Add strokePercentage parameter to Font in order to print outlined text

src/freetype.cpp

@@ -1,4 +1,4 @@
-// Copyright 2007-2022 Jan Niklas Hasse <jhasse@bixense.com>
+// Copyright 2007-2024 Jan Niklas Hasse <jhasse@bixense.com>
 // For conditions of distribution and use, see copyright notice in LICENSE.txt
 
 #define _LIBCPP_DISABLE_DEPRECATION_WARNINGS
@@ -24,8 +24,9 @@
 
 namespace jngl {
 
-Character::Character(const char32_t ch, const unsigned int fontHeight, FT_Face face) {
-	const auto flags = FT_LOAD_TARGET_LIGHT | FT_LOAD_RENDER;
+Character::Character(const char32_t ch, const unsigned int fontHeight, FT_Face face,
+                     FT_Stroker stroker) {
+	const auto flags = FT_LOAD_TARGET_LIGHT | FT_LOAD_DEFAULT;
 	if (FT_Load_Char(face, ch, flags)) {
 		const std::string msg =
 		    std::string("FT_Load_Glyph failed. Character: ") + std::to_string(ch);
@@ -39,6 +40,10 @@ Character::Character(const char32_t ch, const unsigned int fontHeight, FT_Face f
 	if (FT_Get_Glyph(face->glyph, &glyph)) {
 		throw std::runtime_error("FT_Get_Glyph failed");
 	}
+	if (stroker) {
+		FT_Glyph_StrokeBorder(&glyph, stroker, 0, 1);
+	}
+	FT_Glyph_To_Bitmap(&glyph, FT_RENDER_MODE_NORMAL, nullptr, 1);
 	Finally freeGlyph([&]() { FT_Done_Glyph(glyph); });
 	const auto bitmap_glyph = reinterpret_cast<FT_BitmapGlyph>(glyph); // NOLINT
 	const FT_Bitmap& bitmap = bitmap_glyph->bitmap;
@@ -134,12 +139,12 @@ Character& FontImpl::GetCharacter(std::string::iterator& it, const std::string::
 	}
 	if (characters_[unicodeCharacter] == nullptr) {
 		characters_[unicodeCharacter] =
-		    std::make_shared<Character>(unicodeCharacter, height_, face);
+		    std::make_shared<Character>(unicodeCharacter, height_, face, stroker);
 	}
 	return *(characters_[unicodeCharacter]);
 }
 
-FontImpl::FontImpl(const std::string& relativeFilename, unsigned int height)
+FontImpl::FontImpl(const std::string& relativeFilename, unsigned int height, float strokePercentage)
 : height_(static_cast<unsigned int>(height * getScaleFactor())),
   lineHeight(static_cast<int>(height_ * LINE_HEIGHT_FACOTR)) {
 	auto filename = pathPrefix + relativeFilename;
@@ -191,10 +196,20 @@ FontImpl::FontImpl(const std::string& relativeFilename, unsigned int height)
 	// in terms of 1/64ths of pixels.  Thus, to make a font
 	// h pixels high, we need to request a size of h*64.
 	FT_Set_Char_Size(face, height_ * 64, height_ * 64, 96, 96);
+
+	FT_Fixed strokeWidth = std::lround(strokePercentage * static_cast<float>(height) * 0.64);
+	if (strokeWidth != 0) {
+		FT_Stroker_New(library, &stroker);
+		FT_Stroker_Set(stroker, strokeWidth, FT_STROKER_LINECAP_ROUND, FT_STROKER_LINEJOIN_ROUND,
+		               0);
+	}
 }
 
 FontImpl::~FontImpl() {
 	freeFace.reset(); // free face_ with FT_Done_Face
+	if (stroker) {
+		FT_Stroker_Done(stroker);
+	}
 	if (--instanceCounter == 0) {
 		FT_Done_FreeType(library);
 	}

src/freetype.hpp

@@ -1,4 +1,4 @@
-// Copyright 2007-2022 Jan Niklas Hasse <jhasse@bixense.com>
+// Copyright 2007-2024 Jan Niklas Hasse <jhasse@bixense.com>
 // For conditions of distribution and use, see copyright notice in LICENSE.txt
 
 #pragma once
@@ -8,6 +8,7 @@
 
 #include <ft2build.h> // NOLINT
 #include FT_FREETYPE_H
+#include FT_STROKER_H
 
 #include <map>
 
@@ -18,7 +19,7 @@ extern unsigned char fontColorRed, fontColorGreen, fontColorBlue, fontColorAlpha
 
 class Character {
 public:
-	Character(char32_t ch, unsigned int fontHeight, FT_Face);
+	Character(char32_t ch, unsigned int fontHeight, FT_Face, FT_Stroker);
 	Character(const Character&) = delete;
 	Character& operator=(const Character&) = delete;
 	Character(Character&&) = delete;
@@ -36,7 +37,7 @@ class Character {
 
 class FontImpl {
 public:
-	FontImpl(const std::string& relativeFilename, unsigned int height);
+	FontImpl(const std::string& relativeFilename, unsigned int height, float strokePercentage);
 	FontImpl(const FontImpl&) = delete;
 	FontImpl& operator=(const FontImpl&) = delete;
 	FontImpl(FontImpl&&) = delete;
@@ -54,6 +55,7 @@ class FontImpl {
 	static int instanceCounter;
 	static FT_Library library;
 	FT_Face face = nullptr;
+	FT_Stroker stroker = nullptr;
 	std::unique_ptr<Finally> freeFace; // Frees face_ if necessary
 	unsigned int height_;
 	int lineHeight;

src/jngl/font.cpp

@@ -43,7 +43,8 @@ void popFontColor() {
 	rgbs.pop();
 }
 
-Font::Font(const std::string& filename, unsigned int size) : impl(new FontImpl(filename, size)) {
+Font::Font(const std::string& filename, unsigned int size, float strokePercentage)
+: impl(new FontImpl(filename, size, strokePercentage)) {
 }
 
 void Font::print(const std::string& text, int x, int y) {

src/jngl/font.hpp

@@ -19,7 +19,14 @@ class Mat3;
 class Font {
 public:
 	/// Creates a font from \a filename in \a size px
-	Font(const std::string& filename, unsigned int size);
+	///
+	/// You may set \a strokePercentage to a positive or negative % value to increase or decrease
+	/// the font size, without actually changing the position/size of the individual characters.
+	/// This can be used to draw an outlined text by e.g. first drawing with a 5% stroke and then
+	/// printing the same text with 0% (or even a negative stroke) over it.
+	/// Example: To increase the size of each character by 2 pixel for a Font with a \a size of 20
+	/// pixel, you would pass 10.f for \a strokePercentage.
+	Font(const std::string& filename, unsigned int size, float strokePercentage = 0);
 
 	/// Uses the font to print something at \a x \a y. The color can be specified using setFontColor.
 	void print(const std::string&, int x, int y);

src/test/test.cpp

@@ -106,6 +106,9 @@ class Test : public jngl::Work {
 		if (jngl::keyPressed('g')) {
 			jngl::setWork<AsyncLoad>();
 		}
+		if (jngl::keyPressed('e')) {
+			jngl::errorMessage("Hello World!");
+		}
 	}
 	void drawBackground() const;
 	void draw() const override {
@@ -168,9 +171,14 @@ class Test : public jngl::Work {
 		jngl::print(" $", static_cast<int>(jngl::getTextWidth("UTF-8:   ä ö ü ß Ĉ Ψ ≈") + 5), 105);
 		jngl::setFontSize(12);
 		jngl::print("Press 1-9 to test the performance\nPress E to show a error box.", 5, 135);
-		if (jngl::keyPressed('e')) {
-			jngl::errorMessage("Hello World!");
-		}
+
+		auto mv = jngl::modelview().translate({ 5, 175 });
+		jngl::setFontColor(static_cast<unsigned char>(255 * (1 - factor)),
+		                   static_cast<unsigned char>(255 * factor), 255);
+		fontStroke.print(mv, "Text with outline.");
+		jngl::setFontColor(0x000000_rgb);
+		fontNormal.print(mv, "Text with outline.");
+
 		jngl::print("Press S to use the blur shader.", 5, 390);
 		jngl::print("Press F to turn drawing on a FBO " + std::string(drawOnFrameBuffer ? "off" : "on") + ".", 5, 410);
 		jngl::print("Press V to toggle V-SYNC.", 5, 430);
@@ -251,6 +259,8 @@ class Test : public jngl::Work {
 	jngl::Finally soundLoader;
 	std::optional<jngl::Finally> paused;
 	std::unique_ptr<jngl::Channel> music;
+	jngl::Font fontNormal{ "Arial.ttf", 12 };
+	jngl::Font fontStroke{ "Arial.ttf", 12, 5 };
 };
 
 jngl::AppParameters jnglInit() {

src/window.cpp

@@ -57,7 +57,7 @@ void Window::print(const std::string& text, const int xposition, const int yposi
 
 void Window::setFont(const std::string& filename) {
 	if (fonts_[fontSize_].find(filename) == fonts_[fontSize_].end()) {
-		auto font = std::make_shared<FontImpl>(filename, fontSize_);
+		auto font = std::make_shared<FontImpl>(filename, fontSize_, 0);
 		fonts_[fontSize_][filename] = font;
 	}
 	fontName_ = filename;