Ellide by fading

BUG=chromium-os:15552
TEST=Examine tabs when text overflows

Review URL: http://codereview.chromium.org/7105001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@87431 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 79 insertions, 17 deletions

diff --git a/ui/gfx/canvas_skia_linux.cc b/ui/gfx/canvas_skia_linux.cc
index 1d5d298..761d317 100644
--- a/ui/gfx/canvas_skia_linux.cc
+++ b/ui/gfx/canvas_skia_linux.cc
@@ -9,6 +9,7 @@
 #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"
@@ -20,6 +21,13 @@ 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;
+
 // Font settings that we initialize once and then use when drawing text in
 // DrawStringInt().
 static cairo_font_options_t* cairo_font_options = NULL;
@@ -108,22 +116,26 @@ static void SetupPangoLayout(PangoLayout* layout,
   if (width > 0)
     pango_layout_set_width(layout, width * PANGO_SCALE);
 
-  if (flags & gfx::Canvas::NO_ELLIPSIS) {
-    pango_layout_set_ellipsize(layout, PANGO_ELLIPSIZE_NONE);
-  } else {
-    pango_layout_set_ellipsize(layout, PANGO_ELLIPSIZE_END);
-  }
-
   if (flags & gfx::Canvas::TEXT_ALIGN_CENTER) {
     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::MULTI_LINE) {
-    pango_layout_set_wrap(layout,
-        (flags & gfx::Canvas::CHARACTER_BREAK) ?
-            PANGO_WRAP_WORD_CHAR : PANGO_WRAP_WORD);
+  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 (base::i18n::IsRTL()){
+    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
@@ -253,13 +265,63 @@ DrawStringContext::~DrawStringContext() {
 }
 
 void DrawStringContext::Draw(const SkColor& text_color) {
-  cairo_set_source_rgba(cr_,
-                        SkColorGetR(text_color) / 255.0,
-                        SkColorGetG(text_color) / 255.0,
-                        SkColorGetB(text_color) / 255.0,
-                        SkColorGetA(text_color) / 255.0);
-  cairo_move_to(cr_, text_x_, text_y_);
-  pango_cairo_show_layout(cr_, layout_);
+  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;
+
+  if (base::i18n::IsRTL() ||
+      (flags_ & gfx::Canvas::NO_ELLIPSIS) ||
+      text_width_ <= bounds_.width()) {
+    cairo_set_source_rgba(cr_, r, g, b, a);
+    cairo_move_to(cr_, text_x_, text_y_);
+    pango_cairo_show_layout(cr_, layout_);
+  } else {
+    // Fade to gray to ellide.
+    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;
+
+    // Draw left part of text, clipped at fade_width.
+    cairo_save(cr_);
+    cairo_rectangle(cr_,
+                    bounds_.x(),
+                    bounds_.y(),
+                    bounds_.width() - fade_width,
+                    bounds_.height());
+    cairo_clip(cr_);
+    cairo_set_source_rgba(cr_, r, g, b, a);
+    cairo_move_to(cr_, text_x_, text_y_);
+    pango_cairo_show_layout(cr_, layout_);
+    cairo_restore(cr_);
+
+    // Clip to the left of fade_width.
+    cairo_save(cr_);
+    cairo_rectangle(cr_, fade_x, bounds_.y(), fade_width, bounds_.height());
+    cairo_clip(cr_);
+
+    // Create clip for text.
+    cairo_move_to(cr_, text_x_, text_y_);
+    pango_cairo_layout_path(cr_, layout_);
+    cairo_clip(cr_);
+
+    // Create alpha fade pattern.
+    cairo_pattern_t* 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);
+
+    // Draw pattern, clipped by text.
+    cairo_set_source(cr_, pattern);
+    cairo_fill(cr_);
+    cairo_paint(cr_);
+    cairo_pattern_destroy(pattern);
+
+    cairo_restore(cr_);
+  }
 }
 
 void DrawStringContext::DrawWithHalo(const SkColor& text_color,