Implement CTFontGetVerticalTranslationsForGlyphs (#2104)

Fixes #2025 There is a magic number that the reference platform adds to every vertical glyph translation independent of font. With this constant added to all vertical translations we are within 1 design unit of reference platform values.
microsoft · Mar 1, 2017 · 3740a7e · 3740a7e
1 parent 5e79572
commit 3740a7e
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Showing 3 changed files with 50 additions and 10 deletions.
diff --git a/Frameworks/CoreText/CTFont.mm b/Frameworks/CoreText/CTFont.mm
@@ -96,6 +96,9 @@
 const CFStringRef kCTFontDefaultItalicFontName = CFSTR("Arial Italic");
 const CFStringRef kCTFontDefaultMonospacedFontName = CFSTR("Courier New");
 
+// Reference platform adds a constant amount of space (scaled by font size) to each glyph's vertical translation
+static const int sc_verticalTranslationSpace = 102;
+
 using namespace Microsoft::WRL;
 
 struct __CTFont {
@@ -710,8 +713,8 @@ CGPathRef CTFontCreatePathForGlyph(CTFontRef font, CGGlyph glyph, const CGAffine
 }
 
 /**
- @Status Stub
- @Notes
+ @Status NotInPlan
+ @Notes Not much usage, can be easily replaced with CTFontGetGlyphsForCharacters in most common uses
 */
 CGGlyph CTFontGetGlyphWithName(CTFontRef font, CFStringRef glyphName) {
     UNIMPLEMENTED();
@@ -796,11 +799,27 @@ CGRect CTFontGetBoundingRectsForGlyphs(
 }
 
 /**
- @Status Stub
+ @Status Interoperable
  @Notes
 */
 void CTFontGetVerticalTranslationsForGlyphs(CTFontRef font, const CGGlyph glyphs[], CGSize translations[], CFIndex count) {
-    UNIMPLEMENTED();
+    if (font && glyphs && translations && count > 0L) {
+        DWRITE_GLYPH_METRICS metrics[count];
+        if (FAILED(font->_dwriteFontFace->GetDesignGlyphMetrics(glyphs, count, metrics, false))) {
+            TraceError(g_logTag, L"Unable to get glyph metrics");
+            return;
+        }
+
+        std::transform(metrics, metrics + count, translations, [font](const DWRITE_GLYPH_METRICS& metrics) {
+            if (metrics.advanceWidth == metrics.rightSideBearing && metrics.verticalOriginY == metrics.topSideBearing) {
+                // Special case of empty glyph, should just return CGRectZero;
+                return CGSizeZero;
+            }
+
+            return CGSize{ -__CTFontScaleMetric(font, (metrics.advanceWidth / 2)),
+                           -__CTFontScaleMetric(font, metrics.verticalOriginY - metrics.topSideBearing + sc_verticalTranslationSpace) };
+        });
+    }
 }
 
 /**
@@ -951,4 +970,4 @@ DWRITE_FONT_STYLE _CTFontGetDWriteStyle(CTFontRef font) {
         return fontFace3->GetStyle();
     }
     return DWRITE_FONT_STYLE_NORMAL;
-}
+}
diff --git a/include/CoreText/CTFont.h b/include/CoreText/CTFont.h
@@ -229,13 +229,12 @@ CORETEXT_EXPORT CGFloat CTFontGetSlantAngle(CTFontRef font);
 CORETEXT_EXPORT CGFloat CTFontGetCapHeight(CTFontRef font);
 CORETEXT_EXPORT CGFloat CTFontGetXHeight(CTFontRef font);
 CORETEXT_EXPORT CGPathRef CTFontCreatePathForGlyph(CTFontRef font, CGGlyph glyph, const CGAffineTransform* matrix);
-CORETEXT_EXPORT CGGlyph CTFontGetGlyphWithName(CTFontRef font, CFStringRef glyphName) STUB_METHOD;
+CORETEXT_EXPORT CGGlyph CTFontGetGlyphWithName(CTFontRef font, CFStringRef glyphName) NOTINPLAN_METHOD;
 CORETEXT_EXPORT CGRect CTFontGetBoundingRectsForGlyphs(
     CTFontRef font, CTFontOrientation orientation, const CGGlyph glyphs[], CGRect* boundingRects, CFIndex count);
 CORETEXT_EXPORT double CTFontGetAdvancesForGlyphs(
     CTFontRef font, CTFontOrientation orientation, const CGGlyph glyphs[], CGSize* advances, CFIndex count);
-CORETEXT_EXPORT void CTFontGetVerticalTranslationsForGlyphs(CTFontRef font, const CGGlyph glyphs[], CGSize translations[], CFIndex count)
-    STUB_METHOD;
+CORETEXT_EXPORT void CTFontGetVerticalTranslationsForGlyphs(CTFontRef font, const CGGlyph glyphs[], CGSize translations[], CFIndex count);
 CORETEXT_EXPORT CFArrayRef CTFontCopyVariationAxes(CTFontRef font) STUB_METHOD;
 CORETEXT_EXPORT CFDictionaryRef CTFontCopyVariation(CTFontRef font) STUB_METHOD;
 CORETEXT_EXPORT CFArrayRef CTFontCopyFeatures(CTFontRef font) STUB_METHOD;

diff --git a/tests/unittests/CoreText/CTFontTests.mm b/tests/unittests/CoreText/CTFontTests.mm
@@ -1,6 +1,6 @@
 //******************************************************************************
 //
-// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+// Copyright (c) Microsoft. All rights reserved.
 //
 // This code is licensed under the MIT License (MIT).
 //
@@ -740,4 +740,26 @@ virtual void TearDown() {
                    });
     CGPathApply(pathWithFontSizeAndTransforms, &comparePathContext, comparePathToExpected);
     ASSERT_EQ(expectedElements.size(), comparePathContext.count);
-}
+}
+
+TEST(CTFont, GetVerticalTranslationsForGLyphs) {
+    auto font = woc::MakeAutoCF<CTFontRef>(CTFontCreateWithName(CFSTR("Arial"), 20, nullptr));
+    UniChar chars[6] = { 'T', 'e', 's', 't', ' ', '_' };
+    CGGlyph glyphs[6];
+    CTFontGetGlyphsForCharacters(font, chars, glyphs, 6);
+
+    CGSize translations[6];
+    CTFontGetVerticalTranslationsForGlyphs(font, glyphs, translations, 6);
+    EXPECT_NEAR(-6.1035, translations[0].width, c_errorMargin);
+    EXPECT_NEAR(-5.5566, translations[1].width, c_errorMargin);
+    EXPECT_NEAR(-5.000, translations[2].width, c_errorMargin);
+    EXPECT_NEAR(-2.7734, translations[3].width, c_errorMargin);
+    EXPECT_NEAR(0, translations[4].width, c_errorMargin);
+    EXPECT_NEAR(-5.5566, translations[5].width, c_errorMargin);
+    EXPECT_NEAR(-15.3125, translations[0].height, c_errorMargin);
+    EXPECT_NEAR(-11.6016, translations[1].height, c_errorMargin);
+    EXPECT_NEAR(-11.6016, translations[2].height, c_errorMargin);
+    EXPECT_NEAR(-14.9902, translations[3].height, c_errorMargin);
+    EXPECT_NEAR(0, translations[4].height, c_errorMargin);
+    EXPECT_NEAR(1.70898, translations[5].height, c_errorMargin);
+}