ttf: ++thread safety

Properly allow the ttf loader sharable among threads.

issue: https://github.com/thorvg/thorvg/issues/3165

src/loaders/ttf/tvgTtfLoader.cpp

@@ -217,17 +217,16 @@ void TtfLoader::clear()
 /************************************************************************/
 
 
-bool TtfLoader::transform(Paint* paint, float fontSize, bool italic)
+float TtfLoader::transform(Paint* paint, FontMetrics& metrics, float fontSize, bool italic)
 {
-    if (!paint) return false;
     auto shift = 0.0f;
     auto dpi = 96.0f / 72.0f;   //dpi base?
-    scale = fontSize * dpi / reader.metrics.unitsPerEm;
+    auto scale = fontSize * dpi / reader.metrics.unitsPerEm;
     if (italic) shift = -scale * 0.18f;  //experimental decision.
-    Matrix m = {scale, shift, -(shift * reader.metrics.minw), 0, scale, 0, 0, 0, 1};
+    Matrix m = {scale, shift, -(shift * metrics.minw), 0, scale, 0, 0, 0, 1};
     paint->transform(m);
 
-    return true;
+    return scale;
 }
 
 
@@ -270,21 +269,11 @@ bool TtfLoader::open(const char* data, uint32_t size, bool copy)
 }
 
 
-bool TtfLoader::request(Shape* shape, char* text)
+bool TtfLoader::read(Shape* shape, char* text, FontMetrics& out)
-{
-    this->shape = shape;
-    this->text = text;
-
-    return true;
-}
-
-
-bool TtfLoader::read()
 {
     if (!text) return false;
 
     shape->reset();
-    shape->fill(FillRule::EvenOdd);
 
     auto n = strlen(text);
     auto code = _codepoints(text, n);
@@ -306,7 +295,7 @@ bool TtfLoader::read()
             lglyph = rglyph;
             //store the first glyph with outline min size for italic transform.
             if (loadMinw && gmetrics.outline) {
-                reader.metrics.minw = gmetrics.minw;
+                out.minw = gmetrics.minw;
                 loadMinw = false;
             }
         }

src/loaders/ttf/tvgTtfLoader.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023 - 2024 the ThorVG project. All rights reserved.
+ * Copyright (c) 2023 - 2025 the ThorVG project. All rights reserved.
 
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -43,11 +43,12 @@ struct TtfLoader : public FontLoader
     ~TtfLoader();
 
     using FontLoader::open;
+    using FontLoader::read;
+
     bool open(const string& path) override;
     bool open(const char *data, uint32_t size, bool copy) override;
-    bool transform(Paint* paint, float fontSize, bool italic) override;
+    float transform(Paint* paint, FontMetrics& metrices, float fontSize, bool italic) override;
-    bool request(Shape* shape, char* text) override;
+    bool read(Shape* shape, char* text, FontMetrics& out) override;
-    bool read() override;
     void clear();
 };
 

src/loaders/ttf/tvgTtfReader.cpp

@@ -72,12 +72,10 @@ static int _cmpu32(const void *a, const void *b)
 
 bool TtfReader::validate(uint32_t offset, uint32_t margin) const
 {
-#if 1
     if ((offset > size) || (size - offset < margin)) {
         TVGERR("TTF", "Invalidate data");
         return false;
     }
-#endif
     return true;
 }
 
@@ -204,8 +202,11 @@ uint32_t TtfReader::outlineOffset(uint32_t glyph)
 {
     uint32_t cur, next;
 
-    if (!loca) loca = table("loca");
+    auto loca = this->loca.load();
-    if (!glyf) glyf = table("glyf");
+    if (loca == 0) this->loca = loca = table("loca");
+
+    auto glyf = this->glyf.load();
+    if (glyf == 0) this->glyf = glyf = table("glyf");
 
     if (metrics.locaFormat == 0) {
         auto base = loca + 2 * glyph;
@@ -327,8 +328,8 @@ bool TtfReader::header()
     metrics.numHmtx = _u16(data, hhea + 34);
 
     //kerning
-    this->kern = table("kern");
+    auto kern = this->kern = table("kern");
-    if (this->kern) {
+    if (kern) {
         if (!validate(kern, 4)) return false;
         if (_u16(data, kern) != 0) return false;
     }
@@ -339,8 +340,9 @@ bool TtfReader::header()
 
 uint32_t TtfReader::glyph(uint32_t codepoint)
 {
+    auto cmap = this->cmap.load();
     if (cmap == 0) {
-        cmap = table("cmap");
+        this->cmap = cmap = table("cmap");
         if (!validate(cmap, 4)) return -1;
     }
 
@@ -397,7 +399,8 @@ uint32_t TtfReader::glyph(uint32_t codepoint, TtfGlyphMetrics& gmetrics)
 bool TtfReader::glyphMetrics(uint32_t glyphIndex, TtfGlyphMetrics& gmetrics)
 {
     //horizontal metrics
-    if (!hmtx) hmtx = table("hmtx");
+    auto hmtx = this->hmtx.load();
+    if (hmtx == 0) this->hmtx = hmtx = table("hmtx");
 
     //glyph is inside long metrics segment.
     if (glyphIndex < metrics.numHmtx) {
@@ -451,7 +454,8 @@ bool TtfReader::convert(Shape* shape, TtfGlyphMetrics& gmetrics, const Point& of
     if (outlineCnt == 0) return false;
     if (outlineCnt < 0) {
         uint16_t maxComponentDepth = 1U;
-        if (!maxp) maxp = table("maxp");
+        auto maxp = this->maxp.load();
+        if (maxp == 0) this->maxp = maxp = table("maxp");
         if (validate(maxp, 32) && _u32(data, maxp) >= 0x00010000U) { // >= version 1.0
             maxComponentDepth = _u16(data, maxp + 30);
         }
@@ -607,7 +611,7 @@ void TtfReader::kerning(uint32_t lglyph, uint32_t rglyph, Point& out)
 
     if (!kern) return;
 
-    auto kern = this->kern;
+    auto kern = this->kern.load();
 
     out.x = out.y = 0.0f;
 

src/loaders/ttf/tvgTtfReader.h

@@ -23,6 +23,7 @@
 #ifndef _TVG_TTF_READER_H
 #define _TVG_TTF_READER_H
 
+#include <atomic>
 #include "tvgCommon.h"
 #include "tvgArray.h"
 
@@ -55,7 +56,6 @@ public:
             float lineGap;
         } hhea;
 
-        float minw;            //first glyph width (used for italic)
         uint16_t unitsPerEm;
         uint16_t numHmtx;      //the number of Horizontal metrics table
         uint8_t locaFormat;    //0 for short offsets, 1 for long
@@ -68,12 +68,12 @@ public:
 
 private:
     //table offsets
-    uint32_t cmap = 0;
+    atomic<uint32_t> cmap{};
-    uint32_t hmtx = 0;
+    atomic<uint32_t> hmtx{};
-    uint32_t loca = 0;
+    atomic<uint32_t> loca{};
-    uint32_t glyf = 0;
+    atomic<uint32_t> glyf{};
-    uint32_t kern = 0;
+    atomic<uint32_t> kern{};
-    uint32_t maxp = 0;
+    atomic<uint32_t> maxp{};
 
     uint32_t cmap_12_13(uint32_t table, uint32_t codepoint, int which) const;
     uint32_t cmap_4(uint32_t table, uint32_t codepoint) const;

src/renderer/tvgLoadModule.h

@@ -23,6 +23,8 @@
 #ifndef _TVG_LOAD_MODULE_H_
 #define _TVG_LOAD_MODULE_H_
 
+#include <atomic>
+#include "tvgCommon.h"
 #include "tvgRender.h"
 #include "tvgInlist.h"
 
@@ -38,7 +40,7 @@ struct LoadModule
     };
 
     FileType type;                                  //current loader file type
-    uint16_t sharing = 0;                           //reference count
+    atomic<uint16_t> sharing{};                     //reference count
     bool readied = false;                           //read done already.
     bool pathcache = false;                         //cached by path
 
@@ -77,7 +79,7 @@ struct LoadModule
 
 struct ImageLoader : LoadModule
 {
-    static ColorSpace cs;                           //desired value
+    static atomic<ColorSpace> cs;                   //desired value
 
     float w = 0, h = 0;                             //default image size
     RenderSurface surface;
@@ -95,14 +97,21 @@ struct ImageLoader : LoadModule
 };
 
 
+struct FontMetrics
+{
+    //TODO: add necessary metrics
+    float minw;
+};
+
+
 struct FontLoader : LoadModule
 {
-    float scale = 1.0f;
-
     FontLoader(FileType type) : LoadModule(type) {}
 
-    virtual bool request(Shape* shape, char* text) = 0;
+    using LoadModule::read;
-    virtual bool transform(Paint* paint, float fontSize, bool italic) = 0;
+
+    virtual bool read(Shape* shape, char* text, FontMetrics& out) = 0;
+    virtual float transform(Paint* paint, FontMetrics& mertrics, float fontSize, bool italic) = 0;
 };
 
 #endif //_TVG_LOAD_MODULE_H_

src/renderer/tvgLoader.cpp

@@ -22,6 +22,7 @@
 
 #include <string.h>
 
+#include <atomic>
 #include "tvgInlist.h"
 #include "tvgLoader.h"
 #include "tvgLock.h"
@@ -66,7 +67,8 @@ uintptr_t HASH_KEY(const char* data)
 /* Internal Class Implementation                                        */
 /************************************************************************/
 
-ColorSpace ImageLoader::cs = ColorSpace::ARGB8888;
+//TODO: remove it.
+atomic<ColorSpace> ImageLoader::cs{ColorSpace::ARGB8888};
 
 static Key _key;
 static Inlist<LoadModule> _activeLoaders;

src/renderer/tvgText.h

@@ -24,6 +24,7 @@
 #define _TVG_TEXT_H
 
 #include <cstring>
+#include "tvgMath.h"
 #include "tvgShape.h"
 #include "tvgFill.h"
 #include "tvgLoader.h"
@@ -33,6 +34,7 @@ struct Text::Impl
     FontLoader* loader = nullptr;
     Text* paint;
     Shape* shape;
+    FontMetrics metrics;
     char* utf8 = nullptr;
     float fontSize;
     bool italic = false;
@@ -40,6 +42,7 @@ struct Text::Impl
 
     Impl(Text* p) : paint(p), shape(Shape::gen().release())
     {
+        shape->fill(FillRule::EvenOdd);
     }
 
     ~Impl()
@@ -94,27 +97,26 @@ struct Text::Impl
         return PP(shape)->render(renderer);
     }
 
-    bool load()
+    float load()
     {
-        if (!loader) return false;
+        if (!loader) return 0.0f;
 
-        loader->request(shape, utf8);
         //reload
         if (changed) {
-            loader->read();
+            loader->read(shape, utf8, metrics);
             changed = false;
         }
-        return loader->transform(shape, fontSize, italic);
+        return loader->transform(shape, metrics, fontSize, italic);
     }
 
     RenderData update(RenderMethod* renderer, const Matrix& transform, Array<RenderData>& clips, uint8_t opacity, RenderUpdateFlag pFlag, TVG_UNUSED bool clipper)
     {
-        if (!load()) return nullptr;
+        auto scale = 1.0f / load();
+        if (tvg::zero(scale)) return nullptr;
 
         //transform the gradient coordinates based on the final scaled font.
         auto fill = P(shape)->rs.fill;
         if (fill && P(shape)->rFlag & RenderUpdateFlag::Gradient) {
-            auto scale = 1.0f / loader->scale;
             if (fill->type() == Type::LinearGradient) {
                 P(static_cast<LinearGradient*>(fill))->x1 *= scale;
                 P(static_cast<LinearGradient*>(fill))->y1 *= scale;
@@ -134,7 +136,7 @@ struct Text::Impl
 
     bool bounds(float* x, float* y, float* w, float* h, TVG_UNUSED bool stroking)
     {
-        if (!load()) return false;
+        if (load() == 0.0f) return false;
         PP(shape)->bounds(x, y, w, h, true, true, false);
         return true;
     }