Create a cache around fontCalcGlyphPos for ASCII characters

...since this function is pretty slow. This applies both to the system
font and user-loaded fonts. This is cache is now used downstream of
`C2D_TextFontParseLine`, which should improve its performance.

Author: TheGag96

include/c2d/font.h

@@ -86,6 +86,16 @@ charWidthInfo_s* C2D_FontGetCharWidthInfo(C2D_Font font, int glyphIndex);
  */
 void C2D_FontCalcGlyphPos(C2D_Font font, fontGlyphPos_s* out, int glyphIndex, u32 flags, float scaleX, float scaleY);
 
+/** @brief Calculate glyph position of given codepoint. Uses a cached value when the codepoint is ASCII, flags are 0, and scales are 1.
+ * @param[in] font Font to read from, or NULL for system font
+ * @param[out] out Glyph position
+ * @param[in] codepoint The Unicode codepoint of the glyph
+ * @param[in] flags Misc flags
+ * @param[in] scaleX Size to scale in X
+ * @param[in] scaleY Size to scale in Y
+ */
+void C2D_FontCalcGlyphPosFromCodePoint(C2D_Font font, fontGlyphPos_s* out, u32 codepoint, u32 flags, float scaleX, float scaleY);
+
 /** @brief Get the font info structure associated with the font
  * @param[in] font Font to read from, or NULL for the system font
  * @returns FINF associated with the font

source/base.c

@@ -575,7 +575,7 @@ void C2Di_FlushVtxBuf(void)
 	ctx->idxBufLastPos = ctx->idxBufPos;
 }
 
-void C2Di_Update(void)
+void C2Di_Update()
 {
 	C2Di_Context* ctx = C2Di_GetContext();
 	u32 flags = ctx->flags & C2DiF_DirtyAny;

source/font.c

@@ -4,6 +4,8 @@
 #include "internal.h"
 #include <c2d/font.h>
 
+fontGlyphPos_s g_systemFontASCIICache[128];
+
 C2D_Font C2D_FontLoad(const char* filename)
 {
 	FILE* f = fopen(filename, "rb");
@@ -51,6 +53,11 @@ static C2D_Font C2Di_PostLoadFont(C2D_Font font)
 			tex->border = 0;
 			tex->lodParam = 0;
 		}
+
+		for (i = 0; i < NUM_ASCII_CHARACTERS; i++)
+		{
+			fontCalcGlyphPos(&font->asciiCache[i], font->cfnt, fontGlyphIndexFromCodePoint(font->cfnt, i), 0, 1.0, 1.0);
+		}
 	}
 	return font;
 }
@@ -243,6 +250,26 @@ void C2D_FontCalcGlyphPos(C2D_Font font, fontGlyphPos_s* out, int glyphIndex, u3
 		fontCalcGlyphPos(out, font->cfnt, glyphIndex, flags, scaleX, scaleY);
 }
 
+void C2D_FontCalcGlyphPosFromCodePoint(C2D_Font font, fontGlyphPos_s* out, u32 codepoint, u32 flags, float scaleX, float scaleY)
+{
+  // Building glyph positions is pretty expensive, but we could just store the results for plain ASCII.
+	if (codepoint < NUM_ASCII_CHARACTERS && flags == 0 && scaleX == 1 && scaleY == 1)
+	{
+		if (font)
+		{
+			*out = font->asciiCache[codepoint];
+		}
+		else
+		{
+			*out = g_systemFontASCIICache[codepoint];
+		}
+	}
+	else
+	{
+		C2D_FontCalcGlyphPos(font, out, C2D_FontGlyphIndexFromCodePoint(font, codepoint), 0, 1.0f, 1.0f);
+	}
+}
+
 FINF_s* C2D_FontGetInfo(C2D_Font font)
 {
 	if (!font)

source/internal.h

@@ -1,5 +1,6 @@
 #pragma once
 #include <c2d/base.h>
+#include <3ds/font.h>
 
 typedef struct
 {
@@ -77,6 +78,7 @@ struct C2D_Font_s
 	CFNT_s* cfnt;
 	C3D_Tex* glyphSheets;
 	float textScale;
+	fontGlyphPos_s asciiCache[128];
 };
 
 static inline C2Di_Context* C2Di_GetContext(void)
@@ -117,3 +119,6 @@ void C2Di_AppendQuad(void);
 void C2Di_AppendVtx(float x, float y, float z, float u, float v, float ptx, float pty, u32 color);
 void C2Di_FlushVtxBuf(void);
 void C2Di_Update(void);
+
+#define NUM_ASCII_CHARACTERS 128
+extern fontGlyphPos_s g_systemFontASCIICache[NUM_ASCII_CHARACTERS];

source/text.c

@@ -89,6 +89,13 @@ static void C2Di_TextEnsureLoad(void)
 		tex->border = 0;
 		tex->lodParam = 0;
 	}
+
+	// Initialize system font ASCII cache for C2D_FontCalcGlyphPosFromCodePoint
+	for (int i = 0; i < NUM_ASCII_CHARACTERS; i++)
+	{
+		// This will readjust glyph UVs to account for being a part of the combined texture.
+		C2D_FontCalcGlyphPos(NULL, &g_systemFontASCIICache[i], fontGlyphIndexFromCodePoint(font, i), 0, 1.0, 1.0);
+	}
 }
 
 C2D_TextBuf C2D_TextBufNew(size_t maxGlyphs)
@@ -161,7 +168,7 @@ const char* C2D_TextFontParseLine(C2D_Text* text, C2D_Font font, C2D_TextBuf buf
 		p += units;
 
 		fontGlyphPos_s glyphData;
-		C2D_FontCalcGlyphPos(font, &glyphData, C2D_FontGlyphIndexFromCodePoint(font, code), 0, 1.0f, 1.0f);
+		C2D_FontCalcGlyphPosFromCodePoint(font, &glyphData, code, 0, 1.0f, 1.0f);
 		if (glyphData.width > 0.0f)
 		{
 			C2Di_Glyph* glyph = &buf->glyphs[buf->glyphCount++];