),
      cr_(NULL),
      layout_(NULL),
      text_x_(bounds.x()),
      text_y_(bounds.y()),
      text_width_(0),
      text_height_(0),
      text_direction_(base::i18n::GetFirstStrongCharacterDirection(text)) {
  DCHECK(!bounds_.IsEmpty());

  cr_ = skia::BeginPlatformPaint(canvas_);
  layout_ = pango_cairo_create_layout(cr_);

  SetupPangoLayout(
      layout_, text, font, bounds_.width(), text_direction_, flags_);

  pango_layout_set_height(layout_, bounds_.height() * PANGO_SCALE);

  cairo_save(cr_);

  cairo_rectangle(cr_, clip.x(), clip.y(), clip.width(), clip.height());
  cairo_clip(cr_);

  pango_layout_get_pixel_size(layout_, &text_width_, &text_height_);

  if (flags_ & gfx::Canvas::TEXT_VALIGN_TOP) {
    // Cairo should draw from the top left corner already.
  } else if (flags_ & gfx::Canvas::TEXT_VALIGN_BOTTOM) {
    text_y_ += (bounds.height() - text_height_);
  } else {
    // Vertically centered.
    text_y_ += ((bounds.height() - text_height_) / 2);
  }
}

DrawStringContext::~DrawStringContext() {
  cairo_restore(cr_);
  skia::EndPlatformPaint(canvas_);
  g_object_unref(layout_);
  // NOTE: BeginPlatformPaint returned its surface, we shouldn't destroy it.
}

void DrawStringContext::Draw(const SkColor& text_color) {
  double r = SkColorGetR(text_color) / 255.0,
         g = SkColorGetG(text_color) / 255.0,
         b = SkColorGetB(text_color) / 255.0,
         a = SkColorGetA(text_color) / 255.0;

  cairo_pattern_t* pattern = NULL;

  cairo_save(cr_);

  // If we're not eliding, use a fixed color.
  // Otherwise, create a gradient pattern to use as the source.
  if (text_direction_ == base::i18n::RIGHT_TO_LEFT ||
      (flags_ & gfx::Canvas::NO_ELLIPSIS) ||
      text_width_ <= bounds_.width()) {
    cairo_set_source_rgba(cr_, r, g, b, a);
  } else {
    // Fade to semi-transparent to elide.
    int fade_width = static_cast<double>(text_height_) * kFadeWidthFactor;
    if (fade_width > (bounds_.width() / 2)) {
      // Don't fade more than half the text.
      fade_width = bounds_.width() / 2;
    }
    int fade_x = bounds_.x() + bounds_.width() - fade_width;

    pattern = cairo_pattern_create_linear(
        fade_x, bounds_.y(), bounds_.x() + bounds_.width(), bounds_.y());
    cairo_pattern_add_color_stop_rgba(pattern, 0, r, g, b, a);
    cairo_pattern_add_color_stop_rgba(pattern, 1, r, g, b, kFadeFinalAlpha);
    cairo_set_source(cr_, pattern);
  }

  cairo_move_to(cr_, text_x_, text_y_);
  pango_cairo_show_layout(cr_, layout_);

  if (font_.GetStyle() & gfx::Font::UNDERLINED)
    DrawUnderline(cr_, 0.0);

  if (pattern)
    cairo_pattern_destroy(pattern);

  cairo_restore(cr_);
}

void DrawStringContext::DrawWithHalo(const SkColor& text_color,
                                     const SkColor& halo_color) {
  gfx::CanvasSkia text_canvas(bounds_.width() + 2, bounds_.height() + 2, false);
  text_canvas.FillRectInt(static_cast<SkColor>(0),
      0, 0, bounds_.width() + 2, bounds_.height() + 2);

  {
    skia::ScopedPlatformPaint scoped_platform_paint(&text_canvas);
    cairo_t* text_cr = scoped_platform_paint.GetPlatformSurface();

    // TODO: The current approach (stroking the text path to generate the halo
    // and then filling it for the main text) won't work if |text_color| is
    // non-opaque.  If we need to do this at some later point,
    // http://lists.freedesktop.org/archives/cairo/2004-September/001829.html
    // suggests "do[ing] the stroke and fill with opaque paint onto an
    // intermediate surface, and then us[ing] cairo_show_surface to composite
    // that intermediate result with the desired compositing operator."
    cairo_set_source_rgba(text_cr,
                          SkColorGetR(halo_color) / 255.0,
                          SkColorGetG(halo_color) / 255.0,
                          SkColorGetB(halo_color) / 255.0,
                          SkColorGetA(halo_color) / 255.0);

    // Draw the halo underline first so that we can use the same path for the
    // outer/halo text and inner text.
    if (font_.GetStyle() & gfx::Font::UNDERLINED)
      DrawUnderline(text_cr, kTextHaloWidth);

    cairo_move_to(text_cr, 2, 1);
    pango_cairo_layout_path(text_cr, layout_);
    cairo_set_line_width(text_cr, 2 * kTextHaloWidth);
    cairo_set_line_join(text_cr, CAIRO_LINE_JOIN_ROUND);
    cairo_stroke_preserve(text_cr);

    cairo_set_operator(text_cr, CAIRO_OPERATOR_SOURCE);
    cairo_set_source_rgba(text_cr,
                          SkColorGetR(text_color) / 255.0,
                          SkColorGetG(text_color) / 255.0,
                          SkColorGetB(text_color) / 255.0,
                          SkColorGetA(text_color) / 255.0);
    cairo_fill(text_cr);

    if (font_.GetStyle() & gfx::Font::UNDERLINED)
      DrawUnderline(text_cr, 0.0);
  }

  const SkBitmap& text_bitmap = const_cast<SkBitmap&>(
      skia::GetTopDevice(text_canvas)->accessBitmap(false));
  canvas_->DrawBitmapInt(text_bitmap, text_x_ - 1, text_y_ - 1);
}

void DrawStringContext::DrawUnderline(cairo_t* cr, double extra_edge_width) {
  gfx::PlatformFontGtk* platform_font =
      static_cast<gfx::PlatformFontGtk*>(font_.platform_font());
  const double underline_y =
      static_cast<double>(text_y_) + text_height_ +
      platform_font->underline_position();
  cairo_set_line_width(
      cr, platform_font->underline_thickness() + 2 * extra_edge_width);
  cairo_move_to(cr, text_x_ - extra_edge_width, underline_y);
  cairo_line_to(cr, text_x_ + text_width_ + extra_edge_width, underline_y);
  cairo_stroke(cr);
}

}  // namespace

namespace gfx {

CanvasSkia::CanvasSkia(int width, int height, bool is_opaque)
    : skia::PlatformCanvas(width, height, is_opaque) {
}

CanvasSkia::CanvasSkia() : skia::PlatformCanvas() {
}

CanvasSkia::~CanvasSkia() {
}

// static
void CanvasSkia::SizeStringInt(const string16& text,
                               const gfx::Font& font,
                               int* width, int* height,
                               int flags) {
  int org_width = *width;
  cairo_surface_t* surface =
      cairo_image_surface_create(CAIRO_FORMAT_ARGB32, 0, 0);
  cairo_t* cr = cairo_create(surface);
  PangoLayout* layout = pango_cairo_create_layout(cr);

  SetupPangoLayout(
      layout,
      text,
      font,
      *width,
      base::i18n::GetFirstStrongCharacterDirection(text),
      flags);

  pango_layout_get_pixel_size(layout, width, height);

  if (font.GetStyle() & gfx::Font::UNDERLINED) {
    gfx::PlatformFontGtk* platform_font =
        static_cast<gfx::PlatformFontGtk*>(font.platform_font());
    *height += max(platform_font->underline_position() +
                   platform_font->underline_thickness(), 0.0);
  }

  // TODO: If the text is being drawn with a halo, we should also pad each of
  // the edges by |kTextHaloWidth|... except haloing is currently a drawing-time
  // thing, and we don't know how the text will be drawn here. :-(  This only
  // seems to come into play at present if the text is both haloed and
  // underlined; otherwise, the size returned by Pango is (at least sometimes)
  // large enough to include the halo.

  if (org_width > 0 && flags & Canvas::MULTI_LINE &&
      pango_layout_is_wrapped(layout)) {
    // The text wrapped. There seems to be a bug in Pango when this happens
    // such that the width returned from pango_layout_get_pixel_size is too
    // small. Using the width from pango_layout_get_pixel_size in this case
    // results in wrapping across more lines, which requires a bigger height.
    // As a workaround we use the original width, which is not necessarily
    // exactly correct, but isn't wrong by much.
    //
    // It looks like Pango uses the size of whitespace in calculating wrapping
    // but doesn't include the size of the whitespace when the extents are
    // asked for. See the loop in pango-layout.c process_item that determines
    // where to wrap.
    *width = org_width;
  }

  g_object_unref(layout);
  cairo_destroy(cr);
  cairo_surface_destroy(surface);
}

void CanvasSkia::DrawStringWithHalo(const string16& text,
                                    const gfx::Font& font,
                                    const SkColor& text_color,
                                    const SkColor& halo_color,
                                    int x, int y, int w, int h,
                                    int flags) {
  if (!IntersectsClipRectInt(x, y, w, h))
    return;

  gfx::Rect bounds(x, y, w, h);
  gfx::Rect clip(x - 1, y - 1, w + 2, h + 2);  // Bigger clip for halo
  DrawStringContext context(this, text, font, bounds, clip,flags);
  context.DrawWithHalo(text_color, halo_color);
}

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;

  gfx::Rect bounds(x, y, w, h);
  DrawStringContext context(this, text, font, bounds, bounds, flags);
  context.Draw(color);
}

void CanvasSkia::DrawGdkPixbuf(GdkPixbuf* pixbuf, int x, int y) {
  if (!pixbuf) {
    NOTREACHED();
    return;
  }

  skia::ScopedPlatformPaint scoped_platform_paint(this);
  cairo_t* cr = scoped_platform_paint.GetPlatformSurface();
  gdk_cairo_set_source_pixbuf(cr, pixbuf, x, y);
  cairo_paint(cr);
}

ui::TextureID CanvasSkia::GetTextureID() {
  // TODO(wjmaclean)
  return 0;
}

}  // namespace gfx