Rendering Insecure WebVR Warnings into a texture with Skia.

chrome/browser/android/vr_shell/textures/ui_texture.cc

+// Copyright 2017 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 "chrome/browser/android/vr_shell/textures/ui_texture.h"
+
+#include <string>
+#include <vector>
+
+#include "base/memory/ptr_util.h"
+#include "base/strings/string_util.h"
+#include "third_party/skia/include/core/SkCanvas.h"
+#include "ui/gfx/canvas.h"
+#include "ui/gl/gl_bindings.h"
+
+namespace vr_shell {
+
+namespace {
+
+constexpr float kDefaultLineSpacePercentage = 0.25;
+const std::string kWhitespaceChars(base::kWhitespaceASCII);
+
+std::vector<std::string> SplitText(const std::string& text,
+                                   const SkPaint& paint,
+                                   float max_width) {
+  std::vector<std::string> lines;
+  size_t first_char = 0;
+  while (first_char < text.size()) {
+    SkScalar width;
+    size_t char_break = first_char + paint.breakText(text.c_str() + first_char,
+                                                     text.size() - first_char,
+                                                     max_width, &width);
+    if (char_break == text.size()) {
+      lines.push_back(text.substr(first_char));
+      break;
+    }
+    size_t char_break_guess = char_break + 1;
+    while (char_break_guess > first_char &&
+           kWhitespaceChars.find(text[char_break_guess]) == std::string::npos)
+      char_break_guess--;
+
+    if (char_break_guess > first_char)
+      char_break = char_break_guess;
+
+    lines.push_back(text.substr(first_char, char_break - first_char));
+
+    first_char = char_break + (char_break_guess > first_char ? 1 : 0);
+  }
+  return lines;
+}
+
+}  // namespace
+
+// TODO(acondor): Create non-square textures to reduce memory usage.
+UITexture::UITexture(int texture_handle, int texture_size)
+    : texture_handle_(texture_handle),
+      texture_size_(texture_size),
+      surface_(SkSurface::MakeRasterN32Premul(texture_size_, texture_size_)) {}
+
+UITexture::~UITexture() = default;
+
+void UITexture::DrawAndLayout() {
+  cc::SkiaPaintCanvas paint_canvas(surface_->getCanvas());
+  gfx::Canvas canvas(&paint_canvas, 1.0f);
+  canvas.DrawColor(0x00000000);
+  Draw(&canvas);
+  SetSize();
+}
+
+void UITexture::Flush() {
+  cc::SkiaPaintCanvas paint_canvas(surface_->getCanvas());
+  paint_canvas.flush();
+  SkPixmap pixmap;
+  CHECK(surface_->peekPixels(&pixmap));
+
+  glBindTexture(GL_TEXTURE_2D, texture_handle_);
+  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, pixmap.width(), pixmap.height(), 0,
+               GL_RGBA, GL_UNSIGNED_BYTE, pixmap.addr());
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+}
+
+void UITexture::DrawText(gfx::Canvas* canvas,
+                         const std::string& text,
+                         const cc::PaintFlags& flags,
+                         float max_width,
+                         bool v_centered) {
+  // TODO(acondor): Make use of gfx::Canvas::DrawStringRect instead.
+  // Platform specific font rendering capabilities need to be ported to Android.
+
+  const auto& paint = cc::ToSkPaint(flags);
+
+  auto lines = SplitText(text, paint, max_width);
+  if (lines.empty())
+    return;
+
+  float v_pos = flags.getTextSize();
+  if (v_centered) {
+    float height =
+        (lines.size() + (lines.size() - 1) * kDefaultLineSpacePercentage) *
+        flags.getTextSize();
+    v_pos -= height * .5;
+  }
+  for (const auto& line : lines) {
+    canvas->sk_canvas()->drawText(line.c_str(), line.size(), 0, v_pos, flags);
+    v_pos += flags.getTextSize() * (1 + kDefaultLineSpacePercentage);
+  }
+}
+
+}  // namespace vr_shell