Render glyphs at the correct resolution with respect to the current t…

…ransform (flutter#101)
egramond · Apr 27, 2022 · 0aaa84e · 0aaa84e
1 parent 39f4ebd
commit 0aaa84e
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Showing 12 changed files with 93 additions and 24 deletions.
diff --git a/impeller/display_list/display_list_dispatcher.cc b/impeller/display_list/display_list_dispatcher.cc
@@ -247,7 +247,8 @@ void DisplayListDispatcher::setMaskFilter(const flutter::DlMaskFilter* filter) {
 }
 
 // |flutter::Dispatcher|
-void DisplayListDispatcher::setImageFilter(const flutter::DlImageFilter* filter) {
+void DisplayListDispatcher::setImageFilter(
+    const flutter::DlImageFilter* filter) {
   UNIMPLEMENTED;
 }
 
@@ -609,9 +610,10 @@ void DisplayListDispatcher::drawDisplayList(
 void DisplayListDispatcher::drawTextBlob(const sk_sp<SkTextBlob> blob,
                                          SkScalar x,
                                          SkScalar y) {
-  canvas_.DrawTextFrame(TextFrameFromTextBlob(blob),  //
-                        impeller::Point{x, y},        //
-                        paint_                        //
+  Scalar scale = canvas_.GetCurrentTransformation().GetMaxBasisLength();
+  canvas_.DrawTextFrame(TextFrameFromTextBlob(blob, scale),  //
+                        impeller::Point{x, y},               //
+                        paint_                               //
   );
 }
 

diff --git a/impeller/geometry/constants.h b/impeller/geometry/constants.h
@@ -43,4 +43,7 @@ constexpr float kSqrt2 = 1.41421356237309504880;
 // 1/sqrt(2)
 constexpr float k1OverSqrt2 = 0.70710678118654752440;
 
+// 0.001
+constexpr float kEhCloseEnough = 1e-3;
+
 }  // namespace impeller
diff --git a/impeller/geometry/geometry_unittests.cc b/impeller/geometry/geometry_unittests.cc
@@ -212,6 +212,21 @@ TEST(GeometryTest, MatrixTransformDirection) {
   }
 }
 
+TEST(GeometryTest, MatrixGetMaxBasisLength) {
+  {
+    auto m = Matrix::MakeScale({3, 1, 1});
+    ASSERT_EQ(m.GetMaxBasisLength(), 3);
+
+    m = m * Matrix::MakeSkew(0, 4);
+    ASSERT_EQ(m.GetMaxBasisLength(), 5);
+  }
+
+  {
+    auto m = Matrix::MakeScale({-3, 4, 2});
+    ASSERT_EQ(m.GetMaxBasisLength(), 4);
+  }
+}
+
 TEST(GeometryTest, QuaternionLerp) {
   auto q1 = Quaternion{{0.0, 0.0, 1.0}, 0.0};
   auto q2 = Quaternion{{0.0, 0.0, 1.0}, M_PI_4};
@@ -570,6 +585,21 @@ TEST(GeometryTest, CanUsePointAssignmentOperators) {
     ASSERT_EQ(p.x, 1u);
     ASSERT_EQ(p.y, 2u);
   }
+
+  // Arithmetic type on RHS
+  {
+    IPoint p(1, 2);
+    p *= 3;
+    ASSERT_EQ(p.x, 3u);
+    ASSERT_EQ(p.y, 6u);
+  }
+
+  {
+    IPoint p(3, 6);
+    p /= 3;
+    ASSERT_EQ(p.x, 1u);
+    ASSERT_EQ(p.y, 2u);
+  }
 }
 
 TEST(GeometryTest, PointDotProduct) {

diff --git a/impeller/geometry/matrix.cc b/impeller/geometry/matrix.cc
@@ -193,6 +193,15 @@ Scalar Matrix::GetDeterminant() const {
   return b00 * b11 - b01 * b10 + b02 * b09 + b03 * b08 - b04 * b07 + b05 * b06;
 }
 
+Scalar Matrix::GetMaxBasisLength() const {
+  Scalar max = 0;
+  for (int i = 0; i < 3; i++) {
+    max = std::max(max,
+                   e[i][0] * e[i][0] + e[i][1] * e[i][1] + e[i][2] * e[i][2]);
+  }
+  return std::sqrt(max);
+}
+
 /*
  *  Adapted for Impeller from Graphics Gems:
  *  http://www.realtimerendering.com/resources/GraphicsGems/gemsii/unmatrix.c

diff --git a/impeller/geometry/matrix.h b/impeller/geometry/matrix.h
@@ -219,6 +219,8 @@ struct Matrix {
 
   Scalar GetDeterminant() const;
 
+  Scalar GetMaxBasisLength() const;
+
   constexpr bool IsAffine() const {
     return (m[2] == 0 && m[3] == 0 && m[6] == 0 && m[7] == 0 && m[8] == 0 &&
             m[9] == 0 && m[10] == 1 && m[11] == 0 && m[14] == 0 && m[15] == 1);

diff --git a/impeller/geometry/point.h b/impeller/geometry/point.h
@@ -88,6 +88,13 @@ struct TPoint {
     return *this;
   }
 
+  template <class U, class = std::enable_if_t<std::is_arithmetic_v<U>>>
+  inline TPoint operator*=(U scale) {
+    x *= static_cast<Type>(scale);
+    y *= static_cast<Type>(scale);
+    return *this;
+  }
+
   template <class U>
   inline TPoint operator/=(const TPoint<U>& p) {
     x /= static_cast<Type>(p.x);
@@ -102,6 +109,13 @@ struct TPoint {
     return *this;
   }
 
+  template <class U, class = std::enable_if_t<std::is_arithmetic_v<U>>>
+  inline TPoint operator/=(U scale) {
+    x /= static_cast<Type>(scale);
+    y /= static_cast<Type>(scale);
+    return *this;
+  }
+
   constexpr TPoint operator-() const { return {-x, -y}; }
 
   constexpr TPoint operator+(const TPoint& p) const {

diff --git a/impeller/geometry/scalar.h b/impeller/geometry/scalar.h
@@ -14,8 +14,6 @@ namespace impeller {
 
 using Scalar = float;
 
-constexpr Scalar kEhCloseEnough = 1e-3f;
-
 template <class T, class = std::enable_if_t<std::is_arithmetic_v<T>>>
 constexpr T Absolute(const T& val) {
   return val >= T{} ? val : -val;

diff --git a/impeller/typographer/backends/skia/text_frame_skia.cc b/impeller/typographer/backends/skia/text_frame_skia.cc
@@ -12,13 +12,14 @@
 
 namespace impeller {
 
-static Font ToFont(const SkFont& font) {
+static Font ToFont(const SkFont& font, Scalar scale) {
   auto typeface = std::make_shared<TypefaceSkia>(font.refTypefaceOrDefault());
 
   SkFontMetrics sk_metrics;
   font.getMetrics(&sk_metrics);
 
   Font::Metrics metrics;
+  metrics.scale = scale;
   metrics.point_size = font.getSize();
   metrics.ascent = sk_metrics.fAscent;
   metrics.descent = sk_metrics.fDescent;
@@ -28,15 +29,16 @@ static Font ToFont(const SkFont& font) {
   return Font{std::move(typeface), std::move(metrics)};
 }
 
-TextFrame TextFrameFromTextBlob(sk_sp<SkTextBlob> blob) {
+TextFrame TextFrameFromTextBlob(sk_sp<SkTextBlob> blob,
+                                Scalar scale) {
   if (!blob) {
     return {};
   }
 
   TextFrame frame;
 
   for (SkTextBlobRunIterator run(blob.get()); !run.done(); run.next()) {
-    TextRun text_run(ToFont(run.font()));
+    TextRun text_run(ToFont(run.font(), scale));
     const auto glyph_count = run.glyphCount();
     const auto* glyphs = run.glyphs();
     switch (run.positioning()) {

diff --git a/impeller/typographer/backends/skia/text_frame_skia.h b/impeller/typographer/backends/skia/text_frame_skia.h
@@ -10,6 +10,6 @@
 
 namespace impeller {
 
-TextFrame TextFrameFromTextBlob(sk_sp<SkTextBlob> blob);
+TextFrame TextFrameFromTextBlob(sk_sp<SkTextBlob> blob, Scalar scale = 1.0f);
 
 }  // namespace impeller
diff --git a/impeller/typographer/backends/skia/text_render_context_skia.cc b/impeller/typographer/backends/skia/text_render_context_skia.cc
@@ -65,7 +65,8 @@ static bool PairsFitInAtlasOfSize(const FontGlyphPair::Vector& pairs,
 
   for (const auto& pair : pairs) {
     const auto glyph_size =
-        ISize::Ceil(pair.font.GetMetrics().GetBoundingBox().size);
+        ISize::Ceil(pair.font.GetMetrics().GetBoundingBox().size *
+                    pair.font.GetMetrics().scale);
     SkIPoint16 location_in_atlas;
     if (!rect_packer->addRect(glyph_size.width,   //
                               glyph_size.height,  //
@@ -125,21 +126,23 @@ static std::optional<SkBitmap> CreateAtlasBitmap(const GlyphAtlas& atlas,
 
     SkFont sk_font(
         TypefaceSkia::Cast(*font_glyph.font.GetTypeface()).GetSkiaTypeface(),
-        font_glyph.font.GetMetrics().point_size);
+        font_glyph.font.GetMetrics().point_size *
+            font_glyph.font.GetMetrics().scale);
 
     const auto& metrics = font_glyph.font.GetMetrics();
 
     auto glyph_color = SK_ColorWHITE;
 
     SkPaint glyph_paint;
     glyph_paint.setColor(glyph_color);
-    canvas->drawGlyphs(1u,         // count
-                       &glyph_id,  // glyphs
-                       &position,  // positions
-                       SkPoint::Make(-metrics.min_extent.x,
-                                     -metrics.ascent),  // origin
-                       sk_font,                         // font
-                       glyph_paint                      // paint
+    canvas->drawGlyphs(
+        1u,         // count
+        &glyph_id,  // glyphs
+        &position,  // positions
+        SkPoint::Make(-metrics.min_extent.x * metrics.scale,
+                      -metrics.ascent * metrics.scale),  // origin
+        sk_font,                                         // font
+        glyph_paint                                      // paint
     );
     return true;
   });

diff --git a/impeller/typographer/font.h b/impeller/typographer/font.h
@@ -28,6 +28,12 @@ class Font : public Comparable<Font> {
   ///             the baseline with an upper-left-origin coordinate system.
   ///
   struct Metrics {
+    //--------------------------------------------------------------------------
+    /// The scaling factor that should be used when rendering this font to an
+    /// atlas. This should normally be set in accordance with the transformation
+    /// matrix that will be used to position glyph geometry.
+    ///
+    Scalar scale = 1.0f;
     //--------------------------------------------------------------------------
     /// The point size of the font.
     ///
@@ -69,9 +75,9 @@ class Font : public Comparable<Font> {
     }
 
     constexpr bool operator==(const Metrics& o) const {
-      return point_size == o.point_size && ascent == o.ascent &&
-             descent == o.descent && min_extent == o.min_extent &&
-             max_extent == o.max_extent;
+      return scale == o.scale && point_size == o.point_size &&
+             ascent == o.ascent && descent == o.descent &&
+             min_extent == o.min_extent && max_extent == o.max_extent;
     }
   };
 
@@ -107,6 +113,6 @@ class Font : public Comparable<Font> {
 template <>
 struct std::hash<impeller::Font::Metrics> {
   constexpr std::size_t operator()(const impeller::Font::Metrics& m) const {
-    return fml::HashCombine(m.point_size, m.ascent, m.descent);
+    return fml::HashCombine(m.scale, m.point_size, m.ascent, m.descent);
   }
 };
diff --git a/impeller/typographer/glyph_atlas.h b/impeller/typographer/glyph_atlas.h
@@ -47,7 +47,7 @@ class GlyphAtlas {
   const std::shared_ptr<Texture>& GetTexture() const;
 
   //----------------------------------------------------------------------------
-  /// @brief      Record there location of a specific font-glyph pair within the
+  /// @brief      Record the location of a specific font-glyph pair within the
   ///             atlas.
   ///
   /// @param[in]  pair  The font-glyph pair