ttf_loader: changing the reference point for text

After the change, the reference point for text is the left
edge of the baseline.

examples/Text.cpp

@@ -62,12 +62,13 @@ struct UserExample : tvgexam::Example
         text->font("Arial", 80);
         text->text("THORVG Text");
         text->fill(255, 255, 255);
+        text->translate(0, 100); //text baseline at y=100
         canvas->push(text);
 
         auto text2 = tvg::Text::gen();
         text2->font("Arial", 30, "italic");
         text2->text("Font = \"Arial\", Size = 40, Style=Italic");
-        text2->translate(0, 150);
+        text2->translate(0, 180); //text baseline at y=180
         text2->fill(255, 255, 255);
         canvas->push(text2);
 
@@ -75,43 +76,42 @@ struct UserExample : tvgexam::Example
         text3->font(nullptr, 40);  //Use any font
         text3->text("Kerning Test: VA, AV, TJ, JT");
         text3->fill(255, 255, 255);
-        text3->translate(0, 225);
+        text3->translate(0, 275);
         canvas->push(text3);
 
         auto text4 = tvg::Text::gen();
         text4->font("Arial", 25);
         text4->text("Purple Text");
         text4->fill(255, 0, 255);
-        text4->translate(0, 310);
+        text4->translate(0, 330);
         canvas->push(text4);
 
         auto text5 = tvg::Text::gen();
         text5->font("Arial", 25);
         text5->text("Gray Text");
         text5->fill(150, 150, 150);
-        text5->translate(220, 310);
+        text5->translate(220, 330);
         canvas->push(text5);
 
         auto text6 = tvg::Text::gen();
         text6->font("Arial", 25);
         text6->text("Yellow Text");
         text6->fill(255, 255, 0);
-        text6->translate(400, 310);
+        text6->translate(400, 330);
         canvas->push(text6);
 
         auto text7 = tvg::Text::gen();
         text7->font("Arial", 15);
-        text7->text("Transformed Text - 30'");
+        text7->text("Transformed Text - 0'");
         text7->fill(0, 0, 0);
-        text7->translate(600, 400);
-        text7->rotate(30);
+        text7->translate(600, 410);
         canvas->push(text7);
 
         auto text8 = tvg::Text::gen();
         text8->font("Arial", 15);
         text8->fill(0, 0, 0);
         text8->text("Transformed Text - 90'");
-        text8->translate(600, 400);
+        text8->translate(600, 410);
         text8->rotate(90);
         canvas->push(text8);
 
@@ -119,7 +119,7 @@ struct UserExample : tvgexam::Example
         text9->font("Arial", 15);
         text9->fill(0, 0, 0);
         text9->text("Transformed Text - 180'");
-        text9->translate(800, 400);
+        text9->translate(600, 410);
         text9->rotate(180);
         canvas->push(text9);
 
@@ -143,7 +143,7 @@ struct UserExample : tvgexam::Example
         fill->colorStops(colorStops, 3);
         text10->fill(fill);
 
-        text10->translate(0, 350);
+        text10->translate(0, 400);
 
         canvas->push(text10);
 
@@ -166,7 +166,7 @@ struct UserExample : tvgexam::Example
 
         text11->fill(fill2);
 
-        text11->translate(0, 450);
+        text11->translate(0, 500);
 
         canvas->push(text11);
 
@@ -174,7 +174,7 @@ struct UserExample : tvgexam::Example
         text12->font("SentyCloud", 50);
         text12->fill(255, 25, 25);
         text12->text("\xe4\xb8\x8d\xe5\x88\xb0\xe9\x95\xbf\xe5\x9f\x8e\xe9\x9d\x9e\xe5\xa5\xbd\xe6\xb1\x89\xef\xbc\x81");
-        text12->translate(0, 525);
+        text12->translate(0, 600);
         canvas->push(text12);
 
         return true;

inc/thorvg.h

@@ -1576,6 +1576,8 @@ public:
      *
      * @param[in] text The multi-byte text encoded with utf8 string to be rendered.
      *
+     * @note The reference point for text is the left edge of the baseline. Unless the text is explicitly translated,
+     * this point will be placed at (0, 0) of the canvas — which, by default, lies outside the visible rendering area.
      * @since 1.0
      */
     Result text(const char* text) noexcept;

src/loaders/lottie/tvgLottieBuilder.cpp

@@ -900,7 +900,7 @@ static void _fontText(TextDocument& doc, Scene* scene)
     strcpy(buf, doc.text);
     auto token = std::strtok(buf, delim);
 
-    auto cnt = 0;
+    auto cursorY = 0.0f;
     while (token) {
         auto txt = Text::gen();
         if (txt->font(doc.name, size) != Result::Success) {
@@ -913,14 +913,12 @@ static void _fontText(TextDocument& doc, Scene* scene)
 
         float width;
         txt->bounds(nullptr, nullptr, &width, nullptr);
+        txt->translate(width * doc.justify, cursorY);
 
-        auto cursorX = width * doc.justify;
-        auto cursorY = lineHeight * cnt;
-        txt->translate(cursorX, -lineHeight + cursorY);
+        scene->push(txt);
 
         token = std::strtok(nullptr, delim);
-        scene->push(txt);
-        cnt++;
+        cursorY += lineHeight;
     }
 }
 

src/loaders/svg/tvgSvgSceneBuilder.cpp

@@ -867,7 +867,7 @@ static Paint* _textBuildHelper(SvgLoaderData& loaderData, const SvgNode* node, c
     if (node->transform) textTransform = *node->transform;
     else textTransform = tvg::identity();
 
-    translateR(&textTransform, {node->node.text.x, node->node.text.y - textNode->fontSize});
+    translateR(&textTransform, {node->node.text.x, node->node.text.y});
     text->transform(textTransform);
 
     //TODO: handle def values of font and size as used in a system?

src/loaders/ttf/tvgTtfLoader.cpp

@@ -288,7 +288,7 @@ bool TtfLoader::read(Shape* shape, char* text, FontMetrics& out)
 
     //TODO: optimize with the texture-atlas?
     TtfGlyphMetrics gmetrics;
-    Point offset = {0.0f, reader.metrics.hhea.ascent};
+    Point offset = {0.0f, 0.0f};
     Point kerning = {0.0f, 0.0f};
     auto lglyph = INVALID_GLYPH;
     auto loadMinw = true;