Fixes line breaks for CJK characters.

This commit fixes weird line breaks when rendering CJK (Chinese, Japanese, Korean) characters. Each CJK character is more like a word instead of a letter. This commit fixes the logic of line breaks by introducing a new `NVG_CJK_CHAR` code point type and takes special care for formatting text including CJK characters.

src/nanovg.c

@@ -2549,6 +2549,7 @@ enum NVGcodepointType {
 	NVG_SPACE,
 	NVG_NEWLINE,
 	NVG_CHAR,
+	NVG_CJK_CHAR,
 };
 
 int nvgTextBreakLines(NVGcontext* ctx, const char* string, const char* end, float breakRowWidth, NVGtextRow* rows, int maxRows)
@@ -2616,7 +2617,10 @@ int nvgTextBreakLines(NVGcontext* ctx, const char* string, const char* end, floa
 				type = NVG_NEWLINE;
 				break;
 			default:
-				type = NVG_CHAR;
+				if (iter.codepoint >= 0x4E00 && iter.codepoint <= 0x9FFF)
+					type = NVG_CJK_CHAR;
+				else
+					type = NVG_CHAR;
 				break;
 		}
 
@@ -2643,7 +2647,7 @@ int nvgTextBreakLines(NVGcontext* ctx, const char* string, const char* end, floa
 		} else {
 			if (rowStart == NULL) {
 				// Skip white space until the beginning of the line
-				if (type == NVG_CHAR) {
+				if (type == NVG_CHAR || type == NVG_CJK_CHAR) {
 					// The current char is the row so far
 					rowStartX = iter.x;
 					rowStart = iter.str;
@@ -2663,26 +2667,26 @@ int nvgTextBreakLines(NVGcontext* ctx, const char* string, const char* end, floa
 				float nextWidth = iter.nextx - rowStartX;
 
 				// track last non-white space character
-				if (type == NVG_CHAR) {
+				if (type == NVG_CHAR || type == NVG_CJK_CHAR) {
 					rowEnd = iter.next;
 					rowWidth = iter.nextx - rowStartX;
 					rowMaxX = q.x1 - rowStartX;
 				}
 				// track last end of a word
-				if (ptype == NVG_CHAR && type == NVG_SPACE) {
+				if ((ptype == NVG_CHAR && type == NVG_SPACE) || type == NVG_CJK_CHAR) {
 					breakEnd = iter.str;
 					breakWidth = rowWidth;
 					breakMaxX = rowMaxX;
 				}
 				// track last beginning of a word
-				if (ptype == NVG_SPACE && type == NVG_CHAR) {
+				if ((ptype == NVG_SPACE && type == NVG_CHAR) || type == NVG_CJK_CHAR) {
 					wordStart = iter.str;
 					wordStartX = iter.x;
 					wordMinX = q.x0 - rowStartX;
 				}
 
 				// Break to new line when a character is beyond break width.
-				if (type == NVG_CHAR && nextWidth > breakRowWidth) {
+				if ((type == NVG_CHAR || type == NVG_CJK_CHAR) && nextWidth > breakRowWidth) {
 					// The run length is too long, need to break to new line.
 					if (breakEnd == rowStart) {
 						// The current word is longer than the row length, just break it from here.