Added kerning for rendering text

einkfb.c

@@ -167,7 +167,6 @@ static int blitToFrameBuffer(lua_State *L) {
 
 	uint8_t *fbptr;
 	uint8_t *bbptr;
-	uint8_t smask;
 
 	if(xdest & 1) {
 		/* this will render the leftmost column */
@@ -230,6 +229,109 @@ static int blitToFrameBuffer(lua_State *L) {
 	return 0;
 }
 
+static int addblitToFrameBuffer(lua_State *L) {
+	FBInfo *fb = (FBInfo*) luaL_checkudata(L, 1, "einkfb");
+	BlitBuffer *bb = (BlitBuffer*) luaL_checkudata(L, 2, "blitbuffer");
+	int xdest = luaL_checkint(L, 3);
+	int ydest = luaL_checkint(L, 4);
+	int xoffs = luaL_checkint(L, 5);
+	int yoffs = luaL_checkint(L, 6);
+	int w = luaL_checkint(L, 7);
+	int h = luaL_checkint(L, 8);
+	int x, y;
+
+	// check bounds
+	if(yoffs >= bb->h) {
+		return 0;
+	} else if(yoffs + h > bb->h) {
+		h = bb->h - yoffs;
+	}
+	if(ydest >= fb->vinfo.yres) {
+		return 0;
+	} else if(ydest + h > fb->vinfo.yres) {
+		h = fb->vinfo.yres - ydest;
+	}
+	if(xoffs >= bb->w) {
+		return 0;
+	} else if(xoffs + w > bb->w) {
+		w = bb->w - xoffs;
+	}
+	if(xdest >= fb->vinfo.xres) {
+		return 0;
+	} else if(xdest + w > fb->vinfo.xres) {
+		w = fb->vinfo.xres - xdest;
+	}
+
+	uint8_t *fbptr;
+	uint8_t *bbptr;
+
+	if(xdest & 1) {
+		/* this will render the leftmost column */
+		fbptr = (uint8_t*)(fb->data + 
+				ydest * fb->finfo.line_length + 
+				xdest / 2);
+		bbptr = (uint8_t*)(bb->data +
+				yoffs * bb->w / 2 +
+				xoffs / 2 );
+		if(xoffs & 1) {
+			for(y = 0; y < h; y++) {
+				uint8_t v = (*fbptr & 0x0F) + (*bbptr & 0x0F);
+				*fbptr = (*fbptr & 0xF0) | (v < 0x0F ? v : 0x0F);
+				fbptr += fb->finfo.line_length;
+				bbptr += (bb->w / 2);
+			}
+		} else {
+			for(y = 0; y < h; y++) {
+				uint8_t v = (*fbptr & 0x0F) + (*bbptr >> 4);
+				*fbptr = (*fbptr & 0xF0) | (v < 0x0F ? v : 0x0F);
+				fbptr += fb->finfo.line_length;
+				bbptr += (bb->w / 2);
+			}
+		}
+		xdest++;
+		xoffs++;
+		w--;
+	}
+
+	fbptr = (uint8_t*)(fb->data + 
+			ydest * fb->finfo.line_length + 
+			xdest / 2);
+	bbptr = (uint8_t*)(bb->data +
+			yoffs * bb->w / 2 +
+			xoffs / 2 );
+
+	if(xoffs & 1) {
+		for(y = 0; y < h; y++) {
+			for(x = 0; x < (w / 2); x++) {
+				uint16_t v1 = (fbptr[x] & 0xF0) + ((bbptr[x] & 0x0F) << 4);
+				uint8_t v2 = (fbptr[x] & 0x0F) + (bbptr[x+1] >> 4);
+				fbptr[x] = (v1 < 0xF0 ? v1 : 0xF0) | (v2 < 0x0F ? v2 : 0x0F);
+			}
+			if(w & 1) {
+				uint16_t v1 = (fbptr[x] & 0xF0) + ((bbptr[x] & 0x0F) << 4);
+				fbptr[x] = (fbptr[x] & 0x0F) | (v1 < 0xF0 ? v1 : 0xF0);
+			}
+			fbptr += fb->finfo.line_length;
+			bbptr += (bb->w / 2);
+		}
+	} else {
+		for(y = 0; y < h; y++) {
+			for(x = 0; x < (w / 2); x++) {
+				uint16_t v1 = (fbptr[x] & 0xF0) + (bbptr[x] & 0xF0);
+				uint8_t v2 = (fbptr[x] & 0x0F) + (bbptr[x] & 0x0F);
+				fbptr[x] = (v1 < 0xF0 ? v1 : 0xF0) | (v2 < 0x0F ? v2 : 0x0F);
+			}
+			if(w & 1) {
+				uint16_t v1 = (fbptr[x] & 0xF0) + (bbptr[x] & 0xF0);
+				fbptr[x] = (fbptr[x] & 0x0F) | (v1 < 0xF0 ? v1 : 0xF0);
+			}
+			fbptr += fb->finfo.line_length;
+			bbptr += (bb->w / 2);
+		}
+	}
+	return 0;
+}
+
 static int paintRect(lua_State *L) {
 	FBInfo *fb = (FBInfo*) luaL_checkudata(L, 1, "einkfb");
 }
@@ -286,6 +388,7 @@ static const struct luaL_reg einkfb_meth[] = {
 	{"refresh", einkUpdate},
 	{"getSize", getSize},
 	{"blitFrom", blitToFrameBuffer},
+	{"addblitFrom", addblitToFrameBuffer},
 	{"blitFullFrom", blitFullToFrameBuffer},
 	{NULL, NULL}
 };

ft.c

@@ -138,6 +138,29 @@ static int renderGlyph(lua_State *L) {
 	return 1;
 }
 
+static int hasKerning(lua_State *L) {
+	FT_Face *face = (FT_Face*) luaL_checkudata(L, 1, "ft_face");
+	if(FT_HAS_KERNING((*face))) {
+		lua_pushinteger(L, 1);
+	} else {
+		lua_pushinteger(L, 0);
+	}
+	return 1;
+}
+
+static int getKerning(lua_State *L) {
+	FT_Face *face = (FT_Face*) luaL_checkudata(L, 1, "ft_face");
+	int left = FT_Get_Char_Index(*face, luaL_checkint(L, 2));
+	int right = FT_Get_Char_Index(*face, luaL_checkint(L, 3));
+	FT_Vector kerning;
+	FT_Error error = FT_Get_Kerning(*face, left, right, FT_KERNING_DEFAULT, &kerning);
+	if(error) {
+		return luaL_error(L, "freetype error when getting kerning (l=%d, r=%d)", left, right);
+	}
+	lua_pushinteger(L, kerning.x >> 6);
+	return 1;
+}
+
 static int doneFace(lua_State *L) {
 	FT_Face *face = (FT_Face*) luaL_checkudata(L, 1, "ft_face");
 	if(*face != NULL) {
@@ -152,6 +175,8 @@ static int doneFace(lua_State *L) {
 
 static const struct luaL_reg ft_face_meth[] = {
 	{"renderGlyph", renderGlyph},
+	{"hasKerning", hasKerning},
+	{"getKerning", getKerning},
 	{"done", doneFace},
 	{"__gc", doneFace},
 	{NULL, NULL}

rendertext.lua

@@ -23,10 +23,8 @@ end
 function getglyph(face, facehash, charcode)
 	local hash = glyphcachehash(facehash, charcode)
 	if glyphcache[hash] == nil then
-		print("render glyph")
 		local glyph = face:renderGlyph(charcode)
 		local size = glyph.bb:getWidth() * glyph.bb:getHeight() / 2 + 32
-		print("cache claim")
 		glyphcacheclaim(size);
 		glyphcache[hash] = {
 			age = glyphcache_max_age,
@@ -45,13 +43,23 @@ function clearglyphcache()
 	glyphcache = {}
 end
 
-function renderUtf8Text(x, y, face, facehash, text)
+function renderUtf8Text(x, y, face, facehash, text, kerning)
+	-- may still need more adaptive pen placement when kerning,
+	-- see: http://freetype.org/freetype2/docs/glyphs/glyphs-4.html
 	local pen_x = 0
+	local prevcharcode = 0
 	for uchar in string.gfind(text, "([%z\1-\127\194-\244][\128-\191]*)") do
-		local glyph = getglyph(face, facehash, util.utf8charcode(uchar))
-		fb:blitFrom(glyph.bb, x + pen_x + glyph.l, y - glyph.t, 0, 0, glyph.bb:getWidth(), glyph.bb:getHeight())
-		print(uchar, x + pen_x + glyph.l, y - glyph.t, glyph.bb:getWidth(), glyph.bb:getHeight())
+		local charcode = util.utf8charcode(uchar)
+		local glyph = getglyph(face, facehash, charcode)
+		if kerning and prevcharcode then
+			local kern = face:getKerning(prevcharcode, charcode)
+			pen_x = pen_x + kern
+			fb:addblitFrom(glyph.bb, x + pen_x + glyph.l, y - glyph.t, 0, 0, glyph.bb:getWidth(), glyph.bb:getHeight())
+		else
+			fb:blitFrom(glyph.bb, x + pen_x + glyph.l, y - glyph.t, 0, 0, glyph.bb:getWidth(), glyph.bb:getHeight())
+		end
 		pen_x = pen_x + glyph.ax
+		prevcharcode = charcode
 	end
 end
 

rendertext_example.lua

@@ -5,10 +5,16 @@ width, height = fb:getSize()
 
 print("open")
 
-face = freetype.newBuiltinFace("Helvetica", 64)
+-- face = freetype.newBuiltinFace("Helvetica", 64)
+face = freetype.newFace("test.ttf", 64)
 print("got face")
 
-renderUtf8Text(100,100,face,"h","Hello World! äöü")
+if face:hasKerning() then
+	print("has kerning")
+end
+
+renderUtf8Text(100,100,face,"h","AV T.T: gxyt!",true)
+renderUtf8Text(100,200,face,"h","AV T.T: gxyt!",false)
 
 fb:refresh()