Various things

Signed-off-by: Slendi <slendi@socopon.com>

.clangd

@@ -0,0 +1,2 @@
+CompileFlags:
+  Add: [-Wno-c23-extensions]

.gitignore

@@ -1,4 +1,5 @@
 [Bb]uild*
+CMakeLists.txt.*
 result
 .cache
 .direnv

flake.nix

@@ -16,7 +16,19 @@
       system:
       let
         pkgs = import nixpkgs { inherit system; };
-        nativeBuildInputs = [ ];
+        nativeBuildInputs = with pkgs; [
+          pkg-config
+          wayland
+          wayland-protocols
+          wlr-protocols
+          wayland-scanner
+          libGL
+          libportal
+          glib
+          libxkbcommon
+          fontconfig
+          harfbuzz
+        ];
         buildInputs = with pkgs; [
           cmake
           ninja
@@ -31,23 +43,12 @@
                 [
                   llvmPackages_21.clang-tools
                   lldb
+                  gdb
                   codespell
                   doxygen
                   gtest
                   cppcheck
                   inotify-tools
-
-                  pkg-config
-                  wayland
-                  wayland-protocols
-                  wlr-protocols
-                  wayland-scanner
-                  libGL
-                  libportal
-                  glib
-                  libxkbcommon
-                  fontconfig
-                  harfbuzz
                 ]
                 ++ buildInputs
                 ++ nativeBuildInputs

src/App.cpp

@@ -5,6 +5,9 @@
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
+#include <span>
+#include <unordered_set>
+#include <vector>
 #include <poll.h>
 #include <pthread.h>
 #include <signal.h>
@@ -300,7 +303,37 @@ auto App::init_egl() -> void
 	m_tr = TextRenderer();
 	auto const font = find_font_path();
 	assert(font && "Could not find font");
-	auto const font_handle = m_tr->load_font(*font);
+	std::vector<std::filesystem::path> fallback_paths;
+	std::unordered_set<std::string> seen_paths;
+	auto const primary_path_str = font->string();
+
+	constexpr char const *fallback_candidates[] = {
+	    "Noto Sans CJK JP:style=Regular",
+	    "Noto Sans CJK SC:style=Regular",
+	    "Noto Sans CJK KR:style=Regular",
+	    "Noto Sans CJK TC:style=Regular",
+	    "sans-serif:lang=ja",
+	    "sans-serif:lang=ko",
+	    "sans-serif:lang=zh-cn",
+	    "sans-serif:lang=zh-tw",
+	    "sans-serif:lang=zh-hk",
+	};
+	for (auto const *name : fallback_candidates) {
+		if (auto fallback = find_font_path(name)) {
+			auto const path_str = fallback->string();
+			if (path_str == primary_path_str)
+				continue;
+			if (!seen_paths.emplace(path_str).second)
+				continue;
+			fallback_paths.push_back(*fallback);
+		}
+	}
+	if (fallback_paths.empty()) {
+		TraceLog(LOG_WARNING,
+		    "No fallback fonts found; some glyphs may render as missing");
+	}
+	auto const font_handle
+	    = m_tr->load_font(*font, std::span(fallback_paths));
 	assert(font_handle && "Could not load font");
 	m_font = *font_handle;
 }

src/FreetypeHooks.cpp

@@ -0,0 +1,38 @@
+#include <cstdio>
+#include <dlfcn.h>
+
+#include <ft2build.h>
+#include FT_FREETYPE_H
+
+using FtInitFn = FT_Error (*)(FT_Library *);
+using FtDoneFn = FT_Error (*)(FT_Library);
+
+extern "C" FT_Error FT_Init_FreeType(FT_Library *library)
+{
+	static FtInitFn real_fn
+	    = reinterpret_cast<FtInitFn>(dlsym(RTLD_NEXT, "FT_Init_FreeType"));
+	if (!real_fn) {
+		std::fprintf(stderr,
+	    	"FT_Init_FreeType hook: failed to locate real symbol\n");
+		return FT_Err_Invalid_Handle;
+	}
+	FT_Error error = real_fn(library);
+	std::fprintf(stderr, "FT_Init_FreeType -> %p (err=%d)\n",
+	    library ? static_cast<void *>(*library) : nullptr, error);
+	return error;
+}
+
+extern "C" FT_Error FT_Done_FreeType(FT_Library library)
+{
+	static FtDoneFn real_fn
+	    = reinterpret_cast<FtDoneFn>(dlsym(RTLD_NEXT, "FT_Done_FreeType"));
+	std::fprintf(stderr, "FT_Done_FreeType(%p)\n",
+	    static_cast<void *>(library));
+	if (!real_fn) {
+		std::fprintf(stderr,
+	    	"FT_Done_FreeType hook: failed to locate real symbol\n");
+		return FT_Err_Invalid_Handle;
+	}
+	return real_fn(library);
+}
+

src/TextRenderer.cpp

@@ -1,7 +1,6 @@
 #include "TextRenderer.hpp"
 
 #include <algorithm>
-#include <array>
 #include <cassert>
 #include <chrono>
 #include <cmath>
@@ -14,6 +13,7 @@
 #include <unordered_map>
 #include <utility>
 #include <vector>
+#include <limits>
 
 #include <fontconfig/fontconfig.h>
 
@@ -41,7 +41,6 @@ namespace {
 
 constexpr int kAtlasDimension = 1024;
 constexpr int kAtlasPadding = 2;
-constexpr float kDefaultPxRange = 4.0f;
 constexpr float kDefaultEmScale = 48.0f;
 
 constexpr float hb_to_em(hb_position_t value, unsigned upem)
@@ -66,6 +65,78 @@ auto ft_library() -> FT_Library
 	return library;
 }
 
+struct CodepointSpan {
+	uint32_t codepoint {};
+	size_t start {};
+	size_t end {};
+};
+
+auto decode_utf8(std::string_view text) -> std::vector<CodepointSpan>
+{
+	std::vector<CodepointSpan> spans;
+	size_t i = 0;
+	while (i < text.size()) {
+		u8 const byte = static_cast<u8>(text[i]);
+		size_t const start = i;
+		size_t length = 1;
+		uint32_t cp = 0xFFFD;
+		if (byte < 0x80) {
+			cp = byte;
+		} else if ((byte & 0xE0) == 0xC0) {
+			if (i + 1 < text.size()) {
+				u8 const b1 = static_cast<u8>(text[i + 1]);
+				if ((b1 & 0xC0) == 0x80) {
+					uint32_t t
+					    = ((byte & 0x1F) << 6) | (static_cast<uint32_t>(b1) & 0x3F);
+					if (t >= 0x80) {
+						cp = t;
+						length = 2;
+					}
+				}
+			}
+		} else if ((byte & 0xF0) == 0xE0) {
+			if (i + 2 < text.size()) {
+				u8 const b1 = static_cast<u8>(text[i + 1]);
+				u8 const b2 = static_cast<u8>(text[i + 2]);
+				if ((b1 & 0xC0) == 0x80 && (b2 & 0xC0) == 0x80) {
+					uint32_t t = ((byte & 0x0F) << 12)
+					    | ((static_cast<uint32_t>(b1) & 0x3F) << 6)
+					    | (static_cast<uint32_t>(b2) & 0x3F);
+					if (t >= 0x800 && (t < 0xD800 || t > 0xDFFF)) {
+						cp = t;
+						length = 3;
+					}
+				}
+			}
+		} else if ((byte & 0xF8) == 0xF0) {
+			if (i + 3 < text.size()) {
+				u8 const b1 = static_cast<u8>(text[i + 1]);
+				u8 const b2 = static_cast<u8>(text[i + 2]);
+				u8 const b3 = static_cast<u8>(text[i + 3]);
+				if ((b1 & 0xC0) == 0x80 && (b2 & 0xC0) == 0x80
+				    && (b3 & 0xC0) == 0x80) {
+					uint32_t t = ((byte & 0x07) << 18)
+					    | ((static_cast<uint32_t>(b1) & 0x3F) << 12)
+					    | ((static_cast<uint32_t>(b2) & 0x3F) << 6)
+					    | (static_cast<uint32_t>(b3) & 0x3F);
+					if (t >= 0x10000 && t <= 0x10FFFF) {
+						cp = t;
+						length = 4;
+					}
+				}
+			}
+		}
+
+		spans.push_back(CodepointSpan {
+			.codepoint = cp,
+			.start = start,
+			.end = std::min(text.size(), start + length),
+		});
+		i += length;
+	}
+	return spans;
+}
+
 } // namespace
 
 auto TextRenderer::flush_font(FontRuntime &rt, FontData &fd) -> void
@@ -253,50 +324,57 @@ TextRenderer::TextRenderer()
 
 TextRenderer::~TextRenderer()
 {
-	for (usize i = 0; i < m_font_runtime.size(); ++i) {
-		if (m_font_runtime[i]) {
-			FontHandle handle;
-			handle.id = i;
-			unload_font(handle);
-		}
-	}
-	UnloadShader(m_msdf_shader);
+    for (usize i = 0; i < m_font_sets.size(); ++i) {
+        FontHandle handle;
+        handle.id = i;
+        unload_font(handle);
+    }
+    // Not unloading the shader... I have no clue why, but there's some sort of double free. I love C interop!!!!
 }
 
 auto TextRenderer::measure_text(FontHandle const font,
     std::string_view const text, int const size) -> Vector2
 {
-	usize const font_id = font();
-	if (font_id >= m_font_runtime.size() || !m_font_runtime[font_id]
-	    || !m_font_runtime[font_id]->hb_font)
+	usize const handle_id = font();
+	if (handle_id >= m_font_sets.size())
+		return Vector2 { 0.0f, 0.0f };
+	auto const &font_set = m_font_sets[handle_id];
+	if (font_set.font_indices.empty())
 		return Vector2 { 0.0f, 0.0f };
 
-	auto &rt = *m_font_runtime[font_id];
-	auto &fd = m_font_data[font_id];
+	auto placements = shape_text(font, text);
 
-	hb_buffer_t *buffer = hb_buffer_create();
-	hb_buffer_add_utf8(buffer, text.data(), static_cast<int>(text.size()), 0,
-	    static_cast<int>(text.size()));
-	hb_buffer_guess_segment_properties(buffer);
-	hb_shape(rt.hb_font, buffer, nullptr, 0);
+	auto primary_runtime_index = font_set.font_indices.front();
+	if (placements.empty()) {
+		if (primary_runtime_index >= m_font_runtime.size()
+		    || !m_font_runtime[primary_runtime_index])
+			return Vector2 { 0.0f, 0.0f };
+		auto const &rt_primary = *m_font_runtime[primary_runtime_index];
+		float height_em = rt_primary.ascent - rt_primary.descent;
+		return Vector2 { 0.0f, height_em * static_cast<float>(size) };
+	}
 
-	unsigned length = hb_buffer_get_length(buffer);
-	auto *infos = hb_buffer_get_glyph_infos(buffer, nullptr);
-	auto *positions = hb_buffer_get_glyph_positions(buffer, nullptr);
 	float advance_em = 0.0f;
 	float min_x_em = 0.0f;
 	float max_x_em = 0.0f;
 	bool first = true;
+	bool have_metrics = false;
+	float max_ascent = 0.0f;
+	float min_descent = 0.0f;
 
-	for (unsigned i = 0; i < length; ++i) {
-		u32 glyph_index = infos[i].codepoint;
-		if (glyph_index == 0)
+	for (auto const &placement : placements) {
+		usize const runtime_index = placement.runtime_index;
+		if (runtime_index >= m_font_runtime.size()
+		    || !m_font_runtime[runtime_index])
 			continue;
-		auto *entry = ensure_glyph(rt, fd, glyph_index, false);
+		auto &rt = *m_font_runtime[runtime_index];
+		auto &fd = m_font_data[runtime_index];
+		auto *entry
+		    = ensure_glyph(rt, fd, placement.glyph_index, false);
 		if (!entry || entry->width == 0 || entry->height == 0)
 			continue;
 		float const x_offset_em
-		    = hb_to_em(positions[i].x_offset, rt.units_per_em);
+		    = hb_to_em(placement.x_offset, rt.units_per_em);
 		float const left
 		    = advance_em + x_offset_em + entry->glyph.plane_bounds.left;
 		float const right
@@ -309,17 +387,36 @@ auto TextRenderer::measure_text(FontHandle const font,
 			min_x_em = std::min(min_x_em, left);
 			max_x_em = std::max(max_x_em, right);
 		}
-		advance_em += hb_to_em(positions[i].x_advance, rt.units_per_em);
+		if (!have_metrics) {
+			max_ascent = rt.ascent;
+			min_descent = rt.descent;
+			have_metrics = true;
+		} else {
+			max_ascent = std::max(max_ascent, rt.ascent);
+			min_descent = std::min(min_descent, rt.descent);
+		}
+		advance_em += hb_to_em(placement.x_advance, rt.units_per_em);
 	}
 
-	hb_buffer_destroy(buffer);
-
-	if (first)
-		return Vector2 { 0.0f,
-			(rt.ascent - rt.descent) * static_cast<float>(size) };
+	if (first) {
+		if (primary_runtime_index >= m_font_runtime.size()
+		    || !m_font_runtime[primary_runtime_index])
+			return Vector2 { 0.0f, 0.0f };
+		auto const &rt = *m_font_runtime[primary_runtime_index];
+		float height_em = rt.ascent - rt.descent;
+		return Vector2 { 0.0f, height_em * static_cast<float>(size) };
+	}
 
 	float width_em = std::max(max_x_em, advance_em) - min_x_em;
-	float height_em = rt.ascent - rt.descent;
+	float height_em = 0.0f;
+	if (have_metrics) {
+		height_em = max_ascent - min_descent;
+	} else if (primary_runtime_index < m_font_runtime.size()
+	    && m_font_runtime[primary_runtime_index]) {
+		auto const &rt = *m_font_runtime[primary_runtime_index];
+		height_em = rt.ascent - rt.descent;
+	}
+
 	return Vector2 { width_em * static_cast<float>(size),
 		height_em * static_cast<float>(size) };
 }
@@ -330,51 +427,47 @@ auto TextRenderer::draw_text(FontHandle const font, std::string_view const text,
 	auto const draw_start = std::chrono::steady_clock::now();
 	int const pos_x = pos.x;
 	int const pos_y = pos.y;
-	// Don't use pos from here on out!
-	usize const font_id = font();
-	if (font_id >= m_font_runtime.size() || !m_font_runtime[font_id]
-	    || !m_font_runtime[font_id]->hb_font)
+	usize const handle_id = font();
+	if (handle_id >= m_font_sets.size())
+		return;
+	auto const &font_set = m_font_sets[handle_id];
+	if (font_set.font_indices.empty())
 		return;
-	auto &rt = *m_font_runtime[font_id];
-	auto &fd = m_font_data[font_id];
 
-	hb_buffer_t *buffer = hb_buffer_create();
-	hb_buffer_add_utf8(buffer, text.data(), static_cast<int>(text.size()), 0,
-	    static_cast<int>(text.size()));
-	hb_buffer_guess_segment_properties(buffer);
-	hb_shape(rt.hb_font, buffer, nullptr, 0);
+	auto placements = shape_text(font, text);
+	if (placements.empty())
+		return;
 
-	unsigned length = hb_buffer_get_length(buffer);
-	auto *infos = hb_buffer_get_glyph_infos(buffer, nullptr);
-	auto *positions = hb_buffer_get_glyph_positions(buffer, nullptr);
 	float const size_f = static_cast<float>(size);
 	float pen_x_em = 0.0f;
 	float pen_y_em = 0.0f;
-	rt.frame_stamp++;
+	std::vector<usize> updated_stamp;
+	updated_stamp.reserve(font_set.font_indices.size());
 
-	// FIXME: Figure out shader
-	// BeginShaderMode(m_msdf_shader);
-	// if (m_px_range_uniform >= 0) {
-	//	float shader_px_range = rt.px_range;
-	//	SetShaderValue(m_msdf_shader, m_px_range_uniform, &shader_px_range,
-	//	    SHADER_UNIFORM_FLOAT);
-	// }
+	for (auto const &placement : placements) {
+		usize const runtime_index = placement.runtime_index;
+		if (runtime_index >= m_font_runtime.size()
+		    || !m_font_runtime[runtime_index])
+			continue;
+		auto &rt = *m_font_runtime[runtime_index];
+		auto &fd = m_font_data[runtime_index];
+		if (std::find(updated_stamp.begin(), updated_stamp.end(), runtime_index)
+		    == updated_stamp.end()) {
+			rt.frame_stamp++;
+			updated_stamp.push_back(runtime_index);
+		}
 
-	for (unsigned i = 0; i < length; ++i) {
-		u32 glyph_index = infos[i].codepoint;
-		if (glyph_index == 0)
-			continue;
-		auto *entry = ensure_glyph(rt, fd, glyph_index, true);
-		if (!entry)
-			continue;
-		if (entry->width == 0 || entry->height == 0)
+		auto *entry
+		    = ensure_glyph(rt, fd, placement.glyph_index, true);
+		if (!entry || entry->width == 0 || entry->height == 0)
 			continue;
+
 		float const advance_em
-		    = hb_to_em(positions[i].x_advance, rt.units_per_em);
+		    = hb_to_em(placement.x_advance, rt.units_per_em);
 		float const x_offset_em
-		    = hb_to_em(positions[i].x_offset, rt.units_per_em);
+		    = hb_to_em(placement.x_offset, rt.units_per_em);
 		float const y_offset_em
-		    = hb_to_em(positions[i].y_offset, rt.units_per_em);
+		    = hb_to_em(placement.y_offset, rt.units_per_em);
 		float const x_base_em = pen_x_em + x_offset_em;
 		float const y_base_em = pen_y_em + y_offset_em;
 		float const scale_px = size_f / static_cast<float>(rt.em_scale);
@@ -397,23 +490,20 @@ auto TextRenderer::draw_text(FontHandle const font, std::string_view const text,
 		    fd.atlas, source, dest, Vector2 { 0.0f, 0.0f }, 0.0f, color);
 
 		pen_x_em += advance_em;
-		pen_y_em += hb_to_em(positions[i].y_advance, rt.units_per_em);
+		pen_y_em += hb_to_em(placement.y_advance, rt.units_per_em);
 	}
 
-	// EndShaderMode();
-	hb_buffer_destroy(buffer);
-
 	auto const draw_end = std::chrono::steady_clock::now();
 	auto const draw_ms
 	    = std::chrono::duration<double, std::milli>(draw_end - draw_start)
 	          .count();
 	if (draw_ms > 5.0)
 		TraceLog(LOG_INFO, "draw_text took %.2f ms for %zu glyphs", draw_ms,
-		    static_cast<size_t>(length));
+		    placements.size());
 }
 
-auto TextRenderer::load_font(std::filesystem::path const &path)
-    -> std::optional<FontHandle>
+auto TextRenderer::load_single_font(std::filesystem::path const &path)
+    -> std::optional<usize>
 {
 	FT_Library const ft = ft_library();
 	if (!ft)
@@ -422,7 +512,10 @@ auto TextRenderer::load_font(std::filesystem::path const &path)
 	FT_Face face = nullptr;
 	if (FT_New_Face(ft, path.string().c_str(), 0, &face) != 0)
 		return std::nullopt;
-	FT_Select_Charmap(face, FT_ENCODING_UNICODE);
+	if (FT_Select_Charmap(face, FT_ENCODING_UNICODE) != 0) {
+		FT_Done_Face(face);
+		return std::nullopt;
+	}
 
 	auto runtime = std::make_unique<FontRuntime>();
 	runtime->face = face;
@@ -446,10 +539,13 @@ auto TextRenderer::load_font(std::filesystem::path const &path)
 	runtime->line_gap = std::max(0.0f, line_height - adv_height);
 
 	runtime->hb_face = hb_ft_face_create_referenced(face);
+	if (!runtime->hb_face) {
+		FT_Done_Face(face);
+		return std::nullopt;
+	}
 	runtime->hb_font = hb_ft_font_create_referenced(face);
 	if (!runtime->hb_font) {
-		if (runtime->hb_face)
-			hb_face_destroy(runtime->hb_face);
+		hb_face_destroy(runtime->hb_face);
 		FT_Done_Face(face);
 		return std::nullopt;
 	}
@@ -472,18 +568,18 @@ auto TextRenderer::load_font(std::filesystem::path const &path)
 	    = GenImageColor(runtime->atlas_width, runtime->atlas_height, BLANK);
 	if (!font_data.atlas_img.data) {
 		msdfgen::destroyFont(runtime->msdf_font);
+		runtime->msdf_font = nullptr;
 		hb_font_destroy(runtime->hb_font);
 		hb_face_destroy(runtime->hb_face);
-		FT_Done_Face(face);
 		return std::nullopt;
 	}
 	font_data.atlas = LoadTextureFromImage(font_data.atlas_img);
 	if (font_data.atlas.id == 0) {
 		UnloadImage(font_data.atlas_img);
 		msdfgen::destroyFont(runtime->msdf_font);
+		runtime->msdf_font = nullptr;
 		hb_font_destroy(runtime->hb_font);
 		hb_face_destroy(runtime->hb_face);
-		FT_Done_Face(face);
 		return std::nullopt;
 	}
 	SetTextureFilter(font_data.atlas, TEXTURE_FILTER_BILINEAR);
@@ -492,40 +588,175 @@ auto TextRenderer::load_font(std::filesystem::path const &path)
 
 	m_font_data.emplace_back(std::move(font_data));
 	m_font_runtime.emplace_back(std::move(runtime));
+	return m_font_data.size() - 1;
+}
 
+auto TextRenderer::load_font(std::filesystem::path const &path,
+    std::span<std::filesystem::path const> fallback_fonts)
+	-> std::optional<FontHandle>
+{
+	auto primary_index = load_single_font(path);
+	if (!primary_index)
+		return std::nullopt;
+
+	FontSet set;
+	set.font_indices.push_back(*primary_index);
+
+	for (auto const &fallback_path : fallback_fonts) {
+		auto fallback_index = load_single_font(fallback_path);
+		if (!fallback_index) {
+			TraceLog(LOG_WARNING, "Failed to load fallback font: %s",
+			    fallback_path.string().c_str());
+			continue;
+		}
+		set.font_indices.push_back(*fallback_index);
+	}
+
+	m_font_sets.emplace_back(std::move(set));
 	FontHandle handle;
-	handle.id = m_font_data.size() - 1;
+	handle.id = m_font_sets.size() - 1;
 	return handle;
 }
 
+auto TextRenderer::shape_text(FontHandle const font,
+    std::string_view const text) -> std::vector<GlyphPlacement>
+{
+	std::vector<GlyphPlacement> shaped;
+	if (text.empty())
+		return shaped;
+
+	usize const handle_id = font();
+	if (handle_id >= m_font_sets.size())
+		return shaped;
+	auto const &font_set = m_font_sets[handle_id];
+	if (font_set.font_indices.empty())
+		return shaped;
+
+	auto codepoints = decode_utf8(text);
+	if (codepoints.empty())
+		return shaped;
+
+	constexpr usize kNoFont = std::numeric_limits<usize>::max();
+	std::vector<usize> selections(codepoints.size(), kNoFont);
+	for (size_t i = 0; i < codepoints.size(); ++i) {
+		bool matched = false;
+		for (size_t candidate = 0; candidate < font_set.font_indices.size();
+		     ++candidate) {
+			usize runtime_index = font_set.font_indices[candidate];
+			if (runtime_index >= m_font_runtime.size())
+				continue;
+			auto const &runtime_ptr = m_font_runtime[runtime_index];
+			if (!runtime_ptr || !runtime_ptr->face)
+				continue;
+			FT_UInt glyph = FT_Get_Char_Index(
+			    runtime_ptr->face, codepoints[i].codepoint);
+			if (glyph != 0) {
+				selections[i] = candidate;
+				matched = true;
+				break;
+			}
+		}
+		if (!matched)
+			selections[i] = kNoFont;
+	}
+
+	size_t idx = 0;
+	while (idx < codepoints.size()) {
+		size_t font_choice = selections[idx];
+		if (font_choice == kNoFont) {
+			++idx;
+			continue;
+		}
+		if (font_choice >= font_set.font_indices.size())
+			font_choice = 0;
+		usize runtime_index = font_set.font_indices[font_choice];
+		if (runtime_index >= m_font_runtime.size()
+		    || !m_font_runtime[runtime_index]
+		    || !m_font_runtime[runtime_index]->hb_font) {
+			++idx;
+			continue;
+		}
+
+		size_t segment_start = codepoints[idx].start;
+		size_t segment_end = codepoints[idx].end;
+		size_t end_idx = idx + 1;
+		while (end_idx < codepoints.size()
+		    && selections[end_idx] == font_choice) {
+			segment_end = codepoints[end_idx].end;
+			++end_idx;
+		}
+
+		if (segment_end <= segment_start) {
+			idx = end_idx;
+			continue;
+		}
+
+		std::string_view segment
+		    = text.substr(segment_start, segment_end - segment_start);
+		if (segment.empty()) {
+			idx = end_idx;
+			continue;
+		}
+
+		hb_buffer_t *buffer = hb_buffer_create();
+		hb_buffer_add_utf8(buffer, segment.data(),
+		    static_cast<int>(segment.size()), 0,
+		    static_cast<int>(segment.size()));
+		hb_buffer_guess_segment_properties(buffer);
+		hb_shape(m_font_runtime[runtime_index]->hb_font, buffer, nullptr, 0);
+
+		unsigned length = hb_buffer_get_length(buffer);
+		auto *infos = hb_buffer_get_glyph_infos(buffer, nullptr);
+		auto *positions = hb_buffer_get_glyph_positions(buffer, nullptr);
+		for (unsigned i = 0; i < length; ++i) {
+			GlyphPlacement placement;
+			placement.runtime_index = runtime_index;
+			placement.glyph_index = infos[i].codepoint;
+			placement.x_advance = positions[i].x_advance;
+			placement.y_advance = positions[i].y_advance;
+			placement.x_offset = positions[i].x_offset;
+			placement.y_offset = positions[i].y_offset;
+			shaped.emplace_back(placement);
+		}
+		hb_buffer_destroy(buffer);
+		idx = end_idx;
+	}
+
+	return shaped;
+}
+
 auto TextRenderer::unload_font(FontHandle const font) -> void
 {
-	usize const font_id = font();
-	if (font_id >= m_font_runtime.size())
+	usize const handle_id = font();
+	if (handle_id >= m_font_sets.size())
 		return;
 
-	if (m_font_runtime[font_id]) {
-		auto &rt = *m_font_runtime[font_id];
-		rt.glyph_cache.clear();
-		if (rt.msdf_font)
-			msdfgen::destroyFont(rt.msdf_font);
-		if (rt.hb_font)
-			hb_font_destroy(rt.hb_font);
-		if (rt.hb_face)
-			hb_face_destroy(rt.hb_face);
-		if (rt.face)
-			FT_Done_Face(rt.face);
-	}
-	m_font_runtime[font_id].reset();
+	auto &font_set = m_font_sets[handle_id];
+	for (usize runtime_index : font_set.font_indices) {
+		if (runtime_index >= m_font_runtime.size())
+			continue;
 
-	if (font_id < m_font_data.size()) {
-		auto &fd = m_font_data[font_id];
-		if (fd.atlas.id != 0)
-			UnloadTexture(fd.atlas);
-		if (fd.atlas_img.data)
-			UnloadImage(fd.atlas_img);
-		fd.glyphs.clear();
+		if (auto &runtime_ptr = m_font_runtime[runtime_index]) {
+			auto &rt = *runtime_ptr;
+			rt.glyph_cache.clear();
+			// No freeing here because they are already cleaned up somewhere...
+			// idk. fml.
+			rt.face = nullptr;
+		}
+		m_font_runtime[runtime_index].reset();
+
+		if (runtime_index < m_font_data.size()) {
+			auto &fd = m_font_data[runtime_index];
+			if (fd.atlas.id != 0)
+				UnloadTexture(fd.atlas);
+			if (fd.atlas_img.data)
+				UnloadImage(fd.atlas_img);
+			fd.atlas = Texture2D {};
+			fd.atlas_img = Image {};
+			fd.glyphs.clear();
+		}
 	}
+	font_set.font_indices.clear();
 }
 
 auto find_font_path(std::string_view path)

src/TextRenderer.hpp

@@ -3,6 +3,7 @@
 #include <filesystem>
 #include <memory>
 #include <optional>
+#include <span>
 #include <unordered_map>
 #include <utility>
 #include <vector>
@@ -44,7 +45,8 @@ struct TextRenderer {
 	    Vector2 const pos, int const size = 16, Color const color = WHITE)
 	    -> void;
 
-	auto load_font(std::filesystem::path const &path)
+	auto load_font(std::filesystem::path const &path,
+	    std::span<std::filesystem::path const> fallback_fonts)
 	    -> std::optional<FontHandle>;
 	auto unload_font(FontHandle const font) -> void;
 
@@ -103,6 +105,19 @@ private:
 	};
 
 	std::vector<std::unique_ptr<FontRuntime>> m_font_runtime;
+	struct FontSet {
+		std::vector<usize> font_indices;
+	};
+	std::vector<FontSet> m_font_sets;
+
+	struct GlyphPlacement {
+		usize runtime_index {};
+		u32 glyph_index {};
+		i32 x_advance {};
+		i32 y_advance {};
+		i32 x_offset {};
+		i32 y_offset {};
+	};
 
 	static auto flush_font(FontRuntime &rt, FontData &fd) -> void;
 	static auto allocate_region(
@@ -114,6 +129,10 @@ private:
 	    -> std::optional<GlyphCacheEntry>;
 	static auto ensure_glyph(FontRuntime &rt, FontData &fd, u32 glyph_index,
 	    bool mark_usage) -> GlyphCacheEntry *;
+	auto load_single_font(std::filesystem::path const &path)
+	    -> std::optional<usize>;
+	auto shape_text(FontHandle const font, std::string_view const text)
+	    -> std::vector<GlyphPlacement>;
 };
 
 auto find_font_path(std::string_view path = "sans-serif:style=Regular")

src/Tick.cpp

@@ -30,7 +30,7 @@ auto App::tick() -> void
 
 	BeginDrawing();
 
-	ClearBackground(BLANK);
+	ClearBackground(theme().window.background);
 
 	DrawFPS(10, 10);
 	if (m_tr) {

src/main.cpp

@@ -10,12 +10,12 @@
 
 #include "App.hpp"
 
-bool check_or_signal_running();
+bool signal_running();
 
 std::optional<App> g_app{};
 
 auto main() -> int {
-  if (check_or_signal_running()) {
+  if (signal_running()) {
     return 0;
   }
 
@@ -28,7 +28,7 @@ auto main() -> int {
   g_app->run();
 }
 
-bool check_or_signal_running() {
+bool signal_running() {
   const char *lock_path = "/tmp/waylight.lock";
   int fd = open(lock_path, O_CREAT | O_RDWR, 0666);
   if (fd == -1)
@@ -46,7 +46,12 @@ bool check_or_signal_running() {
     return true;
   }
 
-  ftruncate(fd, 0);
+  if (ftruncate(fd, 0) == -1) {
+      close(fd);
+      unlink(lock_path);
+      return false;
+  }
+
   dprintf(fd, "%d\n", getpid());
   return false;
 }