GTK: Step 1 of tab strip refresh.

ui/gfx/pango_util.cc

Index: ui/gfx/pango_util.cc
diff --git a/ui/gfx/pango_util.cc b/ui/gfx/pango_util.cc
index 75043f4a23aadcb5b09c55602624fe9d7224d1f7..bd2a17696c2a8d2013bada50c596fb3b552f5ac2 100644
--- a/ui/gfx/pango_util.cc
+++ b/ui/gfx/pango_util.cc
@@ -12,6 +12,8 @@
 #include "base/utf_string_conversions.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/font.h"
+#include "ui/gfx/platform_font_pango.h"
+#include "ui/gfx/rect.h"
 
 #if !defined(USE_WAYLAND) && defined(TOOLKIT_USES_GTK)
 #include <gtk/gtk.h>
@@ -27,6 +29,13 @@ namespace {
 // Marker for accelerators in the text.
 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;
+
 // Return |cairo_font_options|. If needed, allocate and update it based on
 // GtkSettings.
 cairo_font_options_t* GetCairoFontOptions() {
@@ -193,4 +202,107 @@ void SetupPangoLayout(PangoLayout* layout,
   }
 }
 
+
+PangoDrawString::PangoDrawString(cairo_t* cr,
+                                 const string16& text,
+                                 const gfx::Font& font,
+                                 const gfx::Rect& bounds,
+                                 const gfx::Rect& clip,
+                                 int flags)
+    : bounds_(bounds),
+      flags_(flags),
+      font_(font),
+      cr_(cr),
+      layout_(pango_cairo_create_layout(cr_)),
+      text_x_(bounds.x()),
+      text_y_(bounds.y()),
+      text_width_(0),
+      text_height_(0),
+      text_direction_(base::i18n::GetFirstStrongCharacterDirection(text)) {
+  DCHECK(!bounds_.IsEmpty());
+
+  gfx::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);
+  }
+}
+
+PangoDrawString::~PangoDrawString() {
+  cairo_restore(cr_);
+  g_object_unref(layout_);
+}
+
+void PangoDrawString::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)) {

[Evan Stade, 2011/10/25 23:33:30]

remove excess parens

[Elliot Glaysher, 2011/10/26 21:06:57]

I believe we should make order of operations explicit.

[Evan Stade, 2011/10/26 21:46:05]

the C++ style guide doesn't touch on this, but the js style guide does: "Use
[parentheses] sparingly and in general only where required by the syntax and
semantics."

I think that the problem with adding too many parens (besides clutter) is
consistency. You don't have parens on line 265 -- why not? Same for line 274.
You assume the reader has some knowledge of the order of operations, where do
you draw the line?

+      // 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 PangoDrawString::DrawUnderline(cairo_t* cr, double extra_edge_width) {
+  gfx::PlatformFontPango* platform_font =
+      static_cast<gfx::PlatformFontPango*>(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 gfx