Change TextMetrics to return a dictionary of baselines instead of separate values

Some fonts do not set values for all baselines (hanging, ideographic), and in
those cases we're setting 0, which is a valid value. This new interface
getBaselines(), returns a dictionary with the set baselines and their values.

Bug: 277215
Change-Id: Ie94c74d1c95c7205ed47acaed589ae965f0e32f6
Reviewed-on: https://chromium-review.googlesource.com/1141084Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Commit-Queue: David Quiroz Marin <davidqu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577670}

third_party/WebKit/LayoutTests/external/wpt/html/dom/interfaces.https_exclude=(Document_Window_HTML._)-expected.txt

@@ -646,12 +646,8 @@ PASS TextMetrics interface: attribute emHeightAscent
 PASS Unscopable handled correctly for emHeightAscent property on TextMetrics
 PASS TextMetrics interface: attribute emHeightDescent
 PASS Unscopable handled correctly for emHeightDescent property on TextMetrics
-PASS TextMetrics interface: attribute hangingBaseline
-PASS Unscopable handled correctly for hangingBaseline property on TextMetrics
-PASS TextMetrics interface: attribute alphabeticBaseline
-PASS Unscopable handled correctly for alphabeticBaseline property on TextMetrics
-PASS TextMetrics interface: attribute ideographicBaseline
-PASS Unscopable handled correctly for ideographicBaseline property on TextMetrics
+PASS TextMetrics interface: operation getBaselines()
+PASS Unscopable handled correctly for getBaselines() on TextMetrics
 PASS ImageData interface: existence and properties of interface object
 PASS ImageData interface object length
 PASS ImageData interface object name

third_party/WebKit/LayoutTests/external/wpt/interfaces/html.idl

@@ -1357,9 +1357,7 @@ interface TextMetrics {
   readonly attribute double actualBoundingBoxDescent;
   readonly attribute double emHeightAscent;
   readonly attribute double emHeightDescent;
-  readonly attribute double hangingBaseline;
-  readonly attribute double alphabeticBaseline;
-  readonly attribute double ideographicBaseline;
+  Baselines getBaselines();
 };
 
 [Constructor(unsigned long sw, unsigned long sh),

third_party/WebKit/LayoutTests/fast/canvas-api/canvas-textMetrics-all.html

@@ -13,9 +13,9 @@
 function testTextMetrics(textMetrics, expected)
 {
     var w  = textMetrics.width;
-    var ab = textMetrics.alphabeticBaseline;
-    var hb = textMetrics.hangingBaseline;
-    var ib = textMetrics.ideographicBaseline;
+    var ba = textMetrics.getBaselines().alphabetic;
+    var bh = textMetrics.getBaselines().hanging;
+    var bi = textMetrics.getBaselines().ideographic;
     var fa = textMetrics.fontBoundingBoxAscent;
     var fd = textMetrics.fontBoundingBoxDescent;
     var ea = textMetrics.emHeightAscent;
@@ -27,9 +27,9 @@ function testTextMetrics(textMetrics, expected)
 
     var epsilon = 2;
     assert_approx_equals(w,  expected[0], epsilon, "testing width");
-    assert_approx_equals(ab, expected[1], epsilon, "testing alphabeticBaseline");
-    assert_approx_equals(hb, expected[2], epsilon, "testing hangingBaseline");
-    assert_approx_equals(ib, expected[3], epsilon, "testing ideographicBaseline");
+    assert_approx_equals(ba, expected[1], epsilon, "testing getBaselines().alphabetic");
+    assert_approx_equals(bh, expected[2], epsilon, "testing getBaselines().hanging");
+    assert_approx_equals(bi, expected[3], epsilon, "testing getBaselines().ideographic");
     assert_approx_equals(fa, expected[4], epsilon, "testing fontBoundingBoxAscent");
     assert_approx_equals(fd, expected[5], epsilon, "testing fontBoundingBoxDescent");
     assert_approx_equals(ea, expected[6], epsilon, "testing emHeightAscent");

third_party/WebKit/LayoutTests/fast/canvas-api/textMetrics.html

@@ -21,8 +21,11 @@ function getMetric(ctx, text, baseline, align, rtl, metric) {
   const tm = ctx.measureText(text);
   tm.actualBoundingBoxWidth = Math.abs(tm.actualBoundingBoxRight + tm.actualBoundingBoxLeft);
   tm.actualBoundingBoxHeight = Math.abs(tm.actualBoundingBoxDescent + tm.actualBoundingBoxAscent);
-
-  return tm[metric];
+  if (["alphabetic", "ideographic", "hanging"].includes(metric)) {
+    return tm.getBaselines()[metric];
+  } else {
+    return tm[metric];
+  }
 }
 
 function testMetric(name, ctx, text, baseline, align, rtl, metric, expected_value, epsilon = 0) {
@@ -85,22 +88,22 @@ function testBaselines(ctx) {
   for (const ex of kTexts) {
     for (const bline of ["alphabetic", "ideographic", "hanging"]) {
       for (const align of kAligns) {
-        testMetric("own baselines", ctx, ex.text, bline, align, ex.rtl, bline + "Baseline", 0);
+        testMetric("own baselines", ctx, ex.text, bline, align, ex.rtl, bline, 0);
       }
     }
   }
 
   // Those 3 baselines are font size dependent, so everything should be fixed.
   forEachExample((ex, _, align) => {
-    testMetric("top baseline", ctx, ex.text, "top", align, ex.rtl, "alphabeticBaseline", -44);
+    testMetric("top baseline", ctx, ex.text, "top", align, ex.rtl, "alphabetic", -44);
   });
 
   forEachExample((ex, _, align) => {
-    testMetric("middle baseline", ctx, ex.text, "middle", align, ex.rtl, "alphabeticBaseline", -15);
+    testMetric("middle baseline", ctx, ex.text, "middle", align, ex.rtl, "alphabetic", -15);
   });
 
   forEachExample((ex, _, align) => {
-    testMetric("bottom baseline", ctx, ex.text, "bottom", align, ex.rtl, "alphabeticBaseline", 13);
+    testMetric("bottom baseline", ctx, ex.text, "bottom", align, ex.rtl, "alphabetic", 13);
   });
 }
 

third_party/WebKit/LayoutTests/webexposed/global-interface-listing-expected.txt

@@ -7115,15 +7115,13 @@ interface TextMetrics
     getter actualBoundingBoxLeft
     getter actualBoundingBoxRight
     getter advances
-    getter alphabeticBaseline
     getter emHeightAscent
     getter emHeightDescent
     getter fontBoundingBoxAscent
     getter fontBoundingBoxDescent
-    getter hangingBaseline
-    getter ideographicBaseline
     getter width
     method constructor
+    method getBaselines
 interface TextTrack : EventTarget
     attribute @@toStringTag
     getter activeCues

third_party/blink/renderer/core/core_idl_files.gni

@@ -629,6 +629,7 @@ core_dictionary_idl_files =
                     "geometry/dom_rect_init.idl",
                     "html/focus_options.idl",
                     "html/assigned_nodes_options.idl",
+                    "html/canvas/baselines.idl",
                     "html/canvas/image_data_color_settings.idl",
                     "html/canvas/image_encode_options.idl",
                     "html/track/track_event_init.idl",

third_party/blink/renderer/core/html/canvas/baselines.idl

+// Copyright 2018 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.
+
+dictionary Baselines {
+  double alphabetic;
+  double hanging;
+  double ideographic;
+};

third_party/blink/renderer/core/html/canvas/text_metrics.cc

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "third_party/blink/renderer/core/html/canvas/text_metrics.h"
+#include "third_party/blink/renderer/core/html/canvas/baselines.h"
 #include "third_party/blink/renderer/platform/fonts/character_range.h"
 
 namespace blink {
@@ -101,9 +102,10 @@ void TextMetrics::Update(const Font& font,
   em_height_descent_ = baseline_y;
 
   // TODO(fserb): hanging/ideographic baselines are broken.
-  hanging_baseline_ = ascent * kHangingAsPercentOfAscent / 100.0f - baseline_y;
-  ideographic_baseline_ = -descent - baseline_y;
-  alphabetic_baseline_ = -baseline_y;
+  baselines_.setAlphabetic(-baseline_y);
+  baselines_.setHanging(ascent * kHangingAsPercentOfAscent / 100.0f -
+                        baseline_y);
+  baselines_.setIdeographic(-descent - baseline_y);
 }
 
 }  // namespace blink

third_party/blink/renderer/core/html/canvas/text_metrics.h

@@ -27,6 +27,7 @@
 #define THIRD_PARTY_BLINK_RENDERER_CORE_HTML_CANVAS_TEXT_METRICS_H_
 
 #include "third_party/blink/renderer/core/core_export.h"
+#include "third_party/blink/renderer/core/html/canvas/baselines.h"
 #include "third_party/blink/renderer/platform/bindings/script_wrappable.h"
 #include "third_party/blink/renderer/platform/fonts/font.h"
 #include "third_party/blink/renderer/platform/graphics/graphics_types.h"
@@ -62,9 +63,8 @@ class CORE_EXPORT TextMetrics final : public ScriptWrappable {
   }
   double emHeightAscent() const { return em_height_ascent_; }
   double emHeightDescent() const { return em_height_descent_; }
-  double hangingBaseline() const { return hanging_baseline_; }
-  double alphabeticBaseline() const { return alphabetic_baseline_; }
-  double ideographicBaseline() const { return ideographic_baseline_; }
+  void getBaselines(Baselines& baselines) const { baselines = baselines_; }
+  Baselines getBaselines() const { return baselines_; }
 
   static float GetFontBaseline(const TextBaseline&, const FontMetrics&);
 
@@ -89,9 +89,7 @@ class CORE_EXPORT TextMetrics final : public ScriptWrappable {
   double actual_bounding_box_descent_ = 0.0;
   double em_height_ascent_ = 0.0;
   double em_height_descent_ = 0.0;
-  double hanging_baseline_ = 0.0;
-  double alphabetic_baseline_ = 0.0;
-  double ideographic_baseline_ = 0.0;
+  Baselines baselines_;
 };
 
 }  // namespace blink

third_party/blink/renderer/core/html/canvas/text_metrics.idl

@@ -40,7 +40,5 @@ interface TextMetrics {
     [RuntimeEnabled=ExtendedTextMetrics] readonly attribute double actualBoundingBoxDescent;
     [RuntimeEnabled=ExtendedTextMetrics] readonly attribute double emHeightAscent;
     [RuntimeEnabled=ExtendedTextMetrics] readonly attribute double emHeightDescent;
-    [RuntimeEnabled=ExtendedTextMetrics] readonly attribute double hangingBaseline;
-    [RuntimeEnabled=ExtendedTextMetrics] readonly attribute double alphabeticBaseline;
-    [RuntimeEnabled=ExtendedTextMetrics] readonly attribute double ideographicBaseline;
+    [RuntimeEnabled=ExtendedTextMetrics] Baselines getBaselines();
 };