[Remoting Android] Cursor & Cursor Feedback for OpenGL Renderer

remoting/client/gl_cursor_feedback_texture.cc

+// Copyright 2016 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.
+
+#include "remoting/client/gl_cursor_feedback_texture.h"
+
+#include "remoting/base/util.h"
+
+namespace {
+
+const int kColorRingsCount = 4;
+const int kFeedbackTexturePixelDiameter = 512;
+const int kFeedbackTexturePixelRadius = kFeedbackTexturePixelDiameter / 2;
+
+// RGBA8888 colors. From inside to outside.
+const uint8_t kFeedbackRingColors[kColorRingsCount]
+                                 [remoting::kBytesPerPixelRGB32] = {
+    {0, 0, 0, 0},  // transparent black
+    {0xff, 0xff, 0xff, 0xff},  // white
+    {0, 0, 0, 0xff},  // black
+    {0, 0, 0, 0}  // transparent black
+};
+
+const float kFeedbackRadiusStops[kColorRingsCount] = {0.0f, 0.8f, 0.9f, 1.0f};
+
+}  // namespace
+
+namespace remoting {
+
+void LinearInterpolate(const uint8_t* in1,

[Sergey Ulanov, 2016/07/20 23:51:40]

nit: move to anonymous namespace above.

[Yuwei, 2016/07/21 01:03:37]

Obsolete. Inlined now.

+                       const uint8_t* in2,
+                       uint8_t* out,
+                       int percentage,

[Sergey Ulanov, 2016/07/20 23:51:40]

nit: if you use [0..256] range instead of [0..100] range then this compiler will
be able to optimize division with bit shift.

[Yuwei, 2016/07/21 01:03:37]

Done.

+                       int current_dimension) {
+  out[current_dimension] = (in1[current_dimension] * (100 - percentage) +
+      in2[current_dimension] * percentage) / 100;
+}
+
+void FillColorByRadius(float radius, uint32_t* out) {

[Sergey Ulanov, 2016/07/20 23:51:40]

Maybe replace this with uint32_t GetColorByRadius(radius)?

[Yuwei, 2016/07/21 01:03:37]

Done.

+  int i;

[Sergey Ulanov, 2016/07/20 23:51:40]

ring_index?

[Yuwei, 2016/07/21 01:03:37]

Done.

+  // Find first radius stop that is not smaller than current radius.
+  for (i = kColorRingsCount - 1; radius < kFeedbackRadiusStops[i] && i >= 0;

[Sergey Ulanov, 2016/07/20 23:51:40]

Use while loop here or move the "radius < kFeedbackRadiusStops[i]" condition 
inside and break the loop.
Empty for loop like this is confusing.

int ring_index = kColorRingsCount - 1;
while (radius < kFeedbackRadiusStops[ring_index] && ring_index >= 0) 
  ring_index++;

[Yuwei, 2016/07/21 01:03:37]

Done.

+       i--) {
+  }
+
+  if (i < 0) {
+    NOTREACHED();
+    return;
+  }
+
+  if (i == kColorRingsCount - 1) {
+    // Area outside the circle. Just use the outermost color.
+    *out = *reinterpret_cast<const uint32_t*>(kFeedbackRingColors[i]);
+    return;
+  }
+
+  const uint8_t* first_color = kFeedbackRingColors[i];
+  const uint8_t* second_color = kFeedbackRingColors[i + 1];
+  float first_radius = kFeedbackRadiusStops[i];
+  float second_radius = kFeedbackRadiusStops[i + 1];
+
+  int percentage =
+      (radius - first_radius) * 100 / (second_radius - first_radius);
+  uint8_t* byte_out = reinterpret_cast<uint8_t*>(out);
+  LinearInterpolate(first_color, second_color, byte_out, percentage, 0);

[Sergey Ulanov, 2016/07/20 23:51:40]

for loop?
Also I don't think you actually need LinearInterpolate() function. This code
would be perfectly readable if you just inline that code here.

[Yuwei, 2016/07/21 01:03:37]

Done.

+  LinearInterpolate(first_color, second_color, byte_out, percentage, 1);
+  LinearInterpolate(first_color, second_color, byte_out, percentage, 2);
+  LinearInterpolate(first_color, second_color, byte_out, percentage, 3);
+}
+
+void FillColorMapping(uint32_t* map) {
+  for (int x = 0; x < kFeedbackTexturePixelRadius; x++) {
+    for (int y = 0; y <= x; y++) {
+      float radius =
+          sqrt(x * x + y * y) / kFeedbackTexturePixelRadius;
+      FillColorByRadius(radius, map + x + y * kFeedbackTexturePixelRadius);

[Sergey Ulanov, 2016/07/20 23:51:40]

This code would be simpler if you just set color in 8 pixels at a time:

uint32_t color = GetColorByRadius(radius);
int x2 = kFeedbackTexturePixelDiameter - 1 - x;
int y2 = kFeedbackTexturePixelDiameter - 1 - y;
map[x + y * kFeedbackTexturePixelDiameter] = color;
map[x2 + y * kFeedbackTexturePixelDiameter] = color;
map[x + y2 * kFeedbackTexturePixelDiameter] = color;
map[x2 + y2 * kFeedbackTexturePixelDiameter] = color;
map[y + x * kFeedbackTexturePixelDiameter] = color;
map[y2 + x * kFeedbackTexturePixelDiameter] = color;
map[y + x2 * kFeedbackTexturePixelDiameter] = color;
map[y2 + x2 * kFeedbackTexturePixelDiameter] = color;

[Yuwei, 2016/07/21 01:03:37]

Done.

BTW x and y are related to the center of the texture so your code may draw
something like a curved "x" :P

+    }
+  }
+}
+
+void FillFeedbackTexture(uint32_t* texture) {
+  // Color: RGBA8888. Equivalent to the upper part of the forth quadrant.
+  std::unique_ptr<uint32_t[]> coord_color_map(

[Sergey Ulanov, 2016/07/20 23:51:40]

See my comment above. You can iterate over one 8th of the circle, but fill it in
whole by setting 8 pixels on every iteration. That would make this code simpler.

[Yuwei, 2016/07/21 01:03:37]

Done. Now it take about 8ms to generate the texture. Much faster :)

+      new uint32_t[kFeedbackTexturePixelRadius * kFeedbackTexturePixelRadius]);
+
+  FillColorMapping(coord_color_map.get());
+
+  for (int x = 0; x < kFeedbackTexturePixelDiameter; x++) {
+    for (int y = 0; y < kFeedbackTexturePixelDiameter; y++) {
+      int mapped_x = abs(x - kFeedbackTexturePixelRadius);
+      int mapped_y = abs(y - kFeedbackTexturePixelRadius);
+      if (mapped_x < mapped_y) {
+        int temp_x = mapped_x;
+        mapped_x = mapped_y;
+        mapped_y = temp_x;
+      }
+      texture[x + y * kFeedbackTexturePixelDiameter] =
+          coord_color_map[mapped_x + mapped_y * kFeedbackTexturePixelRadius];
+    }
+  }
+}
+
+GlCursorFeedbackTexture* GlCursorFeedbackTexture::GetInstance() {
+  return base::Singleton<GlCursorFeedbackTexture>::get();
+}
+
+const uint8_t* GlCursorFeedbackTexture::GetTexture() const {
+  return reinterpret_cast<uint8_t*>(texture_.get());
+}
+
+int GlCursorFeedbackTexture::GetTextureDiameter() const {
+  return kFeedbackTexturePixelDiameter;
+}
+
+GlCursorFeedbackTexture::GlCursorFeedbackTexture() :
+    texture_(new uint32_t[kFeedbackTexturePixelDiameter *

[Sergey Ulanov, 2016/07/20 23:51:40]

git cl format please

[Yuwei, 2016/07/21 01:03:37]

Done.

+                          kFeedbackTexturePixelDiameter]) {
+  FillFeedbackTexture(texture_.get());
+}
+
+GlCursorFeedbackTexture::~GlCursorFeedbackTexture() {
+}
+
+}  // namespace remoting