From 69f5cd1a76ce0ee4f61201a5cae460664a5d8ca9 Mon Sep 17 00:00:00 2001
From: Matthew <matthew@sleepy.day>
Date: Wed, 27 Aug 2025 07:02:44 +1000
Subject: [PATCH] fix freetype font loading

---
 fonts.d | 125 ++++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 103 insertions(+), 22 deletions(-)

diff --git a/fonts.d b/fonts.d
index 7e5bb88..54641d6 100644
--- a/fonts.d
+++ b/fonts.d
@@ -88,6 +88,19 @@ CloseFont(FontFace font)
 	}
 }
 
+i32
+Float26(f32 f)
+{
+	return cast(i32)round(cast(f32)(1 << 6) * f);
+}
+
+u8
+DeMultiply(u8 color, u8 alpha)
+{
+	u32 v = cast(u32)(255.0 * cast(f32)(color) / cast(f32)(alpha + f32.epsilon) + 0.5);
+	return v > 255 ? 255 : cast(u8)v;
+}
+
 FontAtlasBuf
 CreateAtlas(Arena* arena, FontFace font, f32 size, u32 dimension)
 {
@@ -105,8 +118,6 @@ CreateAtlas(Arena* arena, FontFace font, f32 size, u32 dimension)
 	// TODO: proper packing algorithm
 	if (font != null)
 	{
-		FT_Set_Pixel_Sizes(font, 0, cast(FT_UInt)((96.0/72.0) * size));
-
 		i64 f_ascent = cast(i64)(font.size.metrics.ascender >> 6);
 		i64 f_descent = cast(i64)(font.size.metrics.descender >> 6);
 		i64 f_height = cast(i64)(font.size.metrics.height >> 6);
@@ -116,8 +127,13 @@ CreateAtlas(Arena* arena, FontFace font, f32 size, u32 dimension)
 		u32 current_h = 0;
 		u32 count = 0;
 
+		i32 font_size = Float26(size);
+
+		FT_Library_SetLcdFilter(FT_LIB, FT_LCD_FILTER_NONE);
+
 		foreach(FT_ULong char_code; 0 .. 0x7F)
 		{
+			FT_Set_Char_Size(font, font_size, 0, 0, 0);
 			FT_Error res = FT_Load_Char(font, char_code, cast(FT_Int32)FT_LOAD_RENDER);
 			if (res != 0)
 			{
@@ -139,16 +155,16 @@ CreateAtlas(Arena* arena, FontFace font, f32 size, u32 dimension)
 			count += 1;
 		}
 
-		max_w = 0;
-		max_h = 0;
+		const u32 PADDING = 2;
+
+		max_w = PADDING;
+		max_h = PADDING;
 		current_h = 0;
 		count = 0;
 
-		u32 font_w = font.size.metrics.x_ppem;
-		u32 font_h = font.size.metrics.y_ppem;
-
 		foreach(FT_ULong char_code; 0 .. 0x7F)
 		{
+			FT_Set_Char_Size(font, font_size, 0, 0, 0);
 			FT_Error res = FT_Load_Char(font, char_code, cast(FT_Int32)FT_LOAD_RENDER);
 			if (res != 0)
 			{
@@ -162,24 +178,88 @@ CreateAtlas(Arena* arena, FontFace font, f32 size, u32 dimension)
 
 			if (max_w + bmp.rows > dimension)
 			{
-				max_h += current_h;
-				max_w = 0;
+				max_h += cast(u32)(size) + PADDING;
+				max_w = PADDING;
 			}
 
-			i32 x, y;
-			foreach(r; 0 .. bmp.rows)
+			switch(bmp.pixel_mode)
 			{
-				y = cast(i32)(max_h + r);
-				foreach(c; 0 .. bmp.width)
-				{
-					x = max_w + c;
-					u64 offset = (y*dimension + x) * 4;
+				case FT_PIXEL_MODE_BGRA:
+					{
+						i32 x, y;
+						foreach(r; 0 .. bmp.rows)
+						{
+							y = cast(i32)(max_h + r);
+							foreach(c; 0 .. bmp.width)
+							{
+								x = max_w + c;
+								u64 offset = (y*dimension + x) * 4;
 
-					atlas.data[offset+0] = 255;
-					atlas.data[offset+1] = 255;
-					atlas.data[offset+2] = 255;
-					atlas.data[offset+3] = bmp.buffer[r*bmp.pitch + c];
-				}
+								u8 p_b = bmp.buffer[offset+0];
+								u8 p_g = bmp.buffer[offset+1];
+								u8 p_r = bmp.buffer[offset+2];
+								u8 p_a = bmp.buffer[offset+3];
+
+								atlas.data[offset+0] = DeMultiply(p_r, p_a);
+								atlas.data[offset+1] = DeMultiply(p_b, p_a);
+								atlas.data[offset+2] = DeMultiply(p_g, p_a);
+								atlas.data[offset+3] = p_a;
+							}
+						}
+					} break;
+				case FT_PIXEL_MODE_MONO:
+					{
+						u32 pitch = bmp.pitch;
+						u8* buf = bmp.buffer;
+					 	i32 x, y;
+						foreach(r; 0 .. bmp.rows)
+						{
+							u8 bits = 0;
+							u8* buf_ptr = buf;
+							y = cast(i32)(max_h + r);
+							foreach(c; 0 .. bmp.width)
+							{
+								if ((c & 7) == 0)
+								{
+									bits = *buf_ptr;
+									buf_ptr += 1;
+								}
+
+								x = max_w + c;
+								u64 offset = (y*dimension + x) * 4;
+
+								atlas.data[offset+0] = 255;
+								atlas.data[offset+1] = 255;
+								atlas.data[offset+2] = 255;
+								atlas.data[offset+3] = (bits & 0x80) ? 255 : 0;
+
+								bits <<= 1;
+							}
+
+							buf += pitch;
+						}
+					} break;
+				case FT_PIXEL_MODE_GRAY:
+					{
+						i32 x, y;
+						foreach(r; 0 .. bmp.rows)
+						{
+							y = cast(i32)(max_h + r);
+							foreach(c; 0 .. bmp.width)
+							{
+								x = max_w + c;
+								u64 offset = (y*dimension + x) * 4;
+
+								atlas.data[offset+0] = 255;
+								atlas.data[offset+1] = 255;
+								atlas.data[offset+2] = 255;
+								atlas.data[offset+3] = bmp.buffer[r*bmp.pitch + c];
+							}
+						}
+					} break;
+				default:
+					assert(false, "Unknown pixel_mode value");
+					break;
 			}
 
 			Glyph* g = atlas.atlas.glyphs.ptr + char_code;
@@ -196,7 +276,7 @@ CreateAtlas(Arena* arena, FontFace font, f32 size, u32 dimension)
 			g.atlas_bottom = max_h + bmp.rows;
 			g.atlas_right = max_w + bmp.width;
 
-			max_w += bmp.width;
+			max_w += bmp.width + PADDING;
 			current_h = bmp.rows > current_h ? bmp.rows : current_h;
 
 			count += 1;
@@ -206,3 +286,4 @@ CreateAtlas(Arena* arena, FontFace font, f32 size, u32 dimension)
 	return atlas;
 }
 
+