color: Add support for shader generation

ui/gfx/color_transform.cc

Index: ui/gfx/color_transform.cc
diff --git a/ui/gfx/color_transform.cc b/ui/gfx/color_transform.cc
index 361a8ba4bb07727a193b9f0aed2ebe7101942ac0..96e73dcfbcb40fd9ab074953bcfa8d0d546d2b1a 100644
--- a/ui/gfx/color_transform.cc
+++ b/ui/gfx/color_transform.cc
@@ -11,6 +11,7 @@
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
+#include "base/strings/stringprintf.h"
 #include "third_party/qcms/src/qcms.h"
 #include "ui/gfx/color_space.h"
 #include "ui/gfx/icc_profile.h"
@@ -250,8 +251,9 @@ class ColorTransformStep {
 
   // Return true if this is a null transform.
   virtual bool IsNull() { return false; }
-
   virtual void Transform(ColorTransform::TriStim* color, size_t num) = 0;
+  virtual bool CanAppendShaderSource() { return false; }
+  virtual void AppendShaderSource(std::string* result) { NOTREACHED(); }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ColorTransformStep);
@@ -264,11 +266,13 @@ class ColorTransformInternal : public ColorTransform {
                          Intent intent);
   ~ColorTransformInternal() override;
 
-  // Perform transformation of colors, |colors| is both input and output.
   void Transform(TriStim* colors, size_t num) override {
     for (const auto& step : steps_)
       step->Transform(colors, num);
   }
+  bool CanGetShaderSource() const override;
+  std::string GetShaderSource() const override;
+  bool IsIdentity() const override { return steps_.empty(); }
   size_t NumberOfStepsForTesting() const override { return steps_.size(); }
 
  private:
@@ -285,11 +289,19 @@ class ColorTransformInternal : public ColorTransform {
   std::list<std::unique_ptr<ColorTransformStep>> steps_;
 };
 
+#define SRC(...)                                                     \
+  do {                                                               \
+    *result += std::string("  ") + base::StringPrintf(__VA_ARGS__) + \
+               std::string("\n");                                    \
+  } while (0)
+
 class ColorTransformNull : public ColorTransformStep {
  public:
   ColorTransformNull* GetNull() override { return this; }
   bool IsNull() override { return true; }
   void Transform(ColorTransform::TriStim* color, size_t num) override {}
+  bool CanAppendShaderSource() override { return true; }
+  void AppendShaderSource(std::string* result) override {}
 };
 
 class ColorTransformMatrix : public ColorTransformStep {
@@ -316,6 +328,17 @@ class ColorTransformMatrix : public ColorTransformStep {
       matrix_.TransformPoint(colors + i);
   }
 
+  bool CanAppendShaderSource() override { return true; }
+
+  void AppendShaderSource(std::string* result) override {
+    const SkMatrix44& m = matrix_.matrix();
+    SRC("color = mat3(%f, %f, %f, %f, %f, %f, %f, %f, %f) * color;",
+        m.get(0, 0), m.get(1, 0), m.get(2, 0),   // column 1
+        m.get(0, 1), m.get(1, 1), m.get(2, 1),   // column 2
+        m.get(0, 2), m.get(1, 2), m.get(2, 2));  // column 3
+    SRC("color += vec3(%f, %f, %f);", m.get(0, 3), m.get(1, 3), m.get(2, 3));
+  }
+
  private:
   class Transform matrix_;
 };
@@ -591,6 +614,11 @@ void ColorTransformInternal::AppendColorSpaceToColorSpaceTransform(
   steps_.push_back(
       base::MakeUnique<ColorTransformMatrix>(Invert(GetTransferMatrix(from))));
 
+  // If the target color space is not defined, just apply the adjust and
+  // tranfer matrices.
+  if (!to.IsValid())
+    return;
+
   SkColorSpaceTransferFn to_linear_fn;
   bool to_linear_fn_valid = from.GetTransferFunction(&to_linear_fn);
   steps_.push_back(base::MakeUnique<ColorTransformToLinear>(
@@ -723,6 +751,24 @@ ColorTransformInternal::ColorTransformInternal(const ColorSpace& from,
     Simplify();
 }
 
+std::string ColorTransformInternal::GetShaderSource() const {
+  std::string result;
+  result += "vec3 DoColorConversion(vec3 color) {\n";
+  for (const auto& step : steps_)
+    step->AppendShaderSource(&result);
+  result += "  return color;\n";
+  result += "}\n";
+  return result;
+}
+
+bool ColorTransformInternal::CanGetShaderSource() const {
+  for (const auto& step : steps_) {
+    if (!step->CanAppendShaderSource())
+      return false;
+  }
+  return true;
+}
+
 ColorTransformInternal::~ColorTransformInternal() {}
 
 void ColorTransformInternal::Simplify() {