Perform population UTF16Mapping only once

Bug: skia: https://bugs.chromium.org/p/skia/issues/detail?id=13396
Change-Id: I043ecfa175f18cde666a034af8290fe98a701855
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/547776
Reviewed-by: Julia Lavrova <jlavrova@google.com>
Commit-Queue: Julia Lavrova <jlavrova@google.com>

modules/skparagraph/src/ParagraphImpl.cpp

@@ -1091,34 +1091,33 @@ TextIndex ParagraphImpl::findNextGraphemeBoundary(TextIndex utf8) {
 }
 
 void ParagraphImpl::ensureUTF16Mapping() {
-    if (!fUTF16IndexForUTF8Index.empty()) {
-        return;
-    }
-    // Fill out code points 16
-    auto ptr = fText.c_str();
-    auto end = fText.c_str() + fText.size();
-    while (ptr < end) {
+    fillUTF16MappingOnce([&] {
+        // Fill out code points 16
+        auto ptr = fText.c_str();
+        auto end = fText.c_str() + fText.size();
+        while (ptr < end) {
 
-        size_t index = ptr - fText.c_str();
-        SkUnichar u = SkUTF::NextUTF8(&ptr, end);
+            size_t index = ptr - fText.c_str();
+            SkUnichar u = SkUTF::NextUTF8(&ptr, end);
 
-        // All utf8 units refer to the same codepoint
-        size_t next = ptr - fText.c_str();
-        for (auto i = index; i < next; ++i) {
-            fUTF16IndexForUTF8Index.emplace_back(fUTF8IndexForUTF16Index.size());
-        }
-        SkASSERT(fUTF16IndexForUTF8Index.size() == next);
+            // All utf8 units refer to the same codepoint
+            size_t next = ptr - fText.c_str();
+            for (auto i = index; i < next; ++i) {
+                fUTF16IndexForUTF8Index.emplace_back(fUTF8IndexForUTF16Index.size());
+            }
+            SkASSERT(fUTF16IndexForUTF8Index.size() == next);
 
-        // One or two codepoints refer to the same text index
-        uint16_t buffer[2];
-        size_t count = SkUTF::ToUTF16(u, buffer);
-        fUTF8IndexForUTF16Index.emplace_back(index);
-        if (count > 1) {
+            // One or two codepoints refer to the same text index
+            uint16_t buffer[2];
+            size_t count = SkUTF::ToUTF16(u, buffer);
             fUTF8IndexForUTF16Index.emplace_back(index);
+            if (count > 1) {
+                fUTF8IndexForUTF16Index.emplace_back(index);
+            }
         }
-    }
-    fUTF16IndexForUTF8Index.emplace_back(fUTF8IndexForUTF16Index.size());
-    fUTF8IndexForUTF16Index.emplace_back(fText.size());
+        fUTF16IndexForUTF8Index.emplace_back(fUTF8IndexForUTF16Index.size());
+        fUTF8IndexForUTF16Index.emplace_back(fText.size());
+    });
 }
 
 void ParagraphImpl::visit(const Visitor& visitor) {

modules/skparagraph/src/ParagraphImpl.h

@@ -13,6 +13,7 @@
 #include "include/core/SkString.h"
 #include "include/core/SkTypes.h"
 #include "include/private/SkBitmaskEnum.h"
+#include "include/private/SkOnce.h"
 #include "include/private/SkTArray.h"
 #include "include/private/SkTHash.h"
 #include "include/private/SkTemplates.h"
@@ -255,6 +256,7 @@ private:
     // They are filled lazily whenever they need and cached
     SkTArray<TextIndex, true> fUTF8IndexForUTF16Index;
     SkTArray<size_t, true> fUTF16IndexForUTF8Index;
+    SkOnce fillUTF16MappingOnce;
     size_t fUnresolvedGlyphs;
 
     SkTArray<TextLine, false> fLines;   // kFormatted   (cached: width, max lines, ellipsis, text align)

modules/skparagraph/tests/SkParagraphTest.cpp

@@ -42,6 +42,7 @@
 #include <string>
 #include <utility>
 #include <vector>
+#include <thread>
 
 struct GrContextOptions;
 
@@ -6924,3 +6925,51 @@ UNIX_ONLY_TEST(SkParagraph_NonMonotonicGlyphsRTL, reporter) {
     REPORTER_ASSERT(reporter, impl->lineNumber() == 1);  // But it's still one line
     paragraph->paint(canvas.get(), 0, 0);
 }
+
+void performGetRectsForRangeConcurrently(skiatest::Reporter* reporter) {
+    sk_sp<ResourceFontCollection> fontCollection = sk_make_sp<ResourceFontCollection>();
+    if (!fontCollection->fontsFound()) {
+        INFOF(reporter, "No fonts found\n");
+        return;
+    }
+    auto const text = std::u16string(42000, 'x');
+    ParagraphStyle paragraphStyle;
+    TextStyle textStyle;
+    textStyle.setFontFamilies({SkString("Roboto")});
+    textStyle.setFontSize(14);
+    textStyle.setColor(SK_ColorBLACK);
+    textStyle.setFontStyle(SkFontStyle(SkFontStyle::kMedium_Weight, SkFontStyle::kNormal_Width,
+                                       SkFontStyle::kUpright_Slant));
+
+    ParagraphBuilderImpl builder(paragraphStyle, fontCollection);
+    builder.pushStyle(textStyle);
+    builder.addText(text);
+    builder.pop();
+
+    auto paragraph = builder.Build();
+    paragraph->layout(std::numeric_limits<float>::max());
+
+    RectHeightStyle heightStyle = RectHeightStyle::kMax;
+    RectWidthStyle widthStyle = RectWidthStyle::kMax;
+    auto t1 = std::thread([&] {
+        auto result = paragraph->getRectsForRange(0, 2, heightStyle, widthStyle);
+        REPORTER_ASSERT(reporter, !result.empty());
+    });
+    auto t2 = std::thread([&] {
+        auto result = paragraph->getRectsForRange(5, 10, heightStyle, widthStyle);
+        REPORTER_ASSERT(reporter, !result.empty());
+    });
+    t1.join();
+    t2.join();
+}
+
+UNIX_ONLY_TEST(SkParagraph_GetRectsForRangeConcurrently, reporter) {
+    auto const threads_count = 100;
+    std::thread threads[threads_count];
+    for (auto& thread : threads) {
+        thread = std::thread(performGetRectsForRangeConcurrently, reporter);
+    }
+    for (auto& thread : threads) {
+        thread.join();
+    }
+}