ppsspp/Common/Render/TextureAtlas.h

#pragma once

#include <cstdint>
#include <cstring>

#include <string_view>

#define ATLAS_MAGIC ('A' | ('T' << 8) | ('L' << 16) | ('A' << 24))

// Metadata file structure v0:
//
// AtlasHeader
// For each image:
//   AtlasImage
// For each font:
//   AtlasFontHeader
//   For each range:
//     AtlasRange
//   For each char:
//     AtlasChar

struct Atlas;

struct ImageID {
public:
	ImageID() {}
	explicit ImageID(std::string_view _id) : id(_id) {}

	static inline ImageID invalid() {
		return ImageID{""};
	}

	bool isValid() const {
		return !id.empty();
	}

	bool isInvalid() const {
		return id.empty();
	}

	bool operator ==(const ImageID &other) {
		return id == other.id;
	}

	bool operator !=(const ImageID &other) {
		return id != other.id;
	}

private:
	std::string_view id;
	friend struct Atlas;
};

struct FontID {
public:
	explicit FontID(const char *_id) : id(_id) {}

	static inline FontID invalid() {
		return FontID{ nullptr };
	}

	bool isInvalid() const {
		return id == nullptr;
	}

private:
	const char *id;
	friend struct Atlas;
};

struct AtlasChar {
	// texcoords
	float sx, sy, ex, ey;
	// offset from the origin
	float ox, oy;
	// distance to move the origin forward
	float wx;
	// size in pixels
	unsigned short pw, ph;
};

struct AtlasCharRange {
	int start;
	int end;
	int result_index;
};

struct AtlasFontHeader {
	float padding;
	float height;
	float ascend;
	float distslope;
	int numRanges;
	int numChars;
	char name[32];
};

struct AtlasFont {
	AtlasFont() = default;
	AtlasFont(const AtlasFont &) = delete;
	AtlasFont &operator=(const AtlasFont &) = delete;
	~AtlasFont();

	float padding;
	float height;
	float ascend;
	float distslope;
	const AtlasChar *charData;
	const AtlasCharRange *ranges;
	int numRanges;
	int numChars;
	char name[32];

	// Returns 0 on no match.
	const AtlasChar *getChar(int utf32) const;
};

struct AtlasImage {
	float u1, v1, u2, v2;
	int w, h;
	char name[32];
};

struct AtlasHeader {
	int magic;
	int version;
	int numFonts;
	int numImages;
};

struct Atlas {
	Atlas() = default;
	Atlas(const Atlas &) = delete;
	Atlas &operator=(const Atlas &) = delete;
	~Atlas();
	bool LoadMeta(const uint8_t *data, size_t data_size);
	bool IsMetadataLoaded() const {
		return images != nullptr;
	}
	void Clear();

	AtlasFont *fonts = nullptr;
	int num_fonts = 0;
	AtlasImage *images = nullptr;
	int num_images = 0;
	// Texels per UI unit that generated images were rasterized at. Not stored in metadata.
	float dpiScale = 1.0f;

	// These are inefficient linear searches, try not to call every frame.
	const AtlasFont *getFont(FontID id) const;
	const AtlasImage *getImage(ImageID id) const;

	bool measureImage(ImageID id, float *w, float *h) const;
};